Rucete ✏ Biology In a Nutshell
1. Menstrual Cycle Overview
- A recurring cycle (~28 days) involving the thickening and shedding of the endometrium in preparation for potential implantation.
2. Key Hormonal Events
a) Hypothalamus
- Releases GnRH (Gonadotropin-releasing hormone)
b) Anterior Pituitary
- Releases FSH (Follicle-Stimulating Hormone) and LH (Luteinizing Hormone) in response to GnRH
- FSH stimulates development of the follicle and maturation of the oocyte
- LH triggers ovulation and the formation of the corpus luteum
3. Ovarian Cycle Phases
a) Follicular Phase (Days 1–13)
- FSH promotes follicle growth
- Maturing follicle secretes estrogen, which thickens the endometrium
b) Ovulation (Day 14)
- A surge in LH triggers the release of the secondary oocyte from the ovary
c) Luteal Phase (Days 15–28)
- Corpus luteum forms and secretes estrogen and progesterone
- These hormones maintain the thickened endometrium
- If no fertilization, the corpus luteum degenerates, hormone levels drop, and menstruation occurs
4. Hormonal Feedback and Pregnancy
- If fertilization occurs, the implanted embryo releases hCG (Human Chorionic Gonadotropin)
- hCG maintains the corpus luteum, allowing continued production of estrogen and progesterone
- This prevents menstruation and supports early pregnancy
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Biology in a nutshell