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It states that the cerebral cortex develops during embryogenesis as an array of interacting cortical columns, or 'radial units', each of which originates from a transient stem cell layer called the ventricular zone, which contains neural stem cells known as radial glial cells.
The ventricular and subventricular zones exist inferior to the intermediate zone and communicate with other zones through cell signalling. These zones additionally create neurons destined to migrate to other areas in the cortex. [1] [6] The marginal zone, along with the cortical zone, make up the 6 layers that form the cortex. This zone is the ...
The marginal zone is the region at the interface between the non-lymphoid red pulp and the lymphoid white-pulp of the spleen. (Some sources consider it to be the part of red pulp which borders on the white pulp, while other sources consider it to be neither red pulp nor white pulp.) A marginal zone also exists in lymph nodes. [1] [2]
Flannery's hypothesis was meant to help explain the adoption of agriculture in the Neolithic Revolution.Unpersuaded by "the facile explanation of prehistoric environmental change" [2] Flannery suggested (following Lewis Binford's equilibrium model) that population growth in optimal habitats led to demographic pressure within nearby marginal habitats as daughter groups migrated.
Cajal–Retzius cells were described to migrate tangentially in the marginal zone, a superficial layer of the preplate in the cortical neuroepithelium, [3] [4] According to some studies, this migration depends on the site where the cell was generated, showing a link between the origin, the migration and the destination of the cell.
Conditions at the centre of the range differ from those at the periphery, therefore adapted alleles at the centre may not benefit marginal populations experiencing different conditions. [11] The asymmetrical gene flow hypothesis posits that there is more gene flow from central to peripheral populations. Empirical data supporting this theory is ...
An ultimate explanation based on sexual selection states that females who display preferences have more vigorous or more attractive male offspring. Proximate causation explains biological function in terms of immediate physiological or environmental factors. Example: a female animal chooses to mate with a particular male during a mate choice ...
In humans the splenic marginal zone B cells have evidence of somatic hypermutation in their immunoglobulin genes, indicating that they have been generated through a germinal centre reaction to become memory cells. While naive MZ B cells produce low-affinity IgM antibodies, memory MZ B cells express high-affinity Ig molecules.