A coiled tube located on the back of each testis where sperm mature and are stored before ejaculation, taking about 2-3 weeks for sperm to travel through its length.
From Greek epi meaning 'upon' and didymos meaning 'twin' or 'testis,' literally meaning 'upon the testis,' accurately describing its anatomical position resting on top of each testicle.
If you uncoiled the epididymis, it would stretch about 20 feet long - all packed into a structure smaller than your thumb! Sperm enter this maze completely immotile and emerge as champion swimmers, gaining the ability to fertilize an egg during their weeks-long journey through this microscopic training ground.
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