Menstrual Cycle Flashcards
What are the two types of pituitary hormones that control the menstrual cycle?
FSH and LH
What are the two types of ovarian hormones that control the menstrual cycle?
Estrogen and progesterone
What do pituitary hormones do?
are released from the anterior pituitary gland and act on the ovaries to develop follicles
What do ovarian hormones do?
act on the uterus to prepare for pregnancy
What is the first phase of the menstrual cycle?
Follicular phase
What does the dominant follicle produce?
Estrogen
What is the function of the estrogen produced by the dominant follicle?
Inhibits FSH secretion (negative feedback) to prevent other follicles growing
How does estrogen act on the uterus?
to stimulate the thickening of the endometrial layer
What is the 2nd phase of the menstrual cycle?
Ovulation
What happens midway through the cycle (~day 12)?
estrogen stimulates the anterior pituitary to secrete hormones (positive feedback)
What is the result of the positive feedback of the anterior pituitary during ovulation?
a large surge of luteinizing hormone (LH) and a lesser surge of FSH
What is the function of the luteinizing hormone (LH)?
LH causes the dominant follicle to rupture and release an egg (secondary oocyte) – this is called ovulation
What is the 3rd step of the menstrual cycle?
Luteal Phase
What happens to the ruptured follicle in the luteal phase?
develops into a slowly degenerating corpus luteum
What does the corpus luteum secrete?
high levels of progesterone, as well as lower levels of estrogen
What do estrogen and progesterone do in the luteal phase?
act on the uterus to thicken the endometrial lining (in preparation for pregnancy)
also inhibit secretion of FSH and LH, preventing any follicles from developing
What is the 4th step of the menstrual cycle?
Menstruation
What happens to the corpus luteum if fertilization occurs?
If fertilization occurs, the developing embryo will implant in the endometrium and release hormones to sustain the corpus luteum
What happens to the corpus luteum if fertilization doesn’t occur?
If fertilization doesn’t occur, the corpus luteum eventually degenerates (forming a corpus albicans after ~ 2 weeks)
What happens when the corpus luteum degenerates?
estrogen and progesterone levels drop and the endometrium can no longer be maintained
How does the menstrual cycle start again?
estrogen and progesterone levels are too now low to inhibit the anterior pituitary
What leaves the body as menstrual blood?
The endometrial layer
