Talk:Draft 2016

Spleen

Spleen Anatomy

Spleen Anatomy
left hypochondriac region	almost entirely surrounded by peritoneum adherent to its capsule

Spleen Function

1. Immune - filters blood in much the way that the lymph nodes filter lymph.
   1. Lymphocytes in the spleen react to pathogens in the blood and attempt to destroy them.
   2. Macrophages then engulf the resulting debris, the damaged cells, and the other large particles.
2. Red Blood Cell Removal - spleen (and liver) removes old and damaged erythrocytes from the circulating blood.
3. Blood Reservoir - The sinuses in the spleen also act as a reservoir for blood. In emergencies (haemorrhage) smooth muscle in the vessel walls and in the capsule of the spleen contracts, squeezes blood out of the spleen into the general circulation.

Spleen Structure

• afferent splenic artery branches into central arterioles, which are sheathed by white pulp areas.
• white pulp areas consist of the T-cell zone (also known as the periarteriolar lymphoid sheath, PALS), arterioles and B-cell follicles.
• arterioles end in cords in the red pulp, from where the blood runs into venous sinuses that collect into the efferent splenic vein.
• larger arteries and veins run together in connective-tissue trabeculae, which are continuous with the capsule that surrounds the spleen.

Spleen Histology

• Capsule with trabeculae (dense connective tissue)
• Reticular fibroblasts - reticular fibres (Type III collagen)

White Pulp	Red Pulp
lymph follicle germinal center central artery periarterial lymphoid sheath (PALS)	splenic cords macrophages reticular fibroblasts splenic sinuses endothelium (discontinuous structure)

Overview - red and white pulp	Overview - blood vessels	Red pulp

File:Spleen_histology_05.jpg|Reticular Fibre overview File:Spleen_histology_04.jpg|Reticular Fibre detail </gallery>

White pulp -periarterial lymphoid sheath (PALS)

Reticular Fibers (type III collagen) act as supporting meshwork.