As sperm move through the ductus deferens into the
ejaculatory duct, the contents of the seminal vesicles empty
into the ejaculatory ducts. This greatly increases the volume
of the ﬂ
uid discharged from the ductus deferens.
Describe the structure of the epididymis.
Trace the path of the ductus deferens.
What is the function of a seminal vesicle?
) is a
chestnut-shaped structure about 4 centimeters across and 3
centimeters thick that surrounds the proximal portion of the
urethra, just inferior to the urinary bladder. It is composed of
many branched tubular glands enclosed in connective tissue.
Septa of connective tissue and smooth muscle extend inward
from the capsule, separating the tubular glands. The ducts of
these glands open into the urethra.
The prostate gland secretes a thin, milky ﬂ uid. This alka-
line secretion neutralizes the fluid containing sperm cells,
which is acidic from accumulation of metabolic wastes from
the sperm cells. Prostatic ﬂ uid also enhances the motility of
sperm cells, which remain relatively nonmotile in the acidic
contents of the epididymis. In addition, the prostatic fluid
helps neutralize the acidic secretions of the vagina, helping to
sustain sperm cells that enter the female reproductive tract.
The prostate gland releases its secretions into the ure-
thra as smooth muscles contract in its capsular wall. As
this release occurs, the contents of the ductus deferens and
the seminal vesicles enter the urethra, which increases the
volume of the ﬂ
uid. Clinical Application 22.1 discusses the
effects of prostate enlargement.
part of the spermatic cord. It passes through the inguinal
canal, enters the abdominal cavity outside the parietal peri-
toneum, and courses over the pelvic brim. From there, it
extends backward and medially into the pelvic cavity,
where it ends behind the urinary bladder.
Near its termination, the ductus deferens dilates into a
portion called the
Just outside the prostate gland, the
tube becomes slender again and unites with the duct of a semi-
nal vesicle. The fusion of these two ducts forms an
which passes through the prostate gland and empties
into the urethra through a slitlike opening (see ± g. 22.4).
g. 22.4) are convoluted, saclike
structures about 5 centimeters long each attached to the
ductus deferens near the base of the urinary bladder. The
glandular tissue lining the inner wall of the seminal vesicle
secretes a slightly alkaline ﬂ
uid. This ﬂ
uid helps regulate the
pH of the tubular contents as sperm cells travel to the out-
side. The secretion of the seminal vesicle also contains
a monosaccharide that provides energy to the sperm
which stimulate muscular contrac-
tions of the female reproductive organs, aiding the move-
ment of sperm cells toward the egg cell.
Sperm in lumen of
Ductus (vas) deferens. (
) Micrograph of a cross
section of the ductus deferens (40×). (
) Light micrograph of the wall of
the ductus deferens (400×).
Secretory cells of the
Lumen of urethra
Light micrograph of the prostate gland (10×).