Vesicular Glands
This is a paired gland formerly called the seminal vesicle because it was erroneously believed to act as a reservoir for semen. Neither the dog nor the cat possess vesicular glands.
The secretion is more viscous than the prostatic secretion. Histologically these glands comprise serous and muscular layers together with a mucous membrane including tubular glands. The paired openings into the urethra are located on an elevated region known as the colliculus seminalis.17.3.1 Species variations
Horse (Figure 15.1): These large (15?5 cm), paired oval sacs extend cranially and dor- sally on either side of the urinary bladder. The wall consists of a serous outer layer, a middle muscular layer and an inner mucous membrane containing tubular glands. The necks of the vesicular glands lie beneath the prostate gland and open together on the colliculus seminalis.
Ox (Figure 15.4): The paired glands are irregular-shaped lobulated masses. Though smaller than those of the pig, they are similar sized to those of the horse and take several years before reaching full size. Each gland consists of a thick-walled tube twisted and folded on itself. Compound glands are located in the wall of the tube, which opens on the colliculus seminalis.
Pig (Figure 15.7): The paired vesicular glands are very large and pyramidal in shape. They are lobulated and firm to the touch. There are many collecting ducts that combine to form a pair of collecting ducts that open at the colliculus seminalis. The large amount of secretion together with that of the bulbourethral gland produces the large volume of ejaculate (see Section 15.5.4).
17.4