Lymphatic system_lymph_flow_function_coolant.pptx

• LYMPHATIC SYSTEM
• Lymphatic system is a closed system of lymph channels or lymph vessels, through which the flow
of lymph takes place..
• It is a one-way system and permits the lymph flow from tissue spaces toward the blood.
• ORGANIZATION OF LYMPHATIC SYSTEM
• Lymphatic system arises from tissue spacesin the form of a meshwork of delicate vessels. These
vessels are termed as lymph capillaries.
• Lymph capillaries begin from tissue spaces as enlarged blind-ended terminals known as capillary
bulbs.

• These bulbs consist of valves, which permit flow of lymph particularly in only one direction.
• There are some muscle fibers around these bulbs. These muscle fibers are responsible for
contraction of bulbs so that, lymph is pushed through the vessels.
• Lymph capillaries are lined by especially endothelial cells. Capillaries unite to form large lymphatic
vessels.
• Lymphatic vessels become larger and larger due to the joining of many tributaries along their
course.
• The structure of lymph capillaries is slightly different from that of the blood capillaries.
• Lymph capillaries are more porous and the cells lie overlapping on one another.
• This permits the fluid to move into the lymph capillaries and not in the opposite direction.
•

• DRAINAGE OF LYMPHATIC SYSTEM
• Larger lymph vessels ultimately form the right lymphatic duct and thoracic duct.
• Right lymphatic duct opens into right subclavian vein and the thoracic duct opens into left subclavian vein.
• Thoracic duct drains the lymph from more than two third of the tissue spaces in the body
•
• LYMPH VESSELS
• Lymph vessels are located in the following regions:
• 1. Deeper layers of skin
• 2. Subcutaneous tissues
• 3. Diaphragm
• 4. Wall of abdominal cavity
• 5. Omentum
• 6. Linings of respiratory tract except alveoli
• 7. Linings of digestive tract
• 8. Linings of urinary tract
• 9. Linings of genital tract
• 10. Liver
• 11. Heart.

• Lymph vessels are absent in the following structures:
• 1. Superficial layers of skin
• 2. Central nervous system
• 3. Cornea
• 4. Bones
• 5. Alveoli of lungs.

• Cortex
• Cortex of lymph node contains primary and secondary lymphoid follicles.
• Primary follicle develops first. When some antigens enter the body and reach the lymph nodes, the
cells of primary follicle show proliferation..
• The active proliferation of the cells takes place in a particular area of the follicle known as the
germinal center.
• After proliferation of cells, the primary follicles are converted into the secondary follicle.
• Cortex also consists of some B lymphocytes, which are usually aggregated into the primary
follicles. Macrophages are also observedin the cortex.

• Paracortex
• Paracortex is in between the cortex and medulla.
• Paracortex consists of T lymphocytes.
•
• Medulla
• Medulla consists of B and T lymphocytes and macrophages.
• Blood vessels of lymph node pass through medulla.
•
• Lymphatic Vessels to Lymph Node
• Lymph node receives lymph by one or two lymphatic vessels termed as afferent vessels.
• Afferent vessels cateorize into small channels.
• Lymph passes through afferent vessels and small channels and reaches the cortex.
• It circulates particularly through cortex, paracortex and medulla of the lymph node.
• From medulla, the lymph leaves the node via one or two efferent vessels.

• Distribution of Lymph Nodes
• Lymph nodes are present along the course of lymphatic vessels in elbow, axilla, knee and groin.
• Lymph nodes are also present in certain points in abdomen, thorax and neck, where many lymph
vessels join.

