Reproductive System - Menstrual Cycle Flashcards
How Long does the Menstrual Cycle occurs (days) and how many phases are there?
28 days, there are 4 phases.
Describe the first phase; The Flow Phase
Flow Phase lasts 1-5 days, although can vary. It is marked by the shedding of the thickened endometrium from the mucosa (memberane that lines the uterus.) due to a drop in progestrone and estrogen.
Produces menstrual flow.
Describe the 2nd phase: Follicular Phase, what happens here?
The Follicular Phase, occurs in day 3-13. This can overlap with the flow phase.
FSH is secreted by the pituitary which is stimulated by the hypothalamus. FSH causes development of follicles in the ovary.
One follicle produces faster than the others. The follicle will secrete estrogen, responsible for secondary sex characteristics in females. (Development of breasts and body hair), increased thickening of the endometrium.
What will the Increased estrogen levels stimulate (Follicular Phase…)
Increased estrogen levels will stimulate the lutenizing hormone (LH) from the pituitary, which will start ovulation. LH levels rise on day 14, and the follicle migrates to the surface of the ovary.
Describe the 3rd Phase: Ovulation
Day 14. The dominant follicle pushes the outer wall of the ovary, causing the outer wall of the ovary to burst. The ruptured follicle releases the ovum (egg)
Where does the ovum go once released from the ruptured follicle.
The ovum gets sweeped up by the fimbriae into the fallopian tube. Follicular cells (from the ruptured follicle), differentiate into the corpeus luteum.
What is the corpus luteum?
The follicle once it has released an egg cell.
Describe the luteal phase…4th phase
Days 15-28. Marked the development of the corpus luteum, estrogen levels decrease due to the oocyte leaving the ovary, although it is somewhat restored due to the corpeus luteum.
Functions of corpus luteum
1.) Secretes estrogen and progestrone
2.) Inhibits ovulation
3.) Prevents uterine contractions
If fertilization doesn’t occur….
The corpus luteum will disintegrates and leaves a scar called the corpus albicans. Causing the concentrations of estrogen and progesterone to decrease leading to weak uterine contractions.
The weak uterine contractions cause….(Luteal Phase)
The endometrium to pull away from the uterine walls, beginning of the flow phase.
If fertilization does occur..the corpus luteum
Will stay in tact to keep the estrogen and progesterone levels high until the placenta forms.
