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Anatomy of the Lymphatic System

What are the various “parts” of the lymphatic system and what exactly do they do?

Lymphatic System

The lymphatic system is not really a separate system of the body. It is considered part of the circulatory system since it consists of lymph, a moving fluid that comes from the blood and returns to the blood by way of the lymphatic vessels. Lymph carries some nutrients around the body, especially fat. It also distributes germ-fighting white cells. Lymph resembles plasma, but is more diluted and contains only about 5% of proteins and 1% of salts and extractives. It is formed from bits of blood and other body liquids, called interstitial fluid or tissue fluid, that collect in the spaces between cells. Some of the interstitial fluid goes back into the body through the capillary membrane, but most enters the lymphatic capillaries to become lymph. Along with this interstitial fluid, the lymph also picks up any particles that are too big to be absorbed through the capillary membrane. These include cell debris, fat globules, and tiny protein particles. The lymph then moves into the larger lymphatic vessels and through the lymph nodes and eventually enters the blood through the veins in the neck region. The lymphatic system is thus a secondary transport system. Lymph has no pump of its own. Its flow depends on pressure from the blood system and the massaging effect of the muscles.

Basic Function of the lymphatic system

The lymphatic system has three primary functions. First of all, it returns excess interstitial fluid to the blood. Of the fluid that leaves the capillary, about 90 percent is returned. The 10 percent that does not return becomes part of the interstitial fluid that surrounds the tissue cells. Small protein molecules may “leak” through the capillary wall and increase the osmotic pressure of the interstitial fluid. This further inhibits the return of fluid into the capillaries, and fluid tends to accumulate in the tissue spaces. If this continues, blood volume and blood pressure decrease significantly and the volume of tissue fluid increases, which results in edema (swelling). Lymph capillaries pick up the excess interstitial fluid and proteins and return them to the venous blood. After the fluid enters the lymph capillaries, it is called lymph.

The second function of the lymphatic system is the absorption of fats and fat-soluble vitamins from the digestive system and the subsequent transport of these substances to the venous circulation. The mucosa that lines the small intestine is covered with fingerlike projections called villi. There are blood capillaries and special lymph capillaries, called lacteals, in the center of each villus. The blood capillaries absorb most nutrients, but the fats and fat-soluble vitamins are absorbed by the lacteals. The lymph in the lacteals has a milky appearance due to its high fat content and is called chyle.

The third and probably most well known function of the lymphatic system is defense against invading microorganisms and disease. Lymph nodes and other lymphatic organs filter the lymph to remove microorganisms and other foreign particles. Lymphatic organs contain lymphocytes that destroy invading organisms.

(Training Seer Cancer)

Axillary Lymph Nodes

The axillary lymph glands are located in the armpit. They are divided into two sets: superficial and deep. These lymph nodes receive lymph from the vessels of the arm and the upper nodes receive lymph from vessels in the upper chest area near the pectoralis muscles (pectoralis major and pectoralis minor muscles) and the mammary glands. There are about 35 lymph nodes in the breast and armpit area. Most of the lymph nodesare located in or near the armpit. If cancer forms in the breast area it often spreads to the nodes because the lymph, along with other debris, can carry cancerous cells. Lymph flows in all directions, but about three-quarters of lymphatic vessels in the breast empty into the axillary nodes, which often become the first site of the cancer spread beyond the breast.

Cervical Lymph Nodes

The cervical lymph nodes are located in the neck. They are divided into two sets: superficial and deep. There are three sets of superficial lymph glands: the submaxillary, near the jaw, the suprahyoid, near the hyoid bone in the throat, and the cervical which are located along the course of the external jugular vein. The deep cervical glands are large glands that are situated near the pharynx, esophagus, and trachea. When you have a sore throat, white blood cells mass together in these nodes to fight the infection, which is why your throat will often feel swollen and tender.

Inguinal Lymph Nodes

The network of lymph vessels in the lower body passes lymph into the bean-sized inguinal nodes deep in the groin. The inguinal lymph nodes can be grouped as superficial and deep. The deep inguinal lymph nodes are situated near the femoral artery and vein. They recieve lymph from the lower limbs, external genitalia, and lower anterior abdominal wall. The superficial inguinal lymph nodes can be found along the greater saphenous vein. The recieve lymph from the external genitalia, and the superficial parts of the lower limbs.

