Page 867 - Atlas of Histology with Functional Correlations

FIGURE 21.20 | Uterus: Early Menstrual Phase

If fertilization of the ovum and implantation of the embryo do not occur, the
uterus enters the menstrual phase, and much of the preparatory changes made for
implantation in the endometrium are lost. During the menstrual phase, the

functionalis layer (1) degenerates and is sloughed off with fragments of
disintegrated stroma, blood clots (7), and uterine glands, some of which are
filled with blood (6). The deeper basalis layer (4) with the bases of the uterine
glands (9) remains intact as the functionalis layer is shed during the menstrual
flow.

The endometrial stroma of the functionalis layer also contains aggregations
of erythrocytes (7) that have been extruded from the torn and disintegrating
blood vessels. In addition, the endometrial stroma exhibits the infiltration of
lymphocytes and neutrophils.

The basalis layer (4) of the endometrium remains unaffected during this
phase. The distal (superficial) portions of the coiled arteries (3, 8) become
necrotic, whereas the deeper parts of these vessels remain intact.

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