Oocyte

Jump to: navigation, search
Oocyte
File:Gray5.svg
Diagram showing the reduction in number of the chromosomes in the process of maturation of the ovum.
Gray's subject #3 38
MeSH Oocytes

WikiDoc Resources for Oocyte

Articles

Most recent articles on Oocyte

Most cited articles on Oocyte

Review articles on Oocyte

Articles on Oocyte in N Eng J Med, Lancet, BMJ

Media

Powerpoint slides on Oocyte

Images of Oocyte

Photos of Oocyte

Podcasts & MP3s on Oocyte

Videos on Oocyte

Evidence Based Medicine

Cochrane Collaboration on Oocyte

Bandolier on Oocyte

TRIP on Oocyte

Clinical Trials

Ongoing Trials on Oocyte at Clinical Trials.gov

Trial results on Oocyte

Clinical Trials on Oocyte at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on Oocyte

NICE Guidance on Oocyte

NHS PRODIGY Guidance

FDA on Oocyte

CDC on Oocyte

Books

Books on Oocyte

News

Oocyte in the news

Be alerted to news on Oocyte

News trends on Oocyte

Commentary

Blogs on Oocyte

Definitions

Definitions of Oocyte

Patient Resources / Community

Patient resources on Oocyte

Discussion groups on Oocyte

Patient Handouts on Oocyte

Directions to Hospitals Treating Oocyte

Risk calculators and risk factors for Oocyte

Healthcare Provider Resources

Symptoms of Oocyte

Causes & Risk Factors for Oocyte

Diagnostic studies for Oocyte

Treatment of Oocyte

Continuing Medical Education (CME)

CME Programs on Oocyte

International

Oocyte en Espanol

Oocyte en Francais

Business

Oocyte in the Marketplace

Patents on Oocyte

Experimental / Informatics

List of terms related to Oocyte


Overview

An oocyte, ovocyte, or rarely oöcyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum. An oocyte is part the ovary development. The germ cells produce a primordial germ cell (PGC) which becomes an oogonia which marks the start of mitosis. After mitosis stops (due to actions of retinoic acid and the mesenephros) meiosis starts. This stage the oogonia is now an Oocyte (pronounced oh'a (like Noah)-site).

Formation

The formation of an oocyte is called oocytogenesis, which is a part of oogenesis[1]. Oogenesis results in the formation of both primary oocytes before birth, and of secondary oocytes after it as part of ovulation.

Cell type ploidy/chromosomes chromatids Process Time of completion
Oogonium diploid/46 2N Oocytogenesis (mitosis) third trimester
primary Oocyte diploid/46 4N Ootidogenesis (meiosis 1) (Folliculogenesis) Dictyate in prophase I until ovulation
secondary Oocyte haploid/23 2N Ootidogenesis (meiosis 2) Halted in metaphase II until fertilization
Ootid haploid/23 1N  ? Minutes after fertilization
Ovum haploid/23 1N

Characteristics

Cytoplasm

Oocytes are rich in cytoplasm which contains yolk granules to nourish the cell early in development.

Nucleus

During the primary oocyte stage of oogenesis, the nucleus is called a germinal vesicle[2]

The only normal type of secondary oocyte has sex chromosomes 23,X (where sperm can be 23,X or 23,Y).

Nest

The space wherein an ovum or immature ovum is located is the cell-nest[3].

Abnormalities

  • nondisjunction -- a failure of proper homolog separation in meiosis I, or sister chromatid separation in meiosis II can lead to aneuploidy, in which the oocyte has the wrong number of chromosomes, for example 22,X or 24,X. This is the cause of conditions like Down syndrome and Edwards syndrome. It is more likely with advance maternal age.
  • Some oocytes have multiple nuclei, although it is thought they never mature.

References

Resources

William K. Purves, Gordon H. Orians, David Sadava, H. Craig Heller, Craig Heller (2003). Life: The Science of Biology(7th ed.), pp. 823–824

See also

External links


Linked-in.jpg