Lecture on the Woman's Menstrual Cycle

Introduction

• Presenter: Sarah Thread Sterner
• Lecture is part of the NCLEX review series for maternity
• Focus on menstrual cycle phases, hormones, and their roles
• Key points for exams: phases, hormone roles

Overview of the Menstrual Cycle

• Typical menstrual cycle: 28 days
• Ovulation: Mid-cycle, around day 14
• Primary goal: Prepare for potential fertilization and pregnancy
• Cycle repeats monthly if fertilization does not occur

Phases of the Menstrual and Ovarian Cycles

Ovarian Cycle Phases

1. Follicular Phase (Days 1-13)

   • Goal: Mature a follicle and egg for release
   • Involves hormones: GnRH, FSH, LH
   • FSH stimulates follicle growth; only one matures fully
   • Estrogen increases as the follicle matures
   • LH surge triggered by estrogen peak, leading to ovulation

2. Ovulation (Day 14)

   • Release of mature egg from the ovary
   • Egg captured by fimbriae and enters the fallopian tube
   • Fertilization potential highest: Cycle Days 9-16 (roughly)

3. Luteal Phase (Days 15-28)

   • Corpus luteum forms from the ruptured follicle
   • Secretes progesterone and estrogen
   • Prepares the endometrium for potential implantation

Uterine Cycle Phases

1. Menstrual Phase (Days 1-6)

   • Shedding of the endometrium
   • Hormone levels (progesterone, estrogen) drop

2. Proliferative Phase (Days 7-14)

   • Rebuilding of the endometrial layer
   • Driven by estrogen from the growing follicle
   • Cervical mucus becomes sperm-friendly

3. Secretory Phase (Days 15-28)

   • Endometrium becomes receptive to implantation
   • Supported by progesterone and estrogen from the corpus luteum

Hormones Involved

• Gonadotropin-Releasing Hormone (GnRH): Initiates cycle
• Follicle Stimulating Hormone (FSH): Stimulates follicle growth
• Luteinizing Hormone (LH): Triggers ovulation
• Estrogen: Promotes endometrial growth; feedback to pituitary
• Progesterone: Prepares endometrium for implantation
• Human Chorionic Gonadotropin (HCG): Maintains corpus luteum if pregnancy occurs

Fertilization and Pregnancy

• If fertilization occurs, HCG maintains the corpus luteum
• Corpus luteum supports pregnancy until placenta takes over
• If no fertilization, corpus luteum degenerates, cycle restarts

Conclusion

• Understand the phases and corresponding hormonal changes
• Check out additional resources for quizzes and further videos
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