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Chapter 11: Ventricles and Coverings of the Brain

VENTRICULAR SYSTEM

Within the brain is a communicating system of cavities that are lined with ependyma and filled with cerebrospinal fluid (CSF): There are two lateral ventricles, the third ventricle (between the halves of the diencephalon), the cerebral aqueduct, and the fourth ventricle within the brain stem (Fig 11–1).

FIGURE 11–1

The ventricular system.

An illustration shows the ventricular system of brain. Illustration marks the following structures: Anterior (frontal) horn; Interventricular foramen (of Monro); Lateral ventricles; Posterior (occipital) horn; Cerebral aqueduct; Third ventricle; Inferior (temporal) horn; and Fourth ventricle.
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Choroid Plexus

The choroid plexus is the site where CSF is produced. It is a fringe-like vascular process of pia mater containing capillaries of the choroid arteries. It projects into the ventricular cavity and is covered by an epithelial layer of ependymal origin (Figs 11–2 and 11–3). The attachment of the plexus to the adjacent brain structures is known as the tela choroidea. The choroid plexus extends from the interventricular foramen, where it joins with the plexuses of the third ventricle and opposite lateral ventricle, to the end of the inferior horn. (There is no choroid plexus in the anterior and posterior horns.)

FIGURE 11–2

Three stages (Top to Bottom) of development of the choroid plexus in the lateral ventricle (coronal sections).

An illustration shows three developmental stages of the choroid plexus. Illustration shows the stages as observed in coronal sections of lateral ventricle. Structures visible during three stages in development of choroid plexus are as follows: Stage 1: Telencephalic vesicle; and Cavity of prosencephalon. Stage 2: Lateral ventricle; Choroid plexus area; and Third ventricle. Stage 3: Corpus callosum; Choroid plexus in third ventricle; Choroid plexus in lateral ventricle; and Inferior horn.
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FIGURE 11–3

Dorsal view of the choroid plexus in the ventricular system. Notice the absence of choroid in the aqueduct and the anterior and posterior horns.

An illustration shows structures in the dorsal view of choroid plexus in the ventricular system. Illustration shows the following structures in the choroid plexus: Anterior horn; Right lateral ventricle; Third ventricle; Posterior horn; and Fourth ventricle with recesses.
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Lateral Ventricles

The lateral ventricles are the largest. They each include two central portions (body and atrium) and three extensions (horns).

The anterior (frontal) horn is in front of the interventricular foramen. Its roof and anterior border are formed by the corpus callosum; its vertical medial wall, by the septum pellucidum; and the floor and lateral wall, by the bulging head of the caudate nucleus.

The central part, or body, of the lateral ventricle extends from the interventricular foramen to a point opposite the splenium of the corpus callosum. Its roof is formed by the corpus callosum and its medial wall by the posterior portion of the septum pellucidum. The floor contains (from medial to lateral side) the fornix, the choroid plexus, the lateral part of the dorsal surface of the thalamus, the stria terminalis, the vena terminalis, and the caudate nucleus. The atrium, or trigone, is a wide area of the body that connects with the posterior and inferior horns (Fig 11–4).

FIGURE 11–4

Drawing of the ventricles showing their relationship to the dura, tentorium, and skull base.

An illustration shows location of ventricles with regards to dura, tentorium, and skull base. Illustration marks the following structures: Falx; Right lateral ventricle; Third ventricle; Cerebral aqueduct; Inferior horn of left lateral ventricle; Atrium of left lateral ventricle; and Tentorium (left half).
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The posterior (occipital) horn extends into the occipital lobe. Its roof is formed by fibers of the corpus callosum. On its medial wall is the ...

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