Spermatozoa freshly deposited in the female tract cannot fertilise an oocyte immediately. The physiological change that renders them capable of fertilisation is called capacitation. Which statement about capacitation is correct?
- A It involves removal of seminal plasma glycoproteins from the sperm head and increased membrane fluidity, taking hours in the female tract ✓
- B It takes place in the epididymis over several weeks
- C It involves the acrosomal enzyme release triggered by zona pellucida glycoproteins
- D It is completed during passage through the rete testis
Correct answer: A. It involves removal of seminal plasma glycoproteins from the sperm head and increased membrane fluidity, taking hours in the female tract
Explanation
Capacitation occurs in the female genital tract over roughly six hours and involves cholesterol efflux, removal of decapacitating factors from semen, membrane remodelling, and hyperactivated motility. It prepares the sperm for the acrosome reaction but is distinct from it, since the acrosome reaction is triggered later by contact with the zona pellucida. Epididymal transit confers motility, not fertilising capacity.
Reference: Ganong's Review of Medical Physiology, 26th ed.
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