Splenic pulp
Encyclopedia
The red pulp of the spleen
is composed of connective tissue known as the cords of Billroth
and many splenic sinuses
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 cell
s, red pulp is made up of several different types of blood cells, including platelets
, granulocytes
, red blood cell
s, and plasma
.
. 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 macrophage
s in the red pulp. In addition to aged red blood cells, the sinusoids also filter out particles that could clutter up the bloodstream, such as nuclear remnants or denatured
hemoglobin.
, continuous with those of the splenic trabeculae, to which are applied flat, branching cells. The meshes of the reticulum are filled with blood
:
, the white pulp atrophies and the red pulp expands.
Spleen
The spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system. In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells and holds a reserve of blood in case of hemorrhagic shock...
is composed of connective tissue known as the cords of Billroth
Cords of Billroth
The Cords of Billroth are found in the red pulp of the spleen between the sinusoids, consisting of fibrils and connective tissue cells with a large population of monocytes and macrophages...
and many splenic sinuses
Sinusoid (blood vessel)
A sinusoid is a small blood vessel similar to a capillary but with a fenestrated endothelium. Fenestrations are pores in the endothelial cells that greatly increase their permeability. In addition, permeability is increased by large inter-cellular clefts and fewer tight junctions...
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
Marginal zone
The marginal zone is the region at the interface between the non-lymphoid red pulp and the lymphoid white-pulp of the spleen. A marginal zone also exists in lymph nodes.-Composition and markers:It is composed of cells derived...
; 76-79% of a normal spleen is red pulp. Unlike white pulp, which mainly contains lymphocytes such as T cell
T cell
T cells or T lymphocytes belong to a group of white blood cells known as lymphocytes, and play a central role in cell-mediated immunity. They can be distinguished from other lymphocytes, such as B cells and natural killer cells , by the presence of a T cell receptor on the cell surface. They are...
s, red pulp is made up of several different types of blood cells, including platelets
Platelet
Platelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes. The average lifespan of a platelet is normally just 5 to 9 days...
, granulocytes
Granulocyte
Granulocytes are a category of white blood cells characterized by the presence of granules in their cytoplasm. They are also called polymorphonuclear leukocytes because of the varying shapes of the nucleus, which is usually lobed into three segments...
, red blood cell
Red blood cell
Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...
s, and plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
.
Sinusoids
The splenic sinuses of the spleen, also known as sinusoids, are wide vessels that drain into trabecular veinsTrabecular veins
The trabecular veins are the largest veins inside the spleen. It drains the blood collected in the sinuses of the pulp.-Details:The blood is collected from the interstices of the tissue by the rootlets of the veins, which begin much in the same way as the arteries end.The connective-tissue...
. Gaps in the endothelium
Endothelium
The endothelium is the thin layer of cells that lines the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall. These cells are called endothelial cells. Endothelial cells line the entire circulatory system, from the heart...
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 macrophage
Macrophage
Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...
s in the red pulp. In addition to aged red blood cells, the sinusoids also filter out particles that could clutter up the bloodstream, such as nuclear remnants or denatured
Denaturation (biochemistry)
Denaturation is a process in which proteins or nucleic acids lose their tertiary structure and secondary structure by application of some external stress or compound, such as a strong acid or base, a concentrated inorganic salt, an organic solvent , or heat...
hemoglobin.
Cells found in red pulp
Red pulp consists of a dense network of fine reticular fiberReticular fiber
Reticular fibers or reticulin is a histological term used to describe a type of fiber in connective tissue composed of type III collagen. Reticular fibers crosslink to form a fine meshwork...
, continuous with those of the splenic trabeculae, to which are applied flat, branching cells. The meshes of the reticulum are filled with blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
:
- White corpuscles 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 corpuscleMalpighian corpuscleThere are at least two anatomical structures called a Malpighian corpuscle. They are also known as:* Renal corpuscles — the initial filtering component of nephrons in the kidneys...
s.
- In the young spleen, macrophageMacrophageMacrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...
s may also be found, each containing numerous nucleiCell nucleusIn cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
or one compound nucleus.
- Nucleated red-blood corpuscles 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 leukemiaMyeloid leukemia
Myeloid leukemia is a type of leukemia affecting myeloid tissue.Types include:* Acute myeloid leukemia* Chronic myelogenous leukemia...
, the white pulp atrophies and the red pulp expands.
