5Lymphatic System The most important functions of the lymphatic system are:Maintenance of fluid balance in the internal environmentCollects and returns interstitial fluid, including plasma protein to the blood to help maintain fluid balanceImmunityTo defend the body against disease by producing lymphocytes To absorb lipids from the intestine
6Lymphatic System The lymphatic system transports a watery clear fluid called lymph fluidDistributes immune cells and other factors throughout the bodyInteracts with the blood circulatory system to drain fluid from cells and tissues
8Lymphatic SystemFrom one-third to two-thirds of the plasma entering a capillary passes into the tissue space.The cells in the tissue space are bathed in this interstitial or extracellular fluid (ECF) that has been filtered from the blood. In the tissue space is where cells acquire all their needs and deposit all their products.Although most of this interstitial fluid returns to the venule end of the capillary, some does not.
9Lymphatic SystemThe small amount of interstitial fluid that remains is picked up by tiny vessels called lymph capillaries.The cells forming the walls of the lymph capillaries are loosely fitted together making the wall very porous.Even the large serum proteins that filtered through the capillary wall pass easily from the tissue space into the interior of the lymph capillary.The lymph capillaries of the intestinal villi, called lacteals, also pick up fat droplets.
10Lymphatic SystemThe lymph capillaries drain into still larger vessels that make up the lymphatic system.The flow through the lymph vessels is slow. Like blood in the veins, contraction of skeletal muscles compresses the lymph vessels and squeezes the lymph.Like the return of blood in the veins, the lymph can flow only in one direction because of valves in the vessels.
11Lymphatic System All the lymph collected from the entire Left side of the bodyDigestive tract andRight side of the lower part of the bodyThe lymph then flows into a single majorvessel, the thoracic duct.
12Lymphatic System The thoracic duct empties about 100 ml of lymph every hour into the leftsubclavian vein.The lymph in the right side of the head,neck, and chest is collected by the rightlymph duct and empties into the right
13Lymphatic System and Edema The production of lymph is increased byincreased blood pressure in the capillaries and/or a decreased concentration of plasma proteins—such as occurs in prolonged malnutrition.The lymphatic system may be unable to handle the increased volume of lymph, and it may accumulate in the tissues and distend them. This condition is known as edema.
14Lymphatic System: Lymph Nodes Lymph nodes act as filters, with an internalhoneycomb of reticular connective tissue thattraps foreign particles.They are bean shapedFrom a few millimeters to about 1-2 cm in sizeHumans have approximately lymph nodesWhen the body is fighting an infection,lymphocytes multiply rapidly and produce acharacteristic swelling of the lymph nodes.
15Lymphatic System: Lymph Nodes Lymph nodes contain cavities, called sinuses, into which the lymph flows.The walls of the sinuses are lined with phagocytic cells, which engulf any foreign particles like bacteria. Tests have demonstrated that over 99% of the bacteria carried into a node are screened out before the lymph leaves the node on its return to the blood.This filtering mechanism is one of the most important body defenses against infectious disease. When combating a heavy infection, the lymph nodes enlarge producing "swollen glands."
16Lymphatic System: Lymph Nodes Several hundred lymph nodes arescattered throughout the bodyespecially in theGroinArmpitsAbdomenNeck
17Lymphatic System: Lymph Nodes Lymph nodes manufactureAntibodiesLymphocyteswhich then enter the blood at thesubclavian veins.
19Lymphatic SystemLymph movement occurs slowly with low pressure due to peristalsis, valves, and the milking action of skeletal muscles.Like veins, lymph travels through vessels in one way only, due to semilunar valves.
20Lymphatic System Lymphocytes The lymphatic system containsimmune cells called lymphocytes.They protect the body against antigens (viruses, bacteria, etc.) that invade the bodyLymphocytes collect and destroy antigens and pathogens
22Lymphatic System and Fat Transport The lymphatic system also absorbs fatty acidsand transports fat, as chyle to the circulatorysystem.Chyle is a milky fluid consisting of lymph andemulsified fats or free fatty acids (FFAs).Formed in the small intestine during digestion of ingested fatty foodsTaken up by lymph vessels known as lactealsPassed to the bloodstream through the thoracic ductLacteals are located in the lining of the GI tract.
23LactealsThe lacteals are lymphatic capillaries that absorbs dietary fats in the villi of the small intestine.
24Lymphatic System and Chyle Chyle is composed of fat globules thatgive it a milky appearanceHas a thin protein coatingIs a micron or less in size—there are about 25,000 microns to an inchAfter a meal it takes two to three hoursfor fat to be absorbed from the smallintestine and travel through ever largerlymph channels.
25Lymphatic System and Lymph Lymph originates as blood plasma that leaksfrom the capillaries becoming interstitial fluidthat fills the space between individual cells oftissue.Plasma is forced out of the capillaries— filtrationForced back in—absorptionDue to interactions of:Hydrostatic pressure—movement out of the capillaries)Oncotic pressure—movement into the capillaries
27Lymphatic System and Fat Transport Because lymph carries lipids it also carries lipid-soluble vitamins absorbed from the gastrointestinal (GI) tract.Since there is no active pump in the lymph system, there is no back-pressure produced. The lymphatic vessels, like veins, have one-way valves that prevent backflow.
28Lymphatic System Lymphatic function supports every other system in the body including:The immune systemDigestive systemDetoxificationNervous systemPoor lymph health contributes tomany conditions from cellulite tocancer.
29Lymphatic SystemLymph is an alkaline fluid (pH > 7.0) that is usually clear, transparent, and colorless.It flows in the lymphatic vessels and bathes tissues and organs in its protective covering.There are no RBCs in lymph and it has a lower protein content than blood. Like blood, it is slightly heavier than water.
30Lymphatic System and the Blood Blood constitutes about 7% of the body's total weight.Blood flows from the heart into arteries, then to capillaries, and returns to the heart through veins.All blood cells are manufactured by stem cells, which live mainly in the bone marrow, by a process called hematopoiesis.
31Lymphatic System and the Blood Stem cells produce hemocytoblasts thatdifferentiate into precursors for all thedifferent types of blood cells.Hemocytoblasts mature into three typesof blood cells:Erythrocytes (red blood cells or RBCs)Leukocytes (white blood cells or WBCs)Thrombocytes (platelets)