Male Reproductive System: Anatomy and Function

• The male reproductive system includes the testes, epididymis, vas deferens, ejaculatory ducts, seminal vesicles, bulbo-urethral glands (Cowper's glands), prostate, scrotum, and penis.

Testes

• Testes are a pair of male reproductive glands that produce sperm and the male hormone testosterone.
• Sperm transport occurs through the epididymis, vas deferens, and ejaculatory ducts into the prostatic part of the urethra.
• Associated glands like seminal vesicles, prostate, and bulbourethral glands secrete fluids into the urethra to nourish sperm and provide a liquid medium for semen.
• Testes, epididymis, and parts of the vasa deferentia are located outside the pelvic cavity.
• The remaining vasa deferentia, seminal vesicles, ejaculatory ducts, and prostate reside inside the pelvic cavity.
• Bulbourethral glands are in the deep perineal pouch.

Perineum

• The perineum is the diamond between the pelvic diaphragm and the legs, including the anus, and in females, the vagina.

Testes Shape and Position

• Testes are oval-shaped and have a rubbery consistency.
• Vertical measurement of the testes is 4-5 cm, antero-posterior measurement is 3 cm, breadth is 2.5 cm, and weight is 10-14 grams.
• Presenting parts of the testes include upper/lower poles, anterior/posterior borders, and medial/lateral surfaces, lying obliquely in the scrotum.
• Testes are suspended in the scrotum by the spermatic cord
• The left testis is typically positioned 1 cm lower than the right due to the left spermatic cord being longer.

Testes Poles

• The upper pole of the testes is directed forwards and laterally, overlapped by the epididymis head, and connected to efferent ductules.
• The upper pole has an appendix of the testis: a remnant of the paramesonephric duct (Mullerian duct).
• The lower pole is directed backwards and medially, attached to the scrotal wall by the scrotal ligament, a remnant of the gubernaculum testis.

Testes Borders and Surfaces

• The anterior border is rounded and convex, covered by tunica vaginalis, and the posterior border is broad and flat, not covered by tunica vaginalis.
• The posterior border gives attachment to the spermatic cord in the upper part and relates to the epididymis postero-laterally and vas deferens postero-medially.
• Medial surface is smooth and convex, while the lateral surface is smooth and convex, overlapped by the epididymis.
• The epididymis is separated from the testis by a semilunar recess of tunica vaginalis, forming the sinus of the epididymis, which helps determine the testis's side.

Epididymis

• The epididymis is a comma-shaped body, a long and coiled tube attached to the posterior margin of the testis.
• This consists of head, body, and tail.
• The epididymis head is attached to the upper pole of the testis by 12-20 efferent ductules that coil to form the head.
• The epididymis sometimes has an appendix remnant of the cephalic part of the mesonephric duct (Wolffian duct).
• The body and tail are a single, highly coiled duct attached to the testis posterolaterally, and attached to the testis posterolaterally
• The epididymis tail attaches to the lower pole through loose connective tissue and continues as the vas deferens.
• Function of Epididymis: temporary storage and maturation of sperm cells

Testes Coverings

• The testis has three coverings which collectively form its capsule: tunica vaginalis, tunica albuginea, and tunic vasculosa, with layers of the scrotal wall positioned outside.
• The tunica vaginalis is a serous sac derived from the processus vaginalis that covers the testis and epididymis, except for the posterior aspect of the testis.
• Consists of 2 layers: parietal and visceral.
• The parietal layer lines the innermost layer of the scrotal wall, and the visceral layer covers the front and sides (medial and lateral surfaces) of the testis and epididymis.
• The two layers have a potential space containing a thin film of fluid.
• On the lateral aspect, the visceral layer dips into the space between the testis and epididymis to form the sinus of the epididymis, aiding in side determination.
• Tunica albuginea is a thick, fibrous layer of dense collagen fibers that projects from the testis's posterior margin into the interior as a septum called the mediastinum testis.
• Blood vessels and lymph traverse this septum.
• Fibrous septae, called septulae testis extend forward and laterally, dividing the testis into 200-300 compartments called lobules.
• Each lobule contains 2-3 convoluted seminiferous tubules that produce sperm.
• Near the mediastinum, the convoluted tubules merge into straight seminiferous tubules, which enter the mediastinum testis to form the rete testis.
• The rete testis connect to 12-20 efferent ductules that leave the testes at the upper pole.
• Efferent ductules become highly convoluted to form the epididymis head, and all tubules forming the head are joined by connective tissue
• Continues as body

Tunica Vasculosa

• Tunica vasculosa lies deep to tunica albuginea that consists of a capillary plexus from the branches of the testicular artery.
• Slender branches from the capillary plexus enter the lobules along the septulae testis and supply seminiferous tubules.

Testicular Artery

• The testicular artery stems off of abdominal aorta at the L2 level, entering the deep inguinal ring and running in the spermatic cord.
• At the posterior border of the testis, it splits into branches, which enter the mediastinum testis to form the tunica vasculosa.
• Testicular supply also comes from the artery to the vas deferens and the cremasteric artery.
• The artery to the vas deferens is a branch of the superior or inferior vesical arteries
• Cremasteric artery is a branch of the inferior epigastric artery.