Lymph Duct

The lymphatic duct is much shorter than the thoracic duct, only about 1/2 of an inch (1 centimeter) long. It receives lymph from right side of body above the liver and empties into right subclavian vein and internal jugular vein. Together with the thoracic, these ducts empty between 4 and 10 milliliters of lymph into the blood every minute.

Lymph Nodes

Lymph nodes, or lymph glands as they are sometimes called, are small oval structures normally the size of small kidney beans. They generally are located in clusters near veins at strategic points along medium-sized lymph vessels at the knee, elbow, armpit, groin, neck, abdomen and chest. blood is cleaned and filtered in the lymph nodes , and germ fighting cells gather there during illness. This filtration process prevents glossary:bacteria|bacteria]], cancer cells, and other infectious agents from entering the blood and circulating through the system. The lymph nodes are the centers for production and storage of some of the white blood cells, namely the lymphocytes and monocytes, which are important elements of the body's immune mechanism. During any kind of infection, the nodes enlarge in their area of drainage due to the multiplication of lymphocytes in the node.

Popliteal Nodes

The small popliteal lymph nodes are four or five in number and surround the popliteal veins and arteries. They are clustered at the back part of the leg behind the knee joint. They help collect excess fluids from your feet and legs.

The spleen is closely associated to both the circulatory and the lymphatic systems. It is an abdominal organ which lies between the bottom of the stomach and the diaphragm. It plays a role in the maintenance of blood volume, production of some types of blood cells, and recovery of material from worn out red blood cells. It is also involved in the removal of blood cells and bacteria from the blood .

Subclavian Vein (Left)

The subclavian vein is a continuation of the axillary vein (vein of the armpit) from the upper arm. A branch of the subclavian vein (right and left) extends from each arm. The vein then converges and extends from the first rib to the clavicle (collar bone), where it merges with the internal jugular vein to form the innominate. The subclavian veins are also important to the lymphatic system as a means of introcucing lymph back into the blood. The thoracic duct, which carries lymph, joins the left subclavian near the junction with the internal jugular vein. The lymphatic duct carries lymph to the right subclavian vein and also joins it near the junction with the internal jugular vein.

The subclavian vein is a continuation of the axillary vein (vein of the armpit) from the upper arm. A branch of the subclavian vein (right and left) extends from each arm. The vein then converges and extends from the first rib to the clavicle (collar bone), where it merges with the internal jugular vein to form the innominate. The subclavian veins are also important to the lymphatic system as a means of introcucing lymph back into the blood. The thoracic duct, which carries lymph, joins the left subclavian near the junction with the internal jugular vein. The lymphatic duct carries lymph to the right subclavian vein and also joins it near the junction with the internal jugular vein.

Thoracic Duct

The thoracic duct is the channel for the collection of lymph from the portion of the body below the diaphragm and from the left side of the body above the diaphragm. It is a long duct, approximately 16 inches (40 centimeters) in the average adult. It extends from the lower spine (2nd lumbar vertebrae) to the left subclavian vein where it drains. The thoracic duct and the lymphatic duct, together, empty between 4 to 10 milliliters of lymph into the blood every minute


Overlying the heart, the twin lobed thymus consists largely of developing lymphocytes. The thymus gland influences the activities of lymphoctyes in the spleen and lymph glands. The thymus produces a hormone which stimulates antibody production in the lymphoid tissue. Lymph carries white blood cells to this organ, where they multiply and change into special infection-fighting cells. After puberty, the thymus begins to shrink in size. Its role in the early years of life is not fully understood. It is believed it is important in the development of immunity.

Lymphoid Tissue

Lymphoid tissue is formed by several types of immune system cells that work together to resist infections. Lymphoid tissue is found in many places throughout the body. These are described below. The main cell type found in lymphoid tissue is the lymphocyte. The 2 main types of lymphocytes are B lymphocytes (B cells) and T lymphocytes (T cells). Although both types can develop into lymphoma cells, B-cell lymphomas are much more common than T-cell lymphomas. These 2 types account for 85% (B-cell) and 15% (T-cell) of cases of non-Hodgkin lymphoma.

