Structure of the male reproductive system

[Luis Fok]

The male reproductive system includes the penis, scrotum, testes, epididymis, vas deferens, prostate, and seminal vesicles.

The penis and the urethra are part of the urinary and reproductive systems.
The scrotum, testes (testicles), epididymis, vas deferens, seminal vesicles, and prostate comprise the rest of the reproductive system.

The penis consists of the root (which is attached to the lower abdominal structures and pelvic bones), the visible part of the shaft, and the glans penis (the cone-shaped end). The opening of the urethra (the channel that transports semen and urine) is located at the tip of the glans penis. The base of the glans penis is called the corona. In uncircumcised males, the foreskin (prepuce) extends from the corona to cover the glans penis.
The penis includes three cylindrical spaces (blood-filled sinuses) of erectile tissue. The two larger ones, the corpora cavernosa, lie side by side. The third sinus, the corpus spongiosum, surrounds most of the urethra. When these spaces fill with blood, the penis becomes large and rigid (erect).
The scrotum is the thick-skinned sac that surrounds and protects the testes. The scrotum also acts as a climate-control system for the testes because they need to be slightly cooler than body temperature for normal sperm development. The cremaster muscles in the wall of the scrotum relax to allow the testes to hang farther from the body to cool or contract to pull the testes closer to the body for warmth or protection.
The testes are oval bodies that average about 1.5 to 3 inches (4 to 7 centimeters) in length and 2 to 3 teaspoons (20 to 25 milliliters) in volume. Usually the left testis hangs slightly lower than the right one. The testes have two primary functions:

Producing sperm (which carry the man