LYMPHATIC SYSTEM has three major functions
- 1)collects interstitial fluid and returns it to blood
- 2)Transfers lipids (fats) from the digestive system to the blood stream.
- 3) Is responsible for defending the body against invading microorganisms and abnormal cells
- 1)a large sac within the posterior body wall
- 2)receives lymph from lymphatic vessels below the waist
- 3) narrows to become the thoracic duct
- 1)drains lymph from the cisterna chyli, the left upper limb, and the left side of the thorax, neck, and head
- 2)carries the lymph to the junction of the left internal jugular vein and left subclavian vein.
RIGHT LYMPHATIC DUCT
- 1)drains lymph from the right upper limb and the right side of the thorax, neck, and head.
- 2)carries lymph to where the right internal jugular vein and right subclavian vein anastomose (join).
- 1)between the lungs and superior to the heart
- 2)During your childhood your thymus gland actively produced huge numbers of T LYMPHOCYTES (T CELLS), each programmed against a specific pathogen.
- 3)By the time the thymus gland atrophies, your body contains a lifetime supply of mature T cells.
T LYMPHOCYTES (T CELLS)
- 1)named because of their maturation in the thymus gland
- 2)whenever a particular microorganism invades your body, T cells are stimulated to divide into an army of additional T cells that defend your body from a specific invader
- 1)contain sinuses packed with crisscrossing reticular fibers.
- 2)As lymph meanders through the sinuses, microorganisms, dead cells, and other debris are trapped on the rough network of reticular fibers, filtering the contaminants out of the lymph.
located in the neck, filter lymph from your head and neck
located in groin area filter lymph from your lower limbs and genital area.
filter lymph from your upper limb and thorax.
- 1)filled with B LYMPHOCYTES (B CELLS)
- 2) When a foreign substance is filtered out of lymph, B cells are activated to divide into a clone of PLASMA CELLS that produce specific antibodies against that foreign substance and MEMORY B CELLS for future encounters.
AGGREGATED LYMPHATIC NODULES
- 1)simple masses of lymphatic tissue found within the walls of the small intestine and the appendix
- 2)positioned to destroy the large number of bacteria that normally inhabit the intestines
- 1)another form of lymphatic nodules
- 2)form a ring of lymphatic tissue around the entrance to the pharynx (throat)
located on either side of the posterior end of the oral cavity.
a lumpy collection of lymphoid follicles at the base of the tongue.
- 1)referred to as the “adenoids” when enlarged
- 2)imbedded in the posterior wall of the nasopharynx (upper throat in back of the nose)
- 1)located in the upper left abdominal cavity behind the stomach and just beneath the diaphragm.
- 2)Blood enters the spleen from the splenic artery, meanders through the VENOUS SINUSES, and then leaves the spleen through the splenic vein. The venous sinuses contain gauzelike networks of reticular fibers that filter blood. As blood slowly percolates through the venous sinuses, macrophages cleanse the blood by phagocytizing microbes, old blood cells, and old platelets. The venous sinuses also function to store large numbers of platelets.
- 1)nucleic acids within a protein coat
- 2) invade our cells, take control of the cellular genetic material, and then force the infected cell to become a virus-producing factory
- 1)diffuse into nearby healthy cells where they stimulate synthesis of protective proteins that “interfere” with viral replication
- 2)not virus-specific
- 1)injured tissue cells release chemicals that induce local arterioles (those at the wound site) to vasodilate
- 2)Vasodilation brings addition blood to the wound area, producing the characteristic REDNESS and HEAT of inflammation
- 3)undamaged cells increase their chemical reaction rates of metabolism, which increases cell division allowing quicker healing of the injury site
- 1)movement due to chemicals in the environment
- 2)Neutrophils and monocytes slip out of local leaky capillaries, migrate to the wound, and ingest then destroy microbes and dead tissue cells, clearing a clean space for healthy new cell growth
lymphocytes' ability to recognize and bind to a specific antigen
- 1)foreign invaders, such as plant pollen and some parasites and bacteria
- 2)they attack our bodies without invading our cells.
engulf exogenous antigens, digest them, then present antigen fragments on the cell surface.
CELL-MEDIATED IMMUNE RESPONSES
1)Antigen-presenting cells initiate and tailored to the particular type of pathogen they have encountered.
- 1)Many antigen-presenting cells
- 2)positioned at the frontiers of our body to act as mobile sentinels.
- 3) long, wispy extensions, dendritic cells are very efficient at catching antigens for later presentation to T cells.
Antibodies can bind to an antigen, forming an ANTIGEN-ANTIBODY COMPLEX that seals off the antigen. Once enclosed within an antigen-antibody complex, previously mobile antigens are unable to spread to other areas. In addition, when enclosed within a shield of antibody molecules, a microbe cannot bind to and infect, or its toxins damage tissue cells. Phagocytes eventually destroy the antigen-antibody complexes.
This mechanism applies to foreign cells. Because antibodies have more than one binding site, they can attach to more than one antigen at a time, linking many antigens together. When antigens on foreign cells are linked together, they clump, a process called AGGLUTINATION. Recall from Chapter 18 that antibodies floating in the serum part of plasma can “agglutinate” antigens on the surface of foreign red blood cells. Once antigens are clumped together, they are easier for phagocytes to ingest.
PRECIPITATION applies to foreign molecules (instead of foreign cells). When antigen molecules are linked together into an antigen-antibody complex, the complex settles out of solution. Like agglutinated bacteria, large precipitated clumps of antigen molecules are much easier for phagocytes to capture and engulf than individual suspended antigen molecules.
COMPLEMENT refers to a group of plasma proteins made by the liver that normally are inactive in the blood. Once several antibodies attach to the same foreign cell, complement binds to the antigen-antibody complex and becomes activated. Once bound to the antigen-antibody complex, complement helps phagocytes attach to the foreign cell, thereby promoting phagocytosis. Activated complement amplifies inflammation, preventing pathogens from spreading to other tissues and promoting healing and phagocytosis. Activated complement also triggers CELL LYSIS by forming a channel through the plasma membrane of the foreign cell. As extracellular fluid rushes in, the foreign cell bursts and dies.
- 1)If you are ever again exposed to the same antigen, whether it is the second or thirty-second time, this occurrs
- 2)faster, more prolonged, and more effective against the antigen
memory B cells recognize and respond promptly to the revisiting antigen.
- 1)first exposure to a pathogen
- 2)system mounts a primary response to the pathogen, the effects of which are hardly noticeable, and stores memory cells against future encounters