HISTOLOGY Male Reproductive System 2024-01.pdf

Histology of Male reproductive tract Author: Dr. Diana Vera Estrada Modified by Dr. Flores and Dr. Guzmán Learning Objectives Identify the histological characteristics and functions of: - Seminiferous tubules - Sertoli Cells - Leydig Cells Identify the histological characteristics - Intra/extra test...

Histology of Male reproductive tract Author: Dr. Diana Vera Estrada Modified by Dr. Flores and Dr. Guzmán Learning Objectives Identify the histological characteristics and functions of: - Seminiferous tubules - Sertoli Cells - Leydig Cells Identify the histological characteristics - Intra/extra testicular ducts - Epididymis, ductus deferens, ejaculatory duct - Bulbourethral Glands - Penis Understand the process of Spermatogenesis. The testes Function: Spermatogenesis Production of testosterone. As they descend into the scrotum, they carry with them a portion of the peritoneum → The tunica Vaginalis Tunica Albuginea = propria Dense irregular collagenous connective tissue Mediastinum testis - Lobuli Testis - 250 intercommunicating compartments Tunica Vasculosa Loose connective layer that contains blood vessels Spermatozoa are produced by the seminiferous epithelium of the seminiferous tubules. 1. 2. 3. 4. Tubuli Recti Rete Testis Efferent Ductules Ductus Epididymis Seminiferous tubules Lobules Specialized stratified epithelium called germinal or spermatogenic epithelium The basement membrane of this epithelium is covered by fibrous connective tissue, with an innermost layer containing flattened, smooth muscle-like myoid cells: allowing weak contractions of the tubule. The germinal epithelium consists of two types of cells: Sertoli cells Spermatogenic cells: Spermatogonia, primary spermatocytes, secondary spermatocytes, spermatids, spermatozoa The tunica propria (albuginea) and the seminiferous epithelium are separated from each other by a welldeveloped basal lamina. Photomicrograph of the capsule of a monkey testis and cross-sectional profiles of seminiferous tubules Lobules converging at rete testis The dense capsule of the testis Sertoli cells Function: SUPPORTING / SUSTENTACULAR CELLS These cells do not replicate after puberty. They are columnar cells with extensive apical and lateral processes that surround the adjacent spermatogenic cells and occupy the spaces between them. Myoid cells (M) and fibroblasts (F) spermatids (ES), late spermatids (LS), Sertoli cells (SC). Sertoli cells Functions: Physical and nutritional support of the developing germ cells. Phagocytosis of cytoplasm eliminated during spermiogenesis Tight junctions between adjacent Sertoli cells form a blood-testis barrier and isolate gametes from autoimmune attack Synthesis and secretion of inhibin, a hormone that inhibits the release of FSH by the anterior pituitary Synthesis and release (during embryogenesis) of antimüllerian hormone, which suppresses the formation of the müllerian duct. Temperature sensitive; decrease sperm production and inhibin B with increase of temperature Seminiferous tubules and tunica albuginea Microscopic image of cross section of testicle (Ladewig trichrome stain, 100x magnification) Large polygonal eosinophilic cells. Lipofuscin pigments. They are steroidsecreting cells Elaborate sER feature that accounts for eosinophilia. Leydig Cells Secrete testosterone in the presence of LH; testosterone production unaffected by temperature Leydig Cells Production of: Testosterone Insulin-like factor 3 (INSL 3). Early fetal life: secretion of testosterone is essential for the normal development of the gonads in the male fetus. Then these cells undergo a period of inactivity beginning at about 5 months of fetal life. At puberty: when Leydig cells are exposed to gonadotropic stimulation, they again become androgen-secreting cells and remain active throughout life. Low-magnification photomicrograph of an H&E–stained section of a human testis shows seminiferous tubules and the tunica albuginea. b. A higher magnification of the previous specimen shows several seminiferous tubules. Seminiferous tubules Microscopic image of cross section of testicle (Ladewig trichrome stain, 100x magnification) Spermatogenic cells: Most of the cells composing the thick seminiferous epithelium are spermatogenic cells in various stages of maturation Spermatogonia Primary spermatocytes Secondary spermatocytes Spermatids Spermatozoa Spermatogenic cells: Spermatogenesis Begins at puberty with spermatogonia. Full development takes 2 months. Occurs in seminiferous tubules. Produces spermatids that undergo spermiogenesis (loss of cytoplasmic contents, gain of acrosomal cap) to form mature spermatozoa. Two processes: - Spermatocytogenesis: Spermatogonia and spermatocytes - Spermiogenesis: