Lecture on the Reproductive System

Introduction

• Focus on the female reproductive system
• No external genitalia differentiation until about 9 weeks of pregnancy
• External genitalia development is hormone-dependent

Development of Genitalia

• Female Development: External genitalia form by default without testosterone.
• Male Development:
  • Around week 10, testosterone secretion begins
  • Testosterone converts clitoris and surrounding tissues into male genitalia
  • Insufficient testosterone results in ambiguous genitalia in XY individuals
  • Brain wiring corresponds with genetic sex, affecting gender identity

Testosterone and External Genitalia

• Testosterone injections in adults can cause clitoral growth into a small penis
• In children, timely testosterone can result in a fully functional penis

Skin and Burn Treatment

• The perineum region is often intact in burn victims
• Skin from the perineum can be grown in labs to treat burns
• Burn wards can grow multiple sheets of skin for grafting

Female Anatomy

• Vulva: External female genitalia, includes clitoris, urethral opening, vaginal opening
• Vaginal Canal: Stretchy, lined with skeletal muscle, significant for childbirth
• Uterus: Supports growing fetus, situated above vaginal canal
• Kegels: Exercises to strengthen vaginal muscles post-pregnancy

Menstrual Cycle

• Hormonal Regulation: GnRH, FSH, LH, and estrogen play crucial roles
• Ovarian Cycle:
  • Follicles mature under the influence of FSH
  • Estrogen increases lead to a positive feedback loop, stimulating ovulation
  • Progesterone maintains uterine lining post-ovulation
• Uterine Cycle:
  • Endometrial lining builds up and sheds if no pregnancy occurs
  • Pregnancy maintained by progesterone, preventing further ovulation

Pregnancy and Hormones

• If fertilization occurs, embryo secretes HCG to maintain the corpus luteum
• Progesterone prevents further ovulation, supporting pregnancy
• Birth and Labor:
  • Myometrium contracts to facilitate childbirth
  • Oxytocin plays a role in labor and delivery

Miscellaneous Topics

• Menstrual Synchrony: Female cycles can synchronize in shared environments
• Impact of Environmental Hormones: Exposure to hormones can affect menstrual regularity
• Men’s Influence: Testosterone from men can regulate female cycles

Male Reproductive System

• GnRH stimulates FSH and LH in males during puberty
• Testosterone production and its effects on male development

These notes cover the central themes and detailed discussions from the lecture on the reproductive system, providing a comprehensive overview of both female and male reproductive processes, hormonal interactions, and associated physiological phenomena.