Male Reproductive System

Male Reproductive System Anatomy Overview

• The male reproductive system (MRS) is comprised of gonads (testes), genital excurrent ducts, accessory glands, the male urethra, and the copulatory organ (penis).
• The primary functions of the MRS are to produce male gametes (spermatozoa) and to be responsible for the endocrine function (production of the androgen – testosterone).
• The testes are the primary reproductive organs of the male and are situated within the scrotum, each testis is encased within a tunica vaginalis, composed of visceral and parietal layers, and a fibrous capsule known as the tunica albuginea.
• The scrotum, a pouch of skin, holds the testes, maintaining a temperature 2-3 °C lower than core body temperature, crucial for healthy sperm production.

Testis Structure & Function

• The testes are divided into lobules, each containing 1-4 seminiferous tubules, where spermatogenesis occurs, and interstitial tissue (Leydig cells).
• Spermatogenesis is the process of sperm development.
• Spermatogonia within seminiferous tubules divide and differentiate into mature spermatozoa, taking 60 to 74 days to complete the cycle.
• Spermiogenesis, the final stage of spermatogenesis, is the transformation of spermatids into mature spermatozoa.

Sertoli Cell Structure & Function

• Sertoli cells, located in the seminiferous tubules, are responsible for supporting and nourishing developing spermatozoa.
• Sertoli cells act as a barrier between the blood and seminiferous tubules, called the blood-testis barrier.
• This barrier strictly regulates what enters and exits the seminiferous tubules, protecting sperm cells from the immune system.
• Sertoli cells synthesize and secrete androgen-binding protein, essential for high levels of testosterone within the seminiferous tubules.
• Sertoli cells also secrete inhibin, a hormone that regulates FSH production in the anterior pituitary gland.

Leydig Cell Structure & Function

• Leydig cells are found in the interstitial spaces between seminiferous tubules.
• Leydig cells synthesize and secrete testosterone, the primary male sex hormone which plays a vital role in spermatogenesis and the development of male secondary sexual characteristics.

Intratesticular Ducts

• Tubuli recti, the straight tubules, transition into the rete testis, a network of channels, and finally, to the efferent ductules, leading to the epididymis.
• The tubules recti are lined with Sertoli cells in the initial portion and simple cuboidal epithelium in the distal region.
• The rete testis is lined with simple cuboidal epithelium.
• Efferent ductules, lined with pseudostratified columnar epithelium, transport sperm from the rete testis to the epididymis.

Excurrent Ducts

• Excurrent ducts include the epididymis, ductus deferens, and the ejaculatory duct.

Epididymis Structure & Function

• The epididymis is a highly convoluted duct located on the posterior aspect of each testis.
• It consists of three parts: head, body, and tail.
• The epididymis is lined with pseudostratified columnar epithelium, where sperm undergo maturation and are stored.
• The structure of the epididymis is highly adapted for sperm maturation and transport.

Ductus Deferens Structure & Function

• The ductus deferens, also known as the vas deferens, is a muscular tube that carries sperm from the epididymis to the ejaculatory duct.
• It serves as a conduit for sperm and exhibits peristaltic contractions to propel sperm during ejaculation.

Accessory Glands: Prostate Gland

• The prostate gland surrounds the urethra and contributes to the formation of seminal fluid.
• The prostate gland secretes a milky, alkaline fluid that helps to neutralize vaginal acidity and enhance sperm motility.
• The prostate gland contains corpora amylacea, small spherical bodies of glycoproteins that may be calcified.

Accessory Glands: Seminal Vesicles

• Seminal vesicles, located at the base of the urinary bladder, produce a viscous, alkaline fluid that makes up a significant portion of semen.
• The fluid they produce is rich in fructose, which provides energy for sperm, as well as prostaglandins, which may aid in sperm transport.

Accessory Glands: Bulbourethral Glands (Cowper's Glands)

• The bulbourethral glands, located near the membranous portion of the urethra, secrete a clear, viscous mucus that lubricates the urethra before and during ejaculation.

Semen Composition & Function

• Semen is a mixture of fluids and sperm cells from various parts of the male reproductive system, primarily seminal vesicles, the prostate gland, the testes, and bulbourethral glands.
• A normal ejaculate contains approximately 70 to 100 million spermatozoa per milliliter.
• Semen is alkaline (pH 7.7) to counteract the acidity in the urethra and vaginal environment.

Penis Structure & Function

• The penis is the male copulatory organ.
• It is composed of erectile tissue arranged in paired dorsal corpora cavernosa and one ventral corpus spongiosum.
• Erectile tissue is comprised of arteries, shunts, venous sinusoids, CT, and smooth muscle.
• During erection, blood fills the sinusoidal spaces within the erectile tissue causing the penis to become stiff and rigid.

Factors Impacting Sperm Cell Development

• Factors that can negatively impact the development of sperm cells include:
  • Chromosome abnormalities
  • Varicose veins
  • Testicular defects
  • Nutritional deficiencies
  • Systemic diseases and infections
  • Increased temperature
  • Endocrine disorders
  • Autoimmune sperm cell damage
  • Toxin exposure
  • Drug use
  • Unhealthy lifestyle
  • Post-testicular causes of male infertility

This quiz explores the anatomy and functions of the male reproductive system, focusing on the structure and function of the testes. Learn how the testes produce sperm and hormones, as well as the importance of temperature regulation for spermatogenesis. Test your knowledge on key components like the scrotum and accessory glands.