18. Physiology of reproduction. Female reproductive system. Ovogenesis. Hormonal activity of ovaries. Estrogens and progesterone – types, physiological effects, and control of secretion. Female monthly cycle. Pregnancy, delivery, and lactation. Tests for early pregnancy

Ovogenesis

• Begins during fetal life, completed after puberty

• Fetal development (cytogenesis):

  1. Oogonium (primordial follicles) → primary oocyte (arrested until puberty)

• After puberty (during menstrual cycle):
  2. Primary oocyte → secondary oocyte + first polar body (meiosis I)
  3. Ovulation: secondary oocyte + first polar body released
  4. Secondary oocyte completes meiosis II if fertilized → becomes mature ovum + 3 polar bodies formed

Hormonal Activity of Ovaries

Estrogens

• Stimulate egg production and female secondary sexual characteristics (breasts, endometrium, menstrual cycle)

• Types:

  • Estradiol: maintains reproductive system

  • Estriol: helps uterus grow, prepares body for labor, increases pregnancy hormone sensitivity

  • Estrone: involved in female sexual development and function

Progesterone

• Prepares uterus for implantation (thickens lining)

• Maintains pregnancy if fertilization occurs

Control of secretion

• Hypothalamus releases GnRH → stimulates anterior pituitary to secrete FSH & LH

• FSH: stimulates granulosa cells (estrogen and progesterone producing cells)

• LH: stimulates theca interna (prog + est) and granulosa cells

• High estrogen → negative feedback on GnRH, LH, FSH (inhibits secretion)

• High estrogen without progesterone → positive feedback on GnRH, LH, FSH (stimulates secretion)

---

Female Monthly Cycle (Menstrual Cycle)

• Duration: 21–31 days (usually 28)

• Luteal phase: 14 days; ovulation ~ day 14

• Menstrual bleeding: 3–8 days (usually 4–5)

1. Follicular Phase

• Low steroids & inhibin → increase FSH & LH

• Follicles mature; estrogen rises → negative feedback reduces FSH; one follicle survives

• High estrogen → LH surge, FSH decrease

2. Ovulation Phase

• LH surge → follicle ruptures, releasing secondary oocyte

• Oocyte viable for fertilization ~24 hrs

3. Luteal Phase

• Corpus luteum forms → produces estrogen, progesterone, inhibin

• If no fertilization → corpus luteum regresses → hormone levels fall (negative feedback)

4. Menses

• Endometrial lining sheds in absence of fertilization

---

Uterine Cycle (Concise bullet points)

• Proliferative Phase (with follicular phase):

  • Endometrium thickens

  • Increased growth & motility of myometrium

  • Prepares for fertilization & implantation

• Secretory Phase (with luteal phase):

  • Progesterone causes further thickening

  • Myometrium motility decreases

• Menstruation:

  • Shedding of endometrium when fertilization does not occur

pregnancy

Pregnancy

• Lasts ~9 months (from last menstrual period to delivery)

• Hormonal changes: ↑ progesterone, estrogen, hCG, prolactin, cortisol, aldosterone

• Cardiovascular: ↑ blood volume (40–50%), heart rate, stroke volume, cardiac output

• Renal: ↑ kidney size, ureters, GFR by 50%

• Respiratory: ↑ minute ventilation by 40% in first trimester (due to progesterone)

• Body size: uterus, fetus, placenta enlarge; fat and water retention increase

Delivery

• Cervix softens and dilates (up to ~10 cm)

• Uterine contractions increase (stimulated by oxytocin)

• Stages:

  1. Latent phase: slow dilation up to 4 cm

  2. Active phase: faster dilation up to 10 cm

  3. Second stage: fetus expelled

     • Passive: fetus descends to pelvic floor

     • Active: mother pushes

Lactation

• Milk secretion from mammary glands

• Prolactin stimulates milk production

• Oxytocin stimulates milk ejection

• Colostrum: first milk, rich in WBCs & antibodies

• Lactogenesis begins late pregnancy; triggered by placenta delivery and drop in progesterone, estrogen, HPL

Tests for Early Pregnancy

• Human chorionic gonadotropin (hCG)

  • Produced by trophoblasts post-implantation (like trophy wife post breast implant)

  • Maintains corpus luteum & progesterone production

  • Detected in urine/blood 6–12 days post-fertilization

• Early Pregnancy Factor (EPF)

  • Detected within 48 hours of fertilization by rosette inhibition assay