Male Genital Organs: Anatomy

• The male genital organs can be divided into external and internal

External Genital Organs

• Scrotum
• Penis

Internal Genital Organs

• Testis
• Epididymis
• Ductus Deferens
• Seminal vesicle
• Ejaculatory duct
• Bulbourethral gland
• Prostate gland
• Spermatic cord

Scrotum

• The scrotum contains layers
• Inside the layers, the testes, epididymis, and spermatic cord are located
• The layers of the scrotum, from superficial to deep, are:
  • Skin
  • Dartos layer
  • External spermatic fascia
  • Cremasteric fascia and muscle
  • Internal spermatic fascia
  • Tunica vaginalis testis, with parietal and visceral layers
• The Dartos smooth muscle is attached to the skin
• When contracted, it gives the scrotum its wrinkled appearance in cold conditions
• It helps regulate heat loss through the skin
• The cremaster muscle contracts when it is cold
• This pulls the testes closer to the body for warmth, which is necessary for viable sperm production
• The scrotum has a septum

Penis

• Common outlet for urine and semen
• The main copulatory organ
• The penis is typically 8-10 cm long, with the glans measuring about 3 cm
• The parts of the penis are the root, body, and glans
• The root of the penis is formed by 2 crura (right and left) and the bulb
• The crus penis is covered by the ischiocavernosus muscle
• The urethra passes through the bulb of the penis
• The bulb of the penis is covered by the bulbospongiosus muscle
• The Ischiocavernosus muscle forces blood from the crura to the distal part, which increases the turgidity of the penis and helps erection
• The bulbospongiosus muscle compresses the bulb, emptying residual urine and semen from the spongy urethra
• It assists erection by increasing pressure, which helps the enlargement and turgidity of the penis
• The Corpus Penis (body) is formed by the corpus cavernosum (double) and corpus spongiosum
• The Corpus Penis is the erectile, free part of the penis
• The Corpus Cavernosum has a trabeculated structure
• The Corpus Spongiosum contains elastic fibers
• The Urethra passes through the corpus spongiosum and opens to its tip at the external urethral orifice
• The tip of the corpus spongiosum is the glans penis, marked by the Corona of the glans
• The Prepuce, or foreskin, is circumcised skin that extends as the skin of the glans
• Trabeculae of the corpora cavernosa fill with blood, increasing turgidity and leading to erection.
• Ligaments of the penis: fundiform and suspensory ligaments
• Arteries supplying the penis originate from the internal pudendal artery
• Veins drain to the internal pudendal vein
• P.S. Fibers from S2-4 (pelvic splanchnic nn.) enable erection
• Symp. Fibres from L 1-2 cause ejaculation
• Pudental nerve innervates the skin and glans penis
• Lymph vessels drain into inguinal lymph nodes

Testis (orchis)

• Located in the scrotum
• Weighs 14 gm
• Large almond shape
• Testis form male germ cells (sperms) and hormones (testosterone)
• The testis are formed by lobules separated by septa testis
• Testicular arteries branch from the Abdominal aorta
• Veins form the pampiniform plexus, then the testicular vein
• The pampiniform plexus is part of the thermoregulatory system of the testis
• The plexus helps keep the testes at a constant temperature
• The right testicular vein drains to the IVC
• The left testicular vein drains to the left renal vein
• Lymphatics drain into lateral aortic and preaortic Lymph nodes
• During intrauterine life, the testis begin in the abdominal cavity then descend into the scrotum through the inguinal canal
• Structure of testis makes lobules with seminiferous tubules that produce spermatozoa
• Fluid from the seminiferous tubules goes in the order below:
  • Straight tubules
  • Rete testis
  • Efferent ductules
  • Epididymis (12-20)

Epididymis

• Comma-shaped organ in the scrotum, tube (L=6 meters)
• Epididymis has a head,body, and tail
• When sperm leave the testes, they are immature and incapable of fertilizing an ovum
• Sperm complete their maturation process and become fertile as they move through the epididymis
• Mature sperm are stored in the tail of the epididymis tail
• Vessels and nerves of the epididymis are the same as the testis

Ductus Deferens

• Ductus Deferens=deferent duct = vas deferens, is the part between the epididymis and ejaculatory duct
• Sperm are stored in the ductus deferens, near the epididymis
• Peristaltic movements move the sperm through this tube

Seminal Vesicle

• Located between the urinary bladder and rectum
• Seminal vesicles don't store sperm
• Excretory duct

Ejaculatory Duct

• The excretory duct of the seminal vesicle + ductus deferens becomes the ejaculatory duct
• The ejaculatory duct is 2.5 cm long and opens to the prostatic urethra under the prostatic utricle

Prostate gland

• Located in the pelvic cavity
• The base of the prostate gland is the urinary bladder
• The apex ends at the urogenital diaphragm
• The prostate gland has two lateral lobes and one middle lobe
• The glandular portion makes up 2/3 and the fibromuscular makes up 1/3 of the prostate gland
• Prostatic fluid provides 20% of the volume of semen (ejaculate)
• The prostate's secretions are thin, milky colored and alkaline
• The prostate enhances the motility of sperm

Bulbo-urethral Glands

• Bulbo-urethral Glands = Cowper glands
• The secreted fluid neutralizes the acidity of urine residue in the urethra
• The duct of bulbo-urethral glands opens to the spongy part of the urethra

Ejaculate Composition

• Ejaculate, Seminal fluid or semen contains:
  • Spermium
  • Prostatic secretions
  • Bulbourethral glands
  • Seminal vesicle
  • Small glands around the urethra
• The volume of semen in a single ejaculation is 1.5 to 6.0 ml

Spermatic Cord

• Spermatic cord contains deferent duct and vessels+nerves
• Courses from the deep inguinal ring to the posterior part of the testis is 15-20 cm length
• Contents:
  • Cremasteric artery
  • Genital branch of the genitofemoral nerve

Homologous Organs

• Female: Ovaries - Male: Testicles
• Female: Labium majus - Male: Scrotum
• Female: Clitoris - Male: Penis
• Female: Bartholin's glands - Male: Cowper glands
• Female: Paraurethral glands - Male: Prostate
• Female: Bulb of vestibule - Male: Corpus spongiosum penis