Male Reproductive System Anatomy and Function

• The Male Reproductive System's histology is detailed.
• The specific objectives include the need to identify structures, describe histology and function, to identify cells, explain the blood testis barrier and describe the histology and function of the epididymis, vas deferens, seminal vesicles and prostate gland.
• Also included is to describe the histology penile urethra and the erectile tissues forming the penis.

Reproductive System Function

• Manufacturing spermatozoa
• Delivering semen to the female reproductive tract
• Producing male sex steroid hormones known as androgen

Male Reproductive System Components

• Testes
• Genital Excretory Ducts: Epididymis, Ductus Deferens, Ejaculatory Duct, Urethra
• Accessory Sex Glands: Seminal Vesicles, Prostate, Bulbourethral Glands
• Penis

Testis Development

• Testes develop retroperitoneal, during migration from the abdominal cavity.
• Each testis carries with it a serous sac known as the tunica vaginalis.
• The testes are enclosed in thick connective tissue capsule, called the tunica albuginea.
• Internal to the tunica albuginea is a vascular layer of the connective tissue called tunica vasculosa.
• The tunica albuginea thickens on the posterior surface as the mediastinum.
• Thin septa subdivide the organ into about 250 lobules.
• Within each lobule are found one to four seminiferous tubules.

Spermatogenesis

• Describes the production of sperm from primordial germ cells.

Spermiogenesis

• Describes the final differentiation process occurring in haploid male germ cells.
• Seminiferous tubules are long, extremely convoluted, and seen sectioned in different planes.
• These tubules are lined with several rows of highly specialized epithelium resting on a thin basement membrane.
• The seminiferous epithelium is composed of spermatogenic cells and sertoli cells/sustentacular cells.

Spermatogenic Cells

• Spermatogonia (SG) - Stem cells at the base.
• Primary Spermatocytes (PS) - Large dividing cells that undergo 1st meiotic division.
• Secondary Spermatocytes - Quickly undergo 2nd meiotic division; difficult to identify.
• Early Spermatids - Have round red nuclei.
• Late Spermatids - Have elongate dark nuclei cells with flagella and remain anchored to Sertoli cells.

Sertoli Cells

• Tall columnar or pyramidal cells, that form the basal lamina of seminiferous tubule.
• Nuclei are typically ovoid or triangular, euchromatic, and have a prominent nucleolus, distinguishing them from neighboring germ cells.

Sertoli Cells Functions

• Support, protect, and nourish other cells.
• Phagocytose cell debris discarded by spermatid.
• Secrete fluid to transport sperms out to ducts.
• Elaborate tight occluding junctions between their basolateral membrane.
• Formation of blood testis barrier in the semineferous tubule.
• Protection for developing sperm cells from autoimmune reactions and blood-borne noxious agents.

Interstitial Tissue

• Located between seminiferous tubules and consists of connective tissue containing fibroblasts, lymphatic and blood vessels.
• Interstitial connective tissue contains groups of epitheloid cells called interstitial cells of Leydig.
• Leydig cells are large, rounded or polygonal cells with granular eosinophilic cytoplasm and a distinct ovoid or wrinkled nucleus.
• These cells produce testosterone.

Clinical Aspects

• Interstitial cell tumors and Sertoli cell tumors are rare.
• Testicular cancer is common after puberty (95%).
• Immotile cilia syndrome results in immotile spermatozoa.
• Consequent infertility results from the lack of dynein and proteins required for ciliary and flagellar motility.
• Failure of descent of testes into the scrotum (cryptorchidism) maintains the testis at 37 degrees, inhibiting spermatogenesis.
• Malnutrition, alcoholism, and certain drugs cause alterations in spermatogonia, resulting in decreased sperm production.

Epididymis

• A long coiled duct (4-5 mm length) surrounded by connective tissue.
• It lies in the scrotum along the superior and posterior sides of each testis.
• It connects to the head where efferent ductules enter and connects its body and tail opening into the ductus deferens.
• The lining is pseudostratified columnar epithelium consisting of principal cells with non-motile stereocilia (long irregular microvilli) on surface.
• While sperm passes through the duct, sperm motile and their surfaces and acrosomes undergo final maturation.
• Few layers of smooth muscle cells, arranged as inner and outer longitudinal layers as well as circular in the tail.
• Clumps of spermatozoa are present in the lumen.

Vas Deferens

• Long, straight tube with a thick, muscular wall, and relatively small lumen.
• This continues towards the prostatic urethra where it empties.
• The mucosa is folded longitudinally.
• The Lamina propria contains many elastic fibers and inner lining of pseudostratified columnar cells with tall stereocilia.
• A small irregular lumen lined by pseudostratified columnar epithelium with underlying lamina propria.
• It has a thick muscle coat with three layers:
  • Inner longitudinal
  • Middle circular
  • Outer longitudinal.
• The outermost layer is adventitia composed of collagen fibers and containing blood vessels.

Vasectomy

• Very small incision is made through the scrotal skin near the two ducts.
• The vas is exposed, cut, and two ends are tied.
• Sperm are still produced, but they degenerate and are removed by macrophages in the epididymis.
• Inflammatory and other changes occur in the mucosa of the Epididymis.
• Any adverse effects are minimal.
• Reversal may be achieved surgically by reconnecting the two ends of each vas deferens, but this often fails to restore fertility.

Seminal Vesicle

• A highly tortuous tube, each 15 cm is length, enclosed by a connective tissue capsule.
• Each seminal vesicle is an elongated sac with a highly convoluted, irregular lumen.
• A section through the wall shows complex primary folds and innumerable thinner secondary folds frequently joined by anastomoses, forming many crypts and cavities.
• The epithelium is usually pseudostratified columnar epithelium composed of short basal cells and low columnar cells.
• Seminal vesicles are made up of a convoluted tubule enclosed by connective tissue.
• These have a thin layer of smooth muscle and an inner mucosa
• The mucosal lining is thrown into numerous folds that branch and anastomose to form a network.
• The lining epithelium is usually simple columnar or pseudostratified.

Prostate Gland

• The largest male accessory gland, pierced by the urethra and ejaculatory duct.
• Covered by a slender capsule composed of richly vascularized, dense irregular collagenous connective tissue interspersed with smooth muscle cells.
• It comprises compound tubuloalveolar glands.
• Each tubuloalveolar gland has its own duct that delivers the secretory product into the prostatic urethra.
• The glandular alveoli vary in size; lumens are wide and markedly irregular in larger alveoli.
• The epithelium is usually single to pseudostratified columnar.
• Alveloi may contain prostatic concretions (corpora amylacea) formed by concentric layers of coagulated secretions.
• These increase with age and may become calcified.
• The gland consists of glandular tissue embedded in a prominent fibromuscular stroma.
• The glandular tissue is in the form of follicles with serrated edges lined by columnar epithelium.
• Lumens may contain amyloid bodies.
• Follicles are separated by broad bands of fibromuscular tissue.

Penis

• Consists of erectile tissue, paired corpora cavernosa, and a single corpora spongiosum around the penile urethra.
• The structures are surrounded by tunica albuginea.
• The tissues are composed of vascular cavernous tissue and small amounts of surrounding smooth muscle and helicine arteries.
• Helicine arteries are central arteries in the corpora cavernosa, branching to form small coiling arteries that lead to the cavernous vascular space of erectile tissue.
• Arteriovenous shunts are formed between central arteries and dorsal veins.
• All three erectile tissues consist of many venous spaces lined with endothelium.
• Smooth muscle and connective tissue are continuous with surrounding tunics.