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

Zoonoses disease-ehrlichiosis, Ehrlichiosis The disease is caused by a ric...

Ehrlichiosis The disease is caused by a rickettisia, called Ehrlichia canis. Dogs and man are the reservoir hosts. The infection is transmitted through bite of infected tick, Rhip

Explain the miracidium larva, Explain the Miracidium larva? Miracidium ...

Explain the Miracidium larva? Miracidium is the first stage larva that comes out from the fertilized egg. i) Miracidium is an oval, microscopic, flattened larva which appear

Explain basic stains (cationic) - types of stains, Explain Basic Stains (Ca...

Explain Basic Stains (Cationic) - Types of Stains? These are chloride or sulfate salts of coloured bases which on ionization give positively charged chromogen. As such, these h

Explain the role of dietitian''s in feeding dilemmas, Explain the role of d...

Explain the role of dietitian's in feeding dilemmas Usually, the dietitian's role in  feeding dilemmas is seen as secondary and the physician's role  is the  focus. In reality,

Genetic, 1. The genes for ruby eyes (rb), tan body (t) and cut wings (ct) a...

1. The genes for ruby eyes (rb), tan body (t) and cut wings (ct) are all found on the X-chromosome of Drosophila melanogaster. All of these are recessive traits. They map in the or

Define binding of protein with other compounds, Define Binding of Protein w...

Define Binding of Protein with Other Compounds? In addition to water, lipids and volatile flavours, food proteins can bind a number of other substances through weak interaction

Structure of the urinary system, It consists of: - Two kidneys that prod...

It consists of: - Two kidneys that produce urine. - The left and right ureters that the urine travels through on leaving the kidneys. - The muscular urinary bladder, which

Organs involved in the digestion process, The various organs involved  in...

The various organs involved  in  the digestion process are: Alimentary tract which  includes mouth, pharynx, esophagus stomach, small intestine, large intestine, appendix,  rec

Infectious and inflammatory conditions for lymphatic system, Q. Why in infe...

Q. Why in infectious and inflammatory conditions may clinical signs related to the lymphatic system occur? The lymph nodes or lymph glands have lymphoid tissue that produces ly

Meiosis, Why is it necessary to have the second division in meiosis even th...

Why is it necessary to have the second division in meiosis even though cells have already been reduced to haploid number after the first division?

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