REPRODUCTION

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Oogenesis

• About 7 million oogonia in utero by 20-24 wks
• Transformation into primary oocytes attrition
• Enter first meiotic division and arrest in
  prophase
• At birth, only 1-2 million primary oocytes
• Approximately 400,000 by puberty
• Of these, only 500 may be ovulated (40yrs x 12)
• Attrition ultimately leads to menopause

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THE MENSTRUAL CYCLE

• Importance of perspective
• Hypothalamo-pituitary axis
• Cyclic and pulsatile nature of hormone secretion
• Mechanism for encoding / effecting
• Ovarian phases
• Follicular phase
• Ovulatory phase
• Luteal phase
• Uterine phases
• Menstrual phase
• Proliferative phase
• Secretory phase

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Human menstrual cycle variation in length
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NEGATIVE FEEDBACK MECHANISMS
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POSITIVE FEEDBACK RESULTS IN LH SURGE AND
OVULATION
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Importance of estrogen derived from dominant
follicle
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THE MIDCYCLE LH SURGE
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ELEVATION IN TEMPERATURE ASSOCIATED WITH
OVULATION
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OK, but what happens to the shell of the follicle
left in the ovary?
-It becomes the corpus luteum!
And what does the CL do?
It makes progesterone (and estrogen too)!
What for?
To keep the uterus happy...
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Several important actions of estrogen

• Stimulation of growth of ovaries and follicles
• Maintenance of smooth muscle and epithelium
• Growth of external genitalia (_at_ puberty)
• Growth of breasts (particularly ducts)
• Development of female appearance
• Stimulation of watery sebaceous gland secretions
• Retention of fluid
• Closure of epiphyses of bone

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Important actions of progesterone

• Stimulation of secretions by endometrial glands
• Induction of thick, sticky cervical secretions
• Stimulation of myometrial growth (pregnancy)
• Decrease in motility of uterine smooth muscle
• Stimulation of breast growth (1o glandular
  tissue)
• Inhibition of prolactin effects during pregnancy
• Feedback effects on hypothalamus and pituitary

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