MENSTRUAL CYCLE Normal cycle length is considered 28 days, however it can range from 20-45 days divided into 4 stages
Stage 1 - Follicle Stage Starts in the hypothalamus gland, this secretes GnRH which stimulates the anterior pituitary gland to release FSH (follicle stimulating hormone) This goes to the ovaries and causes a follicle to mature
Follicular Stage continued… When the follicle begins to mature inside the ovary it releases the hormone ESTROGEN Estrogen causes the uterine lining (also called the endometrium) to thicken in preparation of the egg
Follicular stage continued… When estrogen levels get high enough they cause the release of LH or luteinizing hormone from the anterior pituarity. Estrogen secreted by the follicles inhibits further secretion of FSH. LH causes the release of egg or OVULATION
Stage 2 - Ovulation This is when the egg, or the secondary oocyte, is released from the ovary the follicle pops and the egg comes oozing out causing a crater on the side of the follicle to be formed, called the corpus luteum.
Stage 3 – Luteal Stage The corpus luteum left on the inside of the ovary oozes the hormone PROGESTERONE Progesterone inhibits the development of other follicles that may have been developing (thus only one ovum is released) progesterone also causes the endometrium (uterine lining) to thicken further.
Stage 4- Menstruation No fertilization of the egg occurs in the fallopian tubes and the egg deteriorates when it arrives at the uterus progesterone & estrogen levels drop significantly. Decrease in the progesterone decreases blood supply to the endometrium (uterine lining) which has led to this stage
Menstruation continued… Endometrium disintegrates Blood vessels rupture Tissues and blood flow out of the vagina This signals the first day of the follicular stage once again!
Summary of the Menstrual Cycle: http://msnbcmedia.msn.com/i/msnbc/C omponents/Interactives/Health/Women sHealth/zFlashAssets/menstrual_cycle_d w2%5B1%5D.swf
Some questions to consider: 1. True or False? It is possible to get pregnant every day of the 28 day menstrual cycle?
FALSE! Women have a fertile window of approximately 6 days, occurring around the time of ovulation, however this may vary depending on the female in question.
2. A woman is likely to get pregnant on the days directly following the menstruation stage of the cycle. True or false? - Hint: consider the hormones and how they interact
FALSE! Because the levels of FSH are just stimulating a follicle to develop, and the endometrium has not been thickened due to the presence of estrogen and progesterone, it is unlikely that a woman will become pregnant at this stage. However, this may vary between women!
3. The uterine lining, or the endometrium is its thickest on day 14 of the female menstrual cycle. True or false?
FALSE! The uterine lining is normally the thickest around days 22-26. Why?
Though the hormone estrogen from the ovaries has stimulated the endometrium to thicken, the hormone progesterone (secreted from the corpus leuteum) stimulates the endometrium to thicken further in preparation for possible pregnancy.
SUMMARY: 4 hormones we learned about in this class that were involved with the menstrual cycle: 1.FSH- secreted from pituitary 2.Estrogen- secreted from ovary 3.LH- secreted from pituitary 4.Progesterone- secreted from the corpus luteum
Menstrual Cycle Lab Work: You have been given data by your team in the lab concerning the levels of FSH, LH, Estrogen and Progesterone in a patients blood. Plot the data on a graph as to see how the levels are affected over the 28 day cycle. -Plot Estrogen/Pro on one graph, and FSH/LH on another. -Answer the questions posed on the lab in order to understand the cycle. -What you do not finish in class- finish for homework, you will pass in this lab on Monday.
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