Normal T cells and B cells do different jobs within the immune system.

B cells normally help protect the body against germs (bacteria or viruses) by producing proteins called antibodies. The antibodies attach to the bacteria or viruses and attract immune system cells that surround and digest the antibody-coated germs.

Antibodies also attract certain blood proteins that can kill bacteria. There are several types of T cells, each with a specialized job. Some normal T cells help protect the body against viruses, fungi, and some bacteria. They recognize specific substances found in virus-infected cells and destroy these cells. T cells can also release substances called cytokines that attract certain other types of white blood cells, which then digest the infected cells. T cells are also thought to destroy some types of cancer cells, as well as the cells of transplanted organs. Some types of T cells play a role in stimulating or inhibiting the activity of other immune system cells. Normal B cells and T cells can be recognized by laboratory tests that identify certain distinctive substances on their surfaces. Certain substances are found only on B cells, and others are found only on T cells.

There are also several stages of B-cell and T-cell development that can There are also several stages of B-cell and T-cell development that can be recognized.

This information on types of lymphocytes is helpful because each type of lymphoma tends to resemble a particular subtype of normal lymphocyte at a certain level of development. Determining the type of lymphoma a person has is the first step in considering treatment options.

Pharyngeal Tonsil (Adenoids)

The pharyngeal tonsils (tonsilla pharyngea), also known as adenoids, are a collection of lymphoid nodules located along the roof and posterior wall of the nasopharynx (upper throat). They vary in size in different individuals and are a part of the body's protection against infection. The tonsils contain germ-killing cells. The pharyngeal tonsil is sometimes referred to as Luschka's tonsil, after the German anatomist Hubert Luschka (1820-1875). When the pharyngeal tonsils become infected, they become inflamed and enlarge. The palatine tonsils and pharyngeal tonsils (adenoids) are two pairs of organs that seem to give more trouble than service to the body.

Palatine Tonsil

Two prominent, rounded bodies of lymphatic tissue, the palatine tonsils (tonsilla palatina), are located on each side of the tongue at the back of the mouth in the pharynx (throat). They lie beneath the mucous membrane lining mouth and are closely associated with the soft palate (roof of the mouth). They vary in size in different individuals and are a small part of the body's protection against infection. The tonsils are composed of lymphoid tissue, which contains germ-killing cells. When they become infected, they become inflamed in a condition known as tonsillitis. The tonsils and adenoids (also located in the pharynx) are two pairs of organs that seem to give more trouble than service to the body.

Lingual Tonsil

The lingual tonsils (tonsilla lingualis) are a pair of oval-shaped organs located at the back of the tongue behind the foramen cecum and the sulcus terminalis in the mucous membrane covering the tongue. They enlarge gradually from birth to about seven years of age and then shrinks. Each oval consists of a large number of lymphoid follicles. The lingual tonsils are part of the lymphatic system and are important to the body's defense against infection. They are composed of lymphoid tissue, which contains germ-killing cells. The tonsils help protect against upper respiratory tract infection.

Lymph Fluid

Lymph is a clear-to-white fluid made of:

·Fluid from the intestines called chyle, which contains proteins and fats ·Red blood cells ·White blood cells, especially lymphocytes, the cells that attack bacteria in the blood.

First of all, lymph is important - as important as blood or oxygen. While loss of the lymph system would not be as immediately fatal, it would be fatal nonetheless - in less than 72 hours. Lymph is blood plasma after it has carried its nutrients into the body's tissues, dropped them off for the cells, picked up our metabolic wastes, and re-entered our water reclamation plant, which is the lymph system. Once it has passed through a series of nodes, where it is filtered and detoxified, lymph empties back into the heart where it once again becomes blood plasma.

Keeping the lymph system active is therefore extremely important - the faster we detoxify, the healthier we are. Lymph drainage is always indicated in cases of lymphedema. These can arise following surgery, trauma, or infection. Facial drainage helps with sinusitis and dental problems and is excellent for the skin - even providing a one or two day “face lift.” Lymph drainage hydrates the skin and removes local toxins, softening wrinkles, rejuvenating the skin, and helping to heal acne. It is of particular benefit in clearing cellulite. Drainage also promotes healing, toning, and revitalizing of the internal organs, benefiting irritable bowel syndrome, constipation, Crohn's disease, diverticulosis, gastritis, and chronic pancreatic insufficiency. These are but a few of the benefits - the list goes on almost endlessly.

