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Lymphatic System
Anatomy & Physiology
Question | Answer |
---|---|
lymphatic system | helps immune system defend body against infectious agents, transports and houses lymphocytes and other immune cells, and returns excess fluid to blood to maintain fluid balance |
organs of the lymphatic system | tonsils, lymph nodes, spleen, and lymphatic vessels |
lymph | fluid transported within the lymph vessels |
characteristics of lymph | 15% of fluid entering interstitial spaces not reabsorbed into capillaries (about 3 liters daily), termed lymph once inside lymph vessels, lymph transported through network of increasing larger vessels (lymphatic capillaries, vessels, trunks, & ducts) |
components of lymph | water dissolved solutes and small amount of protein, sometimes cell debris, pathogens, or metastasized cancer cells |
lymphatic vessels | larger structures formed from lymphatic capillaries, superficial vessels positioned adjacent to superficial veins, deep vessels next to deep arteries and veins |
lymphatic vessels continued | have all three vessel tunics (intima, media, and externa), have valves within the lumen, relies on sev. mechanisms to move lymph through vessels, and some connecting directly to lymph nodes |
valves within the lumen of lymphatic vessels | required to prevent lymph from pooling in vessel, prevent lymph backflow in low-pressure system |
several mechanisms that the lymphatic vessels rely on to move lymph through vessels | contraction of nearby skeletal muscles in limbs, contraction of respiratory pump in the torso, pulsatile movement of blood in nearby arteries, and rhythmic contraction of smooth muscle in larger lymph vessel walls |
primary lymphatic structures | involved in formation and maturation of lymphocytes |
primary lymphatic structures include | red bone marrow and the thymus |
secondary lymphatic structures | no involved in lymphocyte formation, house lymphocytes and other immune cells, provide site of immune response initiation |
secondary lymphatic structures include | lymph nodes, spleen, lymphatic nodules, tonsils, and MALT |
red bone marrow | located within spaces between trabeculae in sections of spongy bone and responsible for hemopoiesis and has T-lymphocytes and B-lymphocytes |
hemopoiesis | produces erythrocytes, platelets, granulocytes, and agranulocytes |
two major types of lymphocytes | T-lymphocytes and B-lymphocytes and T-lympocytes migrate to the thymus to complete maturation |
thymus | function in T-lymphocyte maturation, quite large in infants and young children (grows until puberty and begins to regress and much replaced by adipose tissue), consists of two fused thymic lobes |
each thymic lobe... | is surrounded by connective tissue capsule and has an outer cortex and inner medulla (both with epithelial tissue) |
cortex of the thymus | has immature T-lymphocytes |
medulla of the thymus | has mature lymphocytes |
lymph node characteristics | small, round, or oval, encapsulated structures, located along pathways of lymph vessels, and filter lymph and remove unwanted substances |
lymph nodes usually occur in... | clusters receiving lymph from body regions (i.e. axillary lymph nodes in the armpit - receive lymph from breast, axilla, and upper limb, i.e. inguinal lymph nodes in groin - receive lymph from lower limb and pelvis) |
lymph node components | afferent lymphatic vessels, efferent vessels, and capsule enclosing node |
afferent lymphatic vessels | bring lymph into lobe |
efferent vessels | drains node, originates at involuted potion of node, hilum |
capsule enclosing node | subdivide node into compartments |
lymph flow though lymph nodes | enters through afferent lymphatic vessels, makes its way through lymph node sinuses, lymph continuously monitored for pressure of foreign material, macrophages (remove foreign debris from lymph), and lymph exiting lymph node through efferent vessel |
if lymphocyte contacts foreign substance | immune response generated, lymphocytes undergoing cell division, some remaining in lymph node, others transported in lymph and blood (reach areas of infection) |
swollen lymph nodes | become tender with infection, sign that lymphocytes proliferating and fighting infection, and can palpate swollen superficial lymph nodes |
spleen characteristics | largest lymphatic organ, located in left upper abdominal quadrant (lateral to left kidney and posterolateral to stomach), and supplied by the splenic artery and drained by the splenic vein |
spleen characteristics continued | surrounded by connective tissue capsule (has trabeculae extending into the organ and subdivides spleen into red and white pulp) |
white pulp | clusters of T- and B-lymphocytes and macrophages and contains a central artery |
red pulp | contains erythrocytes, platelets, macrophages, and B-lymphoctes, cells housed in reticular connective tissue, forming splenic cords, and has splenic sinusoids, and platelet reservoir to recenter blood as needed |
splenic sinusoids | permeable capillaries, so blood cells easily exiting and drain to small venules leading to splenic vein |
monitoring blood as it flows through the spleen | spleen functioning to filter blood, white pulp lymphatic cells (monitor blood for foreign materials and bacteria), blood first entering through central artery (white pulp) |
monitoring blood as it flows through the spleen (continued) | travel through sinusoids of red pulp (is in contact with splenic cords of red pulp, macrophages here phagocytize bacteria and foreign debris and old and defective erythrocytes and platelets) and travels through venules and out splenic veins |
tonsils | secondary lymphatic structures found in pharynx, help protect against foreign substances inhaled or ingested, contain lymphatic nodules |
lymphatic nodules | small clusters of lymphatic cells with some extracellular matrix, scatter nodules termed diffuse lymphatic tissue, found in every body organ, help defend against infection, and in some areas, group together to form larger structures (i.e. MALT) |
MALT | mucose-associated lymphatic tissue |
MALT | located in gastrointestinal, respiratory, genital, and urinary tracts, found in lamina propria of the mucosa, helps defend against foreign substances, prominent in small intestines (especially ileum - large collections of lymphatic nodules) |