The digestive system is made up of the digestive tract including the esophagus, stomach, small intestine and large intestine along with accessory organs like the liver, gallbladder, pancreas, etc. The digestive tract of a normal adult human being is about 30 feet long.

Mouth

Though the esophagus is the first part of the digestive tract, the process of digestion begins with the mouth where our teeth (premolars and molars) chew (masticate) the food and the food is mixed with enzymes in the saliva secreted by the salivary glands located below the tongue, near the lower jaw. The food is then a soft mass that is easily swallowed and later digested. The tongue and mouth push the soft food, now called a bolus, to the back of the mouth where it is swallowed. The epiglottis, a flap-like covering over the trachea (the windpipe), closes automatically when the bolus enters the esophagus to make sure that the food bolus doesn’t get into the windpipe (trachea) causing choking.

Esophagus

The bolus passes through a long muscular tube called the esophagus. The esophagus is about 10 inches long and connects the throat and the stomach. The process by which the food or bolus is pushed through the esophagus and into the stomach is known as peristalsis, that is, wavelike contractions in the muscle. At the junction of the esophagus and the stomach there is a ring like muscle known as the cardiac sphincter. This allows the food to pass into the stomach but does not permit the food to go back into the esophagus.

Stomach

The connection between the esophagus and the small intestine is a sac-like pear-shaped muscular bag called the stomach. The stomach is approximately 12 inches long and 6 inches broad at the broadest point. However, due to its elastic nature, its size and shape can change depending on the food content. The stomach is made up of five layers. The innermost layer is the mucosa (which produces the acids and digestive juices). The next layer is the submucosa covered by muscularis (which moves and helps in the mixing of the food). Then comes the two layers of covering called subserosa and serosa (the outermost layer).

The food from the esophagus passes into the stomach where it is mixed and churned with the gastric juices (enzymes and acids secreted by the mucosa) and converted into a semifluid state (called chyme) which then passes into the small intestine. However, substances like water and alcohol are absorbed directly from the stomach. A ring-like musculature called the pyloric sphincter separates the stomach from the small intestine.

Small Intestine

The small intestine is divided into three parts, namely, the duodenum, jejunum and ileum.

Duodenum

It is a 10-inch long C-shaped tube found around the head of the pancreas which forms the first part of the small intestine. The food, now converted to chyme, enters from the stomach into the duodenum where it is mixed together with the bile and other digestive juices produced by the accessory digestive organs and drained into the duodenum. Absorption of food also begins here with the absorption of vitamins, minerals and other nutrients. In particular, before the food passes into the next part of the small intestine, that is the jejunum, iron and calcium contained in the food is absorbed here. The remaining of the food is passed into the jejunum.

Jejunum

This second part or the midsection of the small intestine is a coiled tube which is thicker and vascular than the ileum. It lies in the umbilical region of the abdomen. There are small fingerlike projections in the jejunal wall called villi. These villi are covered with smaller projections called microvilli. These increase the surface area and thus aids in the greater absorption of nutrients in this part of the small intestine. Thus majority of absorption of food is done in this portion of the digestive tract. The glucose and amino acids produced in the food is passed from here into the blood stream while the fat is passed into the lymph capillaries. The remainder of food passes into the ileum.

Ileum

The last portion of the small intestine occupies mainly the pelvic region. It looks very similar to the jejunum. Also there is no specific demarcation between the jejunum and the ileum. However, the nature of the intestine gradually changes. It is thinner and less vascular as compared to the jejunum. The final absorption of nutrients from the food takes place here. The terminal ileum is an important part as this is the portion where vitamin B12 is absorbed into the blood capillaries. The unabsorbed and undigested food then passes from the ileum into the cecum, which is the beginning of the large intestine. This residue food is full of bacteria.

Large Intestine

The large intestine forms the last portion of the digestive tract, which is about 5 feet long. The large intestine can be further divided into cecum, colon and rectum. The food passes from the small intestine into the cecum which then passes into the colon (further divided into ascending colon, transverse colon, descending colon and sigmoid colon) where the fluids and salts are absorbed. After absorption, the remaining feces (undigested matter) pass into the rectum, where it is stored until it is passed out through the anus as bowel movement. The anus has voluntary and involuntary sphincter muscles which help to differentiate between gas and solid contents. A vestigial organ, the appendix, is found attached to the large intestine at the cecum. Though this organ is potentially of no use, yet it can cause pains and complications once it gets inflamed, a disorder called appendicitis.

Accessory Digestive Organs

Though not directly part of the digestive tract, the accessory digestive organs play a major role in the digestion process. The accessory digestive organs include the salivary glands, pancreas, liver and gallbladder.

Salivary Glands

There are three pairs of salivary glands, namely, parotid glands (the largest of the salivary glands is located one in each cheek between the ear and the lower jaw), submandibular glands (also called submaxillary glands located on the floor of the mouth) and sublingual glands (located in front of the submandibular glands under the tongue). All three pairs of glands secrete saliva, which is a mixture of mucus and serous fluids that contains enzymes which is necessary to moisten and lubricate the food during mastication and ingestion. It also aids in the breaking down of the starch content of the food.

Pancreas

Located behind and under the stomach, the pancreas acts both as an endocrine gland and an exocrine gland. From the exocrine part it secretes pancreatic juices containing enzymes which pass through the pancreatic duct into the small intestine (the duodenum). These enzymes aid in the further breakdown of the food, mainly the carbohydrate, protein and lipid part of the food. From the endocrine part it secretes insulin and glucagon.

Liver

The liver is the largest organ of the human body located below the diaphragm in the upper epigastric region of the abdomen. It has many functions including production of chemicals necessary for digestion, synthesis of protein and detoxification. The major function of the liver is to produce bile (yellowish-green fluid) which aids in the digestion and absorption of fats. It also stores substances like glucose, iron and vitamins A, B12, D etc.

Gallbladder

The gallbladder is a small organ located just below the liver. Its main function is to store the bile produced by the liver and release it into the duodenum when food containing fat needs to be broken down and absorbed. The bile contained in the gallbladder becomes more concentrated and thus is more effective in burning down the fat.

The teeth and tongue also aid in the digestion process and thus are very much a part of the digestive system.

Digestive System Problems and Diseases

Digestive system disorders can range from common digestive diseases to inflammatory bowel diseases, irritable bowel syndrome, lactose intolerance, ulcers or even cancers of the stomach, colon and/or rectum.

Diarrhea

The condition of watery stools at frequent intervals is called diarrhea. It is a very common problem and most often it resolves on its own. It may be caused by bacteria or virus, which is treated by antibiotics, or can be an intestinal/functional disorder, which needs specific treatment by a physician. Dehydration is a major side effect of this problem and thus the fluid lost should be replaced with constant intake of saline water.

Diverticular Disease

In some people, especially the elderly, the colon begins to have sac like protrusions called diverticula (singular diverticulum). This condition is known as diverticular disease. It is generally caused due to constipation where there is increased pressure to pass stool that is too hard. The pressure causes weak parts of the colon to bulge and thus cause diverticula. This condition occurs in almost 15% of people; however, this rarely causes any symptoms or complications. In cases where the diverticula get infected, a condition called diverticulitis; it needs thorough treatment by a physician or healthcare provider. The abdominal pains caused by diverticulitis may become very severe and may require hospitalization. Rare cases may require surgery to rectify the situation.

Heartburn

Heartburn or GERD (gastroesophageal reflux disease) is a condition where the gastric juices and/or food and fluid from the stomach flow back into the esophagus. This can be caused either by overeating or eating certain foods like citrus or fatty and spicy foods, or even can be a result of some serious underlying medical conditions like hiatal hernia. Hiatal hernia is a condition where the stomach pushes up into the chest via some opening in the diaphragm. In most cases, heartburn is relieved by over-the-counter antacid and/or diet and lifestyle modifications as recommended by the physician. However, heartburn may mimic more serious underlying conditions like heart diseases. In such cases, the chest pains are accompanied by sweating, light-headedness and/or nausea and over-the-counter antacids do not seem to help. In such a condition, immediate medical care should be sought.

Gas in the Digestive Tract

Gas goes into the digestive tract either by swallowing or by the breakdown of certain food particularly in the colon area due to the presence of certain bacteria there. This collection of gas can cause bloating, pain and discomfort in the abdomen. Gas is often released either by belching or flatulence. Some situations may require medications to release the gas and/or diet modification to reduce the formation of gas. Aerophagia or air swallowing can be reduced by removing the causes, namely, rapid eating and drinking, chewing gums, smoking and wearing loose dentures.

Hepatitis

The inflammation of the liver mainly due to viral infections is known as hepatitis. There are six types of hepatitis, namely, hepatitis A, hepatitis B, hepatitis C, hepatitis D, hepatitis E and hepatitis G. Hepatitis A is caused by fecal-oral contact that is by ingestion of fecal infected food or water. Hepatitis B is spread from an infected person by exposure to body fluid like saliva, blood, semen or vaginal secretions. It can also be transmitted to a baby born of an infected mother. Hepatitis C is primarily transmitted by contact with infected blood but can also be transmitted via sexual contact or to a baby born of an infected mother. Infections caused due to hepatitis B or hepatitis C are more severe and has a higher mortality rate as compared to hepatitis A. Effective vaccinations are available for hepatitis A and hepatitis B. Hepatitis D occurs to patients already affected with hepatitis B, either simultaneously or later. Similar to hepatitis A, hepatitis E is also caused by fecal-oral contact. However, it is less common than hepatitis A and is only found in poorly developed countries. The latest form of hepatitis is hepatitis G. Though very little is known about this form, it is believed to spread through the blood especially found in IV drug users. It generally shows no clinical symptoms.

Inflammatory bowel diseases

Ulcerative colitis

In this type of inflammatory bowel disease, the inner lining of the colon and the rectum gets inflamed. This is a chronic disease with an unknown cause. It generally does not affect the small intestine, though at times the ileum (the part of the small intestine that joins with the large intestine) may get affected. The symptoms caused in this condition, like diarrhea and cramping are relieved with medication that soothe the inflammation. However, the patient might need hospitalization in order to treat malnutrition and/or loss of blood, fluid and salts. In very few cases, a patient might need to undergo surgery, especially where there is risk of excessive bleeding, perforated colon or risk of cancer.

Crohn’s Disease

This type of inflammatory bowel disease, of unknown cause, affects the deeper layers of the bowel, mainly the terminal ileum, but may extend to the other parts of the digestive tract. Though there are no sure cures for Crohn’s disease, medications are given to lessen the inflammation and supplements are suggested to correct nutritional deficiencies. Surgeries like removal of a section of the bowel, ileostomy, colostomy etc. are done in certain cases which might help though it cannot be completely cured by surgery. There is a possibility that it might affect the area next to the removed section of the bowel.

