Sperm cells pass through a series of ducts to reach the
outside of the body. After they leave the testes, the sperm
passes through the epididymis, ductus deferens, ejaculatory
duct, and urethra.
Epididymis
Sperm leave the testes through a series of efferent ducts
that enter the epididymis. Each
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epididymis is a long (about 6 meters) tube that is tightly coiled
to form a comma-shaped organ located along the superior and posterior
margins of the testes. When the sperm leave the testes, they are immature
and incapable of fertilizing ova. They complete their maturation process
and become fertile as they move through the epididymis. Mature sperm
are stored in the lower portion, or tail, of the epididymis.
Ductus Deferens
The ductus deferens, also called vas deferens, is a fibromuscular
tube that is continuous ( or contiguous) with the epididymis. It
begins at the bottom (tail) of the epididymis then turns sharply
upward along the posterior margin of the testes. The ductus deferens
enters the abdominopelvic cavity through the inguinal canal and
passes along the lateral pelvic wall. It crosses over the ureter
and posterior portion of the urinary bladder, and then descends
along the posterior wall of the bladder toward the prostate gland.
Just before it reaches the prostate gland, each ductus deferens
enlarges to form an ampulla. Sperm are stored in the proximal portion
of the ductus deferens, near the epididymis, and peristaltic movements
propel the sperm through the tube.
The proximal portion of the ductus deferens is a component of the
spermatic cord, which contains vascular and neural structures that
supply the testes. The spermatic cord contains the ductus deferens,
testicular artery and veins, lymph vessels, testicular nerve, cremaster
muscle that elevates the testes for warmth and at times of sexual
stimulation, and a connective tissue covering.
Ejaculatory Duct
Each ductus deferens, at the ampulla,
joins the duct from the adjacent seminal vesicle (one of the accessory
glands) to form a short ejaculatory duct. Each ejaculatory duct
passes through the prostate gland and empties into the urethra.
Urethra
The urethra extends from the urinary bladder to the external urethral
orifice at the tip of the penis. It is a passageway for sperm and
fluids from the reproductive system and urine from the urinary system.
While reproductive fluids are passing through the urethra, sphincters
contract tightly to keep urine from entering the urethra.
The male urethra is divided into three regions. The prostatic urethra
is the proximal portion that passes through the prostate gland.
It receives the ejaculatory duct, which contains sperm and secretions
from the seminal vesicles, and numerous ducts from the prostate
glands. The next portion, the membranous urethra, is a short region
that passes through the pelvic floor. The longest portion is the
penile urethra (also called spongy urethra or cavernous urethra),
which extends the length of the penis and opens to the outside at
the external urethral orifice. The ducts from the bulbourethral
glands open into the penile urethra.
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