Oogonium
Encyclopedia
"Oogonium" may refer to either a primordial oocyte
in a female fetus
or the female gametangium of certain thallophyte
s.
early in fetal
development from primordial germ cell
s. In humans they start to develop between weeks 4 and 8 and are present in the fetus between weeks 5 and 30.
Once the primordial germ cells have arrived in the ovary
, they develop into oogonia. Oogonia migrate from the yolk sac to the genital ridge (site of the future ovaries) located on the posterior abdominal wall.
Oogonia develop by mitosis
. However, some of them become primary oocytes, which begin meiosis
which is halted in prophase I. When they have entered Prophase I of meiosis they become primary oocyte
s; it is important to note that this process is complete before birth, in contrast to spermatogenesis
. Primary oocytes are present from week 10 until menopause at ~53 years in human females.
and mycology
, oogonium refers to a female gametangium if the union of the male (motile or non-motile) and the female gamete
takes place within this structure.Smyth, G.M. 1955. Cryptogamic Botany. vol. 1. McGraw-Hill Book Company Oogonia are usually rounded cell
s or sacs containing one or more oospheres. The male (antheridium) usually produces many cells with flagella except in the Rhodophyta which have no flagella.
Oocyte
An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell which undergoes a mitotic...
in a female fetus
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
or the female gametangium of 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.
in the fetus
Oogonia are formed in large numbers by mitosisMitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...
early in fetal
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
development from primordial germ cell
Germ cell
A germ cell is any biological cell that gives rise to the gametes of an organism that reproduces sexually. In many animals, the germ cells originate near the gut of an embryo and migrate to the developing gonads. There, they undergo cell division of two types, mitosis and meiosis, followed by...
s. In humans they start to develop between weeks 4 and 8 and are present in the fetus between weeks 5 and 30.
Once the primordial germ cells have arrived in 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 anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
, they develop into oogonia. Oogonia migrate from the yolk sac to the genital ridge (site of the future ovaries) located on the posterior abdominal wall.
Oogonia develop by mitosis
Mitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...
. However, some of them become primary oocytes, which begin meiosis
Meiosis
Meiosis is a special type of cell division necessary for sexual reproduction. The cells produced by meiosis are gametes or spores. The animals' gametes are called sperm and egg cells....
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 reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell which undergoes a mitotic...
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 primary germ cells undergo division, and produce a number of cells termed spermatogonia, from which the primary spermatocytes are derived. Each primary spermatocyte divides into two secondary spermatocytes, and each secondary spermatocyte into two...
. Primary oocytes are present from week 10 until menopause at ~53 years in human females.
in thallophytes
In phycologyPhycology
Phycology is the scientific study of algae. Phycology is a branch of life science and often is regarded as a subdiscipline of botany....
and mycology
Mycology
Mycology is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for tinder, medicinals , food and entheogens, as well as their dangers, such as poisoning or...
, oogonium refers to a female gametangium if the union of the male (motile or non-motile) and the female gamete
Gamete
A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...
takes place within this structure.Smyth, G.M. 1955. Cryptogamic Botany. vol. 1. McGraw-Hill Book Company Oogonia are usually rounded cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
s or sacs containing one or more oospheres. The male (antheridium) usually produces many cells with flagella except in the Rhodophyta which have no flagella.
