Human Anatomy, Part 2 - K. A. Diubenko, A. K. Kolomiitsev, Yu. B. Chaikovskyi 2008

Special Part
Nervous system, systema nervosum - Special Part
Pallium - Cerebral cortex

The Cerebral Cortex, cortex cerebralis, is represented by a layer of Gray matter ranging in thickness from 1.5 mm On the surface of the gyri to 3–5 mm in the depths of the sulci. The cerebral cortex, along with other PARTS OF THE Central Nervous system, regulates all bodily Functions and plays an exceptionally important role in mental and Higher Nervous Activity. The cerebral cortex is characterized by a wide range of complex functions, from intellectual activity to the control of motor Neurons. The cortex consists of Nerve Cells, their processes, and neuroglia. All cortical nerve cells are classified into pyramidal, stellate, and spindle-shaped cells. Pyramidal cells make up approximately 60–70% of all cortical neurons, while stellate cells account for about 20–25%. The large number of sulci and gyri increases the surface area of the cerebral gray matter. The total surface area of the adult human cortex is 220,000 mm², with 2/3 lying deep within the sulci and only 1/3 located on the surface.

Here, it is appropriate to quote I. P. Pavlov: "If, from one point of view, the cerebral cortex can be regarded as a mosaic consisting of a countless number of individual points with a specific physiological role at any given moment, from another, we have in it a highly complex dynamic system that constantly strives for unification (integration) and for a stereotyped unifying activity"**.

In accordance with the stages of evolutionary Development of the central nervous system, the cortex is divided into the paleocortex (ancient cortex), which belongs to the rhinencephalon; the archicortex (old cortex), which belongs to the limbic system; and the neocortex (new cortex), which consists of 6 layers. The paleocortex and archicortex are phylogenetically older structures than the neocortex, which emerged during The Development of the cerebral hemispheres. The neocortex significantly exceeds all other cortical areas in size, accounting for approximately 96% of the entire cerebral surface. The cortex contains about 10–14 billion nerve cells of various SHAPES AND SIZES.

* Hippocampus (hippocampus) - from the Greek *hippokampos*, a sea monster (with the body of a horse and the tail of a fish), synonym: Ammon's horn, cornu Ammonis; This paired Structure is part of the archicortex that has descended into the ventricular cavity, and it belongs to the limbic system. The hippocampus is responsible for The process of learning and long-term memory.

** I. P. Pavlov, Lectures on the Work of the Cerebral Hemispheres. Complete Works, Vol. IV. 1947, p. 195.

Class="center">STRUCTURE OF THE Cerebral Cortex

The human neocortex is characterized by a six-layered arrangement of nerve cells [laminae] (Fig. 153)

1) molecular layer, lamina molecularis [lamina I];

2) external granular layer, lamina granularis externa [lamina II];

3) external pyramidal layer, lamina pyramidalis externa [lamina III];

4) internal granular layer, lamina granularis interna [lamina IV];

5) internal pyramidal layer, lamina pyramidalis interna [lamina V];

6) multiform layer, lamina multiformis [lamina VI].

Fig. 153. Structure of the cortex (A - cortical layers; B - Cell types; C - fiber layers). Comparison of neuronal structure diagrams, cytoarchitectonic, and myeloarchitectonic layers of the cortex (after Ramón y Cajal, Brodmann, and Vogt)

The spatial arrangement of nerve cells (cytoarchitectonics) is characteristic of the main cortical layers described below. The molecular layer, lamina molecularis, consists of spindle-shaped association cells. In adults, it is sparse in nerve cells. The external granular layer is formed by A large number of small nerve cells of various shapes: granular, spherical, and angular. The external pyramidal layer consists of small, medium, and large pyramidal cells. The internal granular layer contains densely packed neurons of various shapes, predominantly stellate. Stellate neurons act as a switching system from afferent to efferent neurons of layers III and V of the cortex. The internal granular layer is the termination site for all ascending cortical pathways. The internal pyramidal layer consists of giant pyramidal cells, or Betz cells, up to 120 μm in height and 80 μm in width, which are concentrated in the precentral gyrus. Giant pyramidal cells were first described by V. O. Betz, a professor of anatomy at Kyiv University, in 1874 (hence the name of the cells). The axons of giant pyramidal cells form descending pathways (corticospinal and corticonuclear) and terminate on the Cells of the motor nuclei of the Brainstem and the motor neurons of the anterior horns of the Spinal Cord. The multiform layer is composed of neurons of various shapes, predominantly spindle-shaped, with a gradual or sharp transition into the White matter OF the hemispheres. The axons of multiform cells form the corpus callosum and the anterior commissure, connecting the cerebral hemispheres with each other. The structure and density of fiber arrangement (myeloarchitectonics) vary in different parts of the cortex, generally coinciding with cytoarchitectonics. The cerebral cortex consists of modules—Structural and functional units (J. Szentágothai). A module is a vertical Column about 300 μm in diameter that penetrates the entire thickness of the cortex.

A module is formed around a cortico-cortical fiber that originates from the pyramidal cells of the same hemisphere (association fiber) or from the adjacent hemisphere (commissural fiber). According to J. Szentágothai, each module is divided into two micromodules with a diameter of less than 100 μm. There are approximately 3 million modules in the human neocortex. The modules contact each other through dendritic and axonal collaterals.