The pyramidal cell layer (large cells) in the hippocampus is most vulnerable to damage in severe circulatory failure and by anoxia of persistent severe seizures, especially CA1. Within the ventricle is the choroid plexus. The medial surface of the section is the posterior portion of the thalamus and a small portion of the cerebral peduncle. Lateral to this structure is the tail of the caudate. Above the temporal (ventral or inferior) horn of the lateral ventricle the lateral geniculate nucleus is present. This coronal section includes the hippocampus (hippocampus = sea horse) and adjacent temporal lobe gyrus (entorhinal cortex). There are also calcific “beads” in the adventitia of some small vessels. The calcification of the walls of arteries in the globus pallidus, while not normal, is often seen independently of atheromatous arteriosclerosis in many older people. Can you identify the putamen and globus pallidus? Notice that most of the neurons in the basal ganglia are smaller than those in the cortex with intermixed larger ones. Also note the optic chiasm, the external and extreme capsules, and the claustrum. The fornix is most medial in the section. Striatum and adjoining insular cortex, internal capsule, anterior commissure, and anterior thalamus. This section includes the corpus callosum, cingulate gyrus, caudate nucleus, putamen, internal capsule, the most anterior portion of the globus pallidus which is abutting on the ventral-lateral portion of the internal capsule, the anterior portion of the lateral ventricle, and the septum pellucidum. This brain has them in subpial and subependymal regions, and in the olfactory bulb stalk. Corpora amylacea, round basophilic bodies ~10 to 20 microns in diameter, accumulate as the years go by especially after the middle decades. A useful term for this matrix is neuropil (neuro + pil = hair, felt). The pink background staining in the gray matter is the fibrillary matrix or feltwork of the cortex which is made up of the myriad of interwoven cytoplasmic processes of the cells of the brain: dendrites of neurons, processes of astrocytes, oligodendroglia, and microglia. They are also in the cortex gray matter as satellite cells around the neurons. Oligodendroglia that make and maintain myelin are represented by round “ink dot” nuclei along the myelinated fibers. Neurons have a vesicular nucleus with a prominent nucleolus and a variable rim of cytoplasm with Nissl substance. Myelinated fibers (axons) tend to parallel this vertical orientation in the cortex. Higher power magnification shows that nerve cell (neuron) bodies tend to be aligned at right angles to the tangent of the cortical surface. The olfactory bulb stalk, on the orbital surface of the brain, is at the right margin of the section. White matter is composed of axons from many of these cell bodies as well as axons coming into this cortex from elsewhere. CEREBRAL CORTEX, BASAL FRONTAL REGION (Luxol) :Ĭortical gray matter, where nerve cell bodies are concentrated, forms an eighth-inch-thick pink layer on the surface white matter is blue.
Remember, some abnormalities will nearly always present in sections derived from autopsy brains, particularly from elderly individuals. All except one of the sections are from a 70-year-old man with minimal cerebral arteriosclerosis who died of lung cancer. Therefore, in these sections, myelin stains blue, Nissl substance and nuclei stain purple, and cytoplasm, glial processes, collagen, and red blood cells stain pink, although RBCs and collagen may unavoidably stain blue. MR imaging of fetuses provides a developmental basis for understanding hippocampal anatomy.Sections are stained with Luxol fast blue, cresyl violet and eosin (Luxol or LFB stain). The CA1-3 fields form an arc and the CA4 field has increased in size within the widened arch of the dentate gyrus. The hippocampus and subiculum approximate each other across a narrow hippocampal sulcus. The dentate gyrus and cornu ammonis have folded into the temporal lobe. By 18 to 20 weeks, the hippocampus begins to resemble the adult hippocampus. The CA1, CA2, and CA3 fields of the cornu ammonis are arranged linearly. The parahippocampal gyrus is larger and more medially positioned. At 15 to 16 weeks, the dentate gyrus and cornu ammonis have started to infold. Dissections and histologic sections of 10 different specimens of similar ages were compared with MR imaging findings.Īt 13 to 14 weeks' gestation, the unfolded hippocampus, on the medial surface of the temporal lobe, surrounds a widely open hippocampal sulcus (hippocampal fissure). Ten human fetal specimens ranging from 13 to 24 weeks' gestational age were examined with MR imaging. To identify changes in the embryology of the hippocampus responsible for its adult anatomy.