Immature ovum
Encyclopedia
An immature ovum is a cell that goes through the process of oogenesis
to become an ovum
. It can be an oogonium
, an oocyte
or an ootid. An oocyte, in turn, can be either primary or secondary, depending on how far it has come in its process of meiosis
.
nic life. All have turned into primary oocytes at late fetal age.
When meiosis I is completed, one secondary oocyte and one polar body
is created.
. Most degenerate by atresia
, but a few go through ovulation
, and that's the trigger to the next step. Thus, an immature ovum can spend up to ~55 years as a primary oocyte (the last ovulation before menopause
).
.
in spermatogenesis
.
Each chromosome is split between the two ootids, leaving only one chromatid per chromosome. Thus, there are 23 chromatids in total (1N).
Oogenesis
Oogenesis, ovogenesis or oögenesis is the creation of an ovum . It is the female form of gametogenesis. The male equivalent is spermatogenesis...
to become an ovum
Ovum
An ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...
. It can be an oogonium
Oogonium
"Oogonium" may refer to either a primordial oocyte in a female fetus or the female gametangium of certain thallophytes.-in the fetus:Oogonia are formed in large numbers by mitosis early in fetal development from primordial germ cells...
, an 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...
or an ootid. An oocyte, in turn, can be either primary or secondary, depending on how far it has come in its process of 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....
.
| Cell type | ploidy Ploidy Ploidy is the number of sets of chromosomes in a biological cell.Human sex cells have one complete set of chromosomes from the male or female parent. Sex cells, also called gametes, combine to produce somatic cells. Somatic cells, therefore, have twice as many chromosomes. The haploid number is... /chromosomes |
chromatids | Process | Process completion >- | Oogonium |
diploid/46 | 2N | Oocytogenesis (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... ) |
>- | diploid/46 | 4N | Ootidogenesis (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.... 1) (Folliculogenesis Folliculogenesis In biology, folliculogenesis is the maturation of the ovarian follicle, a densely-packed shell of somatic cells that contains an immature oocyte... ) |
Dictyate Dictyate The dictyate or dictyotene is a prolonged resting phase in oogenesis. It occurs in the stage of meiotic prophase I in ootidogenesis. It starts late in fetal life and is terminated shortly before ovulation by the LH surge... in prophase I until ovulation >- | secondary Oocyte |
haploid/23 | 2N | Ootidogenesis (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.... 2) |
>- | haploid/23 | 1N | ? | >- | haploid/23 | 1N |
Oogonium
Oogonia are the cells that turn into primary oocytes in oogenesis. They are diploid, i.e. containing both pairs of homologous chromosomes. There are 23 chromosome pairs. Thus there are 46 chromosomes. Each chromosome, however, hasn't yet duplicated itself. Thus, there are only one chromatid on each chromosome, making the total quantity of chromatids 46. This is twice the number of chromosome pairs (2N).Timeline
Oogonia are created in early embryoEmbryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
nic life. All have turned into primary oocytes at late fetal age.
Primary oocyte
The primary oocyte is defined by its process of ootidogenesis, which is meiosis. It has duplicated its DNA, so that each chromosome has two chromatids, i.e. 92 chromatids all in all (4C).When meiosis I is completed, one secondary oocyte and one polar body
Polar body
A polar body is a cell structure found inside an ovum. Both animal and plant ova possess it. It is also known as a polar cell.Asymmetrical cell division leads to the production of polar bodies during oogenesis. To conserve nutrients, the majority of cytoplasm is segregated into the secondary...
is created.
Timeline
Primary oocytes have been created in late fetal life. This is the stage where immature ova spend most of their lifetime, more specifically in prophase I of meiosis. The halt is called dictyateDictyate
The dictyate or dictyotene is a prolonged resting phase in oogenesis. It occurs in the stage of meiotic prophase I in ootidogenesis. It starts late in fetal life and is terminated shortly before ovulation by the LH surge...
. Most degenerate by atresia
Atresia
Atresia is a condition in which a body orifice or passage in the body is abnormally closed or absent.Examples of atresia include:* Imperforate anus - malformation of the opening between the rectum and anus....
, but a few go through ovulation
Ovulation
Ovulation is the process in a female's menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum . Ovulation also occurs in the estrous cycle of other female mammals, which differs in many fundamental ways from the menstrual cycle...
, and that's the trigger to the next step. Thus, an immature ovum can spend up to ~55 years as a primary oocyte (the last ovulation before menopause
Menopause
Menopause is a term used to describe the permanent cessation of the primary functions of the human ovaries: the ripening and release of ova and the release of hormones that cause both the creation of the uterine lining and the subsequent shedding of the uterine lining...
).
Secondary oocyte
The secondary oocyte is the cell that is formed by meiosis I in oogenesis. Thus, it has only one of each pair of homologous chromosomes. In other words, it is haploid. However, each chromosome still has two chromatids, making a total of 46 chromatids (1N but 2C). The secondary oocyte continues the second stage of meiosis (meiosis II), and the daughter cells are one ootid and one polar bodyPolar body
A polar body is a cell structure found inside an ovum. Both animal and plant ova possess it. It is also known as a polar cell.Asymmetrical cell division leads to the production of polar bodies during oogenesis. To conserve nutrients, the majority of cytoplasm is segregated into the secondary...
.
Timeline
Secondary oocytes are the immature ovum shortly after ovulation, to fertilization, where it turns into an ootid. Thus, the time as a secondary oocyte is measured in days.Size
The secondary oocyte is the largest cell in the body, and in humans is just visible to the naked eye.Ootid
An ootid is the haploid result of ootidogenesis. In oogenesis, it doesn't really have any significance in itself, since it is very similar to the ovum. However, it fills the purpose as the female counterpart of the male spermatidSpermatid
The spermatid is the haploid male gametid that results from division of secondary spermatocytes. As a result of meiosis, each spermatid contains only half of the genetic material present in the original primary spermatocyte....
in 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...
.
Each chromosome is split between the two ootids, leaving only one chromatid per chromosome. Thus, there are 23 chromatids in total (1N).