Mod 3.3 Physiological Basis of Menstrual Cycle

Question 1

What are the 2 phases of the Menstrual (Ovarian) Cycle

Answer 1

1. Follicular Phase
2. Luteal Phase

Question 2

What happens during the follicular phase?

Answer 2

Mature follicle and secondary oocyte develop

Question 3

What happens during the luteal phase?

Answer 3

After ovulation and until death of corpus luteum

• formation and death of corpus luteum

Question 4

Hormone patterns in the Normal Menstrual Cycle:

• FSH
• LH
• Estrogen
• Progesterone

Answer 4

Hormone patterns in the Normal Menstrual Cycle:

• FSH
  
  • increases in early follicular phase
  • Steadily decreases except for mid-cycle peak
• LH
  
  • Constant for follicular phase
  • Large mid-cycle LH surge (18 hours before ovulation)
  • Rapidly declines after ovulation
  • Slow decline in luteal phase
• Estrogen
  
  • low during 1st week of cycle
  • Increases rapidly during 2nd week
    
    • due to rapid follicle growth - follicles secrete estrogen
  • Decreases before LH peaks
  • 2nd increase due to corpus luteum secretion
  • Rapid decrease in final days of cycle
• Progesterone
  
  • Small amounts released by ovaries in follicular phase
  • After ovulation, corpus luteum releases large amounts
  • Follows similar pattern of estrogen in later phase of cycle

Question 5

How does the uterus change during the endometrial cycle? (3 phases)

Answer 5

• Day 1 - Menstrual phase
  
  • First day of menstrual flow
  • Endometrium degenerates
• Proliferative phase
  
  • ​At end of menstruation endometrium begins to thicken in response to estrogen
  • ~10 day duration
  • Between cessation of menstruation and ovulation
  • increase endometrial cells
  • increase vasculature
  • increase secretions of thin stringy mucous from cervix
• Secretory phase
  
  • ​Endometrium secretes glycogen in glandular epithelium in response to estrogen and progesterone
    
    • thicken cervical mucous = mucuous plug

Question 6

How do the three phases of the endometrial cycle relate to the phases of the ovarian cycle?

Answer 6

• Ovarian Follicular phase coincides with Uterine Menstrual and Proliferative phases
• Ovarian Luteal phase coincides with Uterine secretory phase

Question 7

What four physiological events occur during menstruation?

Answer 7

1. Constriction of endometrial blood vessels
   
   • Vasoconstriction by prostaglandins
   • Endometrial cells deprived of O2 and nutrients
   • Mediated by prostaglandins produced by endometrium
     
     • Response to decreased circulation progesterone
     • Menstrual cramps (dysmenorrhea), systemic symptoms likely due to prostaglandin overproduction
2. Disintegration of uterine lining
   
   • 14 days after ovulation
   • except for thin base layer
   • Regenerates the endometrium in next cycle
3. Rhythmic contractions of uterine smooth muscle
   
   • due to overproduction of prostaglandin
4. Dilation of endometrial arterioles
   
   • Hemorrhage through capillary walls
   • Blood and endometrial tissue debris exits vagina

Question 8

Menstruation involves the following physiological changes; why? Purpose?

1. Constriction of endometrial blood vessels
   
   • ____________
   • ________ cells deprived of _______
   • Mediated by _________ produced by ________
   • Response to decreased circulating ________
   • Menstrual cramps (dysmenorrhea), systemic symptoms likely due to ________ overproduction
2. Disintegration of uterine lining
   
   • ________ days after ovulation
   • except for ________ layer
   • Regenerates the endometrium in next cycle
3. Rhythmic contractions of uterine smooth muscle
   
   • due to overproduction of ________
4. Dilation of endometrial arterioles
   
   • ________ through ________ walls
   • ________ and ________ ________ debris exits vagina

Answer 8

1. Constriction of endometrial blood vessels
   
   • Vasoconstriction by prostaglandins
   • Endometrial cells deprived of O2 and nutrients
   • Mediated by prostaglandins produced by endometrium
   • Response to decreased circulation progesterone
   • Menstrual cramps (dysmenorrhea), systemic symptoms likely due to prostaglandin overproduction
2. Disintegration of uterine lining
   
   • 14 days after ovulation
   • except for thin base layer
   • Regenerates the endometrium in next cycle
3. Rhythmic contractions of uterine smooth muscle
   
   • due to overproduction of prostaglandin
4. Dilation of endometrial arterioles
   
   • Hemorrhage through capillary walls
   • Blood and endometrial tissue debris exits vagina

Question 9

What are three typical estrogen effects?

Answer 9

1. Mediates paracrine effects on ovaries
2. Modulates anterior pituitary gland, hypothalamus
3. Uterine actions

Question 10

What are the “Pro-progesterone” effects of estrogen? What is this termed?

Answer 10

Increased synthesis of progesterone receptors in many tissues = increased responsiveness to progesterone

Termed: Estrogen priming

Question 11

What are the effects of progesterone?

Answer 11

Because of the Timing of peak progesterone after ovulation = effects of progesterone are taken as evidence that ovulation has occurred:

• Inhibition of vaginal cell proliferation
• Increased basal body temperature

Question 12

How can we tell if ovulation has occurred?

Answer 12

The only direct way to know is if pregnancy occurs

• can use progesterone effects as evidence because progesterone peaks after ovulation