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A&P EXAM 2 - CH 20
Terms in this set (21)
What is lymph? Where does it come from?
Lymph is the fluid inside lymphatic vessels. It enters lymphatic vessels from interstitial fluid. Interstitial fluid, in turn, is a filtrate of blood plasma.
How are lymphatic capillaries different from blood capillaries?
- lymph are one way -begin in tissue end in venous system - but blood circulation is continuous and continues to recirculate without beginning or ending
- lymph can take up larger molecules and particles that blood cannot
What is the main function of lymphatic capillaries as they support the circulatory system?
to drain and process extracellular fluid
what is the driving force behind lymph movement?
lymph movement is driven by the contraction of adjacent skeletal muscles, pressure changes in the thorax during breathing, and the pulsations of nearby arteries
What are lacteals? Where are they located?
specialized lymphatic capillaries
-located in villi of small intestines (intestinal mucosa)
describe lymph vessels
circulate 3L interstitial fluid p/day. "suck" in all Interstitial Fluid + any plasma proteins that escape from the bloodstream & carry it back to the blood to ensure that the cardiovascular system has sufficient blood volume to operate properly.
what are collecting lymphatic vessels?
larger vessels that lymph capillaries drain into. consist of collecting vessels, trunks, and ducts. have structures and tunics similar to veins
what are the main types of lymphoid cells, and what are their specific functions?
1. immune system cells - consist of lymphocytes & mature into T cells or B cells. both protect against antigens. T cells manage immune response. B cells produce plasma cells which secrete antibodies. macrophages & dendritic cells help activate T cells.
2. supporting lymphoid cell - reticular cells produce reticular fibers called stroma, a network-like support that acts as scaffolding for immune cells, in lymphoid organs
what are the functions of the 2 main types of lymphoid tissue (diffuse lymphoid tissue and lymphoid nodules)?
diffuse: loose arrangement of lymphoid cells and some reticular fibers, larger collections in lamina propria of mucous membranes
lymphoid nodules: solid, spherical bodies consisting of tightly packed lymphoid cells and reticular fibers. contain germinal centers of proliferating B cells. may form part of larger lymphoid organs (nodes). Isolated aggregations of Peyer's patches and in appendix
differentiate between the primary and secondary lymphatic organs. why are they defined as primary and secondary?
primary: areas where T & B cells mature--red bone marrow and thymus
secondary: areas where mature lymphocytes first encounter their antigens & become activated--nodes, spleen, MALT & diffuse lymphoid tissues
defined as primary and secondary because the primary are the main organs where lymphocytes grow & are trained for defense. secondary organs the lymphocytes are already trained.
describe the structure of the lymph node
- Usually less than an inch long
- Bean shaped
- External fibrous capsule
- Trabeculae extend inward and divide the node into compartments
2 histologically distinct regions:
what is the purpose of the trabeculae, medullar cords and lymph sinuses in lymph nodes
trabeculae: dense connective tissue that extend from the capsule into the substance of the node, forming a gross framework
medullar cords: portion of the medulla of the lymph node which contains lymphatic tissue and project into the medullary sinus. B cells and plasma cells are the main cell types found in the
lymph sinuses: space between the capsule and the cortex which allows the free movement of lymphatic fluid and so contains few lymphocytes.
what is the overall function of lymph nodes
- filter lymph before its returned to the blood
- slow flow through lymph node to allow time for antigen removal & protection
- defense cells within lymph nodes
what is the benefit of having fewer efferent than afferent lymphatics in lymph nodes?
having fewer efferents causes lymph to accumulate in lymph nodes, allowing more times for its cleansing
how does the spleen compare to a typical lymph node?
spleen filters blood as much as lymph nodes filter lymph. a lymph node is the small mass of tissues located along the lymphatic vessels whereas spleen is an organ found in vertebrates, which is structurally similar to a large lymph node. both secondary lymphoid organs. Their main function is to filter body fluids to capture pathogens, making them in contact with immature lymphocytes.
what are some functions of the spleen
the spleen cleanses the blood, stores breakdown products of RBCs, stores platelets, and is thought to be a site of erythrocyte production in the fetus
what is the purpose of the white and red pulp?
white: site where immune function occurs
red: site where old blood cells are destroyed
what is MALT, where would you find it?
MALT (mucosa-associated lymphoid tissue) is lymphoid tissue found in the mucosa of the digestive, respiratory, and genitourinary tracts
-tonsils, peyer's patches, appendix
what are the functions of MALT
protects from pathogens trying to enter body
what is the function of the thymus gland
Programs T lymphocytes to become regulator or effector T cells. (site of T cell maturation)
where do other white blood cells mature
B cells mature in bone marrow.
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