VAN 211: Veterinary Histology and Embryology (2+2)

CEREBRUM

Note: The Brain consists of many parts (studied in gross anatomy) having its own histological structure only the motor area of the cerebral cortex is described below as an example.

• The cerebral cortex is the external layer of gray matter covering the convolutions and fissures of cerebral hemispheres.
• It contains the bodies of nerve cells, nerve fibres, neuroglia and blood vessels.
• It shows the following layers from without inwards:
• Piamater
• Molecular or plexiform Layer: It is poor in cells and has a framework of the reticulum formed by the glial process and dendrites of the pyramidal cells. There are fusiform cells directed horizontally.
• Layer of small pyramidal cells: Contains cells with their apices directed towards the surface. They are 10-12 microns in size. From the apex a long main dendrite passes to the molecular layer where it forms a feltwork by its ramifications. Laterally and basally from the cells arise dendrites. The axon arises from the base and gets myelinated. Giving off collaterals, it passes into white matter.
• Layer of large Pyramidal cells - giant cells of Betz: Found in the motor cortex. Apical dendrite long and goes towards molecular layer, there are also basal dendrites. Axon arises from the basis to the white matter giving off collaterals on its way.
• Layer of Polymorphous cells: Cells are 5-8 microns in size, irregular and varied in shape. Their short dendrites ramify in all directions. Their axons enter white matter.