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

Discovery of insulin, Q. Discovery of insulin? The discovery of insulin...

Q. Discovery of insulin? The discovery of insulin has dramatically changed the lives of people having type 1 diabetes. With this wonder drug diabetics can lead a normal, enjoya

What are the main human degenerative diseases, Q. What are the main human d...

Q. What are the main human degenerative diseases? The major human degenerative diseases are divided into three groups, neoplastic diseases and degenerative diseases of the nerv

Explain chilling temperatures - method of food preservation, Explain chilli...

Explain chilling temperatures - method of food Preservation? (a) Cellar storage temperatures (about 15° C): It is usually used for the storage of surplus foods like root crops,

Define requirements of iodine during pregnancy period, Define requirements ...

Define requirements of Iodine during pregnancy period? You would be already aware that maternal iodine deficiency leads to cretinism in the off spring. Hence, the material diet

What is an atom referred to in ionic bonds, What is the positive atom refer...

What is the positive atom referred to in ionic bonds and write a monovalent and divalent example.

Define direct measurement of individual''s work capacity, Define Direct mea...

Define Direct measurement of individual's Work Capacity? Direct measurement of VO 2 max is determined by having the subject perform exercise at increased loads, for 12 to 15 m

Post-operative nursing care of cleft palate, Post-operative Nursing Care of...

Post-operative Nursing Care of Cleft Palate  Objective of Care  Provide adequate nutrition  Maintain oral hygiene  Apply restraints  Promote speech  Give

What are the inferior trophic levels, Can the amount of available energy in...

Can the amount of available energy in a given trophic level be larger than the available energy in inferior trophic levels? What does that condition means to the conformation of th

Gene, Gene  is the fundamental physical and functional unit of the heredity...

Gene  is the fundamental physical and functional unit of the heredity (generally DNA, Some of the organisms have RNA a gene). A gene is an ordered series of nucleotides located in

Amnion adaptation to terrestrial life, Q. Why can the amnion also be consid...

Q. Why can the amnion also be considered an adaptation to terrestrial life? The amnion is as well an adaptation to dry land since one of its functions is to prevent desiccation

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