Spermatid Spermatocytogenesis (Differentiation of Spermatogonia) Spermatogonia are small, diploid germ cells located in the basal compartment of the seminiferous. At puberty they become influenced by testosterone to enter the cell cycle. Testis: seminiferous tubules (transverse section). Stain: hematoxylin and eosin (plastic section). ×80. Primary spermatocytes are the largest cells of the seminiferous epithelium, and most abundant. Secondary spermatocytes are relatively small cells, and because they are present for less than 10 hours, they are not readily seen in the seminiferous epithelium. They quickly enter the second meiotic division, forming two haploid (1n DNA) spermatids. Differentiation of Spermatids (Spermiogenesis) Spermatids are small, round haploid cells. (NO further division occurs) During their transformation into spermatozoa, they accumulate hydrolytic enzymes, rearrange and reduce the number of their organelles, form flagella and associated skeletal apparatus, and shed some of their cytoplasm → Form mature sperm (haploid) The four phases of spermiogenesis are the Golgi phase, cap phase, acrosomal phase, and maturation phase. Structure of Spermatozoa The spermatozoa (sperm) (~65 µm). Each spermatozoon is composed of a head, housing the nucleus, and a tail. The acrosomal Cap: Hyaluronidase Neuraminidase Acid phosphatase Acrosin (trypsin-like protease) Scanning electron micrograph of human spermatozoa. The entire spermatozoon is shown: head region (HR), middle piece (MP), principal piece (PP), and end piece (EP) (×650). Inset, Head, neck (NK), and middle piece (MP) (×15130) Spermatogenesis Cycle of the Seminiferous Epithelium It would require about 4 cycles (each 16 days long), or approximately 64 days, for a spermatogonium produced by a stem cell to complete the process of spermatogenesis. It would require approximately 12 days for the spermatozoon to pass through the epididymis. Approximately 300 million sperm cells will be produced daily in the human testis. Newly released sperm cells are nonmotile and are carried from the seminiferous tubules in a fluid secreted by the Sertoli cells. (Can’t fertilize an oocyte.) Intratesticular ducts Extratesticular ducts In the distal portion of the epididymis, they are stored before ejaculation. Only after they enter the female reproductive system do spermatozoa become capacitated (i.e., become capable of fertilization). Intratesticular ducts Extratesticular ducts Tubuli recti: Lined only by Sertoli cells. Rete Testis: lined by simple cuboidal or low columnar epithelium. The efferent ductules: Patches of nonciliated cuboidal cells alternating with ciliated columnar cells. The ductus epididymis 3 regions: head, body, and tail. Lumen of the epididymis: lined by a pseudostratified epithelium composed of two cell types : Short basal cells. Tall principal cells Photomicrograph of the epididymis in a monkey, showing smooth muscle (SM), principal cells (PC), epithelium (Ep), and basal cells (BC) (×270). Ductus Deferens (Vas Deferens) Stereociliated pseudostratified columnar epithelium. The lumen of the ejaculatory duct is lined by a simple columnar epithelium. The ejaculatory duct has no smooth muscle in its wall, the fibromuscular tissue of the prostate substitutes for it. Ejaculatory Duct Seminal Vesicles Prostate Gland Lined by simple to pseudostratified columnar epithelium Photomicrograph of the monkey seminal vesicle, showing spermatozoa (Sz), lumen (L), basal cells (BC), and columnar cells (CC) (×270). Pseudostratified columnar epithelium Each columnar cell has numerous short microvilli and a single flagellum projecting into the lumen of the gland Function: Produce a yellow, viscous, fructose-rich seminal fluid that constitutes 70% of the volume of semen ( energy source). Bulbourethral Glands Penis The bulbourethral glands (Cowper glands) are small (3 to 5 mm in diameter) and are located at the root of the penis. The epithelium of these compound tubuloacinar glands varies from simple cuboidal to simple columnar. Corpora cavernosa Tunica albuginea Corpus spongiosum All are composed of vascular cavernous tissue and small amounts of surrounding smooth muscle The prepuce, which is lined by a mucous membrane, a moist, stratified squamous nonkeratinized (slightly keratinized) epithelium. Bibliography: Anthony L. Mescher. “Junqueira’s Basic Histology Text and Atlas”, 14th edition. Lange McGraw Hill Michael H. Ross. Histology and text Atlas with correlated cell and molecular biology.6th edition. Lippincott Williams and Wilkins. Leslie P. Gartner PhD. Male Reproductive System. Textbook of Histology. 2017. 4TH Edition. Elsevier. William K. Ovalle, PhD. Male Reproductive System. Netter’s essential histology. Second edition. Elsevier.