Irritable Bowel Syndrome

This is a functional disorder of the intestine, mainly the colon. When closely monitored the disease cannot be seen but causes symptoms like pains, bloating, changes in the bowel habits etc. The exact cause of this disorder is unknown but is believed to be caused due to emotional stress and/or improper diet. Physicians generally treat this disorder with diet modifications and medications like antidepressants, laxatives, tranquilizers etc. They may also include a fiber supplement. However, in using these medications the patient may tend to become dependent on laxatives or tranquilizers and it can have a major effect on their lifestyle.

Lactose intolerance

Lactase is an enzyme produced in the small intestine which helps in the breakdown of lactose (found in milk products) into a form that can be easily absorbed by the blood. When there is lack of lactase, the body is unable to digest lactose. This condition is called lactose intolerance. This is generally caused due to injuries to the small intestine. There is no treatment to improve the body’s ability to produce lactase but physicians may suggest additional lactase enzymes. The patient’s lactose intolerance is controlled with diet modifications.

Peptic Ulcers

An open sore or lesion on the skin or mucous membrane is called an ulcer. A peptic ulcer is an ulcer found in the lining of the stomach and duodenum. In particular, the ulcer of the stomach is known as gastric ulcer while that of the duodenum is called duodenal ulcer. Stress and diet were earlier thought to be the cause of this disease, while later it was found that hydrochloric acid and pepsin (the stomach acids) were contributing to this disease. However, recent researches have shown that the primary cause is an infection with a bacterium known as Helicobacter pylori. These ulcers can lead to serious complications like bleeding, perforation or even narrowing and obstruction. These can be treated by lifestyle changes and medications as prescribed by the physician. For patients who do not respond to medications or develop complications, surgeries like vagotomy, antrectomy or pyloroplasty are performed depending on the site of the ulcer.

Cancers

Like any other parts of the body, the digestive tract can also be infected with cancer. The common ones are the stomach cancer and colorectal cancer. What causes these cancers in unknown but it is believed that the cells in the stomach or colon and rectum become cancerous due to the risk factors like diet, tobacco, alcohol, H. pylori in case of stomach cancer and age, diet, polyps, ulcerative colitis, personal/family history in case of colorectal cancer. Treatment includes surgery to remove the cancerous tissues (like gastrectomy or segmental resection of the colon), radiation therapy and chemotherapy.

Anatomic terms describe the directions within the body as well as the body’s reference planes, cavities and regions.

There are many times in medicine that a doctor has to record in a medical record or tell another doctor the exact body part or location of disorders or damage to the body or an organ. To do that, the are standard terms for describing human anatomy including the body and it’s organs. The terms used to describe positions reference the person in the standard anatomical position. The standard anatomical position for humans is standing upright as in the image above. By using this as a standard for descriptions, we avoid confusion even when the person is in some other position. For example, suppose the doctor was describing someone lying down? The doctor’s description would be as if the person were standing up in the standard position.

Anatomy is the study of the structure of the human body.

The standard anatomical position for humans has its feet together (or slightly separated), and the arms are rotated outward so that the palms are forward, and the thumbs are pointed away from the body (forearms supine). As well, the arms are usually moved slightly out from the body, so that the hands do not touch the sides. The positions of the limbs (and the arms in particular) have important implications for directional terms in those appendages. The penis in men is also erect in the anatomical position, hence the dorsal surface of the penis is actually anterior in the flaccid state. The head is upright and facing forward so that certain parts of the eyes and ears are in the same horizontal plane.

For "normal" human bodies, the right and left sides are mirror images if divided right down the center as shown by the sagittal plane in the image. The dotted line represents an axis or dividing line.

Directional Terms

In general, directional terms are grouped in pairs of opposites.

• Superior and inferior. Superior means above, inferior means below. The elbow is superior to the hand. The foot is inferior to the knee.
• Anterior and posterior. Anterior means toward the front of the body, posterior means toward the back.
• Medial and Lateral. Medial means toward the midline of the body, lateral means away from the midline. Ipsilateral means on the same side—the left arm is ipsilateral to the left leg.
• Proximal and distal. Proximal means closest to the point of origin or trunk of the body, distal means farthest. Often used when describing arms and legs.
• Superficial and deep. Superficial means toward the body surface, deep means farthest from the body surface.

Other directional terms:

• Intermediate – means between—your heart is intermediate to your lungs.
• Caudal – at or near the tail or posterior end of the body.
• Visceral – may be used instead of deep.

There are also terms that are used for describing specific body parts. Palmar is used to describe the palm side of the hand, Dorsal describes the back side of the hand. Plantar describes the bottom of the foot.

Anatomical Reference Planes

The body reference planes are used to locate structures in the body. These terms are most often used to describe medica imaging such as CAT scans, PET scans and MRIs where the scans take pictures of the body in slices. Brain scans are often of sagittal plane slices from ear to ear. Abdominal CAT scans are often transverse plane slices.

Main Reference Planes

• Median sagittal plane – this plane divides the body into left and right sides.
• Frontal (or coronal) plane – divides the body into front (anterior) and back (posterior)
• Transverse plane – this plane is parallel to the ground and divides the body into up (cranial or head) and down (tail or caudal)
• Oblique plane is not shown and is a slanted plane that lies between the horizontal and vertical planes.

Body Cavities

Body cavities are the areas in the body that contain our internal organs. The dorsal and ventral cavities are the two main cavities. The dorsal cavity is on the posterior (back side) of the body and contains the cranial cavity and vertebral cavity. In human anatomy, dorsal, caudal and posterior mean the same thing. The ventral cavity is on the front (anterior) of the body and is divided into the thoracic cavity and abdominopelvic cavity.

Dorsal Cavity

The dorsal cavity is further divided into subcavities:

• cranial cavity (also called the calvaria) which surrounds the brain
• vertebral cavity (also called the spinal cavity) which includes the vertebrae and spinal cord.

Ventral Cavity

The ventral cavity is on the front of the trunk and is divided into subcavities:

• thoracic cavity which is surrounded by the ribs and chest muscles is superior (above) the diaphragm and abdominopelvic cavity. It is further divided into the pleural cavities (left and right) which contain the lungs, bronchi, and the mediastinum which contains the heart, pericardial membranes, large vessels of the heart, trachea (windpipe), upper esophagus, thymus gland, lymph nodes, and other blood vessels and nerves.
• abdominopelvic cavity is divided into the abdominal cavity and pelvic cavity. The abdominal cavity is between the diaphragm and the pelvis. It is lined with a membrane and contains the stomach, lower part of the esophagus, small and large intestines (except sigmoid and rectum), spleen, liver, gallbladder, pancreas, adrenal glands, kidneys and ureters. The pelvic cavity contains the bladder, some reproductive organs and the rectum.

Other Cavities

• oral cavity – the space in the mouth inside the teeth and gums and is filled with the tongue when it is relaxed.
• nasal cavity – in the nose
• orbital cavities (left and right) – hold the eyes
• middle ear cavities (left and right) – hold the small bones of the middle ear
• synovial cavities – are inside the joint capsules that surround freely moving joints (such as the hip, knee, elbow, and shoulder)

Body Quadrants

Quadrants are another way our bodies are divided into regions for diagnostic and descriptive purposes.

Body Regions

Body regions are used to describe areas of the body that have a special function or are supplied by specific blood vessels or nerves. The terms most widely used terms are those that describe the 9 abdominal regions shown in the image to the right. The regions are named below and the corresponding regions are labeled.

Abdominal Regions

• right (1) and left (3) hypochondriac regions – on either side of the epigastric region. Contains the diaphragm, some of the kidneys, right side of the liver, the spleen and part of the pancreas.
• epigastric region (2) – superior (above) the umbilical region and contains most of the pancreas, part of the stomach, liver, inferior vena cava, abdominal aorta and duodenum
• right (4) and left (6) lumbar (lateral) regions – on either side of the umbilical region. They contain portions of the large and small intestines and kidneys.
• umbilical region (5) – area around the umbilicus (belly button). Includes sections of the large and small intestines, inferior vena cava and abdominal aorta
• right (7) and left (9) iliac (inguinal) regions – are on either side of the hypogastric region and include portions of the large and small intestines.
• hypogastric (pubic) (8) region – inferior (below) the umbilical region. Contains parts of the sigmoid colon, the urinary bladder and ureters, the uterus and ovaries (women), and portions of the small intestines.

Abdominal Quadrants

Quadrants are another way our bodies are divided into regions for diagnostic and descriptive purposes. The quadrants are defined by drawing an imaginary line vertically and horizontally though the umbilicus (belly button). This following is a list of the organs located in each of the four quadrants.

• Right Upper Quadrant (RUQ) – right lobe of liver, gallbladder, part of the transverse colon, part of pylorus, hepatic flexure, right kidney, and duodenum.
• Right Lower Quadrant (RLQ) – cecum, ascending colon, small intestine, appendix, bladder if distended, right ureter, right spermatic duct (men), right ovary and right tube and uterus if enlarged (women).
• Left Upper Quadrant (LUQ) – Left lobe of liver, stomach, small intestine, transverse colon, splenic flexure, pancreas, left kidney and spleen.
• Left Lower Quadrant (LLQ) – small intestine, left ureter, sigmoid flexure, descending colon, bladder if distended, left spermatic duct (men) left ovary and left tube and uterus if enlarged (women).

The brain, which is housed in and protected by the bones of the skull, makes up all parts of the central nervous system above the spinal cord. A human brain can weigh up to 3 pounds and is one of the largest organs of the body. Like the spinal cord, the brain is made of mainly gray matter and white matter arranged in distinct layers. The top of the brain appears as a soggy, pinkish-gray mass that looks like a walnut.

Parts of the Brain

The brain consists of the:

• cerebrum
• cerebellum
• brain stem
• diencephalon (thalamus and hypothalamus)
• limbic system
• reticular activating system

The brain can be divided into two major parts: the lower brain stem and the higher forebrain.

The brain stem sits above the spinal cord and has many connections between them. The brain stem, the most primitive part of the brain, is made up of the medulla, pons, cerebellum, midbrain, hypothalamus and thalamus. The cerebral cortex, limbic system and basal ganglia make up the forebrain. The forebrain deals with homeostasis, emotions and conscious actions.

The brain’s outer layer is only 1/4 inch thick but if flattened out would cover the size of an office desk. It has about 50 billion nerve cells.

The cerebrum is the largest part of the brain and is part of the forebrain. It houses the nerve center that controls sensory, motor activities and intelligence. The outer layer, the cerebral cortex, is made of nerve fibers called gray matter. The inner layer is made of a different type of nerve fibers called white matter. The basal ganglia is found in the white matter. The cerebrum is divided in to left and right hemispheres. The left half controls the right side of the body and the right half controls the left side of the body. A mass of nerve fibers known as the corpus callosum connects the two hemispheres and allows communication between the two. The surface of the cerebrum is made up of gyri and sulci.

