Page 314 - Veterinary Histology of Domestic Mammals and Birds, 5th Edition

296 Veterinary Histology of Domestic Mammals and Birds

glucuronidase and acid phosphatases, as well as fibrolysin The secretory product of the bulbourethral gland is
VetBooks.ir and prostaglandins. While the secretion of the vesicular mucous, gelatinous and stringy. It is discharged prior to
glands promotes motility of spermatozoa by its alkaline ejaculation serving to neutralise the urethra and lubricate
nature, the secretory product of the prostate gland initiates the vagina (in the pig, bulbourethral gland secretion is part
active progressive movement of ejaculated spermatozoa. of the ejaculate).
The weakly alkaline secretion neutralises the acid environ-
ment of the vagina. Species variation
Horse: The gland is surrounded by striated muscle (m.
Bulbourethral gland (glandula bulbourethralis) bulboglandularis); six to eight ductus glandulae bulbo-
The paired bulbourethral glands lie on the dorsolateral urethrales open into the urethra.
aspect of the pelvic urethra at the level of the proximal Ox and sheep: Short intermediate segments connect
bulbus penis. In the tomcat, boar and billy goat, the gland expanded collecting ducts with secretory end pieces.
is compound and predominantly tubular. The glandular
morphology in the bull, ram and stallion is branched tub- Pig: The glandula bulbourethralis is particularly well
ulo-alveolar. Bulbourethral glands are absent in the dog. developed. The m. bulboglandularis forms a cuff
The gland contains lobules of varying size. Alveolar around the cylindrical gland.
and tubular end pieces open into well-developed collect- Cat: The ducts are expanded into sinus-like chambers.
ing ducts from which the secretion travels through a main These are connected by short, unbranched portions
excretory (bulbourethral) duct into the urethra (Figure to the glandular end pieces. Due to its high glycogen
13.31). The glandular tissue is surrounded by loose con- content, the glandular secretion (pre-ejaculate) may act
nective tissue incorporating solitary smooth muscle cells. as a source of energy for the spermatozoa (fructose-
Denser fibrous trabeculae connect the connective tissue producing vesicular glands are absent in the tomcat).
with a superficial fibro-elastic capsule. As well as smooth
muscle, the capsule encloses striated muscle tissue or Urethra
merges with adjoining skeletal muscles (e.g. m. bulbo- The male urethra commences at the internal opening of the
glandularis, m. bulbospongiosus). neck of the bladder (ostium urethrae internum). It passes
The secretory portion of the gland is lined by simple along the floor of the pelvis to the ischial arch and enters
columnar epithelium with isolated basal cells. The baso- the penis. The urethra ends at the ostium urethrum exter-
philic cytoplasm houses a spherical nucleus. Secretory nae. In the boar and carnivore, the ostium is near the tip of
product is released into collecting ducts lined with cuboi- the penis. In the stallion, bull, ram and billy goat, the exter-
dal to columnar epithelium. In the larger intraglandular nal urethral opening is located at the end of the processus
portions of the duct system, the epithelium gradually urethrae. The urethra is divided into a pelvic portion (pars
becomes pseudostratified. At the end of the bulboure- pelvina urethrae) composed of a pars praeprostatica, pars
thral duct (ductus glandulae bulbourethralis) the lining prostatica and a pars membranacea, and a cavernous penile
transforms into transitional epithelium. portion (pars spongiosa urethrae, pars externa urethrae).

13.31 Lobule of bulbourethral gland (bull). Haematoxylin and eosin stain (x200).

Vet Histology.indb 296 16/07/2019 15:05