FORMATION OF EGG MEMBRANE

Ovum with egg membrane is called ova / egg.  On the basis of origin the egg membrane are of three types &

1.      PRIMARY EGG MEMBRANE

It is formed of oocyte / follicle cells or both. It is present between the plasma membrane and follicle cells of egg.

These are following type -

(i) Vitelline membrane

It is non-cellular mucoproteineous transparent sheath.

In fishes it is called chorion and reptiles and mammals it is called zona pellucida.

It is attached to long phase of cleavage and bounded to blastomere.

(ii) Zona rediata

Shark, bony fishes, amphibians and reptiles this membrane is stratified type.

This membrane is also present in mammals. It's formed by follicle cells.

(ii) Jelly coat

Echinoderms and other sea invertebrates have this coat.

2.      SECONDARY EGG MEMBRANE

They are formed by ovarian tissue.

In insect, ascidian and cyclostome this membrane is chitinous and is called chorione.

Amphibians, reptiles, aves and mammals that membrane is absent.

When mammalian egg reach into fallopian tube some columnars cell sheat present on zona pellucida and that is called corona rediata. It is not a true secondary egg memrbane.

3.      TERTIARY EGG MEMBRANE

They are formed of oviduct / ovary / uterus.

These membranes found in the form of -

(i) jelly coat - found in amphibains

(ii) Chalaza - found in birds

(iii) Albumin layers - found in birds and nematods.

(iv) Shell membrane - found in the birds.

(v) Shell - found in birds, shark and rays