Snell's Clinical Neuroanatomy

271

Structures

A

B

Figure 7-5 Light micrographs of the cerebellum. ( A ) The cerebellum consists of a core of white matter (W) and superficially located gray matter (G). The gray matter is subdivided into the outer molecular layer (ML), a middle Purkinje cell layer (PL), and the inner granular layer (GL), each layer consisting of high concentration of cell bodies belonging to neurons of specialized morphologies and functions. The less-dense appearance of the molecular layer is because of the sparse arrangement of nerve cell bodies, whereas the darker appearance of the granular layer is a function of the great number of darkly staining nuclei packed closely together. (×14). ( B ) Here, the interface between the outer white matter (W) and a core of gray matter (G) is readily evi dent ( asterisks ). The numerous nuclei ( arrowheads ) present in white matter belong to the various neuroglia, which support the axons traveling up and down the spinal cord. The large neuron cell bodies (CB) in the gray matter possess euchromatic nuclei with dense, dark nucleoli. Blood ves sels (BV), which penetrate deep into the gray matter, are surrounded by processes of neuroglial cells, forming the blood–brain barrier (not visible). Small nuclei ( arrows ) in gray matter belong to the neuroglial cells, whose cytoplasm and cellular processes are not evident. (×132). (Reproduced with permission from Gartner LP. Gartner & Hiatt’s Atlas and Text of Histology . 8th ed. Baltimore, MD: Wolters Kluwer; 2002: Fig. 8-7A,B.) Copyright © 2021 Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited.

Functional Areas Clinical observations by neurologists and neurosur geons and the experimental use of positron emission tomography have shown that the cerebellar cortex can be divided into three functional areas. The cortex of the vermis influences the movements of the long axis of the body, namely, the neck, shoul ders, thorax, abdomen, and hips (Fig. 7-6). Immediately

lateral to the vermis is a so-called intermediate zone of the cerebellar hemisphere. This area has been shown to control the muscles of the distal parts of the limbs, especially the hands and feet. The lateral zone of each cerebellar hemisphere appears to be concerned with the planning of sequential movements of the entire body and is involved with the conscious assessment of movement errors.