Lecture Notes: The Gamble of Reproduction

Introduction

• Sex involves significant mental and emotional risks.
• Different physical investments in reproduction between the sexes.

Female Reproductive Investment

• Female gamete (Ovum)
  • A high-stakes biological gamble.
  • Takes over a year to develop; visibly large as cells go (0.1 mm).
  • Supported by uterine tissues, which are cyclically rebuilt.
  • Post-ovulation dedication to fertilization for a significant time (up to 10 months if fertilized).

Male Reproductive Strategy

• Male gametes (Sperm)
  • Low-stakes strategy with high quantity production.
  • Massively smaller than eggs, easily produced like skin cells.
  • Stripped down to basics: nucleus, tail, and mitochondria.
  • High production rate; 1500 sperm per second.

Male Reproductive Anatomy

• Testes and Temperature Sensitivity
  • Testes located outside the body to maintain lower temperature needed for sperm production.
  • Divided into lobules containing seminiferous tubules (sperm factories).
  • Supported by Sertoli cells and testosterone-secreting Leydig cells.

Spermatogenesis Process

• Triggered by hormonal cascade during puberty.
  • Hypothalamus releases GnRH.
  • Pituitary gland secretes FSH and LH.
  • Testosterone produced by Leydig cells.
  • Sertoli cells release ABP to bind testosterone.
• Spermatogonia
  • Stem cells that divide to form sperm.
  • Undergo mitosis during childhood and meiosis after puberty.
• Spermiogenesis
  • Spermatids develop into mobile sperm with tails.
  • Takes about five weeks to complete.

Sperm Maturation and Pathway

• Maturity in the epididymis
  • Gain motility and energy over 20 days.
• Pathway: seminiferous tubules → rete testis → epididymis → vas deferens → ejaculatory duct → urethra.

Role of Accessory Glands

• Seminal Vesicles: Nourish sperm, facilitate transport.
• Prostate Gland: Provides enzymes and citric acid to liquefy semen.
• Bulbo-urethral Glands: Clear urethra prior to ejaculation.

The Male External Genitalia

• Penis Structure
  • Consists of a shaft, glans penis, and foreskin.
  • Contains erectile tissue for penetration.

Conclusion

• Overview of testicular anatomy and spermatogenesis.
• Importance of gonadotropin and testosterone.
• Next focus: fertilization process.

Crash Course Information

• Acknowledgments to contributors and supporters of Crash Course.