Accessory Sex Glands
The accessory glands are located along the pelvic portion of the urethra, with ducts which
empty their secretions into the urethra. They include the vesicular glands, the prostate gland
and the bulbourethral glands .They contribute greatly to the fluid volume of semen. In
addition, their secretions are solution of buffers, nutrients ,and other substances needed to
assure optimum motility and fertility of semen.
Vesicular Glands
The vesicular glands (sometimes called seminal vesicles) are a pair of lobular glands that are easily
that identified because of their knobby appearance. They have been described as having the
appearance of a "cluster of grapes." They are of similar length in the bull, boar ,and stallion (35 to 15
cm),but the width and thickness of the vesicular glands of the bull is approximately half that of the
boar and stallion. They vesicular glands of the ram and buck are much smaller, being about 4 cm in
length .The excretory ducts of the vesicular glands open near the bifurcation where the ampulla
merge with the urethra. In bulls, they contribute well over half of the total fluid volume of semen ,and
appear to make a substantial contribution in other species. Several organic compounds found in
secretion of the vesicular glands are unique in that they are not found in substantial quantities
elsewhere in the body. Two of these compounds, fructose and sorbitol ,are major sources of energy
for bull and ram spermatozoa but are found in lower concentration in boar and stallion .Both
phosphate and carbonate buffers are found in these secretions and are important in that they protect
against shifts in the pH of semen .Such shifts in pH would be detrimental to spermatozoa.
Prostate Gland
The prostate is a single gland located around and along the urethra just posterior to the excretory
ducts of the vesicular glands. A prostate body is visible in excised tracts and can be palpated in bulls
and stallions.In rams, all of the prostate is embedded in urethra muscles as is part of this glandular
tissue in bulls and boars. It makes a small contribution to the fluid volume of semen in most species
studied .However ,some report that the contribution of the prostate gland is at least as substantial as
that of the vesicular glands in boars. The prostate of the boar is larger than that of the bull. The
secretions of the prostate are high in inorganic ions with sodium, chlorine, calcium, and magnesium all
in solution.
Bulbourethral Glands
The bulbourethral (Cowpers)glands are a pair of glands located along the urethra near the point
where it exits from the pelvis. They are about the size and shape of walnuts in bulls, but are much
larger in boars. In bulls, they are embedded in the bulbospongiosum muscle .They contribute very
little to the fluid volume of semen. In bulls, their secretions flush urine residue from the urethra
before ejaculation. These secretions are seen as dribbling from the prepuce just before copulation. In
boars, their secretions account for that portion of boar semen which coagulates. This strained from
boar semen before it is used for artificial insemination. During natural service ,the white lumps
formed by coagulation may prevent semen from flowing back through the cervix into the vagina of
sows.