Histology male reproductive System PDF

28 Tala Alhunaity Waqar Alfaqeer Ghada abu el ghanam  Male genital tract The idea of the male and female genital tract is as follows: These structures are responsible for producing the gametes, ova in females and sperm in males. These cells have half the tot...

28 Tala Alhunaity Waqar Alfaqeer Ghada abu el ghanam  Male genital tract The idea of the male and female genital tract is as follows: These structures are responsible for producing the gametes, ova in females and sperm in males. These cells have half the total number of chromosomes (1n amount of the genetic material). Gametes are produced from germ cells, which are located within the germinal epithelium. These cells contain 46 chromosomes , but they undergo meiosis. Meiosis: A process of cell division that reduces the chromosome number by half. The end product of meiosis is cells that have half the total number of chromosomes. When the gametes meet, they restore the 46 chromosomes, which is the first step in forming the embryo. The primary structures involved are ovaries in females and the testes in males. We also have other accessory structures that carry and help mature the gametes. Differences between males and females: 1. The testes in males are located outside the body, while the ovaries in females are located inside the body, specifically within the pelvis. 2. In males, there is communication between the urinary and the genital tracts at the urethra. However, in females, the urinary and the genital tracts are completely separate. Organs of the Male Genital Tract: 1. Testes: Produce sperm and male hormones. 2. Genital ducts: Responsible for sperm maturation. When sperm exit the testes, They are not yet fully mature. They undergo maturation as they pass through these ducts. 3. Accessory glands: Secrete fluids that contribute to the semen. 4. Penis: Eject the semen. Testis The testes are located outside the body within a skin sac called the scrotum, which provides protection and maintains an optimal temperature. This temperature regulation is crucial for sperm maturation. In some males, the testicles fail to descend and remain inside the body at birth, a condition known as cryptorchidism. If not detected and treated early, this condition can lead to infertility. Therefore, it is important to examine baby boys immediately after birth to confirm the presence of both testes. If the testicles are undescended, surgical intervention is required to prevent future fertility issues. Each testis is surrounded and protected by a dense connective tissue capsule called the tunica albuginea. This capsule extends inward to form fibrous partitions called septa, which divide the testis into approximately 250 pyramidal compartments known as testicular lobules. Within these lobules are the seminiferous tubules, the most critical structures for sperm production. Seminiferous tubules: The seminiferous tubules are lined with specialized germinal epithelium (stratified) responsible for producing immature sperm cells. These sperm cells are not yet fully mature and complete their maturation in the epididymis. Between the seminiferous tubules lies sparse connective tissue known as interstitial tissue, which contains fibroblasts, lymphatics, fenestrated capillaries, and most importantly, Leydig (interstitial) cells. Leydig cells, which are rich in lipid droplets and have a large round central nucleus, play a key role in producing testosterone during puberty. Testosterone Testosterone is a vital hormone that spikes during puberty, leading to the development of secondary male sexual characteristics such as facial hair, a deeper voice, coarse vocal texture, and the prominence of the thyroid cartilage (Adam’s apple). The production of testosterone is regulated by the hypothalamic-pituitary-gonadal axis: 1. The hypothalamus releases gonadotropin-releasing hormone (GnRH), signaling the anterior pituitary gland. 