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

Fats, what are fats

what are fats

Observation or inference for half and full saturation test, Define Observat...

Define Observation or Inference for half and full saturation Test? 1. Starch is precipitated by half saturation with ammonium sulfate whereas dextrin is not precipitated. This

What is absorption, What is absorption?   Absorption involves  the  tr...

What is absorption?   Absorption involves  the  transfer of materials  through  the mucosa of the  alimentary tract  into blood and lymph vessels.

What are phospholipids, What are phospholipids? Phospholipids are molec...

What are phospholipids? Phospholipids are molecules made of glycerol bound to two long molecules of fatty acids and to one phosphate group. Thus, phospholipids are amphipathic

Animal kingdom, If porifers shiw cell aggregate plan tgen how can they also...

If porifers shiw cell aggregate plan tgen how can they also shiw division of labour among cells

Material - separation of amino acid by paper chromatography, Determine Mate...

Determine Materials for Separation of Amino Acids by Paper Chromatography? Petridishes (200 mm diameter) with lid, Whatman Chromatographic paper, brown paper, 500 ml separating

Which are the three parts of the small intestine, Which are the three parts...

Which are the three parts of the small intestine? The small intestine is separated into three portions: duodenum, jejunum and ileum. Digestion System - Image Diversity: smal

Define left posterior hemiblock, Q. Define Left Posterior Hemiblock? Bo...

Q. Define Left Posterior Hemiblock? Bobbna and associated reported four cases in which they proposed that the left posterior hemi block was initiated by exercise. In their pa

Explain ground meristem in primary root growth, Explain Ground Meristem in ...

Explain Ground Meristem in Primary Root Growth? To review, the protoderm is the primary tissue that eventually forms the outside layer that covers the root and shoot and leaves

Open pulmonary valvotomy-types of surgery, Open Pulmonary Valvotomy :  ...

Open Pulmonary Valvotomy :  Open pulmonary valvotomy by technique of inflow occlusion is done without cardio pulmonary bypass. Surface hypothermia is used and inflow occlusio

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