Spleen: red pulp
Capillaries from penicillar arterioles supply the red pulp. Branches of the penicillar arterioles are both sheathed and unsheathed capillaries. Sheathed capillaries, which are surrounded by macrophages, empty directly into the reticular stroma of the cord; unsheathed capillaries are continuous with splenic sinuses. The sheathed capillary pathway allows blood to be exposed to cells of splenic cords before entering the sinus. 400x
Splenic cords >
Splenic cords are composed of lymphocytic cells, phagocytic cells, plasma cells, antigen-presenting cells and red blood cells. All are supported by a reticular connective tissue stroma.
Splenic sinuses >
Sinuses (discontinuous capillaries or sinusoids) are capillaries that have wide lumens, fenestrations, gaps or discontinuities between adjacent endothelial cells, and a basal lamina that is interrupted or may be absent. A variety of cell types are present, including macrophages, whose processes span the lumen, surveying antigens in the blood and phagocytosing red blood cells.
Endothelial cells >
The splenic sinuses are venous sinuses and, hence, are lined by endothelial cells. However, these cells are unique, having large nuclei that bulge into the lumen of the sinusoid. Additionally, these cells are extremely long, with their longitudinal axes oriented parallel to the flow of blood in the sinus.
Red blood cells in stroma >
Blood carried by sheathed capillaries “bleeds” directly into the stroma of the cord. Thus, blood cells are not contained within vessels, and red blood cells can be phagocytosed by macrophages. Blood carried by unsheathed capillaries passes into the sinus, where it is also surveyed by macrophages that span the lumen.
Red blood cells in capillaries
Blood carried by sheathed capillaries “bleeds” directly into the stroma of the cord. Thus, blood cells are not contained within vessels, and red blood cells can be phagocytosed by macrophages. Blood carried by unsheathed capillaries passes into the sinus, where it is also surveyed by macrophages that span the lumen.
Macrophages with hemosiderin >
The major function of the red pulp is the removal of aged and damaged red blood cells by macrophages, which are present both in the cords and sinuses. Red blood cells have a life span of about 120 days in circulation. The iron associated with the hemoglobin, in the form of hemosiderin, is recycled.
Macrophages in sinus lumen
The major function of the red pulp is the removal of aged and damaged red blood cells by macrophages, which are present both in the cords and sinuses. Red blood cells have a life span of about 120 days in circulation. The iron associated with the hemoglobin, in the form of hemosiderin, is recycled.
Plasma cell
The major function of the red pulp is the removal of aged and damaged red blood cells by macrophages, which are present both in the cords and sinuses. Red blood cells have a life span of about 120 days in circulation. The iron associated with the hemoglobin, in the form of hemosiderin, is recycled.
PREVIOUS