The Lymphatic System Diagrams reproduced with permission from also see the page summary of the lymphatic system Diagrams reproduced with permission from Tortora, G. J., and Derrickson, B. (2012). Principles of anatomy and physiology (13th ed.). New Jersey: John Wiley and Sons.

Objectives State the functions of the lymphatic system Briefly describe the formation of lymph Outline the circulation of lymph

Functions of the lymphatic system Drains excess interstitial fluid from tissue spaces and returns it to the blood. As part of the immune system, destroys microbes and abnormal or foreign cells. Transports lipids and lipid-soluble vitamins from the villi in the small intestine to the blood

Formation of lymph Blood capillaries leak fluid Each day approximately 20 litres of plasma leaks into the tissues through the capillary walls, pushed out by blood pressure.

Formation of lymph Once the plasma has leaked out of the capillaries it is called interstitial fluid. Most of the interstitial (tissue) fluid (about 18 litres) is then drawn back into the far end of the capillary. use paper pieces on board to explain

Formation of lymph So about 2 litres of leaked plasma is added to the interstitial fluid each day The excess interstitial fluid then flows into blind-ended lymphatic capillaries Lymphatic capillaries are woven between the tissue cells They are the start of a one-way drainage system that returns the excess interstitial fluid back to the blood.

Lymphatic Capillaries Once the fluid is inside the lymphatic capillary it is called lymph. It may contain bacteria or viruses it has collected from between the cells. think of the stormwater drain in your street that excess rain drains into. so the pressure of the interstitial fluid forces the valve open. What would happen to the valve if the fluid in the lymphatic capillary tried to flow back? Lymph washes the cells

Circulation of lymph Lymph capillaries join up to form larger lymph vessels which carry the lymph to the major lymphatic ducts Lymph is returned to the bloodstream from these ducts Lymph in the lymph vessels passes through lymph nodes which filter out bacteria, cancer cells …. The pressure in the blood capillary is higher than the pressure of the interstitial fluid and this pressure is the driving force behind the leakage of plasma. The pressure inside the lymphatic capillary is the lowest pressure of all and this is the reason the interstitial fluid drains into the lymphatic capillary.

Circulation of lymph blood vessels ↑ right lymphatic and thoracic duct through many lymph nodes lymphatic vessels lymphatic capillaries