A cortex is the outer layer of any organ. The cerebral cortex is the outer layer of the brain, called gray matter. It is where our conscious thoughts and actions take place. Many of the signals our brain receives from our senses are registered in the cerebral cortex. The visual cortex is in the lower back part of the brain and is where our brain registers what we see. The somatosensory cortex is a band that runs over the top of the brain is where our brain registers a touch on any part of our body. The motor cortex is just in front of the somatosensory cortex and it sends out signals to muscles to make them move. The more nerve endings a part of the body has, the more of the sensory cortex it occupies. A big portion of the sensory cortex is taken up by our lips and face. Our hands take up almost as much as our face and our feet almost as much as our hands. This is because we move our hands and lips all the time and both are very sensitive.

The cerebellum, “little brain”, is the second largest region of the brain. It is located behind and below the cerebrum and at the back of the brain stem and attached to the midbrain. It has two hemispheres and an outer cortex of gray matter and an inner core of white matter. The cerebellum is involved in movement and coordination, walking, posture, reflexes, eye and head movement. It coordinates subconscious movements such as balance and coordinated movement. The cerebellum is constantly receiving updates about the body’s position and movement. It also sends instructions to our muscles that adjust our posture and keep our body moving smoothly.

The diencephalon is located between the cerebrum and midbrain. It consists of the thalamus and hypothalamus which lie deep in the cerebral hemispheres. Centers in the hypothalamus regulate our body temperature, blood sugar, hunger, sexual behavior and hormones. The thalamus is involved with sensory signals sent to the higher forebrain, in particular the cerebral cortex. The thalamus also participates in motor control and regulating cortex excitement. Several pathways connect the brainstem to the lower motor centers in the spinal cord and the higher ones in the forebrain.

The brain is the control center of the body and contains billions of nerve cells.

The brain stem lies just below the cerebrum and in front of the cerebellum. It continues from the cerebrum above and connects to the spinal cord below. The brain stem is made up of the midbrain, pons and medulla oblongata. It carries out many vital functions of the body for maintenance and survival such as breathing, heartbeat, and blood pressure. It also controls vomiting, coughing, sneezing and swallowing. It is the body’s “autopilot.” It also provides pathways for nerve fibers between the higher and lower neural centers. It is also the origin for 10 of the 12 cranial nerves. The 12 cranial nerves enter the brain directly and are not connected to the spinal cord.

The midbrain is the reflex center for cranial nerves III and IV and is involved in eye reflexes and movements. The pons helps regular breathing. It connects the cerebellum with the cerebrum and links the midbrain to the medulla oblongata. The pons is the reflex center for cranial nerves V through VIII. The pons is involved in chewing, taste, saliva, hearing and equilibrium. The medulla oblongata joins the spinal cord at the foramen magnum. It influences heart, breathing and circulation. It’s the center for vomiting, coughing and hiccuping.

The medulla—the most primitive brain structure—controls our digestive, respiratory and circulatory systems. The ponsinteracts with the cerebellum, motor control and respiration. Other structures in the pons control sleep and excitement. The pons also relays information between the brain and the spinal cord.

The basal ganglia is found in the forebrain and consist of structures involved in motor processes. The basal ganglia works along with the motor areas of the cortex and cerebellum for planning and coordinating certain voluntary movements. The basal ganglia is made of gray matter.

The limbic system, or limbic lobe, is involved in the expression of intimate behaviors (sexual arousal) and emotions, hunger, aggression. The limbic system also screens all sensory messages to the cerebral cortex. It is located deep in the temporal lobe. The limbic system includes these structures: cingulate gyrus, corpus callosum, mammillary body, olfactory tract, amygdala, and hippocampus. The hypothalamus affects body temperature, appetite, water balance, pituitary secretions, emotions, and autonomic functions including cycles of waking and sleeping.

Even though many functions of the brain are very localized to certain areas and parts of the brain, these parts work together as a whole—particularly in learning, memory, and consciousness.

Ventricles are fluid filled cavities in the brain; there are four of them. The ventricles connect with each other and produce cerebrospinal fluid which is a clear, shock-absorbing liquid that is constantly moving. The cerebrospinal fluid cushions the brain, distributes nutrients and collects wastes.

Blood Vessels in the Brain

The oxygen supply for the brain comes from 4 major arteries, two vertebral arteries and two carotid arteries. The two vertebral arteries supply blood to the back of the brain. The two carotid arteries branch and supply oxygen to the front and middle of the brain. The front and back arteries interconnect at the circle of Willis at the base of the brain. The circle of Willis ensures a continuous blood supply to the brain.

Cross Section Images of the Brain

Sectioning the Brain

Left and Right Hemispheres

The forebrain consists of two almost symmetrical cerebral hemispheres made up of the cerebral cortex, the basal ganglia and the limbic system. The two hemispheres are divided by the longitudinal cerebral fissure and connected by a massive bundle of fibers called the corpus callosum. The surface of the two hemispheres is covered by a large, but thin layer of nerve cells called gray matter. Because of the area size of the gray matter, fitting it into the skull causes folds. The grooves in these folds are called sulci (singular sulcus), the ridges are called gyri (singular gyrus). The deeper grooves are called fissures. The cortex is a large mass of nerve fibers called white matter. These nerve fibers are highly developed and able to analyze both motor and sensory information.

The left and right hemispheres may look the same, but each side functions differently. Speech and language, reasoning and analysis, and certain communications are on the left side for most people. The left side of the brain sends and receives information to the right side of the body including the right hand. The right hemisphere is concerned with sensory input, auditory and visual awareness, creative abilities, and spatial-temporal awareness—that is what is happening around us moment by moment. The right brain controls the left side of the body.

Each of the cerebral hemispheres is divided into four lobes and are name for the cranial (skull) bones that lie over them:

• The frontal lobe extends from the tip of the front of the hemisphere to the central sulcus. The back areas of the frontal lobe specialize in motor functions, including language and voluntary movement; the front areas are involved in learning, planning and other higher psychological processes like our personality and behavior.
• The occipital lobe is at the back of the hemisphere and is involved in interpreting visual stimuli, that is, what we see.
• The parietal lobes are at the top and outside areas between the occipital lobe and the frontal lobe and is involved in sensory functions of the skin including pain, temperature, and touch. It also interprets size, shape, distance, vibrations and texture. Other areas are also important in cognitive and intellectual processes.
• The temporal lobe controls the hearing centers, language comprehension, storing and recalling memories and related areas including some speech centers. Other areas of the brain also affect memory. The front and bottom areas of the temporal lobe are involved in smell and functions of the limbic system.

Brain Injuries and Disorders

• Traumatic Brain Injury
• Coma

Spinal Cord Anatomy

Anterior Fissure

Deep groove along the front of the spinal cord

Arachnoid

This membrane is the middle layer of the three meninges that covers and protects the spinal cord and brain.

Central Canal

Cerebrospinal fluid fills the narrow central canal and protects the neurons

Dura Mater

The outermost, toughest, and most fibrous of the three membranes that cover and protect the spinal cord and brain

Gray Matter

Gray matter is shaped like a butterfly. Gray matter is divided into three functional zones— the dorsal horns are sensory, the ventral horns are involved in motor functions and the middle zone carries out functions between sensory and motor zones. Gray matter is made up of both large and small neurons. The large neurons are either motor or sensory. The fibers of the motor neurons (output neurons), located in the ventral horns, go to the voluntary skeletal muscles. These motor neurons are grouped in clusters and each serves a different muscle. Autonomic neurons are clustered separately.

Meninges

Three membranes that cover and protect the spinal cord and brain—dura mater (outer), arachnoid (middle) and pia mater (inner)

Pia Mater

This thin vascular membrane of collagen fibers is the innermost layer of the three meninges that covers and protects the spinal cord and brain.

Sensory Root

Ganglion Cell bodies of sensory nerves cluster in ganglia

Spinal Nerve

Sensory and motor nerve rootlets merge to form a spinal nerve

Subarachnoid Space

The area between the arachnoid membrane and the pia mater

White Matter

This outer band surrounds the gray matter throughout the length of the spinal cord. Made up of axons of neurons grouped in bundles called funiculi that contain nerve fibers that travel between the spinal cord and the brain. These bundles form pathways that carry signals to and from the brain. Pathways to the brain are usually sensory, and pathways from the brain to the spinal cord are usually motor.

Spinal Cord

The brain and spinal cord make up the central nervous system. The spinal cord is about 16-18 inches long and and is basically a uniform structure throughout it’s length. The spinal cord is contained in the center cavity of the vertebral column (back bone) which protects the spinal cord from injury. It has an inner mass of gray matter and an outer covering of white matter. It carries messages that coordinate movement and sensation. The cord is an ovoid shaped column of nerve tissue that extends from the medulla at the underside of the brain down through cavities in the spinal column to the second lumbar vertebrae. The spinal cord is protected by the bones of the spinal cord and enclosed in the protective tissue of the meninges (mater) and cerebrospinal fluid. The center of the cord is gray matter and shaped like an H. The white matter is arranged in tracts around the gray matter and consists of axons that transmit impulses to and from the brain or between levels of gray matter in the spinal cord.

The spinal cord has two basic functions. It can act as a never center and can work without the brain. The spinal cord carries sensory impulses to the brain and motor impulses from the brain. The spinal cord also controls stretch reflexes, bowel and bladder control. Thirty-one pairs of nerves exit from the spinal cord and innervate our body and limbs. The spinal cord also acts as a nerve center between the brain and the rest of our body.

Spinal Nerves

A spinal nerve is any of the 31 pairs of nerves that arise from the spinal cord. The spinal nerves correspond to where it emerges and passes through the spinal vertebrae: there are 8 cervical (neck), 12 thoracic (chest), 5 lumbar (lower back), 5 sacral (sacrum bone) and one coccygeal (tailbone) nerve(s). Each spinal nerve is attached to the spinal cord by two roots: a dorsal or posterior sensory root and a ventral or anterior motor root. The fibers of the sensory root carry sensory impulses to the spinal cord—pain, temperature, touch and position sense (proprioception)—from tendons, joints and body surfaces. The motor roots carry impulses from the spinal cord. The spinal nerves exit the spinal cord and pass through the intervertebral foramen, then divides into four branches.

Nerve Plexus

A plexus is a network. It can be a network of blood vessels or nerves.

Cervical plexus

A network formed by the first 4 cervical spinal nerves. It innervates parts of the face, neck, shoulder and chest and gives rise to the phrenic nerve to the diaphragm.

