What is the special feature of an egg cell?

The human egg cell is the largest cell in the human body, measuring approximately 0.13 mm in diameter. Its size is 10 times the diameter and 1000 times the volume of most other human body cells. It can actually be seen without the aid of a microscope if one observes keenly. Unlike ordinary body cells which have a cell membrane, the egg has a special outer coat called zona pellucida which is made up of a jelly-like extracellular matrix composed mainly of glycoproteins.