The SpleenThe Spleen

……the spleen…the spleen…

an organ of mystery and perplexity since ancient times

The spleen is the largest organ derived from The spleen is the largest organ derived from mesenchyme and lying in the mesenterymesenchyme and lying in the mesentery

It consists of masses of lymphoid tissuesIt consists of masses of lymphoid tissues is a secondary lymphoid organis a secondary lymphoid organ

……functions…functions…

in the destruction of old red blood cells and in the destruction of old red blood cells and

holding a reservoir of blood holding a reservoir of blood

It is a major site for mounting the immune It is a major site for mounting the immune

responseresponse

site of immune and phagocytic actionsite of immune and phagocytic action

Location…Location…

The spleen is located between the fundus of the

stomach and the diaphragm, while also being in

contact with the left kidney posteriorly

The gastric surface is concave and located at

the level of the eleventh thoracic vertebra. The

lower extremity of the spleen lies against the

flexure of the colon

Size…Size…

weighs about 150 grams approximately 12cm long, 7cm wide, and

3-4cm thick is affected by many factors

Spleen Histology

Capsule and TrabeculaeCapsule and Trabeculae Surface is covered by Surface is covered by

mesotheliummesothelium

Consist of thick Consist of thick connective tissue, connective tissue, smooth muscle cells, smooth muscle cells, and elastic networksand elastic networks

Trabeculae carry Trabeculae carry arteries and veinsarteries and veins

The Red and White PulpThe Red and White Pulp

AreaArea

Red Red pulp pulp

White White pulp pulp

Composition

"sinuses" (or "sinusoids") which are filled with blood

"splenic cords" of reticula fibers

"marginal zone" bordering on white pulp

"periarteriolar lymphoid sheaths" (PALS)

Function

Mechanical filtration. Removes unwanted materials from the blood, including senescent red blood cells

Helps fight infections

White pulpWhite pulp

Forms the Forms the periarteriolar lymphoid sheaths (PALS)

Contains the “germinal center”

Both consist of lymphoid tissues

Has loose irregular network of reticular fibers with associated reticular cells

Contains lymphocytes and some macrophages and plasma cells

Red PulpRed Pulp

Consist of a network of venous sinuses Consist of a network of venous sinuses separated by splenic/pulp cordsseparated by splenic/pulp cords Spongy cellular mass supported by reticular fiberSpongy cellular mass supported by reticular fiber

The mesh of reticulum are filled with free The mesh of reticulum are filled with free cells which includes macrophages, cells which includes macrophages, erythrocytes, platelets, and few plasma erythrocytes, platelets, and few plasma cells.cells.

Spleen Processes

StainsStains

Mallory-Azan stain Reticulin Stain

H&E

Clinical FocusClinical Focus

Hemolytic AnemiaHemolytic Anemia Hereditary Spherocytosis Hereditary Spherocytosis Hereditary Elliptocytosis (Ovalocytosis)Hereditary Elliptocytosis (Ovalocytosis) HyposplenismHyposplenism Etc..Etc..

Leads to splenomegaly (enlargement)Leads to splenomegaly (enlargement) Splenectomy (Spleen Removal) Splenectomy (Spleen Removal)

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