Brachial plexus

A network of the last 4 cervical and first thoracic spinal nerves supplying the arm, forearm and hand.

Lumbar plexus

A network of the first 4 lumbar nerves.

Sacral plexus

A network of the 4th and 5th lumbar nerves and the first four sacral nerves, from which the sciatic nerve originates.

Touch tells us about temperature, pressure, texture, movement and bodily location. Pain seems to be a part of touch, but it has its own receptors and sensory pathways.

Each muscle in the body is supplied with nerves (innervated) by a particular segment of the spinal cord and by its corresponding spinal nerve. A myotome is the group of muscles supplied by a single nerve root. A dermatome is an area of the skin supplied by the nerve fibers from a single sensory nerve root. Each area is named from the spinal nerve that supplies it. These areas on the trunk resemble horizontal bands; on the arms and legs the areas are elongated, vertical strips. There is a good bit of overlap between dermatomes. If sensory function is lost in one spinal nerve, sensation isn’t completely lost in that area because of the overlap of the nearby spinal nerve.

The levels of the spinal cord segments don’t relate exactly to the levels of the vertebral bodies because there are 7 vertebrae and 8 cervical nerve roots coming from the spinal cord. Damage to a vertebrae at a particular level doesn’t mean there is damage to the spinal cord at that same level.

Map of Dermatomes

A dermatome is a band or region of skin supplied by a single sensory nerve. Sensory nerves carry sensory impulses to the spinal cord—pain, temperature, touch and position sense (proprioception)—from tendons, joints and body surfaces. The face is supplied by the cranial nerves.

Map of Dermatomes

Key to Spinal Nerve Regions

Each pair of spinal nerves links to one of four regions of the body.

• Cervical Region (green): 8 pairs of nerves supply the skin covering the back of the head, the neck, shoulders, arms and hands.
• Thoracic Region (blue): 12 pairs of thoracic nerves supply the skin on the chest, back and under arms
• Lumbar Region (pink): 5 pairs of lumbar nerves supply the skin on the lower abdomen, thighs and fronts of the legs
• Sacral Region (yellow): 6 pairs of sacral nerves supply the skin on the rear of the legs, the feet and genial areas

Knuckle cracking does not serve any beneficial purpose and may be harmful to the fingers due to the stretching of the joint capsule.

The hand has 19 bones: 5 elongated metacarpal bones, which are next to the wrist and make up the palm; 14 phalanges which make up the fingers. Each finger has 3 phalanges, the thumb has 2. These 19 bones collectively form 14 separate joints. The knuckle joints, metacarpophalangeal (MCP) joints, join the fingers to the palm. The interphalangeal (IP) joints are the finger joints. There are synovial joints between the metacarpals and phalanges—these bones are also covered with articular cartilage.

The adult skeleton is mainly made of bone and a little cartilage in places. Bone and cartilage are both connective tissues, with specialized cells called chondrocytes embedded in a gel-like matrix of collagen and elastin fibers. Cartilage can be hyaline, fibrocartilage and elastic and differ based on the proportions of collagen and elastin. Cartilage is a stiff but flexible tissue that is good with weight bearing which is why it is found in our joints. Cartilage has almost no blood vessels and is very bad at repairing itself. Bone is full of blood vessels and is very good at self repair. It is the high water content that makes cartilage flexible.

Hand Muscles and Hand Tendons

The muscles in the forearm and palm (thenar muscles) all work together to keep the wrist and hand moving, stable, and aligned. The image below shows the bones from the back side of the hand. The red lines show where the tendons attach the muscles to the bones.

The muscles that move the fingers and thumb are above the wrist in the forearm. Long flexor tendons extend from the forearm muscles through the wrist and attach to the small bones of the fingers and thumb. When you bend or straighten your finger, these flexor tendon slide through a snug tunnel, called the tendon sheath, that keeps the tendon in place next to the bones.

Tendons are white, flexible fibrous cords at the ends of muscles that attach the muscles to the radius, ulna, carpals, metacarpals and phalanges. When the muscles contact, they pull on the tendons to move the bone. The tendons that run down our fingers are held in place by a series of ligaments, called pulleys, that arch over the tendons forming a “tunnel-like” sheath. Normally, the tendons glide easily through the tunnel. Some tendons also serve as stabilizers.

A series of ligaments in a tunnel-like arrangement hold the tendons in place on the bones. A slippery coating, called tenosynovium, surrounds the tendons and keeps the tendons moving smoothly under the ligaments when the hand grasps objects.

Ligaments

Ligaments of the back of the hand

Hand Ligaments are tough bands of fibrous tissue that join bones together. Six major ligaments give stability to the wrist by joining the radius to the carpal bones and binding the two rows of carpal bones together. These ligaments joint with others to link the wrist to the hand.

Joint Capsule

Other stabilizers in the hand include joint capsules, which are made of fibrous connective tissue that surrounds the joints. A synovial membrane inside the joint capsules provides synovial fluid to lubricate all the joints.

Hand Nerves

The median, radial and ulnar nerves are the three major nerves that run the length of the arm through the wrist and down into the hand. These nerves contract specific muscles and gives us sensations of touch, and to feel hot, cold, and pain.

Problems in the Hand and Wrist

• Inflammation
• Muscle Tightness
• Muscle Strain
• Muscle Tear
• Muscle Spasm
• Tendinitis
• de Quervain’s Tenosynovitis
• Trigger Finger
• Jammed Finger
• Arthritis
• Carpal Tunnel Syndrome
• Cubital Tunnel Syndrome
• Wrist Drop
• Fracture
• Dislocation

Bones and Joints of the Foot and Ankle

Ankle

Lateral side of the ankle Joint capsule

The bones of the foot and ankle begin with the ankle joint itself. The ankle joint, talocrural joint, is formed where the leg meets the foot. The ankle joint is formed where the tibia, fibula and talus meet forming a synovial, hinge joint. In a hinge joint, a convex part of one bone fits into the concave part of the other bone. The two bones of the lower leg, the large tibia and the smaller fibula come together at the ankle joint to form a very stable mortise and tenon type joint. The mortise and tenon construct is well known to carpenters and craftsmen who use this type of construction to join everything from furniture to large buildings. The ankle joint allows the foot to bend up (flex) and down (extend). When the foot is extended, the heel is drawn up and the toes point downward. The ankle joint is more stable when it is extended than when it’s flexed (toes up).

The ankle bones are connected by the anterior talofibular ligament, posterior talofibular ligament, and calcaneofibular ligament. The articular capsule surrounds the joint with thin fibrous tissue. A synovial membrane is in under the ligamnents.  Of the ligaments, the deltoid is so strong that it usually resists a force which fractures the bone to which it is attached.

The arteries supplying the ankle joint are derived from the malleolar branches of the anterior tibial and the peroneal.

The nerves of the ankle are derived from the deep peroneal and tibial nerves.

Foot

Bones of the foot as seen from the medial (arch) side.

The foot forms a firm basis of support for the body in the erect posture, and is solidly built up and its parts are less movable on each other than those of the hand. The phalanges (toes) of the foot are smaller and their movements are more limited than the fingers of the hand. Very much more different between the metacarpal bone of the thumb and the metatarsal bone of the great toe. The metatarsal bone of the great toe helps support the weight of the body, is constructed with great solidity, lies parallel with the other metatarsals, and has a very limited amount of movement. The tarsus forms a considerable part of the foot, and is at right angles to the leg, and relates to an erect posture. In order to support our body weight with the least amount of surface area, the tarsus and a part of the metatarsus is made up of a series of arches.

The bones of the foot include the tarsals, metatarsals and phalanges.

Bones of the foot from the lateral side (side opposite the arch.)

The two bones that make up the hindfoot are the talus and the calcaneus (heel). Where the talus meets the calcaneus forms the subtalar joint. The subtalar joint allows the foot to rock from side-to-side.

Tarsal Bones

The tarsal bones work together as a group. The way these bones fit together is very interesting. When the muscles of the foot and leg twists the foot in one direction, the tarsal bones lock together and form a very rigid structure. When they twist in the opposite direction, the bones unlock, allowing the foot to conform to whatever surface the foot is contacting.

There are seven tarsal bones: the calcaneus, talus, cuboid, navicular, and the first, second, and third cuneiforms.

The calcaneus (heel bone) is the largest of the tarsal bones. It transmits the weight of the body to the ground and acts as a lever for the muscles of the calf. The calcaneus joins with the talus and cuboid.

The talus (ankle bone) is the second largest of the tarsal bones and sits atop the calcaneus. It joins on either side with the malleoli and in front with the navicular. The talus forms a joint with four bones: tibia, fibula, calcaneus, and navicular.

The cuboid is on the lateral side (opposite the arch of the foot) and in front of the calcaneus. The cuboid forms a joint with four bones: the calcaneus, third cuneiform, and fourth and fifth metatarsals; occasionally with a fifth, the navicular.

The navicular sits at the medial side of the tarsus, between the talus behind and the cuneiform bones in front. The navicular forms joints with four bones: the talus and the three cuneiforms; occasionally with a fifth, the cuboid.

The first cuneiform forms a joint with four bones: the navicular, second cuneiform, and first and second metatarsals. The second cuneiform forms joints with four bones: the navicular, first and third cuneiforms, and second metatarsal. The third cuneiform forms joints with six bones: the navicular, second cuneiform, cuboid, and second, third, and fourth metatarsals.

Metatarsal Bones

The metatarsus consists of 5 bones and are numbered starting from the arch side of the foot. The tarsal bones are connected to the 5 long bones of the foot called the metatarsals.

There is a fairly rigid connection between the two groups without much movement at the joints. The base of each metatarsal bone forms a joint with one or more of the tarsal bones, and the head with one of the first row of phalanges. The first metatarsal forms a joint with the first cuneiform, the second with all three cuneiforms, the third with the third cuneiform, the fourth with the third cuneiform and the cuboid, and the fifth with the cuboid.

Phalanges

Finally, there are the bones of the toes, called the phalanges. The joints between the metatarsals and the first phalanx is called the metatarsal phalangeal joint. These joints form the ball of the foot, and movement in these joints is very important for a normal walking pattern.

The phalanges of the foot correspond, in number and general arrangement, with those of the hand; there are two in the great toe, and three in each of the other toes. They differ from the hand, however, in their size, the bodies are shorter in length, and, especially in the first row, wider.

Not much motion occurs at the joints between the bones of the toes (phalanges). The big toe, or hallux is the most important toe for walking, and the first metatasal phalangeal joint is a common area for problems in the foot.

In the second, third, fourth, and fifth toes the phalanges of the first row form joints behind with the metatarsal bones, and form joints in front with the second phalanges, which in their turn form joints with the first and third: the ungual phalanges form joints with the second.

