The Female Genital Canal
AS WE have seen in Chapter 3 the female genital canal is an embryonic elaboration of a rudimentary organ from the dim past, derived from the pronephros.
In the embryo the internal orifice of this canal was not overgrown by the reproductive masses as was the Wolffian body. Even in the adult body it is still situated at some distance from the ovary. It has a funnel-shaped enlargement for the better reception of the ripe ova as soon as they are cast off into the abdominal cavity. The moving protoplasmic threads, like huge cilia, which are situated on the edge of the funnel greatly assist the process.
Thus an egg will sometimes succeed in finding its way into the female genital canal. Whereas in man the two sperm-ducts have to take a circuitous route before they open into the urethra behind the bladder, the two egg-ducts (Fallopian tubes) in the female organism converge towards the mid-line and coalesce immediately behind the urinary bladder. Eggs are moved on in these ducts by the ciliated epithelium which lines the internal surfaces.
While in the male the two sperm-ducts on approaching each other are each provided with a separate seminal vesicle, the Fallopian Tubes form a single large reservoir,(1) as soon as they meet, that is to say, after a short distance.
It is of considerable size and consists of red muscle, and is for that reason called uterus or womb instead of vesicle. Here, the egg, even if unfertilised, is kept for some time. It is then, together with the menstrual fluids, squeezed by peristaltic movements into the antechamber, i.e., the vagina, from whence it is able to reach the exterior.
(1) In the female organism, urinary and genital canal are entirely separate, i.e., there is a separation in a coronal section in the male, in a sagittal section in the female. This corresponds to the obstetric dimensions of the pelvis, the male pelvis being more elliptic, the female on the other hand more circular. Only in some few mammals the uterus bicornis points towards a coalescence of the uterus out of two parts as though it were a paired organ.
Only if fertilisation takes place does it remain in this reservoir for several months. The fertilised egg-cell, and later on, the small embryo, surrounded by its special membranes, gradually embeds itself in the moist sero-mucous membrane of the uterus, by which it is then developed. After the third month of pregnancy, two stout blood vessels grow from the foetus towards the uterine wall and form the umbilical cord? The much ramified ends of these vessels known as the placento or afterbirth, grow into and through the mucous membrane after the manner of a tumour. By this means an osmotic connection is established between the maternal and the foetal circulations.
The foetus remains in situ and grows for a further period of six months,(3) until muscular contractions of the uterus occur in consequence of increasing tension, which finally lead to the expulsion of the foetus.
In the female genital tract the musculature of the cervix of the uterus is the involuntary internal sphincter whose contractions may often lead to serious obstetric complications. On other occasions, during an unwanted abortion, the embryo is only too easily allowed to escape. Contractions of this group of muscles often cause severe dysmenorrhoea.
The perineal muscle-layer with its external closing apparatus may also offer a protracted resistance during parturition, if a purely expectant attitude is adopted and no measures are taken against such an occurrence. It may, by spasmodic contractions, delay or prevent any attempt at gynaecological examination on the part of the physician. In some very rare cases it may indeed happen that owing to pain or fear, these muscles contract spasmodically,(4) so as to render coitus impossible, or if this cramp occurs during coitus, the male member may thereby be seized so that the man cannot withdraw and venous congestion takes place in the glans. If the man remains quiet and above all makes no attempts at withdrawal, the cramp will generally pass off in most cases. As soon as it is found that the matter is becoming serious, one should immediately send for a doctor in order to prevent the glans from becoming gangrenous, for this may end fatally for the man. The physician will narcotise the female with chloroform inhalations or subcutaneous injections of morphia, to cause the cramp to pass. These cases generally happen in young girls.
The total length of the female genital canal is very short, like the female urethra. Neither ovaries nor Fallopian Tubes are much higher than the superior margin of the os pubis. They are really only the lateral appendages of the two upper corners of the uterus. The lower part of the uterus and its lowest point, the os uteri, protrude a little into the vault of the vagina.
It is very remarkable how the uterus, which is normally so small, attains such huge dimensions during pregnancy; and even more remarkable how, once it is completely emptied, its muscular fibres contract uniformly, so that the increase in size which took nine months to develop, disappears almost entirely in six weeks.
The vagina is much corrugated. When these corrugations are distended during tamponade or other such procedures, it becomes obvious that the vagina is really balloon-shaped and can be distended to the size of a child’s head. Thus the female genital canal is very well adapted for gestation. Its sensitiveness to pressure is not acute. Only when the uterus is suddenly shaken, the strain will produce an unpleasant sensation, like that of a strangulated hernia.
Even quite harmless procedures in the interior of the uterus may sometimes cause sudden death from shock. This is probably due to over-excitation of he sympathetic nervous system, small groups of nerve centres scattered in the abdominal cavity, and of which the solar plexus (coeliac plexus) is the largest. The mucous membrane lining the uterus is very subject to haemorrhages and to bacterial infections consequent on manipulation. This constitutes a serious danger to life since the uterine cavity is directly continuous with the abdominal cavity through the oviducts.
Per contra, the mucous membrane lining the vagina is very resistant to all external infections. The entrance to the vagina in woman(6) is carefully closed firstly by two small folds of mucous membrane, the labia minora or nymphae; secondly, two larger swelling folds of skin, the labia majora. We shall return to this structure which is known as the vulva (pudenda) later. So, looking at the female body from below, one sees not the vaginal opening but only the vulval slit which is continuous with the navel cleft. The latter contains the anal aperture, the former the vaginal and urethral apertures. These two openings are almost the same size in the female child, but in the adult the vaginal opening is much larger than the urethral.
Between urethra and os pubic there is just space for a small vascular protuberance, the clitoris. We shall see later how in the male these three structures, genital canal, urethra and vascular protuberance, have combined to form a single organ, which is of much larger size.
2 The fact that later on the umbilical cord is spirally twisted is generally attributed to foetal movements and rotations, of which we are reminded by the growth of hair on the vertex. It is perhaps more correct to interpret the rotation of the foetus as a consequence of the torsion of the umbilical cord. A tree or any stem of a plant will grow twisted as soon as the different vascular bundles of which they are composed have a different co-efficient of growth. In the same way, surely, the arteries and veins which together form the stalk have a different co-efficient of growth.
3 These periods are, of eourse, only approximations. The average period of 280 days varies individually and according to external circumstances.
4 During a cramp, even the voluntary muscles are no longer under the control of the will. The opposite condition seen in elderly women who have had several children, where these muscles have ceased to function altogether, is perhaps preferable. 5 Sometimes even very deeply. In a pathological case it may lead to prolapse of the vagina or even of the cevix uteri.
6 In other mammals only one pair of folds is found, which, like our eyelids and nostrils and lips, are lined internally with mucous membrane and externally with skin.