Male Reproductive System: Testes and Epididymis

• Male reproductive system facilitates reproduction
• Primary function is to produce sperm and the male sex hormone, testosterone
• Includes testes, ducts, accessory glands, and the penis

Testes

• The primary male reproductive organs, also known as testicles
• Located within the scrotum
• Responsible for spermatogenesis (sperm production)
• Responsible for producing testosterone
• Oval-shaped, approximately 5 cm long and 3 cm in diameter
• Surrounded by a fibrous capsule called the tunica albuginea
• Divided into lobules containing seminiferous tubules

Seminiferous Tubules

• Coiled tubes within the testes where spermatogenesis occurs
• Contain germ cells (developing sperm) and Sertoli cells
• Sertoli cells support and nourish the germ cells
• Sertoli cells also form the blood-testis barrier: Protects sperm from immune attack

Epididymis

• Coiled tube attached to the posterior surface of the testis
• Site of sperm maturation and storage
• Sperm spend about two to three weeks here to mature
• Divided into head, body, and tail regions

Ductus Deferens (Vas Deferens)

• Muscular tube that transports sperm from the epididymis to the ejaculatory duct
• Part of the spermatic cord, which includes blood vessels and nerves
• Terminates at the ejaculatory duct which then connects to the urethra
• Can store sperm for a short time

Ejaculatory Ducts

• Formed by the union of the ductus deferens and the seminal vesicle duct
• Eject sperm and seminal fluid into the urethra

Urethra

• Tube that carries urine and semen to the outside of the body
• In males, divided into three regions: prostatic, membranous, and spongy (penile) urethra

Accessory Glands

• Produce seminal fluid, which mixes with sperm to form semen
• Include seminal vesicles, prostate gland, and bulbourethral glands

Seminal Vesicles

• Located on the posterior surface of the urinary bladder
• Secrete a viscous, alkaline fluid
• Fluid contains fructose (energy for sperm), prostaglandins, and clotting factors
• Contributes about 60-70% of semen volume

Prostate Gland

• Surrounds the prostatic urethra inferior to the urinary bladder
• Secretes a milky, slightly acidic fluid
• Fluid contains citrate (nutrient), enzymes (PSA), and antimicrobial substances
• Contributes about 20-30% of semen volume

Bulbourethral Glands (Cowper's Glands)

• Located inferior to the prostate gland
• Secrete a clear, alkaline mucus
• Mucus neutralizes acidic urine in the urethra
• Lubricates the urethra and tip of the penis

Semen

• Mixture of sperm and seminal fluid
• Slightly alkaline, which helps neutralize the acidic environment of the female reproductive tract
• Contains nutrients, enzymes, and other substances that support sperm viability and motility

Scrotum

• Sac of skin and superficial fascia that encloses the testes
• Provides a slightly cooler environment for the testes (about 3°C lower than body temperature)
• Essential for optimal spermatogenesis
• Contains the cremaster muscle, which elevates the testes, and the dartos muscle, which wrinkles the scrotal skin; help regulate testicular temperature

Penis

• Male copulatory organ
• Contains the urethra
• Delivers sperm into the female reproductive tract
• Consists of the root, body (shaft), and glans penis
• Contains three cylindrical bodies of erectile tissue: two corpora cavernosa and one corpus spongiosum

Prepuce (Foreskin)

• Cuff of skin covering the glans penis
• Often removed during circumcision

Spermatogenesis

• Process of sperm production in the seminiferous tubules
• Begins with spermatogonia (stem cells)
• Spermatogonia undergo mitosis to produce more spermatogonia
• Some spermatogonia differentiate into primary spermatocytes
• Primary spermatocytes undergo meiosis I to form secondary spermatocytes
• Secondary spermatocytes undergo meiosis II to form spermatids
• Spermatids undergo spermiogenesis to become mature spermatozoa (sperm)

Sperm Structure

• Head: Contains the nucleus with highly condensed DNA; Acrosome contains enzymes to penetrate the oocyte
• Midpiece: Contains mitochondria for energy production
• Tail: Flagellum for propulsion

Hormonal Regulation

• Hypothalamus releases gonadotropin-releasing hormone (GnRH)
• GnRH stimulates the anterior pituitary to release follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
• FSH stimulates Sertoli cells to promote spermatogenesis
• LH stimulates Leydig cells to produce testosterone
• Testosterone stimulates spermatogenesis, development of secondary sexual characteristics, and libido
• Inhibin, produced by Sertoli cells, inhibits FSH secretion

Testosterone

• Male sex hormone produced by Leydig cells in the testes
• Promotes development of male secondary sexual characteristics (e.g., facial hair, deep voice, increased muscle mass)
• Stimulates spermatogenesis
• Contributes to libido (sex drive)
• Has anabolic effects on muscle and bone

Male Sexual Response

• Erection:
  • Parasympathetic nervous system causes vasodilation of penile arteries
• Ejaculation:
  • Sympathetic nervous system causes contraction of smooth muscle in the reproductive ducts and glands
  • Semen is propelled out of the urethra

Overview of the male reproductive system, focusing on the testes and epididymis. Includes the function of sperm production, hormone production, and sperm maturation. Testes are the primary male reproductive organs responsible for spermatogenesis and testosterone production.