Obstetrics for Nurses

by Charles B. Reed

Fig. 2.—The planes of (a) the brim, (b) the cavity and (c) the outlet. (Eden.)

Passing through the brim, a cavity is found below it, midway between the inlet and outlet, which is nearly round in shape. This is the “excavation,” or the true pelvis. Then comes the outlet, bounded in front by the pubic arch and soft parts, and behind by the coccyx pushed back as far as it can go. It is ovoid in shape, but the long axis of this ovoid lies at right angles with the axis of the ovoid inlet.

We find, therefore, a succession of three geometric figures or planes through which the head must pass by means of a spiral motion called rotation. These figures are inclined to one another so markedly in front that a line drawn through the center of each will curve forward at both ends, one end passing out near the umbilicus, the other through the vulva. This is known as the axis of the pelvis or the curve of Carus.

Fig. 3.—Visceral relations. (Redrawn from Gray.)

THE SOFT PARTS

Inside the pelvis are the organs of generation with their accessory structures and supporting tissues.

Of first importance are the ovaries, tubes and uterus, together with the vagina. These special structures are the true genital organs. They are bounded in front by the bladder, behind by the rectum, above by the abdominal viscera, and surrounded everywhere by muscular, mucous and fatty tissues, which support them and aid their function.

The Vagina.—The vagina is a hollow organ, about four inches long, attached to the cervix above and the vulva below. It is an elastic sheath bounded in front by the bladder and behind by the rectum. Under normal conditions, this tube easily admits one or two fingers, but during labor it dilates enormously to allow the head to pass. The vagina is lined with a thick mucous membrane, ridged and roughened by folds, which are called rugæ. Thus a continuous channel connects the ovary with the outside and through it pass, at appropriate times, the ovule, the menstrual blood, the uterine secretions, the child, the placenta, and the lochia.