Male Genital System Anatomy

Study Notes

Male Genital System

The male genital system is divided into external and internal genitalia.

External Genitalia

Penis
- Has a fixed root and a body.
- Root of the penis is made up of three masses of erectile tissue:
  - Bulb of the penis
  - Right and left crura
  - The bulb is in the midline.
  - Each crus is attached to the side of the pubic arch.
  - The bulb continues forward into the body of the penis.
  - The two crura lie side-by-side in the dorsal part of the body.
- Body of the penis is composed of three cylinders of erectile tissue:
  - Corpora cavernosa
  - Corpus spongiosum
  - The corpus spongiosum expands to form the glans penis.
Scrotum
- An outpouching of the lower part of the anterior abdominal wall.
- Contains the testes, epididymides, and lower ends of the spermatic cords.
- The wall of the scrotum has three layers:
  - Skin
  - Superficial fascia
  - Spermatic fascia
  - Tunica vaginalis
Testis
- A firm, mobile organ located within the scrotum.
- Surrounded by a tough fibrous capsule called the tunica albuginea.
- From the inner surface of the capsule are fibrous septa that divide the organ into lobules.
- Each lobule contains one to three coiled seminiferous tubules.
Epididymis
- A firm structure behind the testis.
- Has a head, body, and tail (inferiorly).
- Is a coiled tube (approximately 20 ft or 6 m long).
- Main function is absorption of fluid.
- May add substances to seminal fluid to nourish maturing sperm.
Vas Deferens
- A thick-walled tube (approximately 18 inches or 45 cm long).
- Arises from the lower end (tail) of the epididymis.
- Passes through the inguinal canal.
- Emerges from the deep inguinal ring.
- Terminal part called the ampulla of the vas deferens.
- The inferior end of the ampulla narrows and joins the duct of the seminal vesicle to form the ejaculatory duct.

Internal Genitalia

Seminal Vesicles
- Two lobulated organs (approximately 2 inches or 5 cm long).
- Located on the posterior surface of the bladder.
- The terminal part of the vas deferens is on the medial side of each vesicle.
- Posteriorly, related to the rectum.
- Inferiorly, each narrows and joins the vas deferens of the same side to form the ejaculatory duct.
Ejaculatory Ducts
- Less than 1 inch (2.5 cm) long.
- Formed by the union of the vas deferens and the duct of the seminal vesicle.
- Pierces the posterior surface of the prostate.
- Opens into the prostatic part of the urethra.
- Drains seminal fluid into the prostatic urethra.
Prostate
- A fibromuscular glandular organ (approximately 1.25 inches or 3 cm long).
- Located between the neck of the bladder above and the urogenital diaphragm below.
- Surrounded by a fibrous capsule.
- The two ejaculatory ducts pierce the upper part of the posterior surface of the prostate.
- Produces a thin, milky fluid (containing citric acid and acid phosphatase).
- Added to the seminal fluid during ejaculation.
- The prostatic secretion is alkaline and helps to neutralize vaginal acidity.
Urinary Bladder
- Located immediately behind the pubic bones.
- Has a strong muscular wall.
- The empty bladder is pyramidal, with an apex, a base, and a superior and two inferolateral surfaces.
- Also has a neck.