Spleen Flashcards
Where are HEVs (high endothelial venules) found?
Paracortex of lymph nodes and tonsils
Describe the general structure and function of HEVs.
Oddly shaped, though general cuboidal endothelial cells that have receptors for lymphocytes
Facilitate rapid translocation of lymphocytes from lymph into lymphoid tissue
Where is the spleen located? Describe general structure. What types of cells does it have?
Upper left abdomen, bean-shaped
Surrounded by capsule of dense connective tissue. Trabeculae emerge from hilum of spleen to penetrate the splenic pulp.
Made up of fibroblast-like reticular cells and reticular fibers (collagen Type III)
What is the general function of the spleen?
Filter blood by 1) defending against microorganisms in circulation and 2) detecting and destroying old RBCs
Describe components of red pulp.
1) Sinusoids - lined with leaky endothelial cells, filters blood
2) Cords of Billroth/Splenic Cords - network of reticular cells/fibers filled with B/T lymphocytes, macrophages, other leukocytes, old RBCs - old RBCs are removed here
Describe white pulp components.
1) B cell nodule (what surrounds the central artery and PALS) - site of B cell synthesis
2) PALS (periarteriolar lymphatic sheath) - made up mostly of helper T cells, surrounds central artery
Describe the flow of blood in the spleen including both types of circulation.
Small trabecular arteries leave trabecular CT and enter parenchyma as central arterioles. These central arterioles run from red pulp into white pulp. Once they emerge, they branch into penicillar arterioles. At this point they can:
1) Open circulation - blood dumped from penicillar artery into trabecular space where debris, pathogens, Ags, and aged blood cells are removed by macrophages
2) Closed circulation - penicillar artery connects directly to sinusoids.
Filtered blood leaves the spleen by draining through sinusoids into splenic veins.
What is MALT? Where is it present? Give an example.
Mucosa-Associated Lymphoid tissue
Present in digestive, respiratory, GU tracts
Tonsils
What are tonsils?
Lymphoid tissue that resides as aggregates below epithelia of various organs - usually close to pathogen entry point like upper digestive tract or respiratory tract
What is the purpose of tonsils?
Survey substance brought into mouth and throat, local response
What are they structurally similar to?
Lymph node
What are tonsils in GI tract called?
Peter’s Patches
Where are palatine tonsils? What surrounds them?
Walls of oral pharynx, capsule of dense connective tissue
Where are pharyngeal tonsils? What type of cell covers them?
Superior portion of pharynx, respiratory epithelial
Where are lingual tonsils? What types of cells?
Base of tongue, stratified squamous epithelia