2. The anterior pituitary responds by secreting: Luteinizing hormone (LH)، also known as interstitial cell-stimulating hormone (ICSH) in males. Follicle-stimulating hormone (FSH). LH stimulates Leydig cells to produce testosterone, which influences secondary sexual organs and accessory glands. FSH stimulates Sertoli cells within the seminiferous tubules to produce androgen- binding protein (ABP), which supports spermatogenesis (sperm production). Sertoli cells play a critical role in protecting and nurturing developing sperm cells, making them essential for germ cell development. Sperm Transport and Maturation Sperm production occurs within the seminiferous tubules, which are organized as loops connected by short highly torturous, narrow segments called straight tubules. These straight tubules lead to a network of channels in the testis called mediastinum testis(housing rete testis), where sperm is collected. From the rete testis, sperm are transported via efferent ductules to the head of the epididymis, a worm-like structure that caps the testes. The epididymis is divided into a head, body, and tail. Here, sperm undergo their final maturation to become fully functional. At its distal end, the epididymis connects to the ductus deferens, which carries mature sperm toward the urethra for ejaculation. This cross-section of a seminiferous tubule reveals its structural organization and the types of cells present: - Spermatogenic Epithelium: A specialized stratified epithelium responsible for sperm production. - Basement Membrane: The seminiferous tubule is surrounded by a fibrous connective tissue (CT), with the innermost layer containing flattened, smooth muscle-like myoid cells(peritubular). These cells facilitate weak contractions that help propel the products of spermatogenesis out of the tubule. Two Main Cell Types in the Seminiferous Tubule : Sertoli Cells: ( most important) ▪ Large, non-dividing cells that provide physical and metabolic support for the developing sperm cell precursors. ▪ Sertoli cells make contact with all cells of the spermatogenic lineage and form tight junctions between them. These junctions help create the blood-testis barrier, which protects developing sperm from immune system detection. This barrier is crucial because, during meiosis, sperm cells (46 chromosomes) become haploid (containing 23 chromosomes), and the immune system may recognize them as foreign(non self) potentially triggering an immune response. The Sertoli cells prevent this by isolating the basal compartment from the apical compartment (where sperm develop). Spermatogenic Lineage: ▪ These cells are in various stages of development, ranging from progenitor cells to mature sperm. They are constantly dividing and differentiating. ▪ The spermatogenic cells undergo several stages of development: spermatogonia (stem cells), primary spermatocytes, secondary spermatocytes, spermatids, and finally mature sperm. Function of Sertoli Cells: Sertoli cells are columnar epithelial cells that perform various important functions: They nourish and support the spermatogenic cells. They divide the seminiferous tubules into two compartments: basal (closest to the basement membrane) and adluminal (toward the lumen). All cells in the spermatogenic lineage are closely associated with Sertoli cells, receiving both metabolic and physical support. Sertoli cells adhere to the basal lamina and extend apically toward the lumen. They contain abundant SER, some RER, well-developed Golgi apparatus, mitochondria, and lysosomes. Their nuclei are typically ovoid or triangular in shape, euchromatic, and have prominent nucleoli. Sertoli cells form tight junctions between their basolateral membranes, creating the blood-testis barrier, which prevents immune cells from accessing the developing sperm. Spermatogenic Lineage and Stages of Spermatogenesis: Spermatogenesis begins at puberty and involves the proliferation and differentiation of spermatogonia, which are small round cells (~12 µm in diameter) located in the basal niche of the seminiferous tubules. These cells are closely associated with Sertoli cells. There are two main types of spermatogonia: Type A Spermatogonia: ▪ Type A dark: These cells are reserve stem cells that divide infrequently unless needed to replenish the population. ▪ Type A pale: These are active stem cells that enter meiosis and produce 4 cells one of them Type B spermatogonia (renewing stem cells). Type B Spermatogonia: These cells have more spherical and pale nuclei. They undergo the final mitotic division to produce primary spermatocytes, which are spherical with euchromatic nuclei and will continue through meiosis to eventually form sperm cells. Summary: Sertoli Cells: Provide structural and metabolic support to the developing sperm cells, maintain the blood-testis barrier, and regulate the progression of spermatogenesis. Spermatogenic Lineage: Composed of spermatogonia and their differentiated forms (primary spermatocytes, secondary spermatocytes, spermatids, and sperm cells). The main function of spermatogonia is the proliferation and production of immature sperm cells. Spermatogenesis is a complex and highly regulated process that begins at puberty and continues throughout life, ensuring the continuous production of male gametes (sperm). Notes: ♠ The