1. Series of mitotic cell divisions occurring in the ovum immediately following its fertilization. SYN: segmentation (2). SEE ALSO: c. division. 2. Splitting of a complex molecule into two or more simpler molecules. SYN: scission (2). 3. Linear clefts in the skin indicating the direction of the fibers in the dermis. SEE ALSO: tension lines, under line. 4. Midline depression or furrow between mature female breasts (common).
- abnormal c. of cardiac valve congenital malformation of a valve leaflet with a defect extending from the free margin.
- adequal c. c. resulting in the formation of blastomeres of approximately equal size.
- complete c. SYN: holoblastic c..
- determinate c. c. resulting in blastomeres each capable of developing only into a particular embryonic structure.
- discoidal c. meroblastic c. limited to the small cap (animal pole) of protoplasm of large-yolked eggs, such as the telolecithal eggs of birds.
- enamel c. the splitting of enamel in a plane parallel to the direction of the enamel rods.
- equal c. c. producing blastomeres of like size.
- equatorial c. c. in which the plane of cytoplasmic division is at right angles to the axis of the ovum.
- holoblastic c. c. in which the blastomeres are completely separated; the entire egg participates in cell division. SYN: complete c., total c..
- incomplete c. SYN: meroblastic c..
- indeterminate c. c. resulting in blastomeres of similar developmental potencies, each capable, when isolated, of producing an entire embryonic body.
- meridional c. c. in a plane through the axis of the zygote.
- meroblastic c. incomplete separation of the blastomeres, with the divisions being limited to the nonyolked portion of the egg. SYN: incomplete c..
- phosphoroclastic c. SYN: phosphorolysis.
- progressive c. in fungi, a type of sporulation in which c. planes in the cytoplasm first produce protospores and then sporangiospores in a sporangium.
- pudendal c. SYN: pudendal cleft.
- subdural c. SYN: subdural space.
- superficial c. meroblastic c. with the divisions limited to the peripheral (surface) cytoplasm of a centrolecithal egg.
- thioclastic c. the splitting of a bond in fashion analogous to hydrolysis or phosphorolysis except that the elements of a substituted hydrogen sulfide (usually coenzyme A) are added across the break.
- total c. SYN: holoblastic c..
- unequal c. c. producing blastomeres of different sizes at the two poles.

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cleav·age 'klē-vij n
1) the series of synchronized mitotic cell divisions of the fertilized egg that results in the formation of the blastomeres and changes the single-celled zygote into a multicellular embryo also one of these cell divisions
2) the splitting of a molecule into simpler molecules

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(in embryology) the process of repeated cell division of the fertilized egg to form a ball of cells that becomes the blastocyst. The cells (blastomeres) do not grow between divisions and so they decrease in size.

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cleav·age (kleґvəj) 1. division into distinct parts. 2. the mitotic division of the zygote, the size of the structure remaining unchanged as the cleavage cells, or blastomeres, become smaller and smaller with each division.

Medical dictionary. 2011.

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  • Cleavage — Cleavage. См. Расщепление. (Источник: «Металлы и сплавы. Справочник.» Под редакцией Ю.П. Солнцева; НПО Профессионал , НПО Мир и семья ; Санкт Петербург, 2003 г.) …   Словарь металлургических терминов

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