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An oogonium (plural oogonia) is an immature ovum
Immature ovum

An immature ovum is a cell that goes through the process of oogenesis to become an ovum. It can be either an oogonium, oocyte and an ootid. An oocyte, in turn, can be either primary or secondary, depending on how far it has come in its process of meiosis....
. It is a female gametogonium
Gametogonium

A gametogonium is a germ cell that divides into gametocytes during gametogenesis. Male gametogonia are called spermatogonium, and female gametogonia are called oogonium....
. They are formed in large numbers by mitosis
Mitosis

Mitosis is the process in which a eukaryotic cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter nuclei....
 early in fetal
Fetus

A fetus is a developing mammal or other viviparous vertebrate, after the embryonic stage and before childbirth. The plural is fetuses, or sometimes feti....
 life from primordial germ cell
Germ cell

Germ cells are progenitors of the gametes. These singled-out cells move through the gut to the developing gonads and undergo mitotic Cell proliferation followed by meiosis and Cellular differentiation into either eggs or sperm ....
s, which are present in the fetus between weeks 4 and 8.

Oogonia are present in the fetus between weeks 5 and 30.

Oogonia are also the female reproductive structures in certain thallophyte
Thallophyte

The thallophytes are a polyphyletic group of non-mobile organisms traditionally described as "relatively simple plants" or "lower plants" with undifferentiated bodies ....
s, and are usually rounded cell
Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
s or sacs containing one or more oospheres.

the primordial germ cells have gotten to the ovary
Ovary

The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in females are homology to testicle in males, in that they are both gonads and endocrine glands....
, they develop into oogonia.






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An oogonium (plural oogonia) is an immature ovum
Immature ovum

An immature ovum is a cell that goes through the process of oogenesis to become an ovum. It can be either an oogonium, oocyte and an ootid. An oocyte, in turn, can be either primary or secondary, depending on how far it has come in its process of meiosis....
. It is a female gametogonium
Gametogonium

A gametogonium is a germ cell that divides into gametocytes during gametogenesis. Male gametogonia are called spermatogonium, and female gametogonia are called oogonium....
. They are formed in large numbers by mitosis
Mitosis

Mitosis is the process in which a eukaryotic cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter nuclei....
 early in fetal
Fetus

A fetus is a developing mammal or other viviparous vertebrate, after the embryonic stage and before childbirth. The plural is fetuses, or sometimes feti....
 life from primordial germ cell
Germ cell

Germ cells are progenitors of the gametes. These singled-out cells move through the gut to the developing gonads and undergo mitotic Cell proliferation followed by meiosis and Cellular differentiation into either eggs or sperm ....
s, which are present in the fetus between weeks 4 and 8.

Oogonia are present in the fetus between weeks 5 and 30.

Oogonia are also the female reproductive structures in certain thallophyte
Thallophyte

The thallophytes are a polyphyletic group of non-mobile organisms traditionally described as "relatively simple plants" or "lower plants" with undifferentiated bodies ....
s, and are usually rounded cell
Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
s or sacs containing one or more oospheres.

Further development

Once the primordial germ cells have gotten to the ovary
Ovary

The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in females are homology to testicle in males, in that they are both gonads and endocrine glands....
, they develop into oogonia. During week 6 of development, oogonia migrate from the yolk sac to the genital ridge ( site of the future gonads-ovaries in this case) located on the posterior abdominal wall. Oogonia develop by mitosis
Mitosis

Mitosis is the process in which a eukaryotic cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter nuclei....
. However, some of them become primary oocytes, which begin meiosis
Meiosis

In biology or life science, meiosis is a process of reductional division in which the number of chromosomes per cell is halved. In animals, meiosis always results in the formation of gametes, while in other organisms it can give rise to spores....
 which is halted in prophase I. When they have entered Prophase I of meiosis they become primary oocyte
Oocyte

An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in biological reproduction. In other words, it is an immature ovum, or ovum cell....
s; it is important to note that this process is complete before birth, in contrast to spermatogenesis
Spermatogenesis

Spermatogenesis is the process by which male spermatogonia develop into mature spermatozoa. Spermatozoa are the mature male gametes in many sexually reproducing organisms....
. Primary oocytes are present from week 10 until menopause at ~53 years

Oogamy

Oogamy may be spelt oögamy with a diaresis (or umlaut). The link with other articles may depend on this symbol.

Oogonia


Algae

This term is used in phycology
Phycology

Phycology or algology , a subdiscipline of botany, is the scientific study of alga. Algae are important as primary production in aquatic ecosystems....
 (the study of algae) to refer to the union of the male (motile or non-motile) with the female gamete
Gamete

A gamete is a Cell that fuses with another gamete during fertilization in organisms that sexual reproduction. In species which produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual which produces the larger type of gamete?called an ovum ?and a male produces th...
.The female oogonium is usually enlarged and develops a single ovum. The male (antheridium) usually produces many cells with flagella except in the Rhodophyta which have no flagella. There is no evidence that the red algae ever had flagella, or cilia and it is suggested that they are the most primitive eukaryotes.

Fungi

Oogonia also occur in the fungi.Smyth, G.M. 1955. Cryptogamic Botany. vol. 1. McGraw-Hill Book Company

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