blood-testis barrier is vital for preventing immune system attacks on developing sperm, which have different genetic makeup (haploid) compared to the body’s diploid cells. ♠ The distinction between Type A dark and Type A pale spermatogonia is crucial for understanding stem cell dynamics and the ongoing replenishment of the stem cell population. Spermatogenesis is the process of sperm cell production that takes place in the seminiferous tubules of the testes. It begins with the formation of primary spermatocytes, which are the largest cells found in the germinal epithelium of the seminiferous tubules. These cells are produced from mitosis and contain 46 chromosomes (2n), making them diploid. The primary spermatocytes then undergo meiosis I, which results in two secondary spermatocytes, each with half the number of chromosomes (23 chromosomes or 1n, haploid) and double the amount of genetic material. These secondary spermatocytes are slightly smaller than the primary spermatocytes and have a short lifespan. They immediately enter meiosis II, which produces four haploid spermatids, each with 23 chromosomes (1n), representing half the number of chromosomes and genetic material of the original cell. At this point, spermatogenesis is complete, and the spermatids enter the final maturation phase, called spermiogenesis, which occurs in the epididymis. Final Maturation of Sperm Spermiogenesis is the final stage of sperm production. Unlike spermatogenesis, spermiogenesis does not involve cell division, but it is a temperature-sensitive process where haploid spermatids differentiate into mature spermatozoa. During this phase, the spermatids undergo several key changes: Acrosome formation: A cap-like structure forms over the sperm head, containing enzymes necessary for fertilization. Nuclear condensation and elongation: The nucleus becomes more compact and elongates in preparation for its role in fertilization. Flagellum development: The spermatid develops a tail (flagellum) that enables motility. Loss of excess cytoplasm: Most of the cytoplasm is discarded, streamlining the sperm for efficient movement. The mature spermatozoa are now capable of motility and are released from the Sertoli cells into the lumen of the seminiferous tubules. Role of the Epididymis in Sperm Maturation After spermatogenesis, the spermatozoa enter the epididymis, a highly coiled tube where they undergo further maturation to become fully functional sperm. This maturation process is critical for the development of motility, allowing the sperm to move. The sperm are transformed into specialized, streamlined structures with a flagellum extending from one end. The epididymis also serves as a transport site for immature sperm and the fluids from the seminiferous tubules. In the epididymis, the Sertoli cells continue to support the sperm, ensuring their development into fully functional cells. Stereocilia (structures resembling microvilli) on the principal cells of the epididymis are involved in absorption and help maintain the environment necessary for sperm maturation. It’s important to note that while the stereocilia in the epididymis are involved in sperm maturation, stereocilia in the inner ear are involved in auditory functions (hearing detection). Summary of Spermiogenesis: Spermiogenesis is the final stage of sperm production, where spermatids differentiate into mature sperm. No cell division occurs during spermiogenesis. Spermatids undergo significant structural changes: formation of the acrosome, nuclear condensation and elongation, flagellum development, and cytoplasmic reduction. The fully matured spermatozoa are released into the seminiferous tubules and eventually transported through the epididymis, where they gain motility. Epididymis Structure and Location: -The epididymis is a long, coiled duct measuring 4–5 meters in length, encased in connective tissue. -It is situated within the scrotum. -The epididymis consists of three distinct regions: Head: where the efferent ductules enter. Body: the middle portion of the epididymis. Tail: which connects to the ductus deferens. Function: As sperm travel through the epididymis, they undergo maturation and acquire the ability to fertilize an egg. Epithelium: The epididymis is lined with pseudostratified columnar epithelium, which is specialized in various functions: Principal cells: These are columnar cells with long stereocilia. These cells secrete glycolipids and glycoproteins that help absorb residual materials and cellular debris. Small round stem cells: These are located among the principal cells, though their exact function is less defined. Muscle