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.
- 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.