Spleen

The spleen (lien, s.splen) performs the functions of immune control of blood. It is located on the path of blood flow from the main vessel of the great circle of blood circulation - the aorta into the portal vein system, branching in the liver. The spleen is located in the abdominal cavity, in the region of the left hypochondrium, at the level from IX to XI of the rib. The weight of the spleen in an adult human (20-40 years old) is 192 g for a man and 153 g for a woman, for a length of 10-14 cm, for a width of 6-10 cm and for a thickness of 3-4 cm.

The spleen has the form of a flattened and elongated hemisphere. It is dark red, soft to the touch. Two surfaces are distinguished from the spleen: diaphragmatic and visceral. The smooth convex diaphragmatic surface (facies diaphragmatica) faces laterally and upwards towards the diaphragm. The anterior medial visceral surface (facies visceralis) is uneven, the spinal cord (hilum splenicum) and the areas adjacent to it adhere to it. The gastric surface (facies gastrica) comes into contact with the bottom of the stomach; it is visible in front of the gate of the spleen. The renal surface (facies renalis), located behind the organ gates, is attached to the upper end of the left kidney and the left adrenal gland. The facial colic (facies colica) at the point of contact of the spleen with the left curvature of the colon is below the spleen gate, closer to its anterior end. A little above the surface, directly behind the gate, there is a small area to which the pancreas tail approaches. The upper (front) edge of the spleen (margo superior) separating the gastric surface from the diaphragmatic, acute. There are two or three shallow notches on it. The lower (posterior) margin (margo inferior) is more obtuse. The spleen has two ends (poles): the back and the front. The posterior end (extremitas posterior) is rounded, facing up and back. The anterior end (extremitas anterior) is more acute, protrudes forward and lies just above the transverse colon.

The spleen is covered from all sides with the peritoneum, which is firmly fused to its fibrous membrane. Only in the area of the gate, where the tail of the pancreas is turned, there is a small area, free from the peritoneum. Between the visceral surface of the spleen on one side, the stomach and the diaphragm - on the other, the peritoneum leaves, its ligaments (gastro-splenic, diaphragmatic and splenic) are strained, so the change in the position of these organs (diaphragm excursion during breathing, filling and emptying of the stomach) affects the topography of the spleen .

From the fibrous membrane (tunica fibrosa), which is under the serous cover, connective tissue rails - trabeculae splenicae (trabeculae splenicae) extend into the organ. Between the trabeculae is the parenchyma - the pulp (pulp) of the spleen (pulpa splenica). Isolate red pulp (pulpa rubra), located between the venous sinuses (sinus venuldris) of the spleen and consisting of loops of the reticular tissue, filled with red blood cells, leukocytes, lymphocytes, macrophages. White pulp (pulpa alba) is formed by splenic lymphoid periarterial clutches, lymphoid nodules and macrophage-lymphoid clutches (ellipsoids) consisting of lymphocytes and other cells of lymphoid tissue lying in the loops of the reticular stromg. The weight of white pulp in children and adolescents is 18.5-21% of the total mass of the spleen.

Periarterial tshfoidnye couplings surround the pulp arteries from the place of their exit from the trabeculae and up to ellipsoids. Each pulpar artery is surrounded by 2-4 rows (layers) of cells of the lymphoid series, consisting of small and medium lymphocytes, plasma and reticular cells, macrophages, as well as single large lymphocytes and cells with a picture of mitosis. Directly near the walls of the arteries are located mainly T-lymphocytes. This is an internal thymus-dependent zone of periarterial lymphoid clutches. The outer zone of periarterial lymphoid clutches consists of T- and B-lymphocytes and other cells. This is the so-called marginal (border) zone. It separates the thymus-dependent zone from the red pulp.

Lymphoid nodules with a diameter of 300 μm to 1 mm are located along the lymphoid clutches, forming their thickenings. In this case, the periarterial lymphoid clutch with its artery is part of the lymphoid nodule, occupying its periphery. A part of the lymphoid clutch inside the nodule is called its periarterial zone. Pulpar artery passing through the lymphoid nodule is always located eccentrically. Lymphoid nodules can have a reproductive center, which is located on the side of the artery of the lymphoid nodule. In the center of reproduction there are large lymphocytes, T- and B-cells, macrophages, plasma and mitotically dividing cells. The surrounding mantle center (peripheral) zone, consisting mainly of small and medium lymphocytes, has a thickness of 40 to 120 μm.

Macrophagal lymphoid clutches (ellipsoids) are located in the region of the final branches of the pulpar arteries. They consist mainly of macrophages and lymphocytes, as well as from the reticular cells surrounding the blood capillary. The length of such a lymphoid clutch reaches 50-100 microns, the diameter is 25-50 microns. Upon emergence from macrophagal lymphoid clutches, the capillaries are bristly separated (branched) and fall into wide (up to 40 μm) spleen sinuses, with which the venous bed of the organ begins.

[1],

Development and age features of the spleen

The ligation of the spleen appears on the 5th-6th week of intrauterine development in the form of a small accumulation of mesenchymal cells in the thick of the dorsal mesentery. Soon cells of the lymphoid series appear in the mesenchymal rudiment, and also crevices are formed-the future vessels of the spleen around which tissue differentiation of the organs takes place. Venous sinuses and other blood vessels form on the 2nd-4th month. Simultaneously, inside the spleen from the capsule, the cells grow - the future trabeculae. At the end of the 4th month and at the 5th month, clusters of lymphocytes are found in the spleen - future periarterial lymphoid clutches and lymphoid nodules. Gradually, the number of lymphoid nodules in the spleen increases, and reproductive centers appear in them.

In the newborn, the spleen is rounded, lobed and has a mass of about 9.5 g. During this period, the white pulp is 5 to 10% of the body weight. At the 3rd month of postnatal development, the mass of the spleen increases to 11-14 g (on average), and by the end of the first year of life it reaches 24-28 g. The child has 6 years of age compared with one year old, the weight of the spleen doubles, reaching 10 years 66-70 g, in 16-17 years is 165-171 g.

The relative amount of white pulp (82-85%) during a person's life almost does not change. The content of white pulp (periarterial lymphoid clutches, lymphoid nodules and macrophage-lymphoid clutches, or ellipsoids) in the spleen of a child of 6-10 years is on average 18.6%, by 21-30 years it decreases to 7.7-9.6% and to 50 years does not exceed 6-5% of the body weight.

[2], [3], [4], [5], [6], [7], [8], [9], [10]

Vessels and nerves of the spleen

To the spleen is the same-named (splenic) artery, which is divided into several branches entering the organ through its gate. Splenic branches form 4-5 segmental arteries, and the latter branch into the trabecular arteries. Pulp arteries with a diameter of 140-250 μm are sent to the parenchyma of the spleen, around which are lymphoid periarterial clutches and the periarterial zone of splenic lymphoid nodules. Each pulpar artery is divided into arterioles with a diameter of about 50 microns, and then to capillaries surrounded by macrophage lymphoid clutches (ellipsoids). The capillaries formed during the branching of the arteries flow into the wide splenic venous sinuses located in the red pulp.

Venous blood from the spleen parenchyma flows through the pulpar and then trabecular veins. The splenic vein that forms in the organ's gates empties into the portal vein.

The spleen is innervated by the branches of the vagus nerves and sympathetic fibers that are suitable for the spleen in the same plexus.