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The outermost layer of the brain, the cortex is rich in neurons and is the site of most sophisticated neural processing (See also: cerebral cortex). Or, more generally, the outermost portion of certain biological structures (See below). The human cortex is 1-4mm thick, with an area (if it were spread flat) of about 0.22m2. It comprises perhaps 109 neurons, which appear to be organized in clusters called minicolumns, each having 80-100 neurons in a diameter of 30-50µm.
There is no common origin or structure between the various cortexes, their only commonality is that they are distinctive layers at the surfaces of the organs involved.
Botany
The cortex is the outer portion of the stem or root of a plant, bounded on the outside by the epidermis and on the inside by the pericycle. It is composed mostly of undifferentiated cells, usually large thin-walled parenchyma cells. The outer cortical cells often acquire irregularly thickened cell walls, cand are called collenchyma cells. Some of the outer cortical cells may contain chloroplasts. Its main function is the storage of starch; often, it also provides aeration of cells to allow respiration.
Anatomy
In zoology, a cortex is the outermost (or "superficial") layer of an organ. Organs with well-defined cortical layers include kidneys, adrenal glands, ovaries, the thymus, and portions of the brain.
Archaeology
In lithic analysis, cortex is the outer layer of rock formed on the exterior of raw materials by chemical and mechanical weathering processes. It is often recorded on the dorsal surface of flakes using a three class system: primary (100% cortex), secondary (100%>x>0%), and tertiary (0%). The amount of cortex present on artefacts in an archaeological assemblage may indicate the extent of lithic reduction that has occurred.
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