3. Coronal Sections and the Ventricular System
Revised August 2, 2007
The objectives of this chapter are to identify:
- The major brain divisions in coronal sections.
- The ventricular system in coronal sections.
- The origin, course, and fate of the cerebrospinal fluid (CSF).
I. The Major Brain Divisions in Coronal Sections
Figure 3d Midsagittal Section for Orientation to Coronal Sections
Click on the letters at the top of each of the red lines to see labeled images on each slice.
The labels on each slice are linked to the glossary terms.
Fig 3d indicates the order of the following coronal sections through the brain (Figures 3e-3n). Note that, in general, these sections proceed from anterior (rostral, frontal) to posterior (caudal, occipital) The major divisions of the brain and the ventricular system will be seen as the coronal sections are examined.
The cerebral cortex is a sheet of gray matter surrounding a core of white matter (fig 3e). What does the latter represent? Does the cortex have a uniform thickness? It has been estimated that two thirds of the cortical surface area is buried in the sulci.
Section fig 3g is similar to the previous one except that an oval-shaped mass, the caudate nucleus (a part of the basal ganglia), forms the lateral wall of the lateral ventricle. Observe that the caudate nucleus bulges into the ventricle. The medial wall of the lateral ventricle is formed by the septum pellucidum, which is composed almost entirely of glial cells.
With the intrusion of the thalamus, the next section appears more complicated (fig 3h); (#6120 is slightly enlarged; #4750 is a gross section). However, there are several familiar structures that display the same topographic relationships seen in rostral sections. The caudate ("tailed") nucleus, quite reduced in size, still forms the lateral wall of the lateral ventricle, and the corpus callosum is still the roof of the ventricle. Lateral to the caudate is a group of axons that connect the cerebral cortex with the brain stem (#4756). This is the internal capsule. It separates the caudate nucleus from the other basal ganglia that are seen in this section (the putamen (#4752) and globus pallidus (#4753)). Inferior to the putamen and globus pallidus is yet another nucleus, the amygdala (#4763) ("almond-shaped").
In a slightly enlarged section, the centrally placed diencephalon (the thalamus and hypothalamus) is prominent (fig 3i). You can verify that the diencephalon forms (1) the floor of the lateral ventricle as well as (2) the sidewalls and floor of the third ventricle. The thalamus on one side is usually joined to that of the opposite side by the massa intermedia (or interthalamic adhesion) (#4600). The thalamus is the portal or foyer for information flowing toward the cortex. The hypothalamus is involved in coordinating autonomic and endocrine function.
You can see how the choroid plexus forms the roof of the third ventricle and the medial edge of the floor of the lateral ventricle. In the case of ventricle III, the choroid plexus simply runs along top of the ventricle, between one half of the thalamus and the other. To seal off the lateral ventricle, the choroid plexus extends from the fornix to the nearby thalamus. Centrally located is subarachnoid space, the cistern of the velum interpositum (#6671), which you do not need to identify. It contains the paired internal cerebral veins, which drain in the great cerebral vein (of Galen).
Section fig 3j is at the interface of the diencephalon and the mesencephalon and appears to be more complicated than the previous sections. A small bit of the caudate nucleus is tucked away in the angle of the lateral ventricle. The inferior or temporal horn of the lateral ventricle is clearly seen. Its floor and medial wall are partly formed by the hippocampus.
A practiced eye is needed to distinguish the thalamus from the midbrain. The thalamus, of course, borders the third ventricle and is dorsal to the mesencephalic structures present in this section. The mesencephalic structures present in this section include the substantia nigra and the red nucleus.
The section through the mesencephalon (fig 3k) is not coronal like the earlier sections. It is transverse to the long axis of the brainstem. (See fig 3d for orientation.) It shows the location of the aqueduct (of Sylvius). This is the narrowest portion of the ventricular system. It connects ventricles III and IV. Other midbrain structures present in this section are the substantia nigra, the tectum (superior colliculus) and the cerebral peduncle, which is an important continuation of the internal capsule.
In the next section (fig 3l, the asterisks indicate the subarachnoid space), the telencephalon, again, has much the same appearance as in earlier sections. Note that at this level the telencephalon is not attached to the brain stem. This coronal image cuts obliquely through the midbrain and the pons. (See fig 3d for orientation.) The region around the aqueduct is part of the midbrain or mesencephalon. A thin slice of cerebellum is present to the side of the midbrain and pons. The cerebellum and pons are parts of the metencephalon. Where would the falx cerebri and the tentorium cerebelli be located in this section?
Because the cortical gray matter in fig 3m is continuous around the circumference of the hemisphere, this section must be caudal to the corpus callosum. How does the occipital horn (or posterior horn) of the lateral ventricle, shown here, communicate with the fourth ventricle? In this section, the sidewalls and roof of ventricle IV are formed by the cerebellum. The ventricular floor is the dorsal surface of the brain stem, in this instance, the medulla. In a more rostral section, what structure would form the floor of ventricle IV? As in the previous section, indicate the positions of the falx and tentorium.
II. The Ventricular System
The brain ventricular system is filled with cerebrospinal fluid (CSF) that originates from the choroid plexus (fig 3a), which is continuous with the ependymal lining of the brain. A higher power view of the choroid plexus (fig 3b) shows the apical surface of the choroid plexus epithelial cells facing the ventricle. Their basal ends are next to a core of loose connective tissue that contains numerous capillaries. Ciliated ependymal cells (fig 3c) line the ventricular system.
Review the ventricular system (#42045, #4266). The CSF circulates through the lateral ventricles, which each have a body and three horns, the frontal (#52320), occipital (#52322), and temporal (#52321) horns. The part of the lateral ventricle where the body meets the occipital and temporal horns is the trigone (atrium). Next, the CSF passes through the interventricular foramen (of Monro) into the third ventricle (#52316). It leaves this ventricle and flows through the aqueduct (#4262) into ventricle IV (#4261). The CSF exits from the ventricular system through the lateral apertures of Luschka (#52324, #5637) and the median aperture of Magendie. It then enters the subarachnoid space and circulates around the brain. It is transported across the arachnoid granulations (#4926) into the dural sinuses (#4925) and, thus, into the venous system.
Click for the Syllabus Quiz for Chapter 3
From The Digital Anatomist Interactive Brain Syllabus. John Sundsten and Kate Mulligan, Univ. Washington School of Medicine. 1998 ©
- brain stem with ventricles
- brain stem with ventricles and cerebellum
- translucent brain with diencephalon and ventricles
- Ventricles and transparent brain
- Ventricles alone
- Ventricles alone rotating in other plane
- Ventricles and midsagittal structures
From David Morton & Kurt Albertine
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