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Overview of the cerebrum

In the cerebrum, the left hemisphere in right-handed individuals is a little bit larger than the right and generally termed the dominant hemisphere. Each cerebral hemisphere consists of the following;

  • An outer cerebral cortex: It is an outer layer of grey matter in the cerebrum
  • An inner mass of white matter present here
  • Large masses of grey matter which is embedded in the basal part of the white matter called basal ganglia/basal nuclei.
  • A cavity within it known as the lateral ventricle.

cerebrum

External features

  • Lobes: There are four major lobes present, they are the following: frontal, parietal, occipital, and temporal.
  • Border: In the cerebrum there are the following border present; superomedial border, Inferolateral border, Inferolateral border, Medial occipital border, Medial occipital border, and Superciliary border.
  • Surfaces: There are following surfaces present include; superolateral surface, Medial surface, and Inferior surface

The internal structure of the cerebrum

  • Grey mater: cortex or pallidum
    • Lies externally in it.
  • White mater: medulla
    • Lies internally in it.
  • Grey mater masses in the white mater
  • Basal nuclei or ganglia.

Types of neurons present in the cortex

  • Pyramidal cells
  • Granule (stellate) cells
  • Pleomorphic cells
  • Fusiform cells
  • Cells of Martinotti
  • Horizontal cells of Cajal
  • Basket cells

Cell layers of neocortex

  • Molecular layer( plexiform):
    • It consists of mainly nerve fibers which are coming from pyramidal and fusiform cells.
  • Outer granular layer:
    • It is densely packed granule cells & small-sized pyramidal cells. The dendrites which is passes into the molecular layer where as axons pass to the deeper layers the cerebrum
  • Outer pyramidal cell  layer:
    • It medium-sized & large pyramidal cells present it. The dendrites -molecular layer and axons enter the white matter as an association,  commissural, and projection fibers in the cerebrum of the human brain.
  • Inner granular layer:
    • Granule cells.
    • The outer band of Baillarger which is formed by horizontal fibers of thalamic radiation.
  • Ganglionic layer (inner pyramidal):
    • Inner pyramidal cell layer and Giant pyramidal cells of Betz present on it.
    • Pyramidal cells with granule cells & cells of Martinotti present on it.
    • An inner band of Baillarger which is formed by association fibers.
  • Polymorphous layer (multiform):
    • Fusiform cells and other types of cells of various shapes; hence the name polymorphous.

Types of the cerebral cortex

  • Granular cortex:
    • Mainly granule cells
    • less of pyramidal cells, or absent in this granular cortex.
    • Sensory cortex
  • Agranular cortex:
    • A large number of pyramidal cells present on it.
    • Motor cortex.

 

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