Changes

==Origin==

==Origin==

New Latin, from [[Latin]], egg

New Latin, from [[Latin]], egg

*First Known Use: circa [http://en.wikipedia.org/wiki/18th_century 1706]

*First Known Use: circa [https://en.wikipedia.org/wiki/18th_century 1706]

While the non-mammalian animal egg was obvious, the doctrine ex ova omne vivum ("every living [animal comes from] an egg"), associated with [http://en.wikipedia.org/wiki/William_Harvey William Harvey] (1578-1657), was a rejection of [http://en.wikipedia.org/wiki/Spontaneous_generation spontaneous generation] and [http://en.wikipedia.org/wiki/Preformationism preformationism] as well as a bold assumption that mammals also reproduced via eggs. [http://en.wikipedia.org/wiki/Karl_Ernst_von_Baer Karl Ernst von Baer] discovered the mammalian ovum in 1827, and [http://en.wikipedia.org/wiki/Edgar_Allen Edgar Allen] discovered the human ovum in 1928. The fusion of spermatozoa with ova (of a starfish) was observed by [http://en.wikipedia.org/wiki/Oskar_Hertwig Oskar Hertwig] in 1876.

While the non-mammalian animal egg was obvious, the doctrine ex ova omne vivum ("every living [animal comes from] an egg"), associated with [https://en.wikipedia.org/wiki/William_Harvey William Harvey] (1578-1657), was a rejection of [https://en.wikipedia.org/wiki/Spontaneous_generation spontaneous generation] and [https://en.wikipedia.org/wiki/Preformationism preformationism] as well as a bold assumption that mammals also reproduced via eggs. [https://en.wikipedia.org/wiki/Karl_Ernst_von_Baer Karl Ernst von Baer] discovered the mammalian ovum in 1827, and [https://en.wikipedia.org/wiki/Edgar_Allen Edgar Allen] discovered the human ovum in 1928. The fusion of spermatozoa with ova (of a starfish) was observed by [https://en.wikipedia.org/wiki/Oskar_Hertwig Oskar Hertwig] in 1876.

==Definitions==

==Definitions==

*1:a [[female]] [http://en.wikipedia.org/wiki/Gamete gamete] :  macrogamete —called also ''egg cell''

*1:a [[female]] [https://en.wikipedia.org/wiki/Gamete gamete] :  macrogamete —called also ''egg cell''

*2: a mature [[female]] reproductive [[cell]], esp. of a human or other animal, that can divide to give rise to an [[embryo]] usually only after [[fertilization]] by a [[male]] cell.

*2: a mature [[female]] reproductive [[cell]], esp. of a human or other animal, that can divide to give rise to an [[embryo]] usually only after [[fertilization]] by a [[male]] cell.

==Description==

==Description==

The '''ovum''' or ''egg cell'' is the female haploid reproductive cell (gamete) in [http://en.wikipedia.org/wiki/Oogamy oogamous] organisms. The egg cell is typically not capable of active movement, and it is much larger than the motile [[sperm]] cells. When egg and sperm fuse, a diploid cell (the [http://en.wikipedia.org/wiki/Zygote zygote]) is formed, which gradually grows into a new [[organism]].

The '''ovum''' or ''egg cell'' is the female haploid reproductive cell (gamete) in [https://en.wikipedia.org/wiki/Oogamy oogamous] organisms. The egg cell is typically not capable of active movement, and it is much larger than the motile [[sperm]] cells. When egg and sperm fuse, a diploid cell (the [https://en.wikipedia.org/wiki/Zygote zygote]) is formed, which gradually grows into a new [[organism]].

In [[animals]], egg cells are also known as ''ova'' (singular ovum, from the Latin word ovum meaning egg or egg cell). The term ovule is used for the young ovum of an animal. In higher animals, ova are produced by female [http://en.wikipedia.org/wiki/Gonad gonads] (sexual glands) called ovaries and all of them are present at [[birth]] in [[mammals]] and mature via [http://en.wikipedia.org/wiki/Oogenesis oogenesis].

In [[animals]], egg cells are also known as ''ova'' (singular ovum, from the Latin word ovum meaning egg or egg cell). The term ovule is used for the young ovum of an animal. In higher animals, ova are produced by female [https://en.wikipedia.org/wiki/Gonad gonads] (sexual glands) called ovaries and all of them are present at [[birth]] in [[mammals]] and mature via [https://en.wikipedia.org/wiki/Oogenesis oogenesis].

In [http://en.wikipedia.org/wiki/Viviparous viviparous] animals (which include humans and all other placental mammals), the ''ovum'' is fertilized inside the female [[body]].

