Final Study Guide
Reproductive:
o Endometrial cycle (menstrual cycle) and the occurrence of
ovulation
During menstruation (menses), the functional layer if
endometrium disintegrates and is discharges through the
...
Final Study Guide
Reproductive:
o Endometrial cycle (menstrual cycle) and the occurrence of
ovulation
During menstruation (menses), the functional layer if
endometrium disintegrates and is discharges through the
vagina.
Follicular/proliferative phase - GnRH and a balance
between activin and inhibin from the granulosa cells
contribute to the rise of FSH levels, which stimulates a
number of follicles. The pulsatile secretion of FSH from the
anterior pituitary gland rescues a dominant ovarian follicle
from apoptosis by days 5 to 7 days of the cycle. Together
estrogen and FSH increase FSH receptors in the granulosa
cells of the primary follicle, making them more sensitive to
FSH. FSH and estrogen combine to induce production of LH
receptors on the granulosa cells of the primary follicle, thus
promoting LH stimulation to combine with FSH stimulation,
causing more rapid secretion of follicular estrogen. As
estrogen levels increase, FSH levels drop because of an
increase in inhibin-B secreted by the granulosa cells in the
dominant follicle. This drop in FSH level decreases the
growth of the less-developed follicles. Estrogen causes
cells of the endometrium to proliferate and stimulates
production of LH.
Luteal/secretory phase – ovulation marks the beginning of
this phase. The ovarian follicle begins its transformation
into a corpus luteum. Pulsatile secretion of LH from the
anterior pituitary stimulates the corpus luteum to secrete
progesterone, which in turn initiates the secretory phase of
endometrial development. Glands and blood vessels in the
endometrium branch and curl throughout the functional
layer, and the glands begin to secrete a thin glycogencontaining fluid, the secretory phase. If conception occurs,
the nutrient-laden endometrium is ready for implantation.
Human chorionic gonadotropin (HCG) is secreted 3 days
after fertilization by blastocytes and maintains the corpus
luteum once implantation occurs at about day 6 or 7. HCG
can be detected in maternal blood and urine 8 to 10 days
after ovulation.
Ischemic/menstrual phase
The production of estrogen and progesterone
continues until the placenta can adequately maintain
hormonal production. If conception and implantation
do not occur, the corpus luteum degenerates and
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