Soft Tissues of the Foot and Ankle

The soft tissues of the foot and ankle include ligaments, tendons, nerves and blood vessels.

Ligaments

Ligaments of the medial side of the foot

Ligaments are strong, dense, flexible bands of fibrous connective tissue. The function of ligaments is to attach bones to bones. Ligaments help give the stability of the joint. Ligaments are often named after the the bones they join together. The ankle joint is bound by the strong deltoid ligament and three lateral ligaments: the anterior talofibular ligament , the posterior talofibular ligament and the calcaneofibular ligament.

• The deltoid ligament supports the medial side of the ankle and attaches the tibia to the calcaneus and talus.

• The talofibular ligaments join the talus and the fibula and support the lateral sides (the side opposite the arch of your foot) of the ankle.

• The calcaneofibular ligament joins the calcaneus and the fibula.

Ligaments of the lateral side of the foot

Tendons

Bones (green) and tendons (red) of the foot

Tendons are bands of fibrous connective tissue. The function of ligaments is to attach muscles to bones and enable muscles to move bones when the muscles contract.

The large Achilles tendon is the most important tendon for walking, running and jumping. It attaches the calf muscles to the heel bone to allow us to raise up on the toes. The posterior tibial tendon attaches one of the smaller muscles of the calf to the underside of the foot. This tendon helps support the arch and allows us to turn the foot inward. The toes have tendons attached that bend the toes down(on the bottom of the toes) and straighten the toes(on the top of the toes). The anterior tibial tendon allows us to raise the foot.

Muscles

Nerves

The main nerve to the foot(the posterior tibial nerve) enters the sole of the foot by running down behind the inside bump on the ankle, the medial malleolus. The main blood supply to the foot(the posterior tibial artery) runs right beside the nerve. There are other less important nerves and arteries that enter the foot from other directions.

Blood Vessels

The Spinal Column

The spinal column is made up of 26 bones: 24 unique vertebrae plus the sacrum and coccyx (tail bone) at the end of the backbone. The Vertebrae seem to be chained together). The vertebrae include:
• 7 cervical vertebrae which makes up the neck
• 12 thoracic vertebrae of the chest
• 5 lumbar vertebra or the “lower back”—L1, L2, L3, L4 and L5.

Bones, disks and facet joints of lumbar spine

The back can move in many different directions, it can stiffen as well as be supple. When looked at from the back, the spine appears to be straight, but looked at from the side you can see 2 curves which cause the back to have an “S” shape—it curves forward at the neck (cervical spine) and lower back (lumbar spine) and slightly backwards at the thoracic spine and sacral region. These curves help support the head and provides strength, flexibility and provides super shock absorbing abilities. Many problems with the back are associated with the normal curvature of the back.

Between each vertebra is a cushion called an intervertebral disk. On the anterior side of each vertebra is an oval shaped disk called the vertebral body. On the posterior side of each vertebra is the vertebral foramen, which is an opening through which the spinal cord passes. A crucial job of the back is to protect and support the vital spinal cord and spinal nerves.

A Spinal Segment

Segment is made of two vertebrae, the intervertebral disk, and two spinal nerves

A spinal segment forms a functional unit and is made up of two adjacent vertebrae, the intervertebral disk between them, the two spinal nerves that exit from each side of the spinal cord, ligaments and muscles.

The Sacrum

Side view of the sacrum and tailbone, the body of the sacrum forms a joint with the 5th lumbar vertebra.

The sacrum is the last segment of the spine. At birth, it is made of several vertebrae. By the time you’re an adult these vertebrae have fused together to form the sacrum. The Sacrum is a large, triangular bone, in the lower part of the vertebral column and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones; its upper part or base joins with the 5th lumbar vertebra by intervertebral fibrocartilage and at the bottom it joins with the coccyx or tailbone.

The Lumbar Spine

The Lumbar spine consists of the vertebral body, posterior elements, intervertebral disks, and ligaments. The lumbar spine is made up of the five lumbar vertebrae located between the thoracic spine and the sacrum. This area is commonly called the “lower back”. The lumbar vertebrae are the largest of the vertebrae because of their weight-bearing function supporting the torso and head.

L-5, the 5th lumbar vertebra.

Labeled lumbar vertebra

The function of the structures of the lumbar spine are to protect and support the spinal cord and spinal nerves. The spinal nerves pass through a large hole (foramen) in the center of each vertebrae, which when lined up is called the spinal canal. The lumbar spinal nerves branch off the spinal cord at each level between the vertebrae. The joints—a joint is where two or more bones meet—between the vertebrae contain a disk (intervertebral disk) that acts as a shock absorber.

The vertebrae of the back are “linked” together by pedicles (lamina, transverse process, and spinous process) to form facet joints.

Ligaments of the Back

The function of ligaments is to attach bones to bones and give strength and stability to the back. Ligaments are strong, tough bands that are not very flexible. The vertebral bodies of the back are connected to each other by multiple ligaments which include:
• posterior longitudinal ligaments
• anterior longitudinal ligaments
• intertransverse ligaments
• interspinous ligaments
• supraspinous ligaments

Tendons of the Back

Tendons are elastic tissues that connect muscles to bones.

Muscles of the Back

Muscles support and move the spine.

Nerves of the Back

Lumbar segment, spine, nerves

Vascular structures of the Back

Arteries supply the vertebrae, ligaments, and muscles with nourishment.

Problems, Treatments and Surgery for the Lumbar Spine

• Osteoporosis
• Osteomalacia
• Arthritis
• Ankylosing Spondylitis
• Sacroiliitis
• Lumbosacral sprain and strain
• Acute Cauda Equina Syndrome
• Intervertebral Disk Disease
• Scoliosis
• Spinal Instability
• Herniated Disk
• Spondylolysis
• Spondylolisthesis
• Spinal Stenosis

More About the Back

• Back Injury
• Lumbar Spinal Fusion Surgery
• Sex After Back Surgery or Back Injury

A joint forms where two or more bones meet. The hip joint is a ball-and-socket type joint and is formed where the thigh bone (femur) meets the three bones that make up the pelvis: the ilium at the rear, the ischium at the lower front and the pubis above it. The thighbone has a ball-shaped knob on the end that fits into a socket formed in the hipbone. A smooth cushion of shiny white articular cartilage about 1/4 inch thick covers the femoral head and the acetabulum. The articular cartilage is kept slippery by fluid made in the synovial membrane (joint lining). Since the cartilage is smooth and slippery, the bones move against each other easily and without pain. Large ligaments, tendons, and muscles around the hip joint (called the joint capsule) hold the bones (ball and socket) in place and keep it from dislocating.

Front View of the Hip Joint Bones

The weight-bearing bones in our body are usually protected with articular cartilage, which is a thin, tough, flexible, slippery surface which is lubricated by synovial fluid. The synovial fluid is both viscous and sticky lubricant. Synovial fluid and articular cartilage are a very slippery combination—3 times more slippery than skating on ice, 4 to 10 times more slippery than a metal on plastic hip replacement, and more than 30 times as slippery as metal on metal using the best petroleum-based lubricant. Synovial fluid is what allows us to flex our joints under great pressure without wear.

The hip joint is one of the largest joints in the body and is a major weight-bearing joint. Weight bearing stresses on the hip during walking can be 5 times a person’s body weight. A healthy hip can support your weight and allow you to move without pain. Changes in the hip from disease or injury will significantly affect your gait and place abnormal stress on joints above and below the hip.

It takes great force to seriously damage the hip because of the strong, large muscles of the thighs that support and move the hip. Osteoarthritis affects many people, and the brittle bones from osteoporosis in the elderly can lead to life threatening fractures.

Anatomic Terms

Anatomical terms allow us to describe the body clearly and precisely using planes, areas and lines. Instead of your doctor saying “his knee hurts” she can say “his knee hurts in the anterolateral region” and another doctor will know exactly what is meant. Below are some anatomic terms surgeons use as these terms apply to the hip:

• Anterior — the abdominal side (front) of the hip
• Posterior — the back side of the hip
• Medial — the side of the hip closest to the spine
• Lateral — the side of the hip farthest from the spine
• Abduction — move away from the body (raising the leg)
• Adduction — move toward the body (lowering the leg)
• Proximal — located nearest to the point of attachment or reference, or center of the body
• Distal — located farthest from the point of attachment or reference, or center of the body
• Inferior — located beneath, under or below; under surface

Anatomy of the Hip

Joint capsule of the hip

Like the shoulder, the hip is a ball-and-socket joint, but is much more stable. The stability in the hip begins with a deep socket—the acetabulum. Additional stability is provided by the strong joint capsule and its surrounding muscles and ligaments. It’s the need for such a high degree of stabilization of the joint that limits movement. If you think of the hip joint in layers, the deepest layer is bone, then ligaments of the joint capsule and the tendons and muscles are on top. Nerves and vessels supply the muscles and bones of the hip.

The hip joint capsule is a dense, fibrous structure which includes the iliofemoral, pubofemoral, and ischiofemoral ligaments. These ligaments along with the ligamentum teres and the labrum help give stability of the hip.

Bony Structures of the Hip

The adult skeleton is mainly made of bone and a little cartilage in places. Bone and cartilage are both connective tissues, with specialized cells called chondrocytes embedded in a gel-like matrix of collagen and elastin fibers. Cartilage can be hyaline, fibrocartilage and elastic and differ based on the proportions of collagen and elastin. Cartilage is a stiff but flexible tissue that is good with weight bearing which is why it is found in our joints. Cartilage has almost no blood vessels and is very bad at repairing itself. Bone is full of blood vessels and is very good at self repair. It is the high water content that makes cartilage flexible.

The hip is formed where the thigh bone (femur) meets the three bones that make up the pelvis: the ilium, the pubis (pubic bone) and the ischium. You can feel the arching bones of the ilium by placing your hands on your waist. The pubis attaches to the lower part of the ilium and curves forward. The ischium is slightly behind the pubis. The three bones converge to form the acetabulum, a deep socket on the outer edge of the pelvis.

The shape of the acetabulum is a half of a sphere; the femoral head is about two-thirds of a sphere. Without weight bearing, the ball-and-socket are not completely congruent. As the joint bears more weight, the contact of the surface areas increases as does joint stability. The articular cartilage is thicker on the back part of the socket where most of the force is placed on the joint with walking, running and jumping. When standing, the body’s center of gravity passes through the center of the acetabula. Obviously, injury to the acetabulum can affect its ability to distribute weight bearing.

Bones of the Hip Joint

The hip joins the leg to the trunk of the body at the hip joint. The hip joint is made up of the ball of the femoral head that fits into the cup-shaped acetabulum. The large round head of the femur rotates and glides within the acetabulum. The depth of the acetabulum is further increased by a fibrocartilagenous labrum attached to the acetabulum. The socket of the hip is much deeper than the socket in the shoulder and encompasses a greater area of the ball.

