Summary. From the statements made in the preceding sections, we may draw the following conclusions:
I. The tissue of the neck begins to soften at the very commencement of pregnancy, and the softening, although not very apparent in the early months, and limited to the most inferior part, gradually ascend, o a to invade successively the whole neck from below upward; though it is much less marked and less rapid in its progress in primiparae than in other females.
II. The cavity of the neck dilate simultaneously with the softening of its walls; and further, this enlargement causes it to be spindle-shaped in primiparae; and in females who have already borne children, to resemble a thimble, the finger of a glove, or a funnel with its base below..
III. The external orifice remains either closed, or else very slightly open, in primiparae, up to the very term of pregnancy; whilst in others, it is widely open, and constitutes the base of the funnel.
IV. The whole length of the neck disappears in the last fortnight, being lost in the cavity of the body.
V. Contrary to the opinions hitherto generally adopted, the neck preserves its whole length until the last fortnight; it does not shorten from above downward during the last four months; but the fusion of the neck with the body takes place only within the last few weeks of gestation.
diagram Fig.27 Fig.28 Fig.29
These three give an idea of the gradual dilatation which the cavity of the neck undergoes at various periods of pregnancy.
THE TEXTURE AND PROPERTIES OF THE UTERUS are also greatly modified by the condition of pregnancy. These changes affect the different tissue and structures of which the uterus is composed.
The serous coat, or peritoneum, which constitutes the external tissue of the uterus, like the entire substance of the uterine walls, is extended without being diminished in thickness. Just as the uterus itself grows with the growth of the ovum it contains, so its peritoneal covering absolutely grows, and in proportion to the growth of the uterus which it envelopes.
The mucous coat of the uterus, as already stated in speaking of the formation of the decidua, becomes much more highly developed in pregnancy; and this development belongs to the glands as well as to the mucous tissue itself. This is also the case with the mucous glands of the cervix; these secrete a peculiar dense, semi-transparent, almost insoluble mass of mucus, which close and fills the entire cavity of the neck during pregnancy.
The muscular coat of the uterus also becomes developed in a corresponding manner during pregnancy; so that the various layers of muscular fibres are much more easily demonstrable at this time than in the unimpregnated condition; and the actual muscular character of this middle coat of the uterus is positively ascertained. The various muscular fibres are now seen to cross and inter-cross in such a manner ass to secure the greatest possible amount of strength. And the arrangement of the layers and fibres is such that at every orderly contraction, they all act upon one common centre, the centre of the womb itself. The obliquity of the fibres at the moment of crossing each other, give the arbor vitae appearance seen particularly in the interior surface of the cervix uteri.
The vascular apparatus of the uterus also undergoes very important changes in connection with the advance of pregnancy. These consist in augmented development, which embraces the arteries ass well as the veins. Through these vessels the blood flow into and through the uterus in greatly quantities, and this blood supplies the nutrition for the growth of the uterine walls, and of the foetus which they enclose.
The augmentation in the size of the arteries only becomes considerable as they approach the uterus. Whilst advancing between the peritoneum and the external face of the organ, and before giving off their first divisions, they dilate and swell up, and then they furnish branches to the anterior and lateral parts, which ramify ad infinitum; they are not situated immediately below the peritoneum, but are separated from it by a delicate layer of muscular tissue. All these ramifications anastomose freely and penetrate through to the internal surface, where they generally terminate; but a large number of those corresponding to the placental insertion, traverse the mucous membrane and enter the placental deciduous membrane. Jacquemier. Through these enlarged arteries is conveyed the blood requisite for the growth of the uterine parietes and appendages for the supply of the placenta and of the foetus from thence. The arterial branches become lengthened with the increasing size of the uterus; but do not lose their original tortuousities, which however do not appear to impede the circulation through them. The veins undergo similar and no less extensive change. This will be evident from examining them as they emerge from the uterus; the ovarian veins are nearly as large as the external iliacs, and the uterine veins are but little less in size. In the original state, before pregnancy, they are larger and less tortuous than the arteries; during gestation they become enlarged and developed still more rapidly; and at term they furrow the muscularities in every direction, and form a net-work which lies intermediate between its external and internal face. This muscular tissue or coat of the uterus is traversed by a great number of venous branches running in every direction, which anastomose and form large sinuses at their junction. Some of the canals of this plexus, or net-work, are large enough to admit a goose -quill, or in some instances even the end of the little finger.
This is particularly the case at that part of the interior surface of the uterus to which the placenta becomes adherent. Opposite the insertion of the placenta these venous trunks are largest, and they diminish in size as they recede from this vicinity. And in the substance of the mucous membrane, immediately which the placenta is situated, these vessels form through an enormous dilatation of their branches the long sinuses which exist at the adherent surface of the placenta. These sinuses communicate freely with each other, so as to form a reservoir of blood divided and kept in place by numerous partitions. At intervals may be found a small number of orifices through which this mass of blood communicates with corresponding sinuses in the walls of the uterus. The veins, as well as the arteries, are lengthened, growing thus with the growth of the uterus; since even in their greatest extent, in the last months of pregnancy, they still maintain their tortuousities. The areolar tissue which envelopes the uterine arteries is not found on the veins; these latter being placed in immediate relation with them muscular tissue through which they pass. Neither are there any valves to be found in. these veins; probably their numerous convolutions and sinuosities may serve to to answer the purposes secured by the valves in other venous trunks.
The lymphatic vessels of the uterus also acquire an extraordinary development in pregnancy and gestation. These vessels form several distinct layers or planes in the uterine walls; the superficial being the most fully developed; and, ad previously described, they belong to two distinct group, those of the cervix communicating with the pelvic ganglia, and those of the body of the womb terminating in the lumbar ganglia. The lymphatic system forms, with the arteries and veins, a third and no less indispensable set of vessels; and the necessities of the circulation, of the nutrition (reparation and growth) of the uterine tissues and their contents, require that the augmentation of uterine tissues and their contents, require that the augmentation of the lymphatic vessels should be in some proportion to the increase of those of the arterial and venous systems.
The nerves of the uterus during the period of gestation necessarily partake of the same increased activity as the other uterine structures, and probably receive also a corresponding augmentation in development. Those arising from the ovarian plexus are distributed to the angles of the fundus; those arising from the hypogastric plexus are distributed to the cervix and lower portions of body, these, by branches from the third and fourth sacral nerves, are connected with the spinal nerves; and finally, those arising from the great sympathetic, accompany the uterine arteries, and are lost upon the neck and lateral parts of the womb. Thus the entire structure of the uterus is sure to be supplied with nerves from the nervous system of organic life. A portion only of the nervous filaments distributed to the cervix being in immediate relation with the spinal nervous system.
The complicated arrangement of the various tissue and organized structures which make up the substance of the womb, renders it exceedingly difficult to demonstrate the full development of the nervous system of this organ. But there can be not doubt of the fact that the uterus is so abundantly supplied with nervous substance in itself and so intimately connected with the great ganglia in its vicinity, that it is endowed, especially in the gravid state, with a vitality peculiarly its own, through which it is enabled not only to support the nutrition of the embryo, but also to exert a controlling influence upon the entire economy of the female herself. But these changes in the structures composing the uterus must occasion corresponding changes in the physiological and sensitive conditions of this organ.
