Lecture on Male Reproductive Physiology

Introduction

• Beginning with male reproductive physiology, followed by female reproductive physiology.
• Highlighted that male reproductive physiology is simpler than female's.
• Brief personal story about Easter in Northville, preparing an Easter basket.

Anatomy of Male Reproductive System

• Testes (Testicles):

  • Sperm manufactured in testes located in the seminiferous tubules.
  • Testes are paired gonads in the scrotum, separated into lobules by connective tissue called tunica albuginea.
  • Tunica vaginalis is a remnant of the peritoneal cavity surrounding the testes.

• Sperm Pathway:

  • Manufactured in seminiferous tubules -> rete testis -> epididymis -> vas deferens -> ejaculatory duct -> prostatic urethra -> penile urethra -> exits through glans penis.
  • Mnemonic: S (Seminiferous tubules) -> E (Epididymis) -> V (Vas deferens) -> E (Ejaculatory duct) -> U (Urethra) -> P (Penis)

Temperature Regulation

• Testes need to be maintained at 35°C for proper spermatogenesis, cooler than body temperature.
• Mechanisms:
  • Pampiniform plexus for countercurrent heat exchange.
  • Dartos and cremaster muscles regulate testicular temperature via contraction and relaxation.

Seminiferous Tubules

• Are 400 meters long if stretched out; site of sperm production.
• Cell Types:
  • Spermatogenic cells: Develop into spermatozoa.
  • Sertoli cells: Support and nourish developing sperm; form blood-testis barrier.
  • Leydig cells: Produce testosterone.

Sperm Development

• Spermatogonia (diploid) -> Primary spermatocytes -> Secondary spermatocytes -> Spermatids -> Spermatozoa.
• Sertoli cells produce luminal fluid, androgen binding protein (holds testosterone), and inhibin.

Hormonal Regulation

• GnRH, LH, FSH: Involved in testosterone production and spermatogenesis.
• Testosterone promotes development of male reproductive organs and secondary sex characteristics.

Accessory Glands

• Seminal Vesicles: Produce fructose-rich fluid (~70% of semen volume), cementagellins for semen coagulation.
• Prostate Gland: Produces alkaline fluid (~30% of semen volume); PSA for semen liquefaction.
• Bulbourethral Glands (Cowper's glands): Secrete lubricating fluid to cleanse urethra before ejaculation.

Erection and Ejaculation

• Erection: Engorged with blood due to nitric oxide-mediated vasodilation.
• Ejaculation: Emission (smooth muscle contraction) and expulsion (spinal reflex, bulbospongiosus muscle contraction).

Physiological and Developmental Points

• Testosterone necessary for development and maintenance of male characteristics.
• Spermatogenesis requires high local testosterone concentrations.
• Mini-puberty in utero for male reproductive tract development.
• Males don't experience menopause-like event; testosterone levels can remain relatively stable throughout life.

Clinical and Societal Implications

• Discussion on implications of climate change on male fertility.
• DHT (dihydrotestosterone) critical for external genitalia development.
• Possible effects of endocrine disorders on puberty and fertility.

These notes summarize the lecture given on male reproductive physiology, covering anatomy, physiology, hormonal regulation, and clinical implications.