explain the menstrual cycle with hormonal changes and daigram ....answer this question in deatil . Which will be accepted by rhugs university... 10 marker according to indu khurahna ....with related daigram tooooo
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I now have comprehensive content and diagrams. Let me compose the detailed answer in the style Indu Khurana (textbook of physiology) presents it, suitable for a Rajasthan/Rhugs University 10-marker.
The Menstrual Cycle - Hormonal Changes
(10-Mark Answer | Indu Khurana Style | Rhugs University Standard)
DEFINITION
The menstrual cycle is a series of regular, cyclic changes occurring in the female reproductive organs (especially the ovary and uterus) that prepare the uterus for implantation of a fertilized ovum. If fertilization does not occur, the uterine lining is shed as menstruation.
- Duration: 28 days (average; varies from 21-35 days)
- Counted from Day 1 of menstruation to Day 1 of the next
- It begins at menarche (12-13 years) and ends at menopause (~45-50 years)
HORMONES INVOLVED
| Hormone | Source | Role |
|---|---|---|
| GnRH | Hypothalamus | Stimulates FSH & LH release |
| FSH | Anterior pituitary | Follicle development, estrogen production |
| LH | Anterior pituitary | Ovulation trigger, corpus luteum formation |
| Estrogen (Estradiol) | Granulosa cells of follicle | Endometrial proliferation, +ve feedback for LH surge |
| Progesterone | Corpus luteum | Secretory changes in endometrium, thermogenic |
| Inhibin B | Granulosa cells | Negative feedback on FSH |
PHASES OF THE MENSTRUAL CYCLE
The cycle has two major phases from the ovarian perspective, and three phases from the uterine perspective:
A. OVARIAN PHASES
1. FOLLICULAR PHASE (Day 1-14)
Hormonal Events:
- At the start of the cycle, FSH levels rise (due to reduced estrogen & progesterone from the previous corpus luteum - removal of negative feedback)
- FSH stimulates several primordial follicles to enlarge; one becomes the dominant (Graafian) follicle by Day 6
- The dominant follicle's granulosa cells secrete increasing amounts of estradiol (E2)
- The theca interna cells produce androgens, which are aromatized to estrogen by granulosa cells (two-cell theory)
- Rising estrogen initially exerts negative feedback on FSH (so FSH falls slightly after Day 7)
- Inhibin B (from granulosa cells) also suppresses FSH, helping ensure only one dominant follicle matures
- As estrogen climbs very high near Day 12-13, it switches to positive feedback on the anterior pituitary and hypothalamus
Key Result: A massive LH surge occurs at mid-cycle (Day 13-14), triggering ovulation ~9 hours after the LH peak
2. OVULATION (Day 14)
- Distended Graafian follicle ruptures
- Ovum is extruded into the peritoneal cavity and picked up by the fimbriae of the fallopian tube
- Minor bleeding from follicle rupture can cause mittelschmerz (midcycle pain)
- Basal body temperature (BBT) rises by ~0.5°C after ovulation (due to thermogenic effect of progesterone)
3. LUTEAL PHASE (Day 15-28)
Hormonal Events:
- After ovulation, the ruptured follicle fills with blood (corpus hemorrhagicum), then granulosa and theca cells proliferate under LH influence to form the corpus luteum (yellow, lipid-rich)
- Corpus luteum secretes progesterone (primarily) and estrogen
- Progesterone peaks around Day 21
- Both progesterone and estrogen exert negative feedback on FSH and LH, so pituitary gonadotropins fall
- The corpus luteum is maintained by LH; it has a fixed lifespan of ~14 days
- Without fertilization: corpus luteum degenerates into corpus albicans by Day 26-27; progesterone and estrogen fall sharply
- This hormonal withdrawal triggers menstruation
B. UTERINE (ENDOMETRIAL) PHASES
1. Menstrual Phase (Day 1-5)
- Withdrawal of estrogen + progesterone → vasospasm of spiral arteries (mediated by PGF2α)
- Endometrial necrosis and shedding
- Menstrual flow: ~30-80 mL; contains blood, endometrial debris, prostaglandins, fibrinolysin (prevents clotting)
- Only stratum basale remains; stratum functionale is shed
2. Proliferative Phase (Day 5-14) = Follicular phase
- Estrogen from developing follicle drives endometrial regeneration
- Endometrial thickness increases from 0.5 mm → 3.5 mm
- Endometrial glands elongate but do not secrete
- Cervical mucus becomes thin, watery, elastic (ferning pattern; spinnbarkeit)
- Spiral arteries elongate
3. Secretory Phase (Day 15-28) = Luteal phase
- Progesterone (+ estrogen) from corpus luteum acts on proliferated endometrium
- Uterine glands become tortuous and coiled, accumulate glycogen, increase secretions
- Stroma becomes edematous
- Spiral arteries become more coiled
- Cervical mucus becomes thick, viscid, non-ferning (blocks sperm - fertilization window has passed)
- If implantation occurs: hCG from trophoblast maintains corpus luteum
DIAGRAM 1: Ovarian and Uterine Events During the Menstrual Cycle
Fig: Relationship between ovarian events (follicle → ovulation → corpus luteum) and uterine endometrial changes across a 28-day cycle. Estrogen drives the proliferative phase; progesterone + estrogen drive the secretory phase. (Ganong's Review of Medical Physiology, 26th Ed.)
DIAGRAM 2: Hormonal Changes During the Menstrual Cycle
Fig: Basal body temperature and plasma hormone concentrations during the normal human menstrual cycle. Note: LH surge at Day 0 (midcycle), estradiol peak just before LH surge, progesterone peak in mid-luteal phase (~Day +7), FSH rise at start and small secondary peak at ovulation, BBT rise after ovulation. M = menses. (Ganong's Review of Medical Physiology, 26th Ed.)
SUMMARY TABLE: Hormonal Changes at a Glance
| Phase | Dominant Hormone | FSH | LH | Estrogen | Progesterone |
|---|---|---|---|---|---|
| Menstrual (Day 1-5) | None | Rising | Low | Low | Low |
| Proliferative (Day 5-13) | Estrogen | Falls gradually | Low | Rising | Low |
| Ovulation (Day 14) | LH surge | Small peak | Surge | Peak | Starting to rise |
| Secretory (Day 15-26) | Progesterone | Low | Low | Moderate | High (peaks Day 21) |
| Premenstrual (Day 27-28) | Falling | Starting to rise | Low | Falling | Falling |
KEY POINTS FOR EXAM (Important for 10-Marker)
- Positive feedback of estrogen triggers the LH surge - this is the key mechanism of ovulation
- Corpus luteum lifespan is ~14 days - explains the constant secretory phase (14 days) vs. variable follicular phase
- Progesterone is thermogenic - causes rise in BBT after ovulation (used in natural family planning)
- Prostaglandin PGF2α causes vasospasm of spiral arteries → menstruation
- Inhibin B (follicular phase) and Inhibin A (luteal phase) both suppress FSH
- Ferning of cervical mucus = estrogen effect (follicular phase); non-ferning = progesterone effect (luteal)
- Anovulatory cycles are common at menarche and premenopause - no corpus luteum formed, no progesterone, hence no secretory phase
- hCG from implanted embryo "rescues" the corpus luteum if fertilization occurs - prevents menstruation
Sources: Ganong's Review of Medical Physiology 26th Ed.; Costanzo Physiology 7th Ed.; Berek & Novak's Gynecology - all consistent with standard Indu Khurana physiology curriculum
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