Polarity

Polarity is the presence of two identical (homopolymere) or different (heteropolymer) other areas (poles) in the cell, organism or part thereof. Fabric, are polarity, consists of uniaxial cells (Homo - or heteropolar), the axes of which are parallel to each other. The polarity of the cells forming the body of multicellular, as well as the polarity of the simplest (unicellular) organisms often has the character of heteropolymer (see Cell). For example, single-layer cylindrical epithelium of intestinal apical converted into the lumen of the intestine ends cells equipped with streaked cuticle built, as shown by electronic microscopy, parallel bars microvilli; opposite basal all cells are deprived of such structures; the kernel is located closer to the basal and centrosome - closer to apicalnam the end of epithelial cells. Even amorphous tissue cell polarity clearly detected during their mitotic divisions, and the axis of mitotic figures, and thus its poles, can be located without compliance with the original P. resting (interphase) cells (see Mitosis). Heteropolymer body is expressed in the simplest logical spatial distribution of organelles along the long axis of the body from one pole to another. In multicellular polarity can be detected already at the stage of immature egg cells and then depends on its position in the ovary. More often P. eggs becomes clear in the divisions of puberty when in a certain place the egg surface, a so-called polar bodies. P. Mature, especially fertilized eggs is reflected in the uneven distribution cytoplasmic components - granules of a fat, egg yolks, pigment, etc. from the top (the animal) to the bottom (vegetative) post. Polarity eggs often reflects the distribution therein, employees in the future for construction of certain organs of the future of the embryo. For example, some invertebrates, molluscs and worms) are different in color plots of cytoplasm on one or both poles eggs, the so-called polar plasma their destruction leads to the underdevelopment of the organs of the fetus.