Unit 4 Option C: Human health & fitness 4C.1 Body systems; lymphatic system By Mr Wilson

Lymph The lymphatic system is designed to remove excess tissue fluid. The lymphatic system is designed to remove excess tissue fluid. Some tissue fluid (plasma with contents except the larger proteins) may enter lymph capillaries instead of returning to blood capillaries. Some tissue fluid (plasma with contents except the larger proteins) may enter lymph capillaries instead of returning to blood capillaries. This fluid is now called LYMPH. This fluid is now called LYMPH. Lymph travels through the LYMPHATIC SYSTEM passing through LYMPH NODES. Lymph travels through the LYMPHATIC SYSTEM passing through LYMPH NODES.

Formation of lymph Plasma ‘leaks’ from blood capillaries (ultrafiltration) and adds to tissue (interstitial) fluid. Plasma ‘leaks’ from blood capillaries (ultrafiltration) and adds to tissue (interstitial) fluid. As the volume of tissue fluid increases about 90% is reabsorbed into the blood capillaries at the venous end. As the volume of tissue fluid increases about 90% is reabsorbed into the blood capillaries at the venous end. About 10% passes through the walls of the lymph capillaries, due to a pressure gradient, to become LYMPH. About 10% passes through the walls of the lymph capillaries, due to a pressure gradient, to become LYMPH. What, therefore, might lymph contain? What, therefore, might lymph contain?

Lymphatic system A system of LYMPH VESSELS, LYMPH NODES and LYMPH DUCTS. A system of LYMPH VESSELS, LYMPH NODES and LYMPH DUCTS. Carries lymph from tissues, where lymph capillaries are situated, to SUBCLAVIAN VEINS, which join the VENA CAVA. Carries lymph from tissues, where lymph capillaries are situated, to SUBCLAVIAN VEINS, which join the VENA CAVA. Thus a link is made between the tissue fluid and the CARDIO- VASCULAR SYSTEM. Thus a link is made between the tissue fluid and the CARDIO- VASCULAR SYSTEM.

Lymphatic system An open system whose vessels have semi-lunar valves to prevent back flow. An open system whose vessels have semi-lunar valves to prevent back flow. Lymph moves under low pressure caused by PERISTALSIS and the ‘squeezing’ action of skeletal muscle. Lymph moves under low pressure caused by PERISTALSIS and the ‘squeezing’ action of skeletal muscle. Negative pressure in the thorax on inhalation also aids movement. Negative pressure in the thorax on inhalation also aids movement.

Functions of the lymphatic system What is the function of tissue fluid? What is the function of tissue fluid? Removal of excess tissue fluid. Removal of excess tissue fluid. Production of IMMUNE CELLS such as LYMPOCYTES and MACROPHAGES. Production of IMMUNE CELLS such as LYMPOCYTES and MACROPHAGES. Absorption of fatty acids from lipid digestion in the gut via LACTEALS. Absorption of fatty acids from lipid digestion in the gut via LACTEALS.

The lymphatic system

Major lymphatic structures Thymus – produces mature T- lymphocytes, which have a major role in immunity. Thymus – produces mature T- lymphocytes, which have a major role in immunity. Spleen – Actually filters blood – exposes pathogens to B- lymphocytes, which produce antibody. Removes bacteria & degraded red blood cells. Acts as a blood storage organ. Produces foetal red blood cells. Spleen – Actually filters blood – exposes pathogens to B- lymphocytes, which produce antibody. Removes bacteria & degraded red blood cells. Acts as a blood storage organ. Produces foetal red blood cells.

Major lymphatic structures Lymph nodes – ‘bulges’ of lymphatic tissue situated strategically along lymph vessels. Lymph nodes – ‘bulges’ of lymphatic tissue situated strategically along lymph vessels. Contain a membranous ‘filter’ system with associated macrophages and lymphocytes. It filters the lymph of foreign substances and allows the leucocytes to recognise (the antigens) on potential pathogens. Often swell during infection. Contain a membranous ‘filter’ system with associated macrophages and lymphocytes. It filters the lymph of foreign substances and allows the leucocytes to recognise (the antigens) on potential pathogens. Often swell during infection.

A lymph node

Lymph nodes & immune response LYMPH NODES are NOT glands! Why? LYMPH NODES are NOT glands! Why? They are part of IMMUNE and LYMPHATIC systems. They are part of IMMUNE and LYMPHATIC systems. Lymphocytes constantly circulate through lymph nodes, entering via the blood. Lymphocytes constantly circulate through lymph nodes, entering via the blood. Recognition of antigen by lymphocytes in lymph nodes causes them to migrate to different areas of the node where they will provide a ‘trap’ for the pathogens and coordinate an appropriate immune response to them. Recognition of antigen by lymphocytes in lymph nodes causes them to migrate to different areas of the node where they will provide a ‘trap’ for the pathogens and coordinate an appropriate immune response to them.

Major lymphatic vessels Thoracic duct – Major lymph vessel, which receives lymph from all parts of the body and ‘empties’ it into the LEFT subclavian vein. Thoracic duct – Major lymph vessel, which receives lymph from all parts of the body and ‘empties’ it into the LEFT subclavian vein. Right lymphatic duct – collects lymph from right arm, right side of chest, neck and head and ‘empties’ it into the RIGHT subclavian vein. Right lymphatic duct – collects lymph from right arm, right side of chest, neck and head and ‘empties’ it into the RIGHT subclavian vein.

Thoracic duct

Other lymphatic structures Tonsils – lymphatic nodules offering protection from foreign substances invading via the mouth. Tonsils – lymphatic nodules offering protection from foreign substances invading via the mouth. Peyer’s patches – Aggregations of lymph nodes in the wall of the ileum – protection from foreign substances invading via the digestive system. Peyer’s patches – Aggregations of lymph nodes in the wall of the ileum – protection from foreign substances invading via the digestive system.