Structure of Testes and Male Accessory Ducts

The testes are the male reproductive glands where sperm and the hormone testosterone are made. Each testis is an oval organ about 4 to 5 cm long, kept inside a skin pouch called the scrotum, which hangs outside the body. The scrotum keeps the testes about 2 to 2.5 degrees Celsius cooler than body temperature, and this lower temperature is essential for healthy sperm production.

Understanding the structure of the testes and the tubes connected to them explains how millions of sperm are produced every day, stored, matured and finally delivered out of the body. It also helps explain common problems like blocked ducts, low sperm count and male infertility.

Key Concepts

• Scrotum: the skin sac that holds both testes outside the abdomen and regulates their temperature.
• Seminiferous tubules: tiny coiled tubes inside the testis where sperm are actually produced. Each testis has 1 to 3 highly coiled tubules in each of its roughly 250 testicular lobules.
• Sertoli cells: nurse cells lining the tubules that feed and support developing sperm.
• Leydig cells (interstitial cells): cells lying between the tubules that secrete testosterone.
• Rete testis: a network of small channels that collects sperm from the seminiferous tubules.
• Vasa efferentia: fine ducts carrying sperm from the rete testis to the epididymis.
• Epididymis: a long coiled tube on the back of each testis where sperm mature and are stored.
• Vas deferens: the muscular duct that carries sperm from the epididymis up into the abdomen and towards the urethra.
• Ejaculatory duct and urethra: the final pathway through which semen leaves the body.

How It Works

1. Sperm are produced inside the seminiferous tubules of the testis.
2. Immature sperm pass into the rete testis, a mesh of tiny channels.
3. Through the vasa efferentia they reach the epididymis, where they gain motility and are stored.
4. During ejaculation, the muscular vas deferens pushes sperm upward; the vas joins the duct of the seminal vesicle to form the ejaculatory duct.
5. Semen passes through the urethra and out of the body.

Worked Example

Trace the exact path of one sperm cell from birth to exit. Step 1: it is formed in a seminiferous tubule of the left testis. Step 2: it moves into the rete testis. Step 3: vasa efferentia carry it to the epididymis, where it matures over roughly 2 weeks. Step 4: at ejaculation it travels up the vas deferens, which loops over the urinary bladder. Step 5: it enters the ejaculatory duct, mixes with gland secretions to form semen, and Step 6: exits through the urethra. Total path: tubule, rete testis, vasa efferentia, epididymis, vas deferens, ejaculatory duct, urethra.

Common Misconceptions

• "Sperm are made in the prostate." Wrong. Sperm are made only in the seminiferous tubules of the testes; glands like the prostate only add fluid.
• "The testes are inside the abdomen." In adult males they lie in the scrotum outside the abdomen, because sperm production needs a cooler temperature.
• "Sperm can swim as soon as they are made." Newly made sperm are immotile; they gain swimming ability during maturation in the epididymis.

Real-World Applications

Vasectomy, a male sterilisation method, works by cutting the vas deferens so sperm cannot reach the urethra. Doctors check semen samples under a microscope to diagnose low sperm count. Tight clothing or undescended testes (cryptorchidism) raise testicular temperature and can reduce fertility, which is why early treatment matters in medicine and animal breeding.

In short, the testis is the sperm factory, the epididymis is the training and storage centre, and the duct system is the delivery pipeline that carries sperm safely out of the male body.