The testes, often referred to as the male gonads, are vital organs within the male reproductive system. These paired organs are located within the scrotum, a sac of skin located beneath the penis. Testes serve two primary functions: sperm production (spermatogenesis) and hormone secretion, primarily testosterone.

In summary, the testes are essential organs responsible for sperm production and hormone secretion, playing a central role in male reproductive and sexual health.

What is testis?

The testis, singularly referred to as “testis” and pluralized as “testes” or “testicles,” is one of the primary reproductive organs in males. It’s a paired organ, typically two in number, located in the scrotum. The testes have two primary functions: sperm production (spermatogenesis) and hormone secretion, primarily testosterone. They are crucial for the male reproductive system and contribute to various aspects of male sexual development and function.

Anatomy of the testis

The testis is a complex organ with several anatomical features contributing to its function within the male reproductive system. Here’s a breakdown of its anatomy:

Structure: Each testis is an oval-shaped gland, typically measuring about 4-5 centimeters in length. It is encased in a tough fibrous capsule known as the tunica albuginea, which provides structural support and protection.

Location: The testes are located within the scrotum, a sac of skin situated beneath the penis. This positioning outside the body helps regulate the temperature of the testes, crucial for optimal sperm production.

Internal Components:

• Seminiferous Tubules: These are highly coiled tubules that make up the bulk of the testis. They are the sites of spermatogenesis, the process of sperm cell production. Within the seminiferous tubules, germ cells undergo division and maturation to form spermatozoa.
• Interstitial Cells (Leydig Cells): Found in the spaces between the seminiferous tubules, Leydig cells produce and secrete testosterone, the primary male sex hormone.

Blood Supply:

• Testicular Artery: Each testis receives its blood supply primarily from the testicular artery, which arises from the abdominal aorta.
• Testicular Vein: Blood is drained from the testes by the testicular veins, which typically form the testicular plexus and ultimately drain into the inferior vena cava on the right side and the left renal vein on the left side.

Temperature Regulation: The testes are located outside the body within the scrotum, which helps maintain a lower temperature compared to the core body temperature. This cooler environment is essential for the proper function of spermatogenesis.

Epididymis: While not a part of the testis itself, the epididymis is a tightly coiled tube located on the surface of each testis. It serves as a site for the storage, maturation, and transport of sperm cells produced in the testis before they are ejaculated.

In summary, the testis is a vital organ within the male reproductive system, consisting of various structures and components that contribute to sperm production and hormone secretion, essential for male fertility and sexual function.

Functions of the testis

The testes, or testicles, serve several crucial functions within the male reproductive system:

Sperm Production (Spermatogenesis): The primary function of the testes is to produce sperm cells through a process called spermatogenesis. This complex process involves the continuous division and differentiation of germ cells within the seminiferous tubules of the testes. Sperm production begins at puberty and continues throughout a man’s life.

Hormone Secretion: The testes produce and secrete testosterone, the primary male sex hormone. Testosterone plays a key role in regulating various aspects of male physiology and development.

Regulation of Spermatogenesis: Besides testosterone, the testes also produce other hormones that regulate spermatogenesis. Follicle-stimulating hormone (FSH) and luteinizing hormone (LH), secreted by the pituitary gland, stimulate various cells within the testes to support sperm production and hormone secretion.

Temperature Regulation: The testes are located outside the body within the scrotum, which helps regulate their temperature. Sperm production is optimal at temperatures slightly lower than the body’s core temperature. The scrotum contracts or relaxes in response to temperature changes to maintain an optimal environment for sperm production.

Hormones secreted from testis

The testes, or testicles, secrete several hormones, with testosterone being the primary hormone. Here are the main hormones secreted by the testes:

Testosterone: Testosterone is the primary male sex hormone and an androgen. It plays a crucial role in various physiological processes, including:

• Development and maintenance of male reproductive tissues, such as the testes and prostate gland.
• Development of secondary sexual characteristics during puberty, such as deepening of the voice, growth of facial and body hair, and increased muscle mass and bone density.
• Regulation of libido (sex drive) and sexual function.
• Maintenance of muscle mass, bone density, and red blood cell production.

Inhibin: Inhibin is a hormone secreted by Sertoli cells within the seminiferous tubules of the testes. It plays a role in regulating the production of follicle-stimulating hormone (FSH) from the pituitary gland. Inhibin inhibits FSH secretion, thereby indirectly regulating spermatogenesis.

Estrogens: While primarily associated with females, small amounts of estrogen hormones are also produced by Leydig cells in the testes. Estrogens play various roles in males, including bone metabolism, lipid metabolism, and regulation of reproductive function.

While these hormones are primarily secreted by the testes, their production and secretion can be influenced by various factors, including hormones secreted by other glands such as the pituitary gland and hypothalamus.

Summary

The testes, or testicles, are key organs in the male reproductive system. They are located within the scrotum and serve two primary functions: sperm production (spermatogenesis) and hormone secretion, primarily testosterone. Structurally, the testes consist of seminiferous tubules where spermatogenesis occurs, along with Leydig cells that produce testosterone. Blood supply is provided by the testicular artery and drained by the testicular veins. The temperature-regulated environment of the scrotum is crucial for optimal sperm production. Overall, the testes play a vital role in male fertility, sexual development, and overall reproductive health.

Prof. Dr. Emin ÖZBEK

Urologist

Istanbul- TURKEY