Betz cell
The Betz cell or Betz's giant pyramidal cell (after the anatomist Wladimir Betz ) is a neuronal cell type in the primary motor cortex of the gray matter of the endbrain .
The up to 100 µm large cell bodies ( perikarya ) of these pyramidal cells lie in layer Vb of the cerebral cortex of the precentral gyrus of the frontal lobe and are characteristic of the cytoarchitectural structure of this region ( Brodmann area 4). The giant Betz pyramidal cells make up about 5 percent of the pyramidal cells here; their number in humans is estimated at about 30,000.
The neurites of Betz cells project over long descending pathways to deeper regions of the CNS in the brain stem and spinal cord and sometimes directly form excitatory synapses with motor neurons in the nuclei of cranial nerves or those in the anterior horn of spinal cord segments . Their heavily myelinated axons can be found in these projection tracts as nerve fibers over 10 µm thick , the corticonuclear tract and the corticospinal tract , which also lead several hundred thousand other fibers and are collectively referred to as the pyramidal tract (see pyramis in the medullary brain). The Betz cells are the largest nerve cells - with central appendages that are longer than a meter in adults.
construction
Betz's giant pyramidal cells are multipolar nerve cells . The adjacent figure shows the scheme of a pyramidal cell of the Betz cell type with the branches of its shorter processes in the cerebral cortex . From top to bottom, the image section is almost its thickness, around 2.5 to 3 millimeters; the surface one can obenzu of the brain and the border with medullary white matter think untenhin. The onion-like thickening in the center of the picture is the cell body, the so-called perikaryon or soma, which also houses the cell nucleus ; in Betz cells it is in layer V of the neocortex of the frontal lobe. The strong cell process starting from the tip ( Latin apex ) is a dendrite and pulls upwards, where its branches reach layer I. This apical dendrite receives signals mainly from thalamic and premotor afferents; it represents the main information input of the pyramidal cell. The thorny swellings are each postsynaptic protrusions, thorny processes . In addition to the apical one, a few other dendrites can be seen at the base; these basal dendrites branch out in layers V and VI.
In addition, the basal neurite can be seen, which pulls downwards; it represents the information outlet of the pyramidal cell. The axon gives off a number of collaterals in the cortex , which branch off at approximately right angles. The further course of the axon is considerably longer; in humans, the image section from top to bottom should be up to 500 times longer.
literature
- Wladimir Betz: Anatomical evidence of two brain centers. In: Centralblatt for the medical sciences. 12, 1874, pp. 578-580, 595-599.
Individual evidence
- ↑ a b Benninghoff: Macroscopic and microscopic anatomy of humans, Vol. 3. Nervous system, skin and sensory organs . Urban and Schwarzenberg, Munich 1985, ISBN 3-541-00264-6 , p. 231.