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In the central nervous system (brain, spinal cord and optic nerves), myelination is formed by specialized glial cells called oligodendrocytes, each of which sends out processes (limb-like extensions from the cell body) to myelinate multiple nearby axons; while in the peripheral nervous system, myelin is formed by Schwann cells (neurolemmocytes ...
The subgranular zone (in rat brain). (A) Regions of the dentate gyrus: the hilus, subgranular zone (sgz), granule cell layer (GCL), and molecular layer (ML). Cells were stained for doublecortin (DCX), a protein expressed by neuronal precursor cells and immature neurons. (B) Closeup of subgranular zone, located between the hilus and GCL.
Brain cells make up the functional tissue of the brain. The rest of the brain tissue is the structural stroma that includes connective tissue such as the meninges, blood vessels, and ducts. The two main types of cells in the brain are neurons, also known as nerve cells, and glial cells, also known as neuroglia. [1]
In general, neuroglial cells are smaller than neurons. There are approximately 85 billion glia cells in the human brain, [8] about the same number as neurons. [8] Glial cells make up about half the total volume of the brain and spinal cord. [27] The glia to neuron-ratio varies from one part of the brain to another.
It develops mostly from the mesenchyme, derived from the mesoderm, the middle embryonic germ layer. [2] Connective tissue is found in between other tissues everywhere in the body, including the nervous system. The three meninges, membranes that envelop the brain and spinal cord, are composed of connective tissue. Most types of connective tissue ...
The cells of the brain include neurons and supportive glial cells. There are more than 86 billion neurons in the brain, and a more or less equal number of other cells. Brain activity is made possible by the interconnections of neurons and their release of neurotransmitters in response to nerve impulses.
Layer I, the molecular layer, is the first cortical layer produced during neurogenesis at mice at embryonal days 10.5 to 12.5 (E10.5 to E12.5). [7] Of the six layers found within the neocortex, layer I is the most superficial and is composed of Cajal–Retzius cells and pyramidal cells. [8]
The latter is the thickest and outermost of the three membrane layers; it contains the most collagen, and it is derived from the mesoderm - the middle germ layer or the primary layer of the cells formed in embryogenic development via epigenetic effects induced by developmental cues, in the early embryo. Also there are the two parietal bones and ...