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Male Reproductive System Overview

Jul 28, 2025

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Overview

This lecture covered the male reproductive system, sperm production, structure and function of male reproductive organs, the hormonal regulation of reproduction, and key facts relevant for the final exam.

Meiosis and Gamete Formation

  • Meiosis creates haploid gametes (sperm and egg), each with 23 chromosomes, to maintain the human chromosome count at 46 after fertilization.
  • Sperm and egg are the only haploid cells in humans; all others are diploid.

Male Reproductive Anatomy and Function

  • Testes (inside the scrotum) are paired organs responsible for sperm and testosterone production.
  • Seminiferous tubules in the testes produce sperm; interstitial (Leydig) cells produce testosterone.
  • The spermatic cord surrounds the vas deferens and blood vessels, helps with temperature regulation, and supports the testes.

Sperm Production and Structure

  • Spermatogenesis occurs in seminiferous tubules; each primary spermatocyte yields four sperm.
  • Sperm have a head (nucleus), midpiece (mitochondria for energy), and tail (flagellum for movement).
  • The acrosome (head) contains enzymes to penetrate the egg.

Pathway and Maturation of Sperm

  • Sperm mature and gain motility in the epididymis, where they receive glycogen for energy.
  • Mature sperm travel via the vas deferens, a sperm-only tube, towards the urethra.

Accessory Glands and Semen Composition

  • Seminal vesicles add alkaline fluid, fructose, vitamin C, coagulating enzymes, and prostaglandins to semen.
  • The prostate gland contributes 33% of semen, neutralizing vaginal acidity and activating sperm.
  • Bulbourethral (Cowper’s) glands secrete pre-ejaculate mucus to clean and lubricate the urethra.
  • Only 4% of semen is sperm; the rest is accessory gland secretions.

External Male Anatomy and Physiology

  • The scrotum regulates testes temperature for sperm viability.
  • The penis contains three erectile bodies, enabling erection and ejaculation.
  • Erection is caused by blood flow (parasympathetic), while ejaculation is a sympathetic response.

Hormonal Regulation

  • Hypothalamus releases gonadotropin-releasing hormone (GnRH), signaling the anterior pituitary.
  • Anterior pituitary releases FSH (stimulates sperm production) and LH (stimulates testosterone production).
  • Testosterone develops secondary sex characteristics in males.
  • Negative feedback regulates testosterone levels via GnRH and LH.

Key Terms & Definitions

  • Meiosis — cell division producing haploid gametes.
  • Haploid — cell with half normal chromosomes (23 in humans).
  • Diploid — cell with a full set of chromosomes (46 in humans).
  • Seminiferous tubules — site of sperm production in testes.
  • Leydig (interstitial) cells — cells that produce testosterone.
  • Epididymis — structure where sperm mature and gain motility.
  • Vas deferens — duct transporting mature sperm.
  • Semen — fluid containing sperm and accessory gland secretions.
  • FSH — hormone stimulating sperm production.
  • LH — hormone stimulating testosterone production.

Action Items / Next Steps

  • Complete the meiosis lab worksheet with final exam questions if not done.
  • Review the final exam guide (last page of the class packet).
  • Study key terms and pathways for the male reproductive system for the final exam.

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