• FORMATION OF LYMPH
• The formation of lymph takes place in interstitial fluid, because of the permeability of lymph
capillaries.
• When blood passes via blood capillaries in the tissues, 9/10th of fluid passes into venous end of
capillaries from the arterial end. And, the remaining 1/10th of the fluid passes into lymph capillaries,
which have more permeability compare to blood capillaries.
• So, when lymph passes through lymph capillaries, the composition of lymph is more or less similar
to that of interstitial along with protein content.
• Proteins observed in the interstitial fluid cannot gain entry into the blood capillaries due to their
larger size

• Addition of Proteins and Fats
• Tissue fluid in liver and gastrointestinal tract consists of more protein and lipid substances. 2) So,
proteins and lipids gain entry into the lymph vessels of liver and gastrointestinal tract in large
quantities.
• 3)Thus, lymph in larger vessels consists of more proteins and lipids.

• Concentration of Lymph
• When the lymph passes through the lymph nodes, it is concentrated due to the absorption of water
and the electrolytes.
• Whatever it may be, the proteins and lipids are not absorbed.
•
• RATE OF LYMPH FLOW
• About 120 mL of lymph flows into blood per hour.
• Out of this, approximately 100 mL/hour flows through thoracic duct and 20 mL/ hour flows through
the right lymphatic duct.

• Factors Increasing the Flow of Lymph
• Flow of lymph is promoted by the enhancement in:
• 1. Interstitial fluid pressure.
• 2. Blood capillary pressure.
• 3. Surface area of lymph capillary by means of dilatation.
• 4. Permeability of lymph capillarie

• COMPOSITION OF LYMPH
• Generally, lymph is a clear and colorless fluid.
• It is formed by 96% water and 4% solids.
• Some blood cells are also observed in lymph.

• of lymph is to return the proteins particulary from tissue spaces into blood.
• 2. It is responsible for redistribution of fluid in the body.
• 3. An elimination of bacteria, toxins and other foreign bodies happens from tissues via lymph.
• 4. Lymph flow is responsible for the maintenance of structural and functional integrity of tissue.
Obstruction to lymph flow influences various tissues, especially myocardium, nephrons and hepatic
cells.
• 5. Lymph flow serves as an important route for intestinal fat absorption. So lymph looks like milky
particulatrly after a fatty meal.
• 6. It plays an essential role in immunity by transport of lymphocytes.
•

• FUNCTIONS OF LYMPH NODES
• Lymph nodes serve as filters which filter particularly bacteria and toxic substances from the lymph.
• Functions of the lymph nodes are:
• 1. When lymph passes through the lymph nodes, it is filtered, i.e. the water and electrolytes are
eliminated . But, the retention of proteins and lipids occurs in the lymph.
• 2. The destruction of b acteria and other toxic substances happens by macrophages of lymph
nodes. Because of this, lymph nodes are treated defense barriers.

• APPLIED PHYSIOLOGY – SWELLING OF LYMPH NODES
• During infection or any other processes in a particular region of the body, activities of the lymph
nodes in that region increase.
• This is responsible for occurrence of swelling of the lymph nodes.
• Sometimes, the swollen lymph nodes play an important role regarding pain.
• Most common cause of swollen lymph nodes is infection.
• Lymph nodes located near an infected area swell in an immediate manner.
• When the body recovers from infection, the lymph nodes restore their original size in a gradual
manner, in one or two weeks

• Causes for Lymph Node Swelling
• 1. Skin infection of arm exhibits swelling of lymph nodes particularly in armpit.
• 2. Tonsillitis or throat infection causes swelling of lymph nodes especially in neck.
• 3. Infection of genital organs or leg leads to swelling of lymph nodes in groin.
• 4. Viral infections namely glandular fever which influence the whole body cause swelling of
lymph nodes in various parts of the body.
• 5. Cancer in a particular region may spread into the nearby lymph nodes causing the swelling.

• Examples:
• i. Throat cancer may spread into lymph nodes in neck.
• ii. Lung cancer may spread into lymph nodes in chest.
• iii. Breast cancer may spread into lymph nodes particularly in armpit.
• iv. Intestinal cancer may spread into lymph nodes especially in abdomen.
• v.. Lymphomas (cancer of lymphatic system) and leukemia are responsible for causing swelling of
lymph nodes in many parts of the body.

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Lymphatic system_lymph_flow_function_coolant.pptx

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