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Appendix:
Normal Microscopic Anatomy/Histology

Sections are stained with Luxol fast blue, cresyl violet and eosin (Luxol or LFB stain). 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. All except one of the sections are from a 70-year-old man with minimal cerebral arteriosclerosis who died of lung cancer. Remember, some abnormalities will nearly always present in sections derived from autopsy brains, particularly from elderly individuals.

NP001N. CEREBRAL CORTEX, BASAL FRONTAL REGION (Luxol) [WebScope] [ImageScope]:

Cortical gray matter, where nerve cell bodies are concentrated, forms an eighth-inch-thick pink layer on the