Testicle

Ovary (testis, Greek orchis, s.didymis) - male sexual gland. The testicles are located in the scrotum, covered with a common skin and a fleshy shell of the scrotum, the remaining membranes are formed as a result of protrusion of the sheets of the anterior abdominal wall when the testicle is lowered from the retroperitoneal space into the scrotum. Eggs originate from undifferentiated mesenchymal buds located between the fold of the primary kidney and the root of the mesentery. Testicle - oval body, flattened laterally. The function of the testicles is the formation of male sex cells and hormones, therefore the testes are simultaneously also the glands of external and internal secretion.

In functional terms, the testicles are excretory as well as an endocrine organ. They serve as a target organ for pituitary hormones with a complex negative feedback mechanism.

The main hormone that produces testes (Leydig cells), testosterone. In the testicles, estrogens, mainly estradiol, are also produced.

Testosterone has a pronounced anabolic activity, stimulates erythropoiesis. Testosterone has a number of inactive and active metabolites. Of the active metabolites, the most known are 5-a-dihydrotestosgerone and androsterone. Metabolism of testosterone occurs under the influence of enzymes 5 a-reductase. Androgen receptors are located in the nuclei of sex gland cells in muscles and other organs.

The inner surface of the convoluted tubules is lined with two kinds of cells-sustanocytes and spermatogonia, which are called primary sex cells. In the seminiferous tubules, the maturation of spermatocytes occurs.

Eggs, or testicles, are located in the perineal region in a special container - the scrotum, with the left testicle below the right. They are separated from each other by a septum partition and surrounded by membranes. The surface of each testicle is smooth, shiny. The length of the testicle is 4 cm in average, 3 cm in width, and 2 cm in thickness. The testicle weighs 20-30 g. The testicle has a dense consistency, an oval shape and is somewhat flattened from the sides. It distinguishes two surfaces: a more convex lateral surface (facies lateralis) and a medial surface (facies medialis), as well as two edges: the marginal anterior and margo posterior, to which the appendage of the testicle is attached. The testicles have an upper extremity (extremitas superior) and a lower end (extremitas inferior). At the upper end of the testicle, a small appendix testicle (appendix testis) is often found , which is a rudiment of the cranial end of the parameconeural duct.

The structure of the testis. Outside, the testicle is covered with a whitish color by a fibrous membrane called the tunica albuginea. Under the shell is the substance of the testicle - parenchyma of the testicle (parenchyma testis). From the inner surface of the posterior margin of the gallbladder, a cylindrical outgrowth of the connective tissue is implanted into the testicle parenchyma - the mediastinum testis, from which the thin connective tissue septa testicles (septula testis) dividing the parenchyma into lobuli testis are fan-shaped. The latter have the shape of a cone and its apices are turned toward the mediastinum of the testicle, and the bases are toward the belly. In the testicle there are from 250 to 300 lobules. In the parenchyma of each lobule there are two or three convoluted seminiferous tubules (tubuli seminiferi contorti) containing spermatogenic epithelium. Each of the tubules has a length of about 70-80 cm and a diameter of 150-300 μm. Referring to the mediastinum of the testicle, the convoluted seminiferous tubules in the region of the apices of the lobules merge with each other and form short, direct seminiferous tubules (tubuli seminiferi recti). These tubules flow into the testicle network (rete testis), which is located in the thickness of the mediastinum of the testicle. From the testicle network, 12-15 ductile testicles (ductuli efferentes testis) are sent to their appendage, where they flow into the duct of the epididymis.

The convoluted seminiferous tubules are lined with spermatogenic epithelium and supporting cells (Sertoli cells) located on the basal membrane. Cells of spermatogenic epithelium, located at different stages of spermatogenesis, form several rows. Among them, stem cells, spermatogonia, spermatocytes, spermatids and spermatozoa are distinguished. Spermatozoa are produced only in the walls of the convoluted seminiferous tubules of the testicle. All other tubules and ducts of the testicle are the ways of excretion of spermatozoa.

Vessels and nerves of the testicle and its appendage. The testicle and appendage of the testicle are supplied from the testicle (branch of the abdominal part of the aorta) and partly from the artery of the vas deferens (branch of the internal iliac artery), anastomosing with the testicular artery. Venous blood from the testicle and epididymis drains through the testicular veins forming a lobate venous plexus in the spermatic cord. The veins of this plexus flow to the right into the inferior vena cava, to the left to the left renal vein. Lymphatic vessels of the testicle and epididymis fall into the lumbar lymph nodes.

The egg and its appendage receive sympathetic and parasympathetic innervation from the ovarian plexus. The plexus also contains sensitive nerve fibers.

Supporting cells (Sertoli cells) have a pyramidal shape, well-developed organelles (especially an ungarnished endoplasmic reticulum and the Golgi complex). These cells reach the lumen of the convoluted tubule with their apex. Supporting cells are a microenvironment for the spermatogenic epithelium, they provide their trophic, and also isolate the emerging germ cells from toxic substances, various antigens, impede the development of immune reactions. Sertoli cells can act as phagocytes. Supporting cells synthesize androgen-dependent protein, which transfers male sex hormones to spermatogenic cells.

Outside the basal membrane of the convoluted seminiferous tubule is a thin layer of loose (fibrous) connective tissue containing smooth myocytes (contractile cells that have actin). The direct seminiferous tubules are lined with prismatic epithelium, the tubules of the testicle network are cubic. The epithelium lining the terminal tubules is represented by high ciliated and secretory cells. In addition, the testicle has one more variety of cells - interstitial endocrinocytes (Leydig cells). They are located in a loose fibrous connective tissue between the convoluted seminiferous tubules, around the blood capillaries. Leydig cells are large, round or polygonal, rich in glycoprotein inclusions, and have a pronounced endoplasmic reticulum.