Anatomy and Physiology of Children and Adolescents - M. R. Sapin 2007

The Nervous System (General Plan of Structure and Development of the Nervous System)
Central Nervous System
The Brain - Basal Nuclei and White Matter of the Telencephalon

Deep within the White matter OF each cerebral hemisphere, closer to its base, lie clusters of Gray matter that form separate basal nuclei. The basal (subcortical) nuclei, or ganglia, include the striatum (composed of the caudate and lentiform nuclei), the claustrum, and the amygdaloid body (Fig. 102).

Class="center">

Fig. 101. Cellular and fiber layers of the Cerebral Cortex:

I — molecular layer; II — external granular layer; III — external pyramidal layer; IV — internal granular layer; V — internal pyramidal layer; VI — multiform layer; VII — fibers of the molecular layer; VIII — fibers of the external granular layer; IX — fibers of the internal granular layer; X — fibers of the internal pyramidal layer

The caudate Nucleus lies lateral and superior to the thalamus, separated from it by the terminal stria. The Nucleus consists of a HEAD (which forms the lateral wall of the anterior horn of the lateral ventricle), a body (situated beneath the parietal lobe), and a tail (which contributes to The formation of the roof of the inferior horn of the lateral ventricle). The lentiform nucleus is located lateral to the caudate nucleus. The lentiform nucleus is subdivided into an inner portion, the globus pallidus, and an outer portion, the putamen.

These nuclei serve as subcortical motor centers. Between the caudate nucleus and thalamus medially and the lentiform nucleus laterally lies a layer of white matter known as the internal capsule. This capsule is formed by ascending and descending projection fibers of the Brain that connect the cerebral cortex with the Brainstem and Spinal Cord. Lateral to the lentiform nucleus is a narrow band of white matter called the external capsule, behind which lies a thin nuclear plate, the claustrum. Thus, the claustrum is situated within the white matter of the hemisphere lateral to the lentiform nucleus, between the latter and the insular cortex. It is separated from the insular cortex by a layer of white matter designated as the extreme capsule. The amygdaloid body (nucleus) is embedded in the white matter of the anterior part of the temporal lobe of the hemisphere, 1.5–2 cm posterior to its temporal pole.

Fig. 102. Basal nuclei in a horizontal section of the brain:

1 — cerebral cortex (Pallium); 2 — genu of corpus callosum; 3 — anterior horn of lateral ventricle; 4 — internal capsule; 5 — external capsule; 6 — claustrum; 7 — extreme capsule; 8 — putamen; 9 — globus pallidus; 10 — III ventricle; 11 — posterior horn of lateral ventricle; 12 — thalamus; 13 — cortical substance (cortex) of insula; 14 — head of caudate nucleus; 15 — cavity of septum pellucidum

White matter of the cerebral hemispheres. The white matter of the hemisphere encompasses the internal capsule, corpus callosum, anterior commissure, hippocampal commissure (lyra), fornix, as well as fiber systems that interconnect cortical areas and subcortical centers within a single cerebral hemisphere.

The corpus callosum (the great cerebral commissure) consists of transversely oriented nerve fibers that connect the right and left cerebral hemispheres. The anterior end of the corpus callosum—its genu, which continues inferiorly as the rostrum—curves forward; the posterior end—the splenium—is rounded. The thickened posterior part (splenium) transitions anteriorly into the body of the corpus callosum. Inferiorly, the rostrum continues into the terminal lamina. Situated beneath the corpus callosum is the fornix (also composed of white matter), which appears as two arches joined in the middle. These arches converge anteriorly to form the columns of the fornix, which descend through the Hypothalamus into the mamillary bodies. Posteriorly, the crura of the fornix diverge and are connected by the hippocampal commissure. Each crus extends downward to become the fimbria, which reaches the inferior horn of the lateral ventricle and attaches to the hippocampus. The Inferior surface of the corpus callosum fuses centrally with the body of the fornix. Between the inferior surface of the anterior half of the corpus callosum (including its genu and rostrum) and the columns of the fornix lie the two laminae of the septum pellucidum in the sagittal plane, enclosing its narrow cavity.

Lateral ventricles. The cavities of the cerebral hemispheres are the lateral ventricles (I and II), located within the white matter beneath the corpus callosum. Each ventricle consists of four parts. The anterior horn of the lateral ventricle is situated in the frontal lobe of the cerebral hemisphere, the central part in the parietal lobe, the posterior horn in the occipital lobe, and the inferior horn in the temporal lobe. The anterior horns of both ventricles are separated from each other by the two laminae of the septum pellucidum. The central part of the lateral ventricle arches over the thalamus, continuing posteriorly into the posterior horn and inferiorly into the inferior horn. The medial wall of the inferior horn is formed by the hippocampus, which corresponds to the deep sulcus of the same name on the Medial surface of the hemisphere. Running along the hippocampus is the fimbria, a continuation of the crus of the fornix. On the medial wall of the posterior horn of the lateral ventricle is a prominence, the calcar avis, corresponding to the calcarine sulcus on the medial surface of the hemisphere. Projecting into the ventral part and the inferior horn of the lateral ventricle is the choroid plexus, which communicates through the interventricular foramen with the choroid plexus of the III ventricle.

Review and Self-Assessment Questions:

1. Name the PARTS OF THE Telencephalon and provide their anatomical and functional characteristics.

2. List the major sulci and gyri located on the superolateral, medial, and inferior surfaces of the cerebral hemisphere.

3. List the cellular layers of the cerebral cortex. Characterize The concepts of cortical "cytoarchitectonics" and "myeloarchitectonics".

4. Name the basal nuclei (ganglia) and describe the topographical relationships among these nuclei.

5. Name the structures belonging to the white matter of the cerebral hemispheres and describe their characteristics.

6. What parts are distinguished in the ventricles of the telencephalon, and where are these parts located?

7. Explain what you know about the production and pathways of outflow of CEREBROSPINAL FLUID.