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

Biochemistry, tertiary structure of protein

tertiary structure of protein

What is radioactivity , What is Radioactivity ? Radioactivity :  Som...

What is Radioactivity ? Radioactivity :  Some isotopes, called radioisotopes, have unstable nuclei that release high energy particles or radiant energy, or both. An example

What is active transport--secretion, What is Active Transport--Secretion ...

What is Active Transport--Secretion This method is now a well accepted process of aqueous formation. The rate of aqueous humour formation depends on the rate of active solute

Define the nutritional shortcomings among the elderly, Define the Nutrition...

Define the Nutritional shortcomings among the elderly? Nutritional shortcomings are common among the elderly; most often due to poor choice of foods i.e. they may be consuming

Determine the term - techniques visualise anatomy, Determine the term - tec...

Determine the term - techniques visualise anatomy Some techniques visualise anatomy, provide objective confirmation of structural abnormality. These include neuroradiological i

Explain about the cancer and infertility - obesity, Explain about the Cance...

Explain about the Cancer and Infertility - Obesity? Cancer: Risk of cancers of the colon, rectum and prostrate increases greatly in obese men while obese women are more likely

Define theophrastus of eresus - taxonomy, Define Theophrastus of Eresus - T...

Define Theophrastus of Eresus - Taxonomy The Father of Botany (370-285 B.C.); of all the men who ever lived upon the earth certainly one of the most remarkable was Theophrastu

Explain unacceptable aesthetics, Unacceptable Aesthetics The implant wh...

Unacceptable Aesthetics The implant which has successfully integrated with bone may still be a failure if the Prosthesis which it is designed to support does not meet with the

Basal metabolism and energy expenditure at high altitude, Define Basal Meta...

Define Basal Metabolism and Energy Expenditure at High Altitude? The energy and nutrient requirements depend upon total energy expenditure and metabolic rate of the individual.

Name the skin receptors in humans, Which of the below are skin receptors...

Which of the below are skin receptors in humans which are sensitive to heat? Are they: a) End organs of Krause b) Meissner's corpuscles c) End organs of Ruffini d)

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