Download Lymph II: SPLEEN

Lymph II: SPLEEN
FUNCTIONS:
- Filters blood: it removes old and damaged red blood cells and platelets
- Iron Retrieval and Heme metabolism
- Reserve for red blood cells; it is engorged with blood
- Immune response against blood-borne antigens
- Fetal hematopoiesis.
The spleen is supplied by a single splenic artery and drained by a single splenic vein; all vessels enter the hilum
Splenic artery
Splenic Vein
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
Trabecular arteries
Trabecular veins
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
Central arteries (PALS)
Pulp Veins
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
Penicilli (arterioles)
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Ellipsoids
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Sinusoids
CAPSULE:
- histology:
- dense, fibrous, irregularly-arranged connective tissue
- reticular fibers (Foot’s silver and azo-carmine stain them black)
- trabeculae: extensions from the capsule into the parenchyma
- capsule and trabeculae also contain smooth muscle
- contraction of the spleen pumps stored blood into the circulation.
WHITE PULP: (analogous to cortex; note: stains basophilically on H&E & red on silver stain)
- functions:
- immune function: site of B cell – T cell interaction and antibody production
- here, reticular connective tissue is filled with lymphocytes (B and T cells)
- the Central Artery is surrounded by the Periarteriolar Lymphatic Sheath (PALS) of T cells
- appears basophilic because of the dense heterochromatic nuclei of the lymphocytes
- germinal centers (contains plasmablasts and plasma cells derived from B cells) form after antigenic
stimulation can push the central artery into an eccentric position
PENICILLI:
- straight arteriole branches from the central arteries in the white pulp that lead into red pulp
MARGINAL ZONE:
- lies between White pulp and Red pulp
- site where the white pulp capillaries drain
- immunologic activity: lymphatic tissue is exposed to blood-borne antigens
- there are NO sinusoids here
RED PULP: (analogous to medulla)
- consists of most of the area inside the capsule
- appears red, in fresh states & histologically
- macrophages examine and filter blood
- blood leaves the circulation through the ellipsoids (sheathed capillaries: wrapped by macrophages)
- blood is then filtered through the fenestrated SINUSOIDS
- (gaps between the endothelial cells…will see dotted line in the basal lamina)
- blood encounters macrophages in the sinusoids so that old/compromised blood cells are phagocytosed
CORDS OF BILLROTH: (parenchyma)
- reticular tissue bordering splenic sinusoids in the red pulp
- contains macrophages, lymphocytes, blood cells