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Lesson objectives • To describe the structure of the lymphatic system • To explain how the lymphatic system works • To identify the main lymph nodes of the body Structure of Lymphatic System 1. Lymphatic capillaries 2.Lymphatic vessels 3.Lymph nodes 4.Lymphatic ducts Lymphatic capillaries • Structure: fine, blunt-ended permeable tubes, composed of a single layer of thin cells Lymphatic vessels • Structure: thin-walled, collapsible vessels similar to veins but carrying lymph not blood Lymph nodes • Structure: each node is made of lymphatic tissue, surrounded by a wall of tough, white fibrous tissue Right lymphatic duct • Empties into right subclavian vein to rejoin circulatory system • Function: receives all drained lymph from right side of head, chest and neck and from right arm Thoracic duct • Empties into subclavian vein to rejoin circulatory system • Function: collects and drains lymph from left side of head, the neck, both lower limbs, left side of trunk and left arm What is the lymphatic system? • Lymphatic system is a secondary circulation, helping blood circulation carry out its functions • Blood travels to and from the tissues delivering nutrients and removing waste • Whole blood never leaves capillaries but leucocytes, oxygen, food and water can What is the lymphatic system? • Once outside the capillaries they are carried by a derivative of blood plasma called tissue/interstitial fluid • This fluid circulates throughout the tissues, delivering food, oxygen and water to cells and collecting carbon dioxide • When it has finished its work not all of it can pass through capillary walls because the pressure is too high What is the lymphatic system? • Fluid that is left is picked up by the lymphatic capillaries • These have larger pores in their walls than blood capillaries and the pressure inside is lower • Excess tissue fluid and substances made of large molecules etc. drain away into them • The fluid – called lymph – is filtered by lymph nodes then collected by the lymphatic ducts before entering right/left subclavian veins and returning to the bloodstream Connection between blood and lymph Simplified lymph circuit Lymph – Structure • Structure: plasma, lymphocytes, proteins and waste products Functions of Lymphatic System 1. Transports fat 2. Controls swelling 3. Fights infection Effect of Lymphatic System on Skin and Muscles • Removes waste and toxins from skin and muscles so they can work more efficiently Movement of lymph 1. Contraction of skeletal muscles collapses vessels and because valves are present, lymph is directed towards the upper part of body 2. There is a slight oncoming pressure from tissue fluids 3. Movement of lymph towards thorax during inspiration 4. Negative suction pressure helps pull lymph upwards Structure of lymph node Functions of lymph nodes 1. Filter lymph, remove and destroy harmful microorganisms, tumour cells, damaged or dead tissue cells; filtering system prevents toxic materials from reaching bloodstream and causing septicaemia 2. Produce new lymphocytes and antibodies 3. Lymphatic tissue cells within node may become activated to form antibodies against a particular infection Main lymphatic ducts Lymphatic nodes – head and neck 1. Superficial parotid nodes – in front of ears 2. Mastoid nodes – behind ears 3. Submandibular – beneath mandible 4. Occipital nodes – base of skull 5. Deep cervical nodes – deep within neck 6. Superficial cervical nodes – side of neck Lymphatic nodes – body 1. Axillary nodes – armpit 2. Supratrochlear nodes – elbow crease 3. Iliac nodes – abdomen 4. Inguinal nodes – groin 5. Popliteal nodes – knee Spleen • Lies on upper left-hand side of abdomen Spleen – Functions 1. Forms new lymphocytes 2. Destroys thrombocytes and erythrocytes 3. Helps fight infection Tonsils Tonsils • Lymphoid tissue that plays role in immune function • Tonsils help to fight infection Main Lymphatic Nodes Axillary Abdominal Cubital Pelvic Inguinal Popliteal