🔬 Reproductive System Lesson

STEVE: the path sperm travel from production to ejaculation

Sperm travel through a surprisingly long, specific pathway before ejaculation — and three separate glands each contribute something different to the final product.

Semin. tub.

Str. tub.

Rete testis

Vas def.

Ejac. duct

📖 Full Breakdown

From seminiferous tubules to ejaculation, plus what each accessory gland adds

The epididymis performs a specific job that sperm absolutely require before they can function.

Seminiferous tubules

Sperm production site

Located in the testes. Sertoli cells nourish developing sperm, while Leydig cells produce testosterone — two distinct cell populations with two distinct jobs within the same tubules.

Epididymis

Maturation and storage — 20 days

This is specifically where sperm GAIN MOTILITY — sperm leaving the testes are not yet capable of independent movement, making this maturation step functionally essential, not optional.

Vas deferens

Transport to the ejaculatory duct

This is the structure cut during a vasectomy — a permanent form of male contraception that blocks sperm transport without affecting testosterone production or ejaculation volume much.

Accessory glands

Each contributes distinct fluid components

Seminal vesicles provide 60% of semen volume, rich in fructose for sperm energy. The prostate provides alkaline fluid (neutralizing vaginal acidity) and produces PSA. Bulbourethral glands provide pre-ejaculatory fluid.

🩺 Clinical / Exam Application

A man who had a vasectomy years ago still ejaculates a normal-seeming volume of semen and has no change in testosterone-related characteristics, but is infertile. Because the vas deferens is cut specifically at a point AFTER sperm production but BEFORE the accessory glands (seminal vesicles, prostate) add their fluid contributions, semen volume remains largely unchanged — the seminal vesicles and prostate continue contributing their fluid regardless of whether sperm can get through. The vasectomy blocks only the sperm themselves from reaching the ejaculate, not the fluid volume they would have traveled through.

⚠️ Exam Alert

A frequently tested clinical fact: a vasectomy specifically targets the vas deferens, blocking sperm transport while leaving testosterone production (from Leydig cells in the testes) and the accessory gland fluid contributions completely intact — this is why vasectomy doesn't affect libido, secondary sex characteristics, or significantly change ejaculate volume.

🚧 Common Trap

Don't assume sperm are immediately capable of movement once produced in the seminiferous tubules. They gain motility specifically during their time in the epididymis — sperm collected directly from the testes would not yet be capable of the independent swimming motion needed for fertilization.

✅ Quick Check

Why does a vasectomy not significantly reduce ejaculate volume, even though it makes a man infertile?

📝 Exam Prep

Common Exam Questions

❓ What is the pathway sperm travel from production to ejaculation?

✅ Seminiferous tubules (production) → tubuli recti → rete testis → efferent ductules → epididymis (maturation, ~20 days) → vas deferens → ejaculatory duct → urethra → external. Accessory glands (seminal vesicles, prostate, bulbourethral glands) add fluid along the way.

❓ What is the function of the epididymis, and why is it necessary?

✅ The epididymis is where sperm mature and are stored, specifically gaining motility during this time — sperm are not yet capable of independent movement when they leave the testes, making this maturation step essential for fertility.