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| Lymphatic System |
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| Lymphatic System of a Human |
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| The lymphatic system is an accessory circulatory system which transports lymph, a fluid similar to plasma from the intercellular spaces of tissues to the blood. It is a one way route for the movement of interstitial fluid to blood. The lymphatic system can carry proteins and large particle matter from the tissue spaces into the blood. |
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| The lymphatic system is formed of the following components |
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| a) Lymph |
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| b) Lymph vessels |
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| c) Lymph nodes. |
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| Lymph is the interstitial fluid that flows into the lymphatic system. It is formed from blood by the passage of substances through the wall of the blood capillaries into the inter cellular tissue spaces. It is formed by the process of diffusion and filtration from the blood. |
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| It consists of two parts namely fluid matrix, the plasma, in which float amoeboid cells, the white blood corpuscles or leucocytes. It differs from blood in lacking red corpuscles, platelets and some plasma proteins and having less calcium and phosphorus than the blood. |
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| About 120ml of lymph flows through the lymphatic system per hour into the blood. |
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| Lymphatic System of Right arm and Breast |
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| Lymphatic System of Right Leg |
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| Lymphatic capillaries |
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| The lymphatic system is formed of a tree like branching vessels. It starts among the tissue cells as blind end microscopic vessels called lymphatic capillaries which are similar to veins. Their walls are made up of endothelial cells supported by fibrous connective tissue. |
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| The lymphatic capillaries repeatedly join together to form bigger vessels which pass through lymph nodes, receive more tributaries and gradually increase in size. All the vessels finally join together to form two large vessels called thoracic duct or left lymphatic duct and right lymphatic duct. |
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| Lymph capillaries collecting Lymph among the Tissues |
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| The thoracic duct is about 45 cm long and about 6 mm in diameter. It emerges from the receptaculum chyli situated near the second lumbar vertebra. It collects all the lymph from the hind limbs and alimentary canal. The thoracic duct also receives the left cervical duct which collects lymph from the left forelimb, left side of the neck and chest. The thoracic duct opens into the venous system at the junction of the left internal jugular vein and sub clavian |
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| The lymph vessels that remain in the center of the villi of alimentary canal are called lacteals. They collect milk white fluid called chyle from the intestine after digestion. The lacteals absorb fats from the intestine. |
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| Main drainage routes of Lymphatic System |
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| The right lymphatic duct is a smaller vessel of about 1.25 cm length. It collects lymph from the right side of the head, the right neck, the right upper limb and the right side of the chest. It empties into the venous system at the right subclavian vein and internal jugular vein. |
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| LS through Lymph Vessel showing an internal Valve |
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| The lymphatic vessels are provided with valves. They help the lymph to flow in the direction of the chest. They prevent the reverse flow of lymph. |
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| Section through a Lymph Gland |
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| Lymph nodes are oval or bean shaped bodies placed in the lymphatic vessels. They act as filters and are sites where lymphocytes are formed. The main groups of lymph nodes lie in the neck, axilla, thorax, abdomen and groin. |
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| They help in the production of antibodies and in the development of immunity, Lymph nodes produce gamma globulin. They serve a defensive role against bacterial infection. |
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| A model showing the circulation of lymph |
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| The lymph flow in lymphatic vessels very slowly. Forcing out fluid from the blood capillaries set up some pressure in the tissue fluid. This pressure gradient causes the lymph to flow in the lymphatic vessel. Movements of visver |
| and contractions of the body muscles help by squeezing the lymph along. The valves prevent the backward flow. The villi by their movement help the lymph to flow in the lacteals. |
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| a) The lymph returns fluid and protein from the tissues to the circulation. |
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| b) It transports lymphocytes from the lymphatic glands to the blood. |
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| c) The lacteals transport emulsified fats from the intestine to the blood |
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| d) It destroys the invading microorganism and foreign particle in the lymph nodes. |
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| e) Following an infection the lymph nodes produce antibodies to protect the body against subsequent infection. |
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