Oogenesis in mammals, Biology

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.

Posted Date: 1/24/2013 6:44:21 AM | Location : United States







Related Discussions:- Oogenesis in mammals, Assignment Help, Ask Question on Oogenesis in mammals, Get Answer, Expert's Help, Oogenesis in mammals Discussions

Write discussion on Oogenesis in mammals
Your posts are moderated
Related Questions
State about the Neuropsychological assessment Neuropsychological assessment provides information concerning the status of brain function across the life span. It does so primar

How do chloroplasts multiply? Like mitochondria chloroplasts have their own DNA, RNA and ribosomes and they self-replicate through binary division.

Processes in Succession - Ecology Whether succession is primary or secondary, in terrestrial or aquatic ecosystems, the basic processes involved in succession are similar. The

Blotting  is the technique for detecting one RNA within the mixture of RNAs (a Northern blot) or one type of the DNA within of a mixture of DNAs (a Southern blot). A blot can prove

Depth and Currents Depth The sea is very deep varying in different regions. Generally life extends to all depths but is confined more to the continental shelf and

What is meant by suction force of the plant cell? Does the suction force facilitate or make difficult the entrance of water in the cell? Ans) The suction force (SF) is the osmot

The three charges in the are at the vertices of an isosceles triangle. Let q = 7.00 nC and calculate the electric potential at the midpoint of the base.

Explain the carrying capacity in ecology? Carrying Capacity :  We have seen that natural populations do not normally achieve the maximum intrinsic rate of natural increase, o

Oogenesis Oogenesis is the formation of ovum from oogonial cells that are formed in the ovary from primordial germ cells. And as in spermatogenesis it involves meiosis to pro

Diagnosis of diabetes mellitus which included history taking, symptoms and signs and various tests which can be done to diagnose a case of diabetes. Diabetes Mellitus (DM) or diabe