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

Ribosome in the translation of one mrna molecule, Q. How many of the same p...

Q. How many of the same proteins are made at the same time by each ribosome in the translation of one mRNA molecule? How does successive protein production occur in translation?

What are the micronutrients, What are the Micronutrients   All the micr...

What are the Micronutrients   All the micronutrients except molybdenum, boron and chlorine are available more in acid soils. These elements may limit plant growth either becaus

Economically important fermentation products-beer, Normal 0 fal...

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4

Etiological factor of gastritis, Q. Etiological factor of gastritis? Th...

Q. Etiological factor of gastritis? They are same as acute. Generally acute gastritis if well treated gets healed in 3-4 days, however if untreated can progress to chronic gast

Explain kingdom protista, Kingdom Protista The protistans are a complex a...

Kingdom Protista The protistans are a complex and diverse group of organisms that are placed together simply because they are all single celled eukaryotes but some form rather sp

What are the reagents and products of fermentation, In general what are the...

In general what are the reagents and products of fermentation? In fermentation glucose (sugar) is degraded into pyruvic acid (every glucose molecule forms two pyruvic acid mole

Define standardization - nutritional biochemistry, Define Standardization ...

Define Standardization - Nutritional  Biochemistry? One of the substances involved in a titration must be used as a standard for which the amount of substance present is accura

Explain the types of cell reproduction, Explain the Types of cell Reproduct...

Explain the Types of cell Reproduction ? One of the major characteristics of living organisms is their ability to grow and reproduce. This is accomplished by cell division. In

List disbeliefs which patients have about insulin, Q. List disbeliefs which...

Q. List disbeliefs which patients have about insulin? a) Insulin is not effective. Some patients believe that insulin is not effective for treating diabetes. b) Insulin c

Tetrasporic embryo sacs, Tetrasporic Embryo Sacs In this group neithe...

Tetrasporic Embryo Sacs In this group neither of the meiotic divisions is accompanied by wall formation so that at the end of meiosis all the four haploid nuclei remain in a

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