The femur is the longest bone in the body. The neck of the femur connects the femoral head with the shaft of the femur. The capsular ligament of the hip joint attaches to the posterior part of the femoral neck. The neck ends at the greater and lesser trochanter prominences. The greater trochanter serves as the site of attachment for the abductor muscles. The lesser trochanter is the site of the iliopsosas tendon.

The greater trochanter is a very prominent bump on the femur and easy to feel on the outside of your thigh. It is the widest part of the lower legs and is where the tendons of several muscles attach including the gluteus, obturator, gemelli and piriformis muscles. The lesser trochanter serves as the attachment for the iliopsoas and iliacus muscle tendons.

Hip Ligaments

The liofemoral ligament in the hip

The stability of the hip is increased by the strong ligaments that encircle the hip (the iliofemoral, pubofemoral, and ischiofemoral ligaments). These ligaments completely encompass the hip joint and form the joint capsule. The iliofemoral ligament is the strongest ligament in the body. Damage to the ligamentum teres can result in avascular necrosis because of injury to the small artery within the ligament that supplies most of the blood to the head of the femur. Death of the bone in the femoral head is one cause for hip replacement.

The ischiofemoral ligament of the hip

Muscles of the Hip

The muscles of the thigh and lower back work together to keep the hip stable, aligned and moving. It is the muscles of the hip that allow the 4 basic movements of the hip:

• flexion – bend
• extension – straighten
• abduction – take the leg away from the body
• adduction – bring the leg back toward the body

The hip muscles are divided up into three basic groups based on their location: anterior, posterior, and medial. The muscles of the anterior thigh make up the quadriceps group (vastus medialis, intermedius, lateralis and rectus femoris muscles). The quads make up about 70% of the thigh’s muscle mass. The purpose of the quads is flexion (bending) of the hip and extension (straightening) of the knee.

The gluteal, hamstring and piriformis muscles are located in the buttocks. The gluteus maximum is the main hip extensor and helps keep up the normal tone of the iliotibial band. The gluteal and sartorius muscles also help abduct the hip—that is, move the leg away from the midline of the body (using the spine as a midline reference point). It is abduction that allows us to walk sideways.

Adduction—bringing the leg back towards the midline—is performed by the hip adductor muscle group (gracilis muscle, pectineus muscle).

The hip also has the ability to rotate internally (medially)—turning the foot in (pigeon-toed) and externally (laterally)—turning the foot out. Medial rotation is needed for squatting. The piriformis muscle assist in lateral rotation of the hip. Lateral rotation is needed for crossing the legs.

The hip muscles do not attach right at the hip joint, thereby giving the hip more stability. The gluteus medius muscle connects to the greater trochanter, a bony prominence on the neck of the femur. The gluteus medius helps keep the pelvis level when you walk.

The facia lata, which is not a muscle but the deep fascia of the thigh, is known as the iliotibial band. The function of this band is to prevent dislocation of the hip. If this band is too tight, it can cause hip and knee problems.

Blood Vessels and Nerves of the Hip

The sciatic nerve is located where it could get injured from a backwards dislocation of the femoral head.

The nerves in the hip supply the various muscles in the hip. These nerves include the femoral nerve, lateral femoral cutaneous nerve, and obturator nerve . The obturator nerve is also responsible for sensation over the thigh. The sciatic nerve is the most commonly recognized nerve in the hip and thigh. The sciatic nerve is large—as big around as your thumb—and travels beneath the gluteus maximus down the back of the leg and then branches on down to the foot. Hip dislocation can cause injury to the sciatic nerve. Nerves carry signals from the brain to the muscles to move the hip and carries signals from the muscles back to the brain about pain, pressure and temperature.

The blood supply to the hip is primarily from the internal and external iliac, femoral, obturator, and superior and inferior gluteal arteries. The femoral artery is well-known because of its use in cardiac cath; it travels from deep within the hip down the leg to the knee. The main blood supply for the femoral head comes from vessels that branch off the femoral artery.

Bursae

Bursae are fluid filled sacs lined with a synovial membrane which produce synovial fluid. The synovial fluid is similar in consistency to raw egg white. Bursae are often found near joints. Their function is to lessen the friction between tendon and bone, ligament and bone, tendons and ligaments and between muscles. There are as many as 20 bursae around the hip. Inflammation or infection of the bursa called bursitis.

The greater trochanteric bursa is located between the greater trochanter (the bony prominence on the femur) and the muscles and tendons that cross over the greater trochanter. This bursa can get irritated if the iliotibial band is too tight. Two other bursa that can get inflamed are the iliopsoas bursa, located under the iliopsoas muscle and the bursa located over the ischial tuberosity (the bone you sit on).

Common Problems of the Hip

Simple dislocation from upward pressure

• Aseptic or Avascular necrosis
• Congenital Dislocation
• Perthes’ disease
• Aplasia of the acetabulum
• Coxa valga
• Coxa vara
• Osteoarthritis
• Dislocation (see image above of simple dislocation)
• Bursitis
• Legg-Perthes disease
• Bone tumor
• Fracture

Surgery of the Hip

• Hip Replacement
• Sex After Total Joint Replacement

The shoulder is not a single joint, but a complex arrangement of bones, ligaments, muscles, and tendons that is better called the shoulder girdle. The primary function of the shoulder girdle is to give strength and range of motion to the arm. The shoulder girdle includes three bones—the scapula, clavicle and humerus. There are three joints in the shoulder girdle. One joint is where the head of the humerus articulates inside the glenoid cavity of the scapula, called the glenohumeral joint which includes the ligaments, tendons and muscles attached to these two bones. The acromioclavicular joint (A/C Joint) includes the ligaments, tendons, and bones where the acromion (on the shoulder blade) joins at the clavicle (collar bone). The third joint is the sternoclavicular joint which forms where the sternum (breastbone) joins the clavicle (collar bone).

Anatomic Terms

Anatomy terms allow us to describe the body clearly and precisely using planes, areas and lines. Instead of your doctor saying “his knee hurts” she can say “his knee hurts in the anterolateral region” and another doctor will know exactly what is meant. Below are some anatomic terms surgeons use as these terms apply to the shoulder:

• Anterior — the abdominal side of the shoulder
• Posterior — the back side of the shoulder
• Medial — the side of the shoulder closest to the spine
• Lateral — the side of the shoulder farthest from the spine
• Abduction — move away from the body (raising the arm)
• Adduction — move toward the body (lowering the arm)
• Proximal — located nearest to the point of attachment or reference, or center of the body
• Distal — located farthest from the point of attachment or reference, or center of the body
• Inferior — located beneath, under or below; under-surface

Shoulder Anatomy

If you think of the shoulder in layers, the deepest layer is bone, then ligaments of the joint capsule, and the tendons and muscles are on top. Nerves and blood vessels supply the muscles and bones of the shoulder. Nerves carry signals from the brain to the muscles to move the shoulder and carries signals from the muscles back to the brain about pain, pressure and temperature.

The Shoulder Joints

A joint is formed where two or more bones meet. There are three joints in the shoulder girdle:

• the glenohumeral joint (GH) is a ball-and-socket joint where the humerus meets the glenoid on the scapula; this joint is informally known as the shoulder joint.
• the acromioclavicular joint (AC) is a gliding joint where the acromial process on the scapula links to the collar bone (clavicle)
• the sternoclavicular joint (SC) is a double gliding joint between the sternum (breastbone) and the clavicle (collar bone)

The glenohumeral (GH) joint forms what people commonly think of as the shoulder joint and is the most important of the shoulder joints. The GH joint links the humerus (arm) with the thorax (chest). The stability of the GH joint depends on keeping the humeral head centered in the glenoid fossa (socket) on the scapula. The humerus is held in place with ligaments, tendons and muscles, mainly the muscles and tendons of the rotator cuff.

The Glenohumeral Joint (GH)

The extremely mobile shoulder joint is naturally unstable and not surprisingly, the most commonly dislocated joint in the body.

The glenohumeral joint provides most of the motion in the shoulder girdle. The GH joint allows us to move our arm forward, backward and side-to-side, to rotate it inward and outward, move it across the body in front and behind, and make a circle with our arm both clockwise and counterclockwise. The glenohumeral joint has the greatest mobility of any joint in the body and it seems as if movement would be possible in all directions—but certain structures limit raising the arm straight out behind us to about 60 degrees. This great range of motion can lead to several common problems and injuries affecting the shoulder girdle.

The glenohumeral joint is a ball-and-socket joint like the hip joint. The shoulder is different from the hip in that the hip is a weight-bearing joint and the shoulder is a suspension joint. The large, almost perfectly round head of the humerus (ball) fits into the small, shallow glenoid fossa (socket) on the lateral side of the scapula. The shoulder socket is very shallow and comes in very little contact with the round head of the humerus—similar to a golf ball on a tee. Also, the cup of the socket is much lager than the ball that fits into it. At any point in the shoulder’s arc of motion this poor fit and contact of the bones make the glenohumeral joint unstable. Therefore, it is the soft tissues in the joint that maintain stability and mobility.

The soft tissues of the glenohumeral joint include:

• the joint capsule
• the glenohumeral ligaments – function as static stabilizers of the GH joint
• the glenoid labrum – this is a ring of fibrocartilaginous tissue structure that attaches to the rim of the glenoid cavity on the scapula; it increases the depth of the glenoid “socket” by 50%. Its function is to increase the surface contact area for the ball on the humerus to create a better fit. The glenoid labrum also serves as an attachment point for the shoulder capsule, glenohumeral ligaments, and the long head of the biceps tendon.
• the long head of the biceps tendon
• the rotator cuff tendons and muscles

These soft tissues are where most degenerative (wear and tear) and traumatic conditions of the shoulder occur. A smooth cushion of shiny white articular cartilage less than 1/4 inch thick covers the end of the humerus and in the glenoid socket of the scapula. The articular cartilage is kept slippery by fluid made in the synovial membrane (joint lining). Since the cartilage is smooth and slippery, the bones of the joint move against each other easily and without pain.

The adult skeleton is mainly made of bone and a little cartilage in places. Bone and cartilage are both connective tissues, with specialized cells called chondrocytes embedded in a gel-like matrix of collagen and elastin fibers. Cartilage can be hyaline, fibrocartilage and elastic and differ based on the proportions of collagen and elastin. Cartilage is a stiff but flexible tissue that is good with weight-bearing which is why it is found in our joints. Cartilage has almost no blood vessels and is very bad at repairing itself. Bone is full of blood vessels and is very good at self repair. It is the high water content that makes cartilage flexible.