Venous Drainage of Testes

• Testicular veins form a venous network called the pampiniform plexus.
• At the superficial inguinal ring, 4 plexus veins form.
• At the deep inguinal ring, they form 2 which further up turn into one vein.
• The right testicular vein drains into the IVC, and the left drains into the left renal vein.
• Varicocele is a condition, where the pampiniform plexus of veins becomes tortuous and dilated, which the spermatic cord feels like when palpated.
• Varicocele left-side commonness is due to the left testicular being longer, opening at a right angle into the left renal vein, and passing posterior to the descending colon.
• Tumors of the left kidney may grow along the left renal vein blocking the testicular vein opening.
• Scrotal temperature rising because of varicocele may interfere with spermatogenesis.

Testicular Lymph Nodes

• Lymphatic drainage occurs through preaortic and para-aortic (lateral aortic) lymph nodes on, the posterior abdominal wall.
• These includes the testis and epididymis.
• Testicular cancer may only make itself known through such lymph node enlargement.

Testicular Nerve Supply

• The nerve supply is via sympathetic efferent fibers which pass through the coeliac and testicular plexuses.
• Afferent fibers travel in the same segments of the spinal cord through less splanchnic nerves.
• Testicular pain is referred to the umbilical region because of segmental innervations (T10).

Testicular Thermoregulation

• Testicular temperature stands roughly 3 degrees lower than body temperature.
• Numerous scrotal sweat glands and a lack of subcutaneous fat aids temperature control.
• Dartos muscle contraction reduces scrotal skin surface area in cold conditions.
• The countercurrent heat exchange mechanism transfers heat from the testicular artery to the entwined venous plexus in the spermatic cord.
• Pre-cooled blood subsequently reaches the testis.

Epididymis Microanatomy

• Transverse sections of the epididymis reveal varied tubule sizes enclosed by connective tissue
• The tubules are lined with pseudostratified columnar epithelium resting on a base membrane
• There are cells with stereocilia for secreting and nourishing germ cells.
• A layer of circularly arranged muscle encases the tubules with plenty of spermatozoa in their lumen.

Testes Microanatomy

• The testes comprises a thick fibrous capsule of collagen called tunica albuginea.
• Septa extend inward in order to divide it into lobules featuring seminiferous tubules that are lined by stratified epithelium with 2 types of cells.
• Supporting (Sertoli) cells: slender elongated cells extending toward the tubule lumen with stained cytoplasm, oval nuclei and mechanical support for devoping germinal cells.
• Sertoli cells also aid in nourishment of spermatozoa.
• Spermatogenic cells: large cells arranged among Sertoli cells that lie on the basement membrane
• Daughter spermatogenic cells line inside one another towards the lumen
• The arrangement of spermatogenic cells from the basement membrane towards the lumen is as follows: spermatogonia cells, primary spermatocytes, secondary spermatocytes and spermatids
• Transformation of spermatogonia into spermatids is called Spermatogenesis
• Spermatids then undergo Spermiogenesis (forming spermatozoa which reside in attached Sertoli cells or tubular lumen)
• Interstitial connective tissue with blood vessels, fibers and lymphatics sit between the seminiferous tubules.
• Leydig cells: Special cells contained. They secrete androgen/testosterone.

Clinical Correlations

• Torsion of the testis is twisting or rotation of the spermatic cord within the scrotum, usually just above the upper pole of the testis.
• Torsion obstructs venous drainage, which leads to edema leading to arterial destruction.
• Testicular torsion is commonly seen in adolescents and calls for a surgical emergency. If untwisted necrosis of the entire testis is possible.
• Incision can reduce testicle rotation around the cord in the scrotum.

Hydrocele

• Hydrocele marks an excess of fluids in the persistent processes that distends testicles and may see indirect inguinal hernia
• This accumulation can be seen from visceral layers of the tunica vaginalis.
• Size contingent on processes.
• Confined testis extends the tunica vaginalis wall around it and is confined in the cord/spermatic cord if congenital.
• A congenital version of the condition means both may communicate and be visible with light in scrotal enlargement in a dark room

Hydrocele Fluid

• Hydrocele fluid, if blood (hematocele) or pus (pyocele), can be removed from the tunica vaginalis through a trocar or cut.
• Cannulas traverse dartos' muscle and superficial and spermatic layers (cremaster/internal).

Hematoceles Vs Hydroceles

• Newborn males typically may have peritoneal fluids that can accumulate up to their first year that may look inflamed but resolve. Transillumination differentiates hydroceles from hematoceles where blood accumulates from arteries or trauma.
• A "red glow" is usually seen in hydrocele, or that light is not transmitted, indicating another serious problem.

Carcinoma & Cysts

• Testicular carcinoma (seminoma) arises from germ cells and metastasizes to the retroperitoneal lumbar lymph nodes and can undergo spread to the mediastinal supralaviclular areas.
• Epididymal cysts can collect fluids and display as asymptomatic.
• Surgical fixes by removing to prevent growth.

Cryptochidism Vs Ectopy

• Ectopy may or may not follow normal paths and may also be located on the inguinal ring while cryptochidism shows descent.
• One can be usually unilateral and show in 3-4% of males.

Hypogonadism

The condition in which smaller balls and lack of developed characteristics, tall patients and low intelligence is apparent.

Spermatocele

• Symptomatic
• Small requiring generally no therapy.