Testis Structure and Why the Scrotum Keeps It Cooler
Biology · Human Reproduction · NEET
The testes lie outside the body in a skin pouch called the scrotum. The scrotum keeps them 2–2.5°C cooler than normal body temperature, and this low temperature is needed for spermatogenesis (sperm formation). Memory hook: "Cool balls make good sperm" — sperm factories need to stay cold, so they hang outside.
The testes hang in the scrotum outside the body, keeping them 2–2.5°C cooler than the 37°C body core — the low temperature needed for spermatogenesis. Each testis has ~250 lobules; inside the seminiferous tubules are spermatogonia and Sertoli cells, while Leydig cells sit outside them.
Your doubts, answered
Why are the testes located outside the body in the scrotum?
Because sperm formation (spermatogenesis) needs a temperature lower than the body core. If the testes stayed inside the warm abdomen, sperm would not form properly. The scrotum holds them outside so they stay cool.
Exactly how much cooler does the scrotum keep the testes?
NCERT states 2–2.5°C lower than the normal internal body temperature. This exact figure is a common one-mark point in NEET, so remember the number 2–2.5°C.
What is the size and shape of one testis?
In adults each testis is oval in shape, about 4 to 5 cm in length and about 2 to 3 cm in width. It is covered by a dense covering.
How many lobules and seminiferous tubules are inside a testis?
Each testis has about 250 compartments called testicular lobules. Each lobule contains one to three highly coiled seminiferous tubules where sperms are made.
Which cells line the seminiferous tubule, and which cells lie outside it?
Inside, the tubule is lined by male germ cells (spermatogonia) and Sertoli cells. Outside the tubules, in the interstitial spaces, are the interstitial cells or Leydig cells that make androgens. Do not mix these up — Sertoli inside, Leydig outside.
What happens if a testis fails to descend into the scrotum?
If a testis stays in the warm abdomen (undescended testis), the higher temperature stops normal spermatogenesis, which can cause infertility. This shows why the cooler scrotum is essential.
⚠️ The NEET trap ✗ Leydig cells are inside the seminiferous tubules and provide nutrition to sperms. ✓ Sertoli cells are inside the seminiferous tubules and provide nutrition to germ cells; Leydig cells lie OUTSIDE the tubules in the interstitial spaces and secrete androgens. 🧠 Sertoli = inside + food; Leydig = outside + hormone. NEET loves swapping these two, so lock the position first.
Solved Human Reproduction NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The scrotum holds the testes outside the abdominal cavity and keeps them 2–2.5°C cooler than body temperature, which is necessary for spermatogenesis.
Is spermatogenesis possible at normal body temperature?
No. Sperm formation needs a temperature lower than the body core. That is why the testes are kept in the cooler scrotum instead of inside the warm abdomen.
How many seminiferous tubules are in one lobule?
Each testicular lobule contains one to three highly coiled seminiferous tubules. There are about 250 lobules per testis.
What produces androgens in the testis?
Leydig cells (interstitial cells), which lie outside the seminiferous tubules in the interstitial spaces, synthesise and secrete androgens.
Where exactly are the testes situated?
The testes are situated outside the abdominal cavity, within a pouch called the scrotum.