The muscles on the lateral side of the shoulder allow movement and stabilize the joint. These muscles are strong on the upper and back sides of the arm, but not on the underside. A strong outside force in this area can cause the head of the humerus to slip out of the glenoid socket, called dislocation.

The Acromioclavicular Joint (AC)

The AC joint helps link the arm to the body at the chest. Since there is little bony stability in this joint, a number of ligaments and other soft tissues stabilize this joint. The superior AC ligament is the most important horizontal stabilizer. The coracoclavicular ligaments help stabilize the clavicle vertically. A significant amount of rotation occurs in the clavicle and about 10% occurs at the AC joint.

The Sternoclavicular Joint (SC)

Most of the rotation occurs at the sternoclavicular joint and joint stability comes from the soft tissues. The posterior sternoclavicular joint capsule is the most important structure for preventing forward and backward displacement of the medial clavicle.

The Rotator Cuff

The rotator cuff consists of four muscle-tendon units that originate on the scapula and attach to the tuberosities of the humerus. The role of the rotator cuff is to keep the head of the humerus centered in the glenoid fossa throughout the shoulder’s range of motion and when raising the arm. The rotator cuff is the primary stabilizer during movement of the GH joint. Both overuse and traumatic injuries to the rotator cuff are the most common problems in the shoulder girdle.

The Subacromial Space

The subacromial space is beneath the acromion and above the rotator cuff. The subacromial bursa outlines this space and provides frictionless gliding of the rotator cuff beneath the arch formed by the acromion and coracoacromion. Bone spurs on the underside of the acromion narrow this space, irritate the bursa and contribute to tears in the rotator cuff.

Bones of the Shoulder Girdle

Click on image for larger labeled, picture.

The bones of the shoulder girdle include the humerus, the scapula, and the clavicle. There are four articulations (movements) in the shoulder named for their anatomic locations:

• coracoclavicular
• acromioclavicular
• glenohumeral (the only true synovial joint)
• coracoacromial

Scapula (shoulder blade). The scapula is the most complex of the bones in the shoulder and is part of the shoulder girdle. The scapula floats on the rib cage, and is attached to it only with muscles. There are three landmarks on the scapula; the spine, acromion and coracoid processes. The roof of the glenohumeral joint is formed by the acromion. The acromion articulates with the clavicle forming the acromioclavicular (AC) joint. A spine divides the back of the scapula into two sections. The muscles that attach below this spine are called infraspinatus muscles; the ones that attach above this spine are called supraspinatus muscles.

Humerus (upper arm). The humerus is the ball part of the ball-and-socket joint. The head (ball) of the humerus articulates within the glenoid fossa. Below the humeral head is the anatomic neck which separates the head (ball) from the tuberosities. Each tuberosity provides a place for the attachment for the muscles of the rotator cuff—the 4 rotator cuff muscles originate from the scapula and their tendons attach at the humerus. The bicipital groove separates the tuberosities. Just below the tuberosities is the surgical neck of the humerus and is the most common area for fractures of the proximal humerus.

Clavicle (Shoulder Blade) – lateral view

Clavicle (collar bone) . The clavicle originates at the sternum (breastbone) just above the first rib, and is held in place by the acromioclavicular ligament, several muscles and the coracoclavicular ligament. The clavicle helps hold the shoulder out to the side while allowing the scapula to move around.

Shoulder Ligaments

Click on image to see larger picture.

There are several important ligaments about the shoulder girdle. Ligaments are soft tissue structures that connect bones to bones. Ligaments are strong, tough bands that are not particularly flexible. Once stretched, they tend to stay stretched and if stretched too far, they snap.

Ligaments, along with muscles and tendons, are the main source of stability for the shoulder. Shoulder ligaments also form the joint capsule that surround the glenohumeral joint. These passive stabilizers serve to keep the joints of the shoulder from dislocating. Some of the main ligaments are the acromioclavicular, coracoclavicular and the coracoacromial.

When injured, the ligament that attaches the clavicle to the acromion—the acromioclavicular ligament—is called a separated shoulder. Two ligaments connect the clavicle to the scapula by attaching to the coracoid process—the coracoclavicular and the coracoacromial ligaments. The coracoacromial prevents upward dislocation of the shoulder. When the head of the humerus dislocates, it’s usually in a downward direction.

Shoulder Ligaments

• Ligaments of the AC joint: Capsular; superior and inferior acromioclavicular; articular disk; coracoclavicular (trapezoid and conoid)
• Ligaments of the Sternoclavicular joint: Capsular; anterior and posterior sternoclavicular; inter- and costo- clavicular; articular disk
• Ligaments of the GH joint: Capsular; coracohumeral; glenohumeral; transverse humeral; glenoid of humerus

Shoulder Muscles and Shoulder Tendons

Muscles in the back, neck, shoulder, chest and upper arm all work together to support and move the shoulder. One of the most important is the deltoid.

Tendons are elastic, soft, connective tissue structures that attach muscles to bone. Muscles move the bones by pulling on the tendons. The rotator cuff tendons are a group of tendons that connect the deepest layer of muscles to the humerus. As they form their tendinous attachment to the humerus, they become a fibrous capsule. The rotator cuff muscles and tendons control our ability to raise the arm from our side (abduction).

Each muscle of the shoulder assists with specific movements. The deep muscle group that moves the shoulder are the rotator cuff muscles and tendons. Keeping the head of the humerus inside the glenoid fossa is the primary function of the rotator cuff muscles. This important group of muscles lies just outside the glenohumeral joint and helps rotate the shoulder in the many directions. The rotator cuff muscles include the:

• supraspinus
• infraspinatus
• teres minor muscles (SIT)
• subscapularis

The rotator cuff muscles are the muscles most often involved in shoulder rehab.

The biceps tendon is attached to the biceps muscle and runs from the humerus across the front of the shoulder to the glenoid. The biceps tendon attaches to the glenoid and becomes part of the labrum. The biceps tendon can cause problems if it’s damaged and pulled away from its attachment to the glenoid.

The outer muscle layer is formed by the large deltoid muscle which overlies the SIT muscles. This is probably the largest, strongest muscle of the shoulder. The deltoid takes over lifting the arm once the arm is away from the side. Other muscles include the biceps.

Shoulder Bursae

Subscapularis-bursa

Sandwiched between the rotator cuff muscle layer and the outer layer of large bulky muscles is the large subacromial bursa, called the subdeltoid bursa. Bursae are everywhere in the body. A bursa is simply a padlike sac found between two moving surfaces that is lined with synovial membrane and contains a small amount of lubricating fluid inside—synovial fluid is similar in consistency to raw egg white—to reduce friction and aid movement. Bursae occur in connective tissue wherever two body parts—other than joints—move against each other. Their function is to lessen the friction between tendon and bone, ligament and bone, tendons and ligaments, and between muscles. Inflammation or infection of the bursa is called bursitis.

Blood Vessel and Nerves in the Shoulder

There are several important nerves in the shoulder including the radial nerve, ulnar nerve, and median nerve. But the most important is the brachial plexus nerve which supplies all the muscles that contribute to the function of the arm and shoulder girdle. The most vulnerable to direct injury are the brachial plexus and its nerve branches, the spinal accessory nerve and the long thoracic nerve. Shoulder dislocation is most often responsible for damage to the brachial plexus. Direct trauma to the scapula that causes fracture or dislocation can damage the spinal accessory or thoracic nerves. Injury to spinal nerves can result in the alteration of movement and sensation in the shoulder.

The subclavian artery and vein are the two main vascular structures in the shoulder and are part of the thoracic outlet. Trauma and fractures to the clavicle can injure these vessels. There are many blood vessels that supply the rotator cuff. The large axillary artery can be felt pulsing in your armpit. The axillary artery branches into many smaller vessels that supply blood to different parts of the shoulder.

Problems of the Shoulder

• Acromioclavicular degeneration
• Acromioclavicular joint separation
• Adhesive capsulitis (Frozen Shoulder)
• Arthritis—rheumatoid, traumatic
• Baseball shoulder
• Calcific Tendonitis
• Cervicobrachial syndrome
• Fractures
• Impingement Syndrome (Bursitis)
• Labral tear
• Growths or Tumors, benign or malignant (Neoplasm)
• Muscle spasm
• Necrosis (cell or tissue death)
• Osteoarthritis
• Painful Arc Syndrome
• Rotator cuff injury or disease
• Shoulder instability
• Supraspinatus syndrome
• Sprengel’s deformity

Diagnosis, Treatment, and Surgery for Shoulder Problems

• Shoulder Arthroscopy
• Shoulder Replacement
• Shoulder Rehab and Shoulder Replacement Recovery Time

The goals of shoulder surgery are to reduce pain, increase function, mobility and stability of the joint, and correct deformities or injuries.

The knee joint connects the femur, our thigh bone and longest bone in the body, to the tibia, our shinbone and second longest bone. There are two joints in the knee—the tibiofemoral joint, which joins the tibia to the femur and the patellofemoral joint which joins the kneecap to the femur. These two joints work together to form a modified hinge joint that allows the knee to bend and straighten, but also to rotate slightly and from side to side.

The knee is part of a chain that includes the pelvis, hip, and upper leg above, and the lower leg, ankle and foot below. All of these work together and depend on each other for function and movement.

The knee joint bears most of the weight of the body. When we’re sitting, the tibia and femur barely touch; standing they lock together to form a stable unit. Let’s look at a normal knee joint to understand how the parts (anatomy) work together (function) and how knee problems can occur.

Anatomical terms allow us to describe the body clearly and precisely using planes, areas and lines. Instead of your doctor saying “his knee hurts” she can say “his knee hurts in the anterolateral region” and another doctor will know exactly what is meant. Below are some anatomic terms surgeons use as these terms apply to the knee:


• Anterior — facing the knee, this is the front of the knee
• Posterior — facing the knee, this is the back of the knee, also used to describe the back of the kneecap, that is the side of the kneecap that is next to the femur
• Medial — the side of the knee that is closest to the other knee, if you put your knees together, the medial side of each knee would touch
• Lateral — the side of the knee that is farthest from the other knee (opposite of the medial side)

Structures often have their anatomical reference as part of their name, such as the medial meniscus or anterior cruciate ligament. The medial meniscus would refer to the meniscus on the inside of the knee, the anterior crucial ligament would be on the anterior side (front) of the knee.

Structures of the Knee

(click for larger image)

The main parts of the knee joint are bones, ligaments, tendons, cartilages and a joint capsule, all of which are made of collagen. Collagen is a fibrous tissue present throughout our body. As we age, collagen breaks down.

