PHYSIOLOGICAL AND ANATOMICAL CHANGES. Where fecundation does not occur, in copulation, the orgasm of the female sexual apparatus is as temporary as that of the male. But when fecundation does result, the excitement, congestion and turgescence of the uterus and Fallopian tubes become continuous; and numerous physiological and anatomical changes are established. Some of these are local; some more general; some are transient, others through the whole period of gestation; some affect the physical economy only, others in a remarkable degree disturb the mental states and moral sensibilities; and finally, some of these changes are purely healthy and normal; these we shall consider in the present chapter, while others, being accidental, morbid conditions, or the developments of inherent morbid predispositions, will be subsequently described.
The UTERUS becomes the seat of the most remarkable and first apparent of these changes, in which both the cervix and fundus partake. Those which occur in the neck being separate from although simultaneous with those occurring in the body; the former also resulting from the latter. Thus the cervix softens and enlarges from below upwards, as the body softens and enlarges from above downwards, during almost the entire period of pregnancy. And the alterations affects this organ in every respect, principally in its volume, form, situation, structure and functions. Let us first examine the changes in the body body of the uterus.
As explained in a previous chapter, the congestion attendant upon a menstrual crisis produces a temporary increase in the uterine parietes. A similar and more permanent result attends fecundation. The orgasm of coition seems in some measure perpetuated; and a permanently hypertrophied condition of the uterine walls becomes established.
Volume, Size. The mucous lining membrane becomes congested and almost double in thickness. And in consequence of this development of its vessels, as described by Cazeaux, and especially of the minute glands of which it is partly composed, it has its thickness so much increased in proportion to the size of the uterine cavity, as to be thrown, in a great many subjects, into soft, projecting folds or circumvolutions, which are so pressed together as to leave not vacant place in the cavity of the uterus. This, as will be subsequently explained, constituted the decidua or enveloping membrane into which the fecundated ovule is received upon its entrance into the uterus from the Fallopian tube of the side corresponding to that of its ovarian birth-place.
Immediately upon its reception of the embryo, the uterus commences to increase in size, not uniformly, but in a ration proportioned to the larger development of the foetus. That is, the larger the foetus thee more rapid the enlargement of the uterus. This growth of the uterus takes place in every direction; and is not a mere mechanical, as if arising from the outward pressure of the increasing ovum, since its walls are not thinned, but it is proved to be a true physiological development, in which both ovum and uterus partake simultaneously and in unison.
Form. The uterus instead of remaining flattened, on its two surfaces, becomes rounded, and then pyriform in the earlier stages of pregnancy. While in the later months, it becomes spheroidal, and finally assumes the form of an avoid, which is slightly, flattened from before backwards, and has its point looking downwards. “Of dimensions nearly equal in every direction, about the fifth or sixth month the uterus exhibits the figure of a spheroidal vase terminated by a very short neck; it might be compared to a hog’s bladder, with the urethral extremity surrounded with thread for an inch or two; supposing some on should unwind the thread by degrees, from above downwards, while another blows into the bladder from the fundus, so a to distend it we should acquire a pretty clear idea of the gradual effacement of the cervix of the womb. Velpeau.
In the latter months of utero-gestation, the shape of the uterus if modified by the exact relative position of the foetus. That side of the fundus which is occupied by one of its extremities is sometimes more elevated that the other. And since in the most usual presentations the trunk of the foetus is found to incline to the right side, this portion of the fundus of the womb will be found most elevated. These general statements as to the shape of the gravid uterus are, however, liable to exceptions, which may arise from the number of the foetuses, or from the varieties in the original shape of the uterus itself.
In its situation the gravid is subject to important changes. These changes arise in the first instance from the change in size of the organ itself. Remaining in the pelvic cavity, during the first three months of gestation, the uterus sometimes becomes at first slightly depressed, so that its cervix approaches nearer to vulva. This is especially the case in those in whom the pelvis is large. Still this depression of the uterus, when it does occur, is but temporary; and at three months, the position is in all respects almost exactly the same as before impregnation.
From the third and a half to the fourth month, the uterus finding itself more and more incommoded as it increase in size, gradually forces itself upwards from the excavation of the pelvis; rise above the superior strait; then to the level of the umbilicus; and towards the close of pregnancy it reaches the epigastric region. Butt during the last two weeks of gestation the uterus commences to sink down somewhat; and this, which is regarded as one of the earliest sings of approaching parturition, is in fact almost the commencement of this process, since in most instances it results from the approximation of the foetal head towards the cavity of the pelvis, and in some cases from its actual entrance into the cavity itself.
Direction. The changes in the direction of the womb in pregnancy are no less remarkable than those of size and form. While still remaining within the pelvic cavity, the uterus, form the greater weight of the posterior portion of the fundus or upper portion, inclines backwards, as in partial retroversion; and the os uteri looks forward towards the public arch. But this is not always the case in the earlier, or first months of gestation. In many such cases the fundus will be found inclining forward more in its natural position; while the os tincae will be reached only by the farthest extension of the finger towards the hollow of the sacrum.
As the uterus in the fourth and fifth months rises above the level of the superior strait, two remarkable directions are assumed and maintained usually till the close of gestation. These are, the inclination forward, as if leaning over the arch of the pubis; and the inclination to one side, usually the right side. The forward inclination of the gravid uterus is the necessary result of the hard, unyielding nature of the lumbar vertebrae behind and of the less rigid structure of the abdominal parietes in front, in combination with the constant pressure from above of the contents of the abdomen itself. The line of motion which alone is possible for the gravid uterus on emerging from the pelvic cavity, being the axis of the superior strait, as guided by the projecting promontory of the sacrum, will even from the first have given it a decided inclination forward. The lateral inclination, to one side or the other, is the other, is the necessary result of the projecting ridge of the lumbar vertebrae; as it would be little less than impossible to balance the uterus on this high-raised median line. The proportion of cases in which the uterus is found inclining to the right side i state by various authorities to be a high as eight out of ten. But there is less unanimity of opinion as to the causes which produce such a result. Among the various causes proposed to account for this general tendency, no one seems entirely sufficient; nor do many of them unite with any degree of constancy in a given number of cases. Thus if the inclination is to be attributed to the greater weight form the attachment of the placenta, it is found that the placenta is far form being always on the side towards which the uterus is inclined. The same is true of the relation of the colon loaded with fecal matter; of the position of the female while at rest on the right or left side. For the present, the most plausible opinion appears to be that of Madame Boivin, that the round ligament of the right side is shorter, stronger and contains more muscular fibres than that of the left, and that to the more powerful action of this ligament is to be attributed the usual inclination of the uterus to the right aide. Still there is no doubt that the more active physiological influences do much to determine this matter of the lateral inclination of the gravid uterus;; and in confirmation of what is here implied, it may be sufficient to state that according to the observations of some authors, the uterus inclines to the left in women who are left handed.
