Red pulp

The red pulp of the spleen is composed of connective tissue known also as the cords of Billroth and many splenic sinusoids that are engorged with blood, giving it a red color. Its primary function is to filter the blood of antigens, microorganisms, and defective or worn-out red blood cells. The spleen is made of red pulp and white pulp, separated by the marginal zone; 76–79% of a normal spleen is red pulp. Unlike white pulp, which mainly contains lymphocytes such as T cells, red pulp is made up of several different types of blood cells, including platelets, granulocytes, red blood cells, and plasma. The red pulp also acts as a large reservoir for monocytes. These monocytes are found in clusters in the Billroth's cords (red pulp cords). The population of monocytes in this reservoir is greater than the total number of monocytes present in circulation. These stored monocytes, contrary to previous belief, are not progenitors to the self-sustaining red pulp macrophages; their purpose lies in responding to inflammatory signals around the body. They can be rapidly mobilised to leave the spleen and assist in tackling ongoing infections.

The red pulp of the spleen is composed of connective tissue known also as the cords of Billroth and many splenic sinusoids that are engorged with blood, giving it a red color. Its primary function is to filter the blood of antigens, microorganisms, and defective or worn-out red blood cells. The spleen is made of red pulp and white pulp, separated by the marginal zone; 76–79% of a normal spleen is red pulp. Unlike white pulp, which mainly contains lymphocytes such as T cells, red pulp is made up of several different types of blood cells, including platelets, granulocytes, red blood cells, and plasma. The red pulp also acts as a large reservoir for monocytes. These monocytes are found in clusters in the Billroth's cords (red pulp cords). The population of monocytes in this reservoir is greater than the total number of monocytes present in circulation. These stored monocytes, contrary to previous belief, are not progenitors to the self-sustaining red pulp macrophages; their purpose lies in responding to inflammatory signals around the body. They can be rapidly mobilised to leave the spleen and assist in tackling ongoing infections.

Sinusoids

The splenic sinusoids, are wide vessels that drain into pulp veins which themselves drain into trabecular veins. Gaps in the endothelium lining the sinusoids mechanically filter blood cells as they enter the spleen. Worn-out or abnormal red cells attempting to squeeze through the narrow intercellular spaces become badly damaged, and are subsequently devoured by macrophages in the red pulp. In addition to clearing aged red blood cells, the sinusoids also filter out cellular debris, particles that could clutter up the bloodstream.

Cells found in red pulp

Red pulp consists of a dense network of fine reticular fiber, continuous with those of the splenic trabeculae, to which are applied flat, branching cells. The meshes of the reticulum are filled with blood: White blood cells are found to be in larger proportion than they are in ordinary blood. Large rounded cells, termed splenic cells, are also seen; these are capable of ameboid movement, and often contain pigment and red-blood corpuscles in their interior. The cells of the reticulum each possess a round or oval nucleus, and like the splenic cells, they may contain pigment granules in their cytoplasm; they do not stain deeply with carmine, and in this respect differ from the cells of the Malpighian corpuscles. In the young spleen, macrophages may also be found, each containing numerous nuclei or one compound nucleus. Nucleated red blood cells have also been found in the spleen of young animals.

Diseases

In lymphoid leukemia, the white pulp of the spleen hypertrophies and the red pulp shrinks. In some cases the white pulp can swell to 50% of the total volume of the spleen. In myeloid leukemia, the white pulp atrophies and the red pulp expands.

References

External links

- "Spleen: Red Pulp"

Text derived from https://en.wikipedia.org/w/index.php?oldid=1322839648 under CC BY-SA 4.0; modifications have been made.