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

Circulation, Circulation, Respiration and Excretion of Asteroidea Aste...

Circulation, Respiration and Excretion of Asteroidea Asteroids depend upon the circulation of coelomic fluid for the transport of gases and some nutrients. The blood vascular

Biochemical function - essential elements, Biochemical Function - Essential...

Biochemical Function - Essential Elements Elements Mg, Mn, K, Ca and Fe are cofactors for many enzymatic reactions. Fe is carrier of electrons in electron transfer chain. Phos

Mollusca, how mollusca bore into hard substrate

how mollusca bore into hard substrate

What are the main cellular functions of potassium, Q. What are the main cel...

Q. What are the main cellular functions of potassium? Moreover being important for the osmotic regulation and for the acid-base equilibrium (pH) potassium is fundamental for th

Determine the major demographic processes, Determine the major demographic ...

Determine the major demographic processes? There are five major demographic processes, which are continually at work within the population namely, fertility, mortality, marriag

Define the management of obesity, Define the Management of Obesity? Man...

Define the Management of Obesity? Management of obesity should be taken up with a clear understanding of the harsh realities of the problem and its outcome. It may be a frustra

Explain biological mechanisms, Biological mechanisms Annual rhythm....

Biological mechanisms Annual rhythm. Innate behaviour pattern stimulated by environmental cues (shortened day length is the cue for preparation - candidates should exp

Pregnancy, What are the physiological changes during pregnancy

What are the physiological changes during pregnancy

What are fibroids, Fibroids, also called as leiomyomas, are benign smooth m...

Fibroids, also called as leiomyomas, are benign smooth muscle tumors that happen in the uterus. They grow under the influence of estrogen and progesterone, and are therefore seen i

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