In [https://en.wikipedia.org/wiki/Viviparous viviparous] animals (which include humans and all other placental mammals), the ''ovum'' is fertilized inside the female [[body]].

The human ova grow from primitive germ cells that are embedded in the substance of the [http://en.wikipedia.org/wiki/Ovary ovaries]. Each of them divides repeatedly to give secretions of the uterine glands, ultimately forming a [http://en.wikipedia.org/wiki/Blastocyst blastocyst].

The human ova grow from primitive germ cells that are embedded in the substance of the [https://en.wikipedia.org/wiki/Ovary ovaries]. Each of them divides repeatedly to give secretions of the uterine glands, ultimately forming a [https://en.wikipedia.org/wiki/Blastocyst blastocyst].

The ovum is one of the largest cells in the human body, typically visible to the naked eye without the aid of a [[microscope]] or other magnification device. The human ovum measures approximately 0.12 mm in diameter.

The ovum is one of the largest cells in the human body, typically visible to the naked eye without the aid of a [[microscope]] or other magnification device. The human ovum measures approximately 0.12 mm in diameter.

Ooplasm (also: oöplasm) is the [http://en.wikipedia.org/wiki/Yolk yolk] of the ovum, a cell substance at its center, which contains its [[nucleus]], named the [http://en.wikipedia.org/wiki/Germinal_vesicle germinal vesicle], and the [http://en.wikipedia.org/wiki/Nucleolus nucleolus], called the germinal spot.

Ooplasm (also: oöplasm) is the [https://en.wikipedia.org/wiki/Yolk yolk] of the ovum, a cell substance at its center, which contains its [[nucleus]], named the [https://en.wikipedia.org/wiki/Germinal_vesicle germinal vesicle], and the [https://en.wikipedia.org/wiki/Nucleolus nucleolus], called the germinal spot.

The ooplasm consists of the [http://en.wikipedia.org/wiki/Cytoplasm cytoplasm] of the ordinary animal cell with its spongioplasm and hyaloplasm, often called the formative yolk; and the nutritive yolk or deutoplasm, made of rounded granules of fatty and albuminoid substances imbedded in the cytoplasm.

The ooplasm consists of the [https://en.wikipedia.org/wiki/Cytoplasm cytoplasm] of the ordinary animal cell with its spongioplasm and hyaloplasm, often called the formative yolk; and the nutritive yolk or deutoplasm, made of rounded granules of fatty and albuminoid substances imbedded in the cytoplasm.

Mammalian ova contain only a tiny amount of the nutritive yolk, for nourishing the embryo in the early stages of its [[development]] only. In contrast, bird eggs contain enough to supply the chick with nutriment throughout the whole period of incubation.

Mammalian ova contain only a tiny amount of the nutritive yolk, for nourishing the embryo in the early stages of its [[development]] only. In contrast, bird eggs contain enough to supply the chick with nutriment throughout the whole period of incubation.

In the oviparous animals (all birds, most fish, amphibians and reptiles) the ova develop protective layers and pass through the [http://en.wikipedia.org/wiki/Oviduct oviduct] to the outside of the body. They are fertilized by male [[sperm]] either inside the female body (as in birds), or outside (as in many fish). After fertilization, an [[embryo]] develops, nourished by nutrients contained in the egg. It then hatches from the egg, outside the mother's body.  

In the oviparous animals (all birds, most fish, amphibians and reptiles) the ova develop protective layers and pass through the [https://en.wikipedia.org/wiki/Oviduct oviduct] to the outside of the body. They are fertilized by male [[sperm]] either inside the female body (as in birds), or outside (as in many fish). After fertilization, an [[embryo]] develops, nourished by nutrients contained in the egg. It then hatches from the egg, outside the mother's body.  

The egg cell's cytoplasm and mitochondria are the sole means the egg is able to reproduce by mitosis and eventually form a blastocyst after fertilization.

The egg cell's cytoplasm and mitochondria are the sole means the egg is able to reproduce by mitosis and eventually form a blastocyst after fertilization.

There is an intermediate form, the [http://en.wikipedia.org/wiki/Ovoviviparity ovoviviparous] animals: the embryo develops within and is nourished by an egg as in the oviparous case, but then it hatches inside the mother's body shortly before [[birth]], or just after the egg leaves the mother's body. Some fish, reptiles and many invertebrates use this technique.

There is an intermediate form, the [https://en.wikipedia.org/wiki/Ovoviviparity ovoviviparous] animals: the embryo develops within and is nourished by an egg as in the oviparous case, but then it hatches inside the mother's body shortly before [[birth]], or just after the egg leaves the mother's body. Some fish, reptiles and many invertebrates use this technique.

[[Category: Biology]]

[[Category: Biology]]