THE BLADDER AND FEMALE URETHRA

The neck region of the bladder lies directly on the pelvic floor, and when the organ is fully contracted it forms a firm, globular swelling about the size of a clenched fist; it is so far withdrawn into the pelvic cavity that it is almost wholly retroperitoneal.

The relations of the bladder depend on the degree of filling and on the sex. When empty, its vertex is gener­ally in contact with the pelvic flexure of the colon, but as the bladder enlarges, the vertex and adjacent parts obtain a more extensive and more varied relationship to the intestine. In the mare the dorsal surface is in contact with the cranial part of the vagina, the cervix, a variable part of the body of the uterus, and sometimes the rectum (Figure 22-8). The corresponding relations in the male are the genital fold, the deferent ducts, the vesicular glands, the prostate, and the rectum.

The relatively large neonatal bladder is entirely intraabdominal. It slowly adjusts to the adult propor­tions and position with the postnatal enlargement of the pelvis and the development of the intestines. Leakage at the navel from a still-patent urachus is not uncom­mon in the first period after birth and provides a poten­tial portal for infection.

Figure 22-6 The disposition of the peritoneum in the pelvis of the mare (transverse section). 1, Rectum; 2, vagina; 3, bladder; 4, parietal peritoneum; 5, broad ligament; 6, lateral ligament of bladder; 7, median ligament of bladder; 8, recto- genital pouch; 8', pararectal fossa; 9, vesicogenital pouch; 10, pubovesical pouch; 11, ureter.

The female urethra is very short (only 6 cm or there­abouts) and opens into the vestibule, immediately caudal to the transverse fold of the hymen. It is rather wide; it admits one finger without difficulty and by gentle manipulation may be persuaded, with low epidu­ral anesthesia, to accept a small hand, which is conve­nient when returning a bladder prolapse or removing a kidney or bladder stone from the bladder. The short­ness, wide caliber, and dilatable nature of the urethra permit occasional prolapse of the bladder into the vestibule.

The male urethra is described with the reproductive organs.