1 Bio 230-Lymphatic System Major Functions: 1. Fluid Balance- collects excess water and proteins from interstitial fluid and returns it to the blood stream. 2. Fat (lipid) absorption and transportation to blood stream - Special lymphatic capillaries (lacteals) receive all absorbed fat (chyle) from the small intestine and transport it through the Thoracic Duct to the venous system. 3. Defends the body against pathogens (disease causing agents such as bacteria, viruses, fungi, parasites, cancer) Components of the Lymphatic System: 1. Lymph 2. Lymphatic vessels 3. Lymphatic Tissue/Organs ______________________________________________________________________________________________ What is LYMPH? (First component of the Lymphatic System) As blood flows through systemic capillaries a small amount of fluid is exuded (discharged) into the interstitial space, most of the fluid is returned to the circulation by veins, but about 3 liters a day is left and returned to the circulation via lymphatic vessels. This fluid is called lymph…kinda like plasma, mostly water, some proteins and lots of WBC’s (mostly lymphocytes and some monocytes). Lymph is Latin for “clear water”. Lymph flows in one direction…always back to the heart. _____________________________________________________________________________________________________________ Lymphatic Vessels (Second component of the Lymphatic System) include: Lymphatic capillaries, lymphatic collecting vessels, lymphatic trunks and lymphatic ducts. a. Lymphatic capillaries -these capillaries are found alongside most blood capillaries in the body (not found in CNS). Composed of loosely attached overlapping simple squamous epithelial cells. Thus they are quite permeable (even more so than blood capillaries). Fluid enters easily, as do proteins, WBC’s, pathogens and cancer cells. Remember the specialized lymphatic capillaries mentioned above called LACTEALS? Lymph within lacteals is called CHYLE. b. Lymphatic collecting vessels = receive lymph from lymphatic capillaries. Similar to veins (tunics similar), but contain more valves. These lymphatic collecting vessels pass through LYMPH NODES, where lymph is cleaned of pathogens and cancer cells. c. Lymphatic trunks = formed by the union of the largest lymphatic vessels. There are 5. 1. Jugular trunks (paired)- located at the base of each internal jugular vein; drain the head and neck. 2. Subclavian trunks (paired)- drain the upper limbs, superficial thoracic wall, and mammary glands. 3. Bronchomediastinal trunks (paired)- drain thoracic organs and the deep thoracic wall. 4. Intestinal trunk (unpaired)- drains the intestines, stomach, pancreas, spleen, and liver. 5. Lumbar trunks (paired)- drain the lower limbs, pelvic and abdominal walls, pelvic organs, gonads, kidneys, and adrenal glands.
