isolecithal ovum


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ovum

 [o´vum] (pl. o´va) (L.)
the female reproductive or germ cell which after fertilization is capable of developing into a new member of the same species; called also egg. The term is sometimes applied to any stage of the fertilized germ cell during cleavage and even until hatching or birth of the new individual. The human ovum consists of protoplasm that contains some yolk, enclosed by a cell wall consisting of two layers, an outer one (zona pellucida) and an inner, thin one (vitelline membrane). There is a large nucleus (germinal vesicle) within which is a nucleolus (germinal spot). adj., adj o´vular.
Ovum.
centrolecithal ovum one with the yolk concentrated at the center of the egg, surrounded by a peripheral shell of cytoplasm, and with an island of cytoplasm surrounding the nucleus, such as that of an arthropod.
holoblastic ovum one that undergoes total cleavage.
isolecithal ovum one with a small amount of yolk evenly distributed throughout the cytoplasm.
meroblastic ovum one that undergoes partial cleavage.
primitive ovum (primordial ovum) any oocyte very early in its development.
telolecithal ovum one with a comparatively large amount of yolk massed at one pole, such as that of a reptile or bird.

i·so·lec·i·thal o·vum

an ovum in which the yolk is evenly distributed throughout the cytoplasm.

ovum

(o'vum) plural.ova [L., egg]
1. The female reproductive or germ cell.
2. A cell that is capable of developing into a new organism of the same species. Usually fertilization by a spermatozoon is necessary, although in some lower animals ova develop without fertilization (parthenogenesis). See: conception; fertilization; menstrual cycle; menstruation

alecithal ovum

An ovum with a small yolk portion that is distributed throughout the protoplasm. Synonym: isolecithal ovum

centrolecithal ovum

An ovum having a large central food yolk, as in a bird's egg.

holoblastic ovum

An ovum that undergoes complete cleavage, as opposed to partial or meroblastic cleavage.
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HUMAN OVUM

human ovum

The female gamete, required for reproduction. The ovum develops from an oogonium within the graafian follicle of the ovary and matures through the meiotic process of oogenesis. A mature ovum is about 0.13 to 0.14 mm (0.0051 to 0.0055 in) in diameter. At ovulation, the ovum is bounded by a translucent cellular membrane (the zona pellucida), which is connected to a layer of follicular cells (the corona radiata); these cells enclose the cytoplasm, nuclei, and chromatin material. The exact time during which a human ovum is capable of fertilization and further development before degenerating is not known; however, it is probably 24 hr. See: illustration; oogenesis; ovulation

isolecithal ovum

Alecithal ovum.

mature ovum

A secondary oocyte that has completed its second meiotic division as a result of contact with a sperm. The nucleus of the mature ovum becomes the female pronucleus.

meroblastic ovum

An ovum in which only the protoplasmic region undergoes cleavage, characteristic in ova containing a large amount of yolk.

permanent ovum

An ovum ready for fertilization.

primordial ovum

A germ cell that arises very early in the development of the embryo, usually in the yolk sac endoderm, migrates into the urogenital ridge, and is the precursor for the functional gamete.

telolecithal ovum

An ovum in which the yolk is fairly abundant and tends to concentrate in one hemisphere.

ovum

pl. ova [L.] egg; the female reproductive or germ cell which, after fertilization, is capable of developing into a new member of the same species; sometimes applied to any stage of the fertilized germ cell during cleavage and even until hatching or birth of the new animal.

centrolecithal ovum
one with the yolk concentrated at the center of the egg, surrounded by a peripheral shell of cytoplasm, and with an island of cystoplasm surrounding the nucleus.
holoblastic ovum
one that undergoes total cleavage.
isolecithal ovum
one with a small amount of yolk evenly distributed throughout the cytoplasm.
meroblastic ovum
one that undergoes partial cleavage.
ovum penetration assay
a biological assay using hamster, or other, zona-free ova as the test medium for the penetrating ability of individual samples of semen.
primitive ovum, primordial ovum
any egg cell very early in its development.
telolecithal ovum
one with a comparatively large amount of yolk massed at one pole.
ovum transplant
an ovum that has been fertilized in utero is recovered from the dam by flushing from the uterus, inspected under the microscope to ensure viability and transferred to the uterus of an estral female. The donor female has usually been superovulated so that a number of ova can be salvaged in the one operation.