Primary egg envelopes, Biology

Assignment Help:

Primary Egg Envelopes

These are the egg envelopes which develop in the ovary between oocyte and follicle cells in the space occupied by the interdigitating microvilli. Such envelopes have been named variously in different animals.

a) It is named as vitelline envelope or vitelline membrane in insects, molluscs, amphibians and birds.

b) In tunicates and fishes, it is known as chorion. In many sharks and bony fishes the primary envelope has striated appearance and is referred to as zona radiata representing the degraded microvilli of the growing oocyte. The perforation in the zona radiata becomes the micropyle through which the spermatozoa can enter the egg.

c) In mammals, the unstriated and modified zona pellucida is formed as a result of joint efforts of egg and follicle cells. While escaping the Graafian follicle mammalian oocyte carries on the surface of zona pellucida a layer of follicle cells known as corona radiata. The primary envelopes usually stick closely to the egg surface. These later on participate in the formation of fertilization membrane.


Related Discussions:- Primary egg envelopes

Meiosis, Meiosis is the special type of cell division in which the numbers ...

Meiosis is the special type of cell division in which the numbers of chromosomes in daughter cell are reduced to half, as compared to parent cell. Occurrence: It takes place

What is the way of life of sponges, Q What is the way of life of sponges? ...

Q What is the way of life of sponges? Sponges live exclusively in an aquatic environment and they are attached by their base to a substrate fixation ground. Sponges are filteri

Endosperm with chalazal haustorium, Endosperm with Chalazal Haustorium ...

Endosperm with Chalazal Haustorium In Grevillea robusta, a member of Proteaceae the endosperm is of the free nuclear type. The upper part of endosperm becomes cellular, where

Human reproduction, Describe the events which lead to the formation of (a) ...

Describe the events which lead to the formation of (a) identical twins, (b) fraternal twins in detail

Corelation of st depressoin with coronary angiography, Q. Corelation of ST ...

Q. Corelation of ST Depressoin with Coronary Angiography? Various investigators considered 1 mm of horizontal or downsloping ST depression to denote a positive test and used fr

Define the recommended dietary allowance for thiamin (rda), Define the Reco...

Define the Recommended Dietary Allowance for Thiamin (RDA)? Thiamin, as it must be clear by now, is needed mainly for the metabolism of carbohydrate, branch-chained amino aci

Explain cardiac examination auscultation and its techniques, Explain cardia...

Explain cardiac examination auscultation and its techniques? Auscultation of the heart sound and associatcd sound is very important to diagnose the cardiovascular diseases. It

Zoology, differences regarding Tiger Planaria and the Iridescent Phyllodoce...

differences regarding Tiger Planaria and the Iridescent Phyllodoce

Explain about colloidal system, Explain about colloidal system A colloi...

Explain about colloidal system A colloidal system, on the other hand, is a heterogeneous system. The material that forms the base of the system is called  the dispersion medium

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd