OpenStax_Ch24 +25__reproduction_

The Reproductive System

Introduction

  • A newborn's birth is a testament to the healthy reproductive systems of both parents.
  • The endocrine systems regulate the production and release of gametes (reproductive cells).
  • Gametes contain the parents' genetic material (23 chromosomes).
  • Reproductive behavior facilitates sperm transfer to the female reproductive tract for fertilization.
  • Fertilization must occur, followed by implantation and development.

27.1 Anatomy and Physiology of the Male Reproductive System

  • A gamete is a specialized sex cell with 23 chromosomes.
  • A sperm (male gamete) combines with an oocyte (female gamete) during fertilization.
  • The male reproductive system produces sperm and transfers them to the female reproductive tract.
  • Paired testes produce sperm and androgens (e.g., testosterone).
  • Accessory organs and ducts aid sperm maturation and transport sperm to the penis.

Scrotum

  • The scrotum is a skin-covered, muscular sac that houses the testes.
  • It maintains the testes at 2 to 4°C below core body temperature for efficient sperm production.
  • The dartos muscle is a subcutaneous muscle layer within the scrotum that divides it into two compartments.
  • Cremaster muscles, descending from the internal oblique muscle, cover each testis.
  • The dartos and cremaster muscles elevate the testes in cold weather and relax in warm weather to regulate temperature.
  • The scrotum has a raised medial thickening called the raphae.

Testes

  • The testes (singular: testis) are the male gonads, producing sperm and androgens (e.g., testosterone).
  • They are active throughout a male's reproductive lifespan.
  • Paired ovals, each testis is 4 to 5 cm long and housed within the scrotum.
  • The testes are surrounded by two protective layers of connective tissue:
    • Tunica vaginalis: A serous membrane with parietal and visceral layers.
    • Tunica albuginea: A tough, white, dense connective tissue layer that covers the testis and invaginates to form septa, dividing the testis into 300 to 400 lobules.
  • Within the lobules, sperm develop in seminiferous tubules.
  • During fetal development (seventh month), each testis descends into the scrotal cavity, called the