A collapsed membranous vesicle that covers the anterior part of the nucleus of the spermatozoon, derived from the acrosomal granule; the carbohydrate-rich substance of the cap is associated with hydrolytic enzymes that aid in sperm penetration of the zona pellucida of the ovum. ... Synonym: head cap. ... (05 Mar 2000) ... 
Type: Term Synonyms: acrosome