Mostly lymph is water - about 96%. It is also rich in minerals, about the same as seawater, as well as proteins and white blood cells. All together these make up the other 4%. Lymph is the clear fluid you see seeping out of a scrape or shallow cut, often before there is any blood. The bulk of our lymph fluid circulates just beneath the skin, where it is quickly available as the immune system|immune system's first line of defense and the body's first response to minor injuries.

Our bodies are about 50% water by weight. Of this, about 30% is lymph. The rest is blood plasma, interstitial fluid (in the tissues), and cerebral spinal fluid. By volume, our bodies contain about three times as much lymph as they do blood. But because lymph is clear (the root word is “limpa,” meaning limpid, clear), the vessels that carry it are difficult to see. Thus, it was not really discovered until 1622, when Gasparo Aselli dissected a dog that had just eaten a meal high in fat, temporarily making the largest vessels visible as “milky veins.”

Another way of thinking about the lymph system is to consider it a scavenging system for interstitial fluid. If it fails, even partially, this fluid is not sufficiently collected and the result is an area of swelling known as edema. If it fails altogether, the entire body swells and bloats until the toxic overload becomes too great for life to continue. Too keep it healthy requires drinking plenty of water and exercising, especially swimming and stretching and rhythmic movements. Of course, a good session of lymph drainage does not hurt.

The Immune System

The human body is continually exposed to disease producing organisms, called pathogens, and other harmful substances in the environment. Your immune system is your body's personal defense against these harmful invaders. The body's ability to counteract the effects of pathogens and other harmful agents is called resistance and it is dependent on a variety of defense mechanisms. Your immune system is made up of billions of special cells called white blood cells, lymphocytes, unique proteins called antibodies, chemicals that mediate immune response, and special organs that replenish and integrate the whole immune process. All of these defense mechanism must act together and are designed to react rapidly to provide protection against disease-producing organisms and their toxins. There are two aspects of the immune system's response to disease: innate and acquired. Natural, or innate, immunity is present from birth and is the first line of defense against the vast majority of infectious agents. Innate immunity involves barriers that keep harmful material from entering your body.

Your skin provides an impenetrable barrier. The eyes use fluids, such as tears, and the presence of enzymes, such as lysozyme, that destroy bacteria. The respiratory system utilizes cilia, mucus, and coughing to get rid of foreign materials. If infection-causing organisms gets past these defenses, the body produces fever, inflammation, and other reactions designed to conquer the unwelcome invader. Inflammation causes an increase in the local blood supply so that large numbers of white blood cells can be brought to the area to fight the infection. Some of these white blood cells are phagocytes and macrophages that literally eat the invading microorganism. In most cases of minor glossary:infection|infection]], these cells solve the problem. If the pathogen succeeds in passing this barrier, a more complex process, involving other cells of the immune system, necessary. To understand this process, lets examine what happens when a virus enters the body. When a virus enters your body an immune response begins automatically.

A scavenger macrophage will eat the virus and display the viral antigen on its surface. Anything that can trigger an immune response is called an antigen. An antigen can be a germ such as a virus, or even a part of a virus. Other white blood cells in your body called “helper T-cells” will see the viral antigen and produce toxins that will destroy it. The helper T-cells then send chemical messages that activate lymphocytes called B-cells which make antibodies that recognize the viral antigen. These cells “remember” the specific disease organism and divide into many more cells. The resulting “clone” of identical cells starts producing very large numbers of antibodies that bind to all the organisms of that disease and destroy them. This process is called acquired immunity. It is a learning process of the immune system that develops either through exposure to invading microorganisms or as a result of immunization. It is estimated that your body has more than 100 million different kinds of antibodies, each one custom-built to identify a particular pathogen. If your body is exposed a second time, no symptoms occur because the organism is destroyed quickly- you are now immune to that particular pathogen.

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Updated Nov. 14, 2011

anatomy_of_the_lymphatic_system.txt · Last modified: 2012/10/16 14:40 (external edit)