The thick transparent membrane surrounding a mammalian ovum before implantation.
- ‘The embryo must hatch out of the zona pellucida prior to implantation into the uterine wall.’
- ‘The secondary oocyte and the polar body remain surrounded by the zona pellucida and the cumulus oophorus.’
- ‘At this stage the embryo releases itself from the zona pellucida still surrounding it, and implants into the uterine wall.’
- ‘The scientists drilled through the egg's protective layer, the zona pellucida, removed a plug, and then extracted the DNA and polar body through the hole.’
- ‘The onset of hyperactive movement occurs near the site of fertilization and is crucial for penetrating the egg's zona pellucida.’
Mid 19th century: from Latin, literally ‘pellucid girdle’.
We take a look at several popular, though confusing, punctuation marks.