Sagittal Sections

This chapter, the last of three showing sections of entire human brains, illustrates para sagittal planes. Forebrain structures continue to be emphasized, but parts of the brainstem and cerebellum are indicated as well. The organization of various functional systems in the forebrain (e.g., thalamus, hippocampus) is presented in Chapter 8 .

Colored diagrams showing typical areas of arterial supply in each section are provided in this and the preceding two chapters. We simplified these in two major ways. First, arterial territories are shown as sharply demarcated from each other when in reality there is significant interdigitation and overlap. Second, perforating arteries arise from all the vessels of the circle of Willis, but we lumped together those from the posterior communicating and posterior cerebral arteries and those from the anterior communicating and anterior cerebral arteries.

Figure 7.1

The axial sections from Figs. 6.3G and 6.3N , used in much of this chapter to indicate planes of section.

Figure 7.2

The planes of section shown in this chapter, indicated on three-dimensional reconstructions.

(Courtesy Dr. John W. Sundsten, Department of Biological Structure, University of Washington School of Medicine.)

Figure 7.3

(A–P) Sixteen para sagittal sections of the right half of a brain. The sections are arranged in a lateral-to-medial sequence extending from the insula to the midline. Anterior is toward the left, so the view is as though you were backing through the brain, always looking from inside the brain out toward the lateral sulcus.

(A) The first section passes tangentially through the insula (5) and shows nicely how the lateral sulcus (6) leads to it and the circular sulcus (4) outlines it. The precentral (1) and postcentral (3) gyri can also be seen, separated from each other by the central sulcus (2) , which, cut obliquely, seems deeper than it really is.

(B) The circular sulcus (1) is still present, partially surrounding the insula (2) , but now the plane of section begins to reveal structures just deep to insular cortex—in this case the claustrum (3, 6) . The most lateral part of the lateral ventricle, the inferior horn (5) , also appears, with the tail of the caudate nucleus (4) cut tangentially in its wall.

(C) Now the putamen (1) appears and the claustrum (5) , a sheet of gray matter that covers the curved lateral aspect of the putamen, appears to partially surround it in this two-dimensional view. The tail of the caudate nucleus (2) is cut tangentially in the wall of the inferior horn of the lateral ventricle (3) . Across the ventricle, the hippocampus (4) makes its appearance. Shown enlarged in Fig. 7.4 .

(D) The putamen (1) continues to increase in size, still partially surrounded by the claustrum (9) . The tail of the caudate nucleus (2, 5) is now cut in two places as it curves into the temporal lobe with the inferior horn of the lateral ventricle (6) . The posterior horn of the lateral ventricle (3) extends back toward the occipital lobe. The hippocampus (4) increases in size, and the amygdala (7) appears at its anterior end. A downward extension (8) of the putamen merges with the amygdala, much as the tail of the caudate nucleus merges with both in a nearby plane (see Fig. 7.3E ). Fibers that have collected from the temporal lobe and will cross in the anterior commissure (10) mass underneath the putamen.

Sagittal sections. (E) The globus pallidus ( 1 , part of its external segment) appears adjacent to the putamen (2) , with fibers of the anterior commissure (3) traveling beneath them. The caudate nucleus is again cut twice, once (11) as it curves around from the body to the inferior horn of the lateral ventricle and a second time (4) as it merges with the amygdala (5) . Fibers of the fimbria (7) are cut tangentially as they emerge from the hippocampus (6) . An enlarged mass of choroid plexus ( 9 , the glomus) protrudes into the atrium of the lateral ventricle (10) , and the posterior horn of the ventricle (8) extends back into the occipital lobe. Shown enlarged in Fig. 7.5 .

(F) Now both the internal (3) and external (2) segments of the globus pallidus can be seen adjacent to the putamen (1) . The plane of section has reached the thalamus; the pulvinar (10) appears, as well as the lateral geniculate nucleus (6) with the optic tract (4) ending in it. The fimbria, cut tangentially in Fig. 7.3E , is now cut in two places (5, 8) . The posterior horn of the lateral ventricle (7) appears in this plane to be a detached cavity in the occipital lobe but is in fact continuous with the atrium (9) .

(G) The head of the caudate nucleus (2) appears, with fibers of the anterior limb of the internal capsule (1) emerging from the cleft between it and the putamen (3) . Strands of gray matter (6) extend between the caudate nucleus and putamen, emphasizing the common embryological origin and similar pattern of connections of these two parts of the striatum. The most lateral of the deep cerebellar nuclei, the dentate nucleus (4) , can be seen, and the parietooccipital sulcus (5) is now distinct. Shown enlarged in Fig. 7.6 .

Dec 29, 2019 | Posted by in NEUROLOGY | Comments Off on Sagittal Sections
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