Spleen and Thymus Flashcards
what is the largest lymphoid organ?
spleen
function of spleen
filtering blood
describe spleen
- surrounded by CT capsule (outer layer of mesothelium)
- trabeculae from capsule to interior and anastamose (contains blood vessels)
- splenic pulp: red and white
white pulp
surrounds and follows arteries - thickens to form splenic nodules
red pulp
occurs in irregular masses - splenic cords
where is the CT capsule heaviest in the spleen?
at the hilus where splenic blood vessels enter
what supports splenic pulp?
meshwork of reticular fibers
what types of lymphatics does the spleen have?
- only efferent lymphatics
- in capsule, large trabeculae, and some white pulp
describe blood vessels as they leave the trabeculae in the white pulp
ensheathed in lympathic tissue (PALS) - w/ concentrations of T cells
PALS = peri-arterial lymphatic sheath
how do splenic nodules form?
along a central artery
what is at the periphery of the white pulp?
marginal zone w/ marginal sinuses where white pulp transitions to red pulp
-important for immune function
what is splenic red pulp infiltrated with?
all elements of circulating blood - particularly macrophages
what supports red pulp?
reticular fibers and cells
function of macrophages in splenic red pulp
erythrophagia - removal of old RBCs
how do antigens enter spleen and how are they detected?
enter via blood and are detected by antigen-presenting cells in splenic nodules - especially in marginal sinuses
describe general spleen vascular supply
splenic a. -> course in trabeculae -> leave and get PALS, now are central a. -> formation of splenic nodules around these -> central a. branches w/i nodules to follicular/radial arterioles -> empty into marginal sinuses -> into pencillar arterioles (red pulp) -> empties into sinuses (closed circulation) or into red pulp (open circulation) -> venous or splenic sinuses -> splenic cords -> venous circulation