part of part of zona pellucida UBERON:0000086 oolemma uberon vitelline membrane ZFA:0001111 BTO:0003135 pellucid zone EHDAA2:0002220 EMAPA:16035 EHDAA:31 striated membrane zona striata Outside the plasma membrane, three envelopes surround the ovum. The first, the primary egg envelope, lies between the plasma membrane and the surrounding cells of the ovary. The most consistent component of this primary layer is the vitelline membrane, a transparent jacket of fibrous protein. In mammals, the homologous structure is called the zona pellucida.[well established][VHOG] A glycoprotein membrane surrounding the plasma membrane of an oocyte. It is a vital constitutive part of the latter, external but not extraneous to it. The zona pellucida first appears in multilaminar primary oocytes. zona pellucida - vitelline membrane UMLS:C0043519 GAID:410 zona radiata TAO:0001111 FMA:18674 MESH:D015044 VHOG:0000720 MA:0001715 EHDAA:62 vitelline envelope cell part acellular anatomical structure female gonad reproductive structure