The adult skeleton is mainly made of bone and a little cartilage in places. Bone and cartilage are both connective tissues, with specialized cells called chondrocytes embedded in a gel-like matrix of collagen and elastin fibers. Cartilage can be hyaline, fibrocartilage and elastic and differ based on the proportions of collagen and elastin. Cartilage is a stiff but flexible tissue that is good with weight bearing which is why it is found in our joints. Cartilage has almost no blood vessels and is very bad at repairing itself. Bone is full of blood vessels and is very good at self repair. It is the high water content that makes cartilage flexible.

Bones of the Knee

The bones give strength, stability and flexibility in the knee. Four bones make up the knee (see above image):
• Tibia —commonly called the shin bone, runs from the knee to the ankle. The top of the tibia is made of two plateaus and a knuckle-like protuberance called the tibial tubercle. Attached to the top of the tibia on each side of the tibial plateau are two crescent-shaped shock-absorbing cartilages called menisci which help stabilize the knee.
• Patella—the kneecap is a flat, triangular bone; the patella moves when the leg moves. It’s function is to relieve friction between the bones and muscles when the knee is bent or straightened and to protect the knee joint. The kneecap glides along the bottom front surface of the femur between two protuberances called femoral condyles. These condyles form a groove called the patellofemoral groove.
• Femur—commonly called the thigh bone; it’s the largest, longest and strongest bone in the body. The round knobs at the end of the bone are called condyles.
• Fibula—long, thin bone in the lower leg on the lateral side, and runs along side the tibia from the knee to the ankle.

(click for larger image)

Ligaments in the knee

The knee works similarly to a rounded surface sitting atop a flat surface. The function of ligaments is to attach bones to bones and give strength and stability to the knee as the knee has very little stability. Ligaments are strong, tough bands that are not particularly flexible. Once stretched, they tend to stay stretched and if stretched too far, they snap.
• Medial Collateral Ligament (tibial collateral ligament) – attaches the medial side of the femur to the medial side of the tibia and limits sideways motion of your knee.
• Lateral Collateral Ligament (fibular collateral ligament) – attaches the lateral side of the femur to the lateral side of the fibula and limits sideways motion of your knee.
• Anterior cruciate ligament – attaches the tibia and the femur in the center of your knee; it’s located deep inside the knee and in front of the posterior cruciate ligament. It limits rotation and forward motion of the tibia.
• Posterior cruciate ligament – is the strongest ligament and attaches the tibia and the femur; it’s also deep inside the knee behind the anterior cruciate ligament. It limits the backwards motion of the knee.
• Patellar ligament – attaches the kneecap to the tibia

The pair of collateral ligaments keep the knee from moving too far side-to-side. The cruciate ligaments crisscross each other in the center of the knee. They allow the tibia to “swing” back and forth under the femur without the tibia sliding too far forward or backward under the femur. Working together, the 4 ligaments are the most important in structures in controlling stability of the knee. There is also a patellar ligament that attaches the kneecap to the tibia and aids in stability. A belt of fascia called the iliotibial band runs along the outside of the leg from the hip down to the knee and helps limit the lateral movement of the knee.

Tendons in the Knee

Tendons are elastic tissues that technically part of the muscle and connect muscles to bones. Many of the tendons serve to stabilize the knee. There are two major tendons in the knee—the quadriceps and patellar. The quadriceps tendon connects the quadriceps muscles of the thigh to the kneecap and provides the power for straightening the knee. It also helps hold the patella in the patellofemoral groove in the femur. The patellar tendon connects the kneecap to the shinbone (tibia)—which means it’s really a ligament.

(click for larger image)

Cartilage of the knee

The ends of bones that touch other bones—a joint—are covered with articular cartilage. It’s gets its name “articular” because when bones move against each other they are said to “articulate.” Articular cartilage is a white, smooth, fibrous connective tissue that covers the ends of bones and protects the bones as the joint moves. It also allows the bones to move more freely against each other. The articular cartilages of the knee cover the ends of the femur, the top of the tibia and the back of the patella. In the middle of the knee are menisci—disc shaped cushions that act as shock absorbers.

• medial meniscus—made of fibrous, crescent shaped cartilage and attached to the tibia
• lateral meniscus—made of fibrous, crescent shaped cartilage and attached to the tibia
• articular cartilage is on the ends of all bones in any joint—in the knee joint it covers the ends of the femur and tibia and the back of the patella. The articular cartilage is kept slippery by synovial fluid (which looks like egg white) made by the synovial membrane (joint lining). Since the cartilage is smooth and slippery, the bones move against each other easily and without pain.

In a healthy knee, the rubbery meniscus cartilage absorbs shock and the side forces placed on the knee. Together, the menisci sit on top of the tibia and help spread the weight bearing force over a larger area. Because the menisci are shaped like a shallow socket to accommodate the end of the femur, they help the ligaments in making the knee stable. Because the menisci help spread out the weight bearing across the joint, they keep the articular cartilage from wearing away at friction points.

The weight bearing bones in our body are usually protected with articular cartilage, which is a thin, tough, flexible, slippery surface which is lubricated by synovial fluid. The synovial fluid is both viscous and sticky lubricant. Synovial fluid and articular cartilage are a very slippery combination—3 times more slippery than skating on ice, 4 to 10 times more slippery than a metal on plastic knee replacement. Synovial fluid is what allows us to flex our joints under great pressure without wear.

Muscles

The muscles in the leg keep the knee stable, well aligned and moving—the quadriceps (thigh) and hamstrings. There are two main muscle groups—the quadriceps and hamstrings. The quadriceps are a collection of 4 muscles on the front of the thigh and are responsible for straightening the knee by bringing a bent knee to a straight position. The hamstrings is a group of 3 muscles on the back of the thigh and control the knee moving from a straight position to a bent position.

The Joint Capsule

The capsule is a thick, fibrous structure that wraps around the knee joint. Inside the capsule is the synovial membrane which is line by the synovium, a soft tissue that secretes synovial fluid when it gets inflamed and provides lubrication for the knee.

Bursae

There are up to 13 bursa of various sizes in and around the knee. These fluid filled sacs cushion the joint and reduce friction between muscles, bones, tendons and ligaments. The prepatellar bursa is one of the most significant bursa and is located on the front of the knee.

Plicae

Plicae are folds in the synovium. Plicae rarely cause problems but sometimes they can get caught between the femur and kneecap and cause pain.

Knee Arteries and Veins

Knee arteries and veins

Knee Function

So now we have all the parts, let’s see how the knee moves (articulates)—which is how we walk, stoop, jump, etc.  The knee has limited movement and is designed to move like a hinge.

The Quadriceps Mechanism is made up of the patella (kneecap), patellar tendon, and the quadriceps muscles (thigh) on the front of the upper leg. The patella fits into the patellofemoral groove on the front of the femur and acts like a fulcrum to give the leg its power. The patella slides up an down the groove as the knee bends. When the quadriceps muscles contract they cause the knee to straighten. When they relax, the knee bends.

In addition the hamstring and calf muscles help flex and support the knee.

Problems in the Knee

The knee doesn’t have much protection from trauma or stress (pressure or force).

Symptoms

Knee symptoms come in many varieties. Pain can be dull, sharp, constant or off-and-on. Pain can also be mild to agonizing. The range of motion in the knee can be too much or too little. You may hear grinding or popping, the muscles may feel weak or the knee can lock. Some knee problems only need rest and ice, others need physical therapy or even surgery.

• Swelling: One of the most common symptoms is local swelling. There are two types of swelling. One is caused by the knee producing too much synovial fluid and the other is caused by bleeding into the joint (hemarthrosis). Swelling within the first hour of an injury is usually from bleeding. Swelling from 2-24 hours is more likely to be from the joint producing large amounts of synovial fluid trying to lubricate an abnormality inside the knee.  The best home treatment for swelling is R.I.C.E. therapy. Chronic swelling can distend the knee, prohibit full range of motion and the muscles can atrophy from non-use. Also, if the cause of the swelling is blood, the blood can be destructive to the joint.

• Locking. Locking is when something is keeping the knee from fully straightening out. This is usually a loose body in the knee. The loose body can be as small as a grain of sand or as big as a quarter. The best treatment is removal of the loose body by arthroscopy. Another type of locking is when the knee hurts so bad that you just won’t use it. The best treatment here is rest and maybe some ice; swelling is not usually present.

• Giving Way. If your kneecap slips out of is groove for an instant, it causes your thigh muscles to loose control causing the feeling of instability—that is, you don’t feel like  your knee is stable, won’t support your weight—and you usually try to grab hold of something for support. Giving way can also be caused by weak leg muscles or an old ligament injury.

• Snaps, Crackles and Pops. Noises coming from  your knee without pain are likely nothing to worry about. Sometimes the noise is caused by loose bodies that just float around and are not causing pain or injury to the knee. However, If you have pain, swelling or loss of knee function, you should see an orthopedist. The most common cause—chondromalacia patella—is caused by an injury. Another common cause is a dislocating kneecap—that is, a kneecap that keeps slipping out of its groove. Pops without trauma (injury) are not worrisome, pops with trauma can mean ligament tears. Crackling, grinding or grating (crepitus) means there is a roughness to the bone surfaces and likely from degenerative disease or wear-and-tear arthritis (osteoarthritis).

• Pain and Tenderness. Where and how bad the pain is will help find the underlying cause. It also helps to know what caused it and what makes it hurt. Pain that gets worse with activity is often tendinitis or stress fractures. Pain and tenderness accompanied by swelling can be more serious such as a tear or sprain. Some pain can be caused by muscles spasms associated with trauma.

Pathological Conditions and Syndromes

• Osteochondritis Dissecans
• Osteoarthritis (Degenerative Arthritis)
• Infectious Arthritis
• Chondromalacia Patellae
• Gout
• Plica Syndrome
• Rheumatoid Arthritis
• chondromalacia
• osteoarthritis

Traumatic Knee Injuries

• Anterior cruciate ligament (ACL) Injury
• Meniscus tear
• Lateral and Medial Collateral Ligament Injury
• Posterior Cruciate Ligament (PCL) Injury
• Patellar Injuries
• Dislocation of the Patella
• Rupture of the Patellar Tendon
• Fracture and Stress Fracture

Repetitive Knee Injuries

• Patellofemoral Syndrome (Runner’s Knee)
• Tendonitis
• Bursitis (Housemaid’s Knee)
• Illiotibial Band Syndrome
• Osgood-Schlatter Disease

Types of Knee Surgery

• Knee Replacement
• Knee Arthroscopy

If Things Go Wrong

Sometimes no matter how much you plan and prepare, things can go wrong. If you think you have been the victim of medical malpractice or a surgical mistake while having an operation, you can learn about your options through an attorney. If your quality of life has been effected due to an error made during an operation or surgery, get in touch with Patient Lawyers, experts in medical negligence claims. Alexander Harris Solicitors also offer advice for those considering medical negligence claims, visit their website for more information about healthcare law.