Q.Describe the structure of a seminiferous tubule.

Male Reproductive Anatomy – A First Look

Think of the male reproductive system as a production and delivery line. Its job is to make tiny cells called sperm (the male contribution to reproduction) and then safely deliver them into the female body. Unlike the female system, which is mostly internal, the male system has several parts that are visible outside the body. That’s the first big clue: the system is built for external production and internal delivery.

The Two Main Jobs

The male reproductive system does two things at once:

• Spermatogenesis – making sperm inside the testes.
• Hormone production – making the male sex hormone testosterone, which drives puberty, muscle growth, voice deepening, and sex drive.

These two jobs happen in the same organs, but they are separate processes. Testosterone is made by special cells between the sperm-making tubes, not inside the tubes themselves.

The Key Parts (from outside to inside)

1. The Testes (the factories)

The two testes (singular: testis) are oval organs about the size of a large olive. They hang outside the body in a pouch of skin called the scrotum. Why outside? Because sperm production needs a temperature about 2–3°C lower than normal body temperature. The scrotum can contract (pull testes closer to the body when cold) or relax (let them hang lower when warm) to regulate this temperature.

Inside each testis are about 250–300 coiled tubes called seminiferous tubules. This is where sperm are actually made. Between these tubules are the interstitial cells (Leydig cells) that produce testosterone.

2. The Duct System (the conveyor belt)

Once sperm are made, they need to travel. The path is:

Seminiferous tubules → Rete testis → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra

The epididymis is a long, coiled tube stuck to the back of each testis. Sperm are stored here and become motile (able to swim) as they pass through. It takes about 2–3 weeks for a sperm to travel the full length of the epididymis.

The vas deferens (plural: vasa deferentia) is a thick-walled muscular tube that runs from the scrotum up into the abdomen. You can feel it as a firm cord just above the testis – it’s part of the spermatic cord. During a vasectomy, this tube is cut or blocked to prevent sperm from reaching the urethra.

3. The Accessory Glands (the fluids)

Sperm alone are just a tiny fraction of the fluid that comes out during ejaculation. Most of the volume comes from three sets of glands:

• Seminal vesicles – two sac-like structures behind the bladder. They secrete a thick, fructose-rich fluid that provides energy for the sperm. This makes up about 60–70% of the semen volume.
• Prostate gland – a walnut-sized gland that surrounds the urethra just below the bladder. It secretes a thin, milky fluid that makes the semen more fluid and slightly alkaline (to protect sperm from the acidic vagina).
• Bulbourethral glands (Cowper’s glands) – two pea-sized glands near the base of the penis. They secrete a clear, slippery fluid before ejaculation that lubricates the urethra and neutralises any leftover urine acidity.

4. The Penis (the delivery tube)

The penis is the external organ that deposits semen into the female vagina. It contains three columns of erectile tissue that fill with blood during arousal, causing an erection. The urethra runs through the centre of the penis and carries both urine and semen – but never at the same time. A sphincter (a ring of muscle) at the base of the bladder closes off the urine passage during ejaculation.

The tip of the penis is called the glans penis, which is covered by a loose fold of skin called the foreskin (prepuce) in uncircumcised males.

Why This Matters (beyond reproduction) …