Layers: The epididymis is surrounded by several layers of smooth muscle cells, arranged in inner and outer longitudinal layers. The contraction of these muscle layers aids in propelling sperm rapidly along the duct, facilitating the movement of sperm through the epididymis and its eventual emptying. Sperm Maturation and Transport: After maturation, sperm move from the tail of the epididymis into the vas deferens for further transport. Ductus (Vas) Deferens The vas deferens is a long, straight tube with a thick muscular wall and a small lumen. It is responsible for carrying sperm from the epididymis to the pelvis. Along the way, sperm will mix with secretions from accessory glands, specifically the seminal vesicles and prostate gland, before eventually being expelled through the penis during ejaculation. The vas deferens continues toward the prostatic urethra, where it empties. Its mucosa is slightly folded longitudinally, and the lamina propria contains many elastic fibers. The epithelial lining is pseudostratified, with some cells featuring sparse stereocilia. The muscularis of the vas deferens is thick, consisting of longitudinal inner and outer layers, and a middle circular layer. These muscular layers contract strongly during ejaculation to propel sperm upward. Each vas deferens passes over the urinary bladder, where it enlarges into an ampulla. The ampulla joins with the ducts of the seminal vesicles to form the ejaculatory ducts. The ejaculatory ducts then empty their contents into the prostatic urethra. Accessory Glands 1. Seminal Vesicles The seminal vesicles are paired glands that produce secretions that are mixed with sperm during ejaculation to form semen. The vesicles are highly tortuous tubes enclosed by a connective tissue capsule. The mucosa of the seminal vesicles is made up of complex folds, lined with simple or pseudostratified columnar epithelial cells, which are rich in secretory granules. The lamina propria contains elastic fibers and is surrounded by smooth muscle with inner circular and outer longitudinal layers. These muscles help expel the gland's contents during ejaculation. The seminal vesicles are exocrine glands that rely on testosterone for their o function. 2. Prostate Gland The prostate is a dense, glandular organ located below the bladder, surrounding the urethra. The prostate consists of tubuloacinar glands embedded in a dense fibromuscular stroma. The smooth muscle in the stroma contracts during ejaculation. The ducts from the individual glands within the prostate converge and empty directly into the prostatic urethra, which runs through the center of the prostate. The prostate is divided into three major zones: the transition zone, central zone, and peripheral zone. The glandular epithelium lining the prostate is either simple or pseudostratified columnar. The prostate secretes fluid that contains various glycoproteins, enzymes, and small molecules, such as prostaglandins, which are stored until ejaculation. Ejaculation Process and Formation of Semen The vas deferens ascends into the pelvis and curves around the posterior aspect of the urinary bladder, where it enlarges into an ampulla. The ampulla merges with the ducts of the seminal vesicles, and together, they open into the prostatic urethra. This is where the sperm, now mixed with the seminal vesicle secretion, is deposited. The seminal vesicle secretion is crucial for sperm survival and motility. In addition to the seminal vesicle secretion, the prostate gland also contributes its fluid, which is rich in enzymes and other molecules. This mixture of sperm, seminal vesicle secretion, and prostate fluid forms the final product known as semen. Meanwhile, the bulbourethral glands secrete a clear, mucus-like fluid that is released into the urethra to help neutralize any acidic urine residue and lubricate the passage. All of these secretions combine in the prostatic urethra and are then expelled through the penis during ejaculation. The prostate can sometimes undergo hyperplasia (proliferation of tissue), which may be either benign (benign prostatic hyperplasia, or BPH) or malignant (prostate cancer). Regardless of the type of hyperplasia, the prostate tissue increases in size, which can put pressure on the urinary bladder. This pressure can lead to a reduction in bladder capacity, causing urinary retention and an increased urgency to urinate. Males with an enlarged prostate may experience more frequent and urgent urination as a result of this pressure. ‫تمت كتابة هذا الشيت صدقة جارية عن روح والدة زميلنا عمرو رائد من دفعة تيجان‬ ‫دعواتكم لها بالرحمة والمغفرة‬ ‫‪Thank you‬‬