FEMALE URETHRA ANATOMY.
The female urethra is from 3 to 4 cm. (1-1- to 1+ in.) long and 7 mm. (4 in.) wide. It is almost straight, with a slightly sigmoid curve. Its external orifice normally appears as a vertical slit, the section of its canal proper stellate, while its internal orifice is transverse.
The urethra is lined by mucous membrane which in the con tracted state is thrown into numerous folds. Many blood-vessels penetrate the mucosa and the connective tissue immediately beneath it, forming a cavernous network. Immediately outside the mucosa is a layer of circular muscular fibres, and outside of these again a layer of longitudinal fibres. At the neck of the bladder the cir cular fibres are so thickened as to form a distinct sphincter which controls the retention of the urine. No such sphincter has been satisfactorily demonstrated at the external orifice, although Luschka contended that one existed. Analogous to, and connected with, the sphincter vayince, the mucous folds of the urethra form three princi pal folds, one median on the wall toward the vagina, and one on each side. In the depressions to the right and left of the median fold lie pits and glands arranged longitudinally in groups. A dozen or more of these are found in a group. Near the lower end of the urethra these depressions are never more than little sacs in the mu cosa lined with the same epithelium as the mucosa itself. Similarly placed near the upper part of the urethra are the acinous glands.
Just within the cutaneous margin of the urethra, one can dis cover on either side, posteriorly, a little orifice not quite a millimetre in diameter. Upon pressing the posterior surface of the urethra up against the pubis sometimes a small drop of fluid may be made to exude from these orifices. If a sound 1 mm. in diameter be intro duced, it will be found to enter from to 2 or even 3 cm. to 1iin.), never, however, passing beyond the internal orifice of the urethra. The tract thus sounded runs parallel to the urethra on either side and is sometimes considerably dilated. These openings are the orifices of the "glands," discovered by Prof. A. J. C. Skene and described in the American Journal of Obstetrics, April, 1880. They are entirely different from the other small glands and pits found in groups throughout the urethra. The orifices of the urethral pits are for the most part wider than the portion of the pits immediately be low, while on the contrary the orifices of these urethral tubules are regularly narrower than the succeeding portion of the canal. Care must be taken in sounding them not to push the sound through the gland wall, establishing a false passage. A further difference be tween these tubules and the urethral pits lies in the fact that the former are regularly confined to the most superficial layers of the mucosa, while the tubules enter the deeper layers. They are lined
with a well-vascularized mucosa, upon which numerous fine openings are seen. These tubules attain their greatest development in the years of greatest sexual activity. Not infrequently their orifices lie exposed to view in multiparu.
Schueller found occasionally a third tubule in the middle line, half-way between the normal orifices. Cross sections of these tubules show the lumen to be usually stellate, or linear, and the farther the section is made from the orifice, the mare irregular is the form, the lumen dividing itself into numerous depressions and folds. Some of the higher sections show several canals lying close together, demon strating the fact that the tubules have ended in a number of blind sacs. The course of the tubules is not straight. They are lined with mucosa like that of the urethra with loose connective tissue below it, and are abundantly supplied with the cavernous vessels. It is not probable, as has been asserted, that they represent or have any thing to do with the terminal ends of Giirtner's ducts, which in foetal life are lined with cuboidal ciliated epithelium.
One important anatomical peculiarity of the urethra has, strange to say, entirely escaped the notice of anatomists and clinicians. If a virginal vaginal orifice be examined, taking care merely to expose the parts without separating them, the urethral orifice will be found completely hidden, being covered by two lips, one on either side, in close connection with the anterior part of the hymen. By the ap proximation of these lips the cutaneous orifice forms a simple verti cal line, from 2 or 3 to 10 mm. beyond the level of the vestibule. These folds are connected with the posterior part of the urethral ori fice, and project up over the anterior portion of the orifice with the patient lying in the dorsal position. They are sometimes short and inconspicuous, at others long—longer relatively to the urethral orifice than are the labia minora relatively to the vaginal orifice. They are most marked at the period of greatest sexual activity, disappearing with age. They are also wont to disappear after numerous child births, being replaced by a patulous urethral orifice, without distinct labia. In cases where they have been partially destroyed their previous position is often indicated by a line crossing the urethral orifice, giving it a characteristic cruciform shape. These folds have a mechanical function, and are clearly intended to protect the mucous membrane of the urethra from mechanical injury and invasion by the micro-organisms so abundant in the vaginal secretions.