Oogenesis in mammals, Biology

Assignment Help:

Oogenesis in Mammals

In mammals also the oogonial cells are derived from primordial germ cells. The multiplication phase, that is all of the oogonial divisions and transformation of oogonia into oocyte are completed either before or shortly after birth. A number of oocytes are produced, all of which are held in meiotic arrest in prophase I.

Essentially in mammals the period of oogenesis covers the entire life of an individual from birth to ovulation. The meiotic arrest is released at the time of puberty after which a group of oocytes begin development during each cycle. A large percentage of oocytes fail to undergo maturation and therefore degenerate. The oocytes in mammals are found in close association with non-germ cells in the ovary. The non-germ cells or the accessory cells produce steroid hormones, transport some of the essential cytoplasmic components into the oocyte and are also involved in the formation of cellular or non-cellular layers that surround the fully differentiated egg. The accessory cells that surround the egg are of two types -

(1) Follicle cells,

(2) Nurse cells.

The follicle cells are somatic cells which surround the oocyte as a single layer of the cells and are known as follicular epithelial cells. The nurse cells are derived from germ cell line and are connected with the oocyte by cytoplasmic bridges. During the growth of the oocyte, the single layered follicular epithelium proliferates and becomes multilayered and the cells are called granulosa cells. The granulosa cells and the oocyte are separated by a space which is filled with sulphated glycoproteins. This layer becomes the zona pellucida of the oocyte. When proliferation of the granulosa cells is completed they secrete a fluid that accumulates in the intercellular spaces. The fluid filled spaces coalesce to form a cavity called antrum.


Related Discussions:- Oogenesis in mammals

Aquatic biomes, If you look up a world atlas you would notice that most of ...

If you look up a world atlas you would notice that most of the earth's surface is covered by the waters of the oceans (about 71%). Beneath the water surface is a fascinating world

How environmental temperature affect requirement of protein, How Environmen...

How Environmental temperature affect requirement of protein? Environmental temperature: As environmental temperatures rise or fall above or below the range of thermic neutralit

Explain phylum ascomycetes, Phylum Ascomycetes 1) Sexual reproduction i...

Phylum Ascomycetes 1) Sexual reproduction is by conjugation and is followed by the formation of ascospores inside a sac called ascus. 2) The asci may be grouped together to

Biomolecules, indicator for testing for the presence of sugar

indicator for testing for the presence of sugar

Iodine test, what will happen to a plant kept in dark for 72 hours

what will happen to a plant kept in dark for 72 hours

Demonstrate the counselling process in the form of role play, Q. Demonstrat...

Q. Demonstrate the counselling process in the form of role play? Role playing refers either to the unconscious changing of one's behavior to assume a social role or roles in lif

What are the antigen-respective antibodies abo blood group, What are the an...

What are the antigens and the respective antibodies of the ABO blood group system? The ABO blood system contain the erythrocytic antigens A and B that can be attacked by the an

Ammonification, Ammonification Many heterotrophic bacteria actinomycet...

Ammonification Many heterotrophic bacteria actinomycetes and fungi in soil and water metabolise the organic nitrogen and release it in an inorganic form as ammonia. This proce

What is iris coloboma, What is Iris Coloboma Coloboma is a congenital a...

What is Iris Coloboma Coloboma is a congenital abnormality due to non-fusion of the embryonic choroidal fissure. It can affect any part of the eye and may involve the optic ner

Types of stress caused by freezing, Types of Stress Caused by Freezing ...

Types of Stress Caused by Freezing Thus, freezing can cause the following kinds of stresses Lowering of temperature to suboptimum thus reducing the activity of mo

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