68 DECIDUA 



very soft and markedly oedematous. The glands are enlarged and the blood- 

 vessels much dilated. There is considerable effusion of blood from ruptured vessels ; 

 the blood occupying spaces in the loose connective tissue, and even the interior 

 of gland-tubes, which show desquamation of their epithelium and breaking down 

 of their walls. 



The decidua undergoes further structural changes during the early months of 

 pregnancy, some of these changes being common to all three parts of the membrane, 

 whilst others are special to that part (d. basalis) which enters into the construction 

 of the placenta. The following is a brief account of these changes. 



Decidua vera. With the supervention of pregnancy the mucous membrane 

 lining the uterus becomes thickened and the tubular glands become both dilated 

 and greatly elongated. This thickening of the membrane and enlargement of 

 the glands goes on during the early months of pregnancy until, between the second 

 and third months, the decidua vera reaches its maximum thickness of more than 

 a quarter of an inch. Its glands have further undergone so considerable an elonga- 

 tion that they now no longer pass nearly straight through the membrane, but run 

 in a tortuous manner from the inner surface to the vascular layer, so that a vertical 



vs- 



FIG. 96. SECTION OF UTERINE MUCOUS MEMBRANE DURING MENSTRUATION (Sellheim). 



section of the membrane exhibits them cut quite as often obliquely or transversely 

 as longitudinally. They are also generally dilated, but the dilatation is by far most 

 marked at the mouths of the glands, which come thus to have a funnel-like shape, 

 and in the deeper part of the membrane, where the dilatations look in sections like 

 a series of cavities, lined by cubical or flattened epithelium and separated from 

 one another by a relatively small amount of interglandular substance. This 

 gives a spongy appearance to the part in question, and it has been accordingly 

 termed the stratum spongiosum of the decidua (fig. 95, sp). The deepest part of 

 the glands that, namely, which is in contact with, and is imbedded in the superficial 

 portion of the muscular coat does not share in this dilatation, and its epithelium 

 also retains the columnar character. The part of each gland between the funnel- 

 shaped mouth and the dilatations above described also becomes enlarged, but 

 not to so great an extent, the hypertrophy of the mucous membrane being here 

 chiefly confined to the interglandular tissue, which becomes filled with large 

 epithelium-like cells (decidual cells of Friedlander) and with numerous and large 

 capillary blood-vessels. This layer of the decidua has been termed the stratum 

 compactum in contradistinction to the stratum spongiosum external to it 

 (fig. 95, c). 





