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

Rigs pattern - types of nursing units, Rigs Pattern: The nursing unit ...

Rigs Pattern: The nursing unit has been divided into small cubicles for 1,2,4  and 6 beds.  The beds are arranged parallel to the  longitudinal wall.  The pattern was first bu

Explain etiology and clinical feature of parkinson''s disease, Explain the ...

Explain the Etiology and Clinical Features of Parkinson's disease? The cause of Parkinson's is unknown. Genetic predisposition (in most cases the reason for the death of these

Define types of non enzymatic browning reaction, Define Types of Non Enzyma...

Define Types of Non Enzymatic Browning Reaction? Two major types of non enzymatic browning reaction have been recognized to occur in foods during processing. 1. Maillard Rea

Define the term underweight, Define the term Underweight? Just as overw...

Define the term Underweight? Just as overweight is the result of a positive energy balance irrespective of the etiology, underweight results when the energy balance is negative

What do you mean by age pyramids, Q. What are age pyramids? Age pyramid...

Q. What are age pyramids? Age pyramids are the graphical representations in form of superposed rectangles each representing the number of individuals included in age ranges int

Explain about salivary glands in humans, Q. What is the location of the sal...

Q. What is the location of the salivary glands in humans? There are six major salivary glands and they are located one in each parotid gland, two beneath the mandibles (submand

Defects in human development, Defects in Human Development 1) For inst...

Defects in Human Development 1) For instance, when a pregnant woman drinks alcohol her embryo is exposed to similar concentration of alcohol as is in her blood. The alcohol ma

What is an ecosystem?, What is an ecosystem? An ecosystem is the system...

What is an ecosystem? An ecosystem is the system that composed of biotic and abiotic factors in interaction.

What are gene interactions?, What are gene interactions? What are the three...

What are gene interactions? What are the three main types of gene interactions? The Gene interaction is the phenomenon in which a given phenotypical trait is conditioned by two

Explain about modifiable risk factors, Q. Explain about Modifiable Risk Fac...

Q. Explain about Modifiable Risk Factors? 1. Behavioural Smoking Sedentary Lifestyle Habits Dietary Errors 2. Physiological Hyperlipidemia Hypertension Obe

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