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

Kidney function test, Kidney impairment is one of the long term complicatio...

Kidney impairment is one of the long term complications of diabetes mellitus. Measurement and monitoring of kidney function parameters such as urea and creatinine, in addition to u

What is the typical shape of poriferans, What is the typical shape of porif...

What is the typical shape of poriferans? Sponges have bodies in the type of tubular vases or globes open in the upper extremity. They have an internal central cavity and porous

Define instrument for absorbed radiation - spectrophotometer, Define Instru...

Define Instrument for Absorbed Radiation - Spectrophotometer? In contrast to colorimeter, spectrophotometer is an instrument that is capable of splitting the incident radiation

Relationship between the ovulation and menstrual cycle, Q. What is the rela...

Q. What is the relationship between the ovulation and menstrual cycle? Ovulation is the releasing of the female gamete from the ovary and Ovulation is a periodical event that o

Insulin dependent diabetes mellitus, Q. What is Insulin Dependent Diabetes ...

Q. What is Insulin Dependent Diabetes Mellitus? Mostly children and adolescents suffer from this type of diabetes however; it may appear in adults and elderly too. In this, the

Role of private sector in health care - competition, Role of Private Sector...

Role of Private Sector in Health Care - Competition When the private sector is driven by competition it tends to be more efficient. With competition, benefits like cost reduct

Homework, The Waldorf family was caught in a fire but escaped. Unfortunatel...

The Waldorf family was caught in a fire but escaped. Unfortunately, the father and daughter suffered burns. The father had second-degree burns on his entire chest, abdomen, and bot

Urine collection, Urine Collection: Untimed or random urine specimens ...

Urine Collection: Untimed or random urine specimens are suitable only for few chemical tests (mainly qualitative test). Usually urine sample is collected over a predetermined

Lamarckism theory of organic evolution, THEORY OF ORGANIC EVOLUTION - ...

THEORY OF ORGANIC EVOLUTION - LAMARCKISM Theory of the inheritance of acquired characters or Lamarckism put forwarded by Jean Baptist de Lamarck (1809) in his book "

Who are atopic individuals, Atopic individuals are those who are having abn...

Atopic individuals are those who are having abnormal high levels of circulating IgE and more than normal number of oesinophils.

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