The red pulp splenic cord contains a network of stromal cells. It is surrounded by an endothelial cell wall with elongated stress fibers that allow slits between the endothelial cells to be opened. Red blood cells and migrating cells are transported through these slits. The red pulp cord also contains macrophages closely associated with the sinus wall.
fibroblasts
Red pulp consists of reticular tissue and sinusoids. The latter are large, irregular venous spaces lined with a reticular cell lining. These cells harbor many lymphocytes, platelets, and macrophages. The reticular tissue also has groups of plasma cells located along the trabeculae and marginal zones. Among these cells are red pulp macrophages.
Human splenic red pulp arterioles may correspond to lymphocyte migration pathways. Lymphocytes are known to be attracted to arterioles of specific diameters, which may be a determinant of their migration. This migration may occur early in ontogeny and may be a consequence or cause of a particular fibroblast phenotype.
Macrophages located in red pulp are highly diverse. They play an essential role in maintaining blood homeostasis. They phagocytose injured or senescent erythrocytes, as well as blood-borne particles. Macrophages are necessary for blood homeostasis and are maintained throughout adulthood. In addition to their role in blood homeostasis, these cells store immune complexes and secrete cytokines.
Branches of splenic artery
The spleen is a highly vascular organ. The blood flow in the spleen is complex, with branches from the main artery to arteries that branch off in various ways. The main street enters the spleen through a hilus and then divides into trabecular arteries and smaller arterioles within the red and white pulp. These smaller arteries supply the white and red pulp capillary beds.
The splenic artery branches into two types of arteries: penicillin and trabecular. The penicillin branches terminate in the red pulp, and the trabecular units turn back into the marginal zone and open to the marginal cavernous and venous sinuses. The main component, the trabecular artery, branches into several smaller streets and drains into the venous system.
The branches of the splenic artery in the red pulp are composed of cellular cords. The central artery branching into penicillin and becoming arterial capillaries may be surrounded by a macrophage sheath and connect with the venous sinuses. Some arterial capillaries open directly into the reticular meshwork of cellular cords. They are lined with endothelial cells, which lie parallel to the axial length of the vessel.
Macrophages
Macrophages are immune cells that have a central role in the immune system. They are a type of phagocyte found in the spleen, composed of red and white pulp. Macrophages are also present in the marginal zone and sinusoids. They are generated from bone marrow and migrate into the spleen as monocytes. Moreover, these immune cells can increase locally, and many migrate into the red pulp.
The spleen’s red pulp is a network of fibers and cells. It contains dendritic cells, macrophages, and erythrocytes. These cells filter the blood and select those that are defective or older. They also serve as a reservoir for monocytes that rapidly leave the spleen.
In addition to their functions in filtering the blood, these cells also aid in producing antibodies. Several studies have shown that these immune cells help treat various diseases. The role of the spleen is to protect the vascular compartment of the body by generating immunological responses against pathogens that may be found in the blood.
Lymphatic sheaths
Lymphatic sheaths surround red pulp capillaries and provide blood to the surrounding cells. They comprise capillary endothelial cells, pericytes, and special CD271+ stromal sheath cells. The sheaths are elongated and resemble cuboidal epithelium. They cover up to four sequential bifurcations of post-arteriolar capillaries. These sheaths are surrounded by a thin mantle zone and a broader marginal zone of lymphocytes.
The lymphatic sheaths surrounding the spleen contain T-cell-dependent cells. T-cells are found in the peri-arteriolar lymphatic sheath. The red pulp contains lymphocytes and contains large lymphocytes. In addition, large lymphocytes are surrounded by macrophages and plasma cells. The splenic cord contains large lymphocytes and reticular cells, which are best identified using specific labeling techniques.
Lymphatic sheaths are located in the red pulp and are closely related to the splenic ellipsoids in most vertebrates. The red pulp and the spleen contain dendritic cells, macrophages, and erythrocytes. These cells filter blood to detect defective erythrocytes and choose them for breakdown. They also serve as reservoirs for monocytes, which can quickly leave the spleen and return to the bloodstream.
Storage capacity
The spleen is a reservoir for blood and can respond to sympathetic stimulation, contracting its fibroelastic capsule to increase the blood supply to the body during hemorrhage—this organ stores about 25% of the body’s red blood cells and platelets. Abnormal enlargement of the spleen is known as splenomegaly and can result from several factors. The eccentric erythrocyte work hypertrophy in sickle cell anemia or hereditary spherocytosis may indicate an increased splenic function.
The red pulp contains thin-walled vascular sinusoids separated by fibrovascular splenic cords. The red pulp is lined with macrophages that have long, dendritic processes, allowing them to pass through the tissue and trap red cell inclusions. The red pulp filters approximately two liters of blood per minute.
The spleen has a highly vascular system. Blood flow in the spleen is complex and varies from person to person. The splenic artery enters the spleen at the hilus and divides into trabecular arteries and small arterioles. The trabecular arteries then branch into smaller arterioles that feed the white pulp capillary beds.
Melanocytes
The red pulp of a splenic cord is made up of macrophages with intracytoplasmic pigments, including melanin and ceroid/lipofuscin. These pigments are formed when erythrocytes are phagocytized. This pigmentation is characteristic of splenic tissue and is more prevalent in females than males.
The spleen contains lymphatic tissue that monitors incoming blood for pathogens. Lymphocytes line the central arteries of the spleen and are found in clusters of spherical aggregations called B-cells. A mantle zone surrounds these cells. The spleen also has a capsule made of trabeculae and dense connective tissue.
In addition to melanocytes, the red pulp contains other types of cells. There are two regions in the red pulp, each with its cellular composition. The marrow-like portion includes a higher number of cells than the cortex.
Location
The red pulp is a unique location that houses macrophages associated with plasma and red blood cells. This specialized tissue is created before birth and continues to be maintained throughout life. The macrophages are unique because they are independent of bone marrow-derived hematopoietic cells and can rapidly multiply during inflammation.
The red pulp capillary network comprises capillaries with open ends that carry blood to surrounding cells via short asymmetric side branches. These capillaries are covered by a sinus network that impedes most veins. In addition, most capillary branches leaving the sheath are very short and only connect to the red pulp capillary network on one side. This network may contain several sheaths at various locations in the splenic cord.
The red pulp comprises a complex meshwork of fibers and cells arranged three-dimensionally. The fibers and cells include dendritic cells, macrophages, and erythrocytes. These cells filter the blood to remove defective erythrocytes. The red pulp also acts as a reservoir for monocytes, which are large blood cells.
