Male Reproductive system First lecture
Dr. Ahmed Nazar Abduljawad The male reproductive system consists of (a) the testes surrounded by the tunica vaginalis and the testicular tunics, (b) the epididymides, (c) the ductus deferens, (d) the accessory glands (glandular portion of the ductus deferens, vesicular and bulbourethral glands, prostate), (e) the urethra, and (f) the penis surrounded by the prepuce.
Testis: paired ovoid organs, serve both exocrine (sperm production) and endocrine (testosterone production) functions, suspended in the scrotum.
*Scrotum: skin pouch contains sweat and sebaceous gland , scrotum maintains the testes at a temperature about 2 to3 Cº below body temperature. Tunica dartos is a special layer of smooth muscle within the scrotum, it's arranged randomly, these muscle fibers play an important role in the regulation of testicular temperature. *Capsule of testis consist of three tunics: 1.Tunica vaginalis: consists of mesothelium and a connective tissue layer that blends with underlying connective tissue of the scrotum, tunica vaginalis consist of visceral layer and parietal layer, When the testis is removed from the scrotum, the parietal layer of the tunica vaginalis remains attached to the inner surface of the scrotum, while the visceral layer, remains associated with the (tunica albuginea) of the testis. 2. Tunica Albuginea: Is a solid capsule of dense irregular connective tissue. It consists of collagen fibers, a few elastic fibers, the tunica albuginea is continuous with connective-tissue trabeculae to formed the testis trabeculae or called septula testis. The septula testis divide the testicular parenchyma into a varying number of testicular lobules, each lobule containing one to four convoluted seminiferous tubules. The septula testis converges posteriorly in equine and Centrally in canine and ruminants to form the mediastinum testis. The mediastinum testis which is actually a thickened portion of the tunica albuginea, contains the rete testis.
Tunica vasculosa: it's constitute by branches of the testicular artery and a network of anastomosing veins. Interstitial Endocrine cells (Leydig cells): It's present as clusters located between the intertubular spaces of the testis. These cells are polyhedral and has spherical Euchromatic nucleus. Possessing Eosinophilic cytoplasm filled with smooth endoplasmic reticulum and mitochondria .Leydig cells produce testicular androgens (testosterone) under the influence of luteinizing hormone (LH). Among the main functions of testosterone are: - promotion of normal sexual behavior (libido). -Responsible for the appearance of secondary sexual characteristics. -control of spermatogenesis (together with follicle-stimulating hormone [FSH]). -the prenatal maintenance of the wolffian duct and its differentiation into the epididymis and ductus deferens.
Seminiferous tubule Seminiferous tubules: The convoluted seminiferous tubules in most mammals are tortuous with a diameter between 150 and 300 µm. They are lined by the stratified spermatogenic epithelium (germinal epithelium), surrounded by a lamina propria. The length of all seminiferous tubules in the testis of the adult bovine amounts to approximately 5000m. Histologically , the seminiferous tubules have three components:1 lamina propria, 2 sustentacular cells (Sertoli cells), and 3 spermatogenic cells. Sustentacular cell (Sertoli cell): The adult sertoli cells are irregularly outlined because it’s surrounded by spermatocytes set in pockets-like shape. - Sertoli cells are elongated cells, Their broad base rests on the basement membrane, while their apex extend upward to the tubular lumen. - It have oval or triangular nucleus is located in the basal portion of the cell, and contains a large nucleolus. -cytoplasm of Sertoli cells contain mitochondria, Golgi complex, abundant smooth ER, little rough ER, microtubules, microfilaments, and lysosomes. -approximately 20 sertoli cells are seen in a cross section of an adult seminiferous tubule.
Functions of Sertoli cells:- 1. supportive, and nutritive functions for the spermatogenic cells. 2. phagocytic function of residual bodies and degenerated cells. 3. Release the spermatozoa into the lumen of the seminiferous tubules (spermiation). 4. Secretory function: a. In embryo produce antiparamesonephric hormone(anti- Müllerian hormone), a glycoprotein that inhibit development of uterine tubes, uterus, and vagina in the male. b. In post puberty secrete : 1. testicular fluid to push the newly sperms from seminiferous tubules toward the testicular ducts. 2. androgen-binding protein: that acts to increase testosterone concentration within the seminiferous.(under control of FSH) 3. inhibin: that inhibit the secretion of FSH. 5. It formed the blood-testis barrier, which protects against immunologic attack.