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

How much dna is in each stage, In meiosis - starting from stage G1 through ...

In meiosis - starting from stage G1 through the completion of meiosis, how much DNA is in each stage/phase when referring to the nucleus of spermatagonia?

What are nymph and imago, What are nymph and imago? Nymphs are larvae o...

What are nymph and imago? Nymphs are larvae of hemimetabolic insects (like grasshoppers). They are very same to the adult insect although smaller. In holometabolic insects (lik

State the term - myasthenia gravis, Myasthenia Gravis Myasthenia gravis...

Myasthenia Gravis Myasthenia gravis (severe muscle weakness) is characterised by muscular fatigue in the wake of very little exercise. It may be apparent after a short period o

Induction of antimicrobial substances, Induction of antimicrobial substance...

Induction of antimicrobial substances Phytoalexins are antimicrobial substances produced by plants in response to pathogen. They accumulate at the site of infection. For exam

Reflexes, Reflexes It is used to assess the neurobehavioural status....

Reflexes It is used to assess the neurobehavioural status. Rooting reflex - Being a primitive reflex, if cheek is rubbed, the infant will turn his head into that dire

What are the characteristics of thick gingiva, Characteristics of Thick Gin...

Characteristics of Thick Gingiva  Relatively flat soft tissue and bony architecture  Dense fibrotic soft tissue  Relatively large amount of attached gingiva  Thick und

C dna amplification, Steps of C dna amplification 1.  Smart-pcr amplif...

Steps of C dna amplification 1.  Smart-pcr amplification of cdna is the technique which initiates with the change of mrna to cdna utilizing mmlv-rt, mutated in the rnase h dom

Kingdom fungi, what are the characteristis in species in the phyla division...

what are the characteristis in species in the phyla division

Define the interaction of vitamin c with lead and mercury, Define the inter...

Define the interaction of vitamin c with lead and mercury? Vitamin C, lead and mercury: Iron alleviates lead toxicity but ascorbic acid is ineffective. Ascorbic acid alleviat

Explain the flower in diversity of life, Explain the Flower in diversity of...

Explain the Flower in diversity of life? In order for plants to evolve from an aquatic existence to a terrestrial existence, specific adaptations in their basic modes of reprod

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