247.A 29-year-old woman is trying to become pregnant. She presents
with irregular menstrual cycles and heavy, prolonged, irregular uterine
bleeding and undergoes an endometrial biopsy. The biopsy has the appear-
ance shown in the photomicrograph below. Which of the following is char-
acteristic of this stage of the menstrual cycle?
368 Anatomy, Histology, and Cell Biology
a. It precedes ovulation
b. It depends on progesterone secretion by the corpus luteum
c. It coincides with the development of ovarian follicles
d. It coincides with a rapid drop in estrogen levels
e. It produces ischemia and necrosis of the stratum functionale
248.The low pH in the vagina is maintained by which of the following?
a. A proton pump similar to that of parietal cells and osteoclasts
b. Acid secretion derived from intracellular carbonic acid
c. Secretion of lactic acid by the stratified squamous epithelium
d. Bacterial metabolism of glycogen to form lactic acid
e. Synthesis and accumulation of acid hydrolases in the epithelium