DECIDITA.
a. Changes in the increase in volume and number, so that the mucosa seems formed of tubes placed alongside one another per pendicular to its surface (or slightly inclined), but parallel one to the other. For one half their length they are straight, but near their round base they enlarge and undulate. They end in a cul-de-sac on the muscu lar layer, and open ou the mucous surface by an orifice somewhat bell shaped. They have a grey, granular cell wall, with longitudinal striations, lined or filled with an epithelium which is pale grey, angular or polyhedral. Externally, this epithelium forms a regular layer for the internal sur face of the follicular tube.
When we squeeze the mucous membrane of the uteri of women who died early in pregnancy, a semi-fluid lactescent matter exudes, consisting of a viscid liquid, holding in suspension a number of fine granulations, partly fatty, and a large number of epithelial cells like those which fill the glandular tubes.
b. Changes in the Proper Cells of the Uterine Mucnsa.—During preg nancy, these cells so multiply that, in the third month, they predominate in the mucous membrane. Friedlander calls them decidual cells, and, when they are larger, giant cells; now they have different forms, accord ing to their locality in the decidua. (Fig. 89). In the superficial layer, where they are compact, they are spherical; in the deep layer they are fusiform or spindle. The longest (Ch. Robin) are in the decidua reflexa. All have one or more nuclei. They are for replacing the uterine mucosa, which disappears during pregnancy (Friedlander), for this was made up of only two layers, a glandular and a special cell layer. These two are distinct layers, according to Friedlander; but do Sinety and others do not regard them as separable.
c. Interglandular Tissue.—The proper cells multiply, and embryo plastic nuclei appear in them, so that fusiform bodies and laminated fibres are lost to view in the mass.
d. Vessels.—The vessels of the mucosa, continuations from the muses laris, are usually larger than those of the latter. Where the mucous and muscular layers join, they form a kind of glomerulus, whence starts the capillary, which runs parallel with the glands, anastomosing with neigh boring capillaries to form a species of plexus about the glands, withou t exactly touching them. At the surface of the mucosa they ramify in a. mesh-work, whence springs a superficial capillary plexus.
The vessels are arranged differently at the level of the inter-utero placental mucosa. These vessels, at first possessing walls of their own,. have, at the end of gestation, only endothelium on a thin layer of connec tive tissue, which is not distinct from the adjoining tissue (Tarsier). At term, these disappear, by obliteration and atrophy, in the uterine decidua; while, on the other hand, they develop greatly in the inter-utero-placental mucosa.
e. epithelium of the ovular and uterine decidua changes from cylindrical and prismoidal into the pavement variety, not from transformation, but by exfoliation, and substitution of pavement cells, large and many-sided. At two and a half months, larger and longer join these, and, at term, the latter predominate. In spots, the epi thelium is wanting; at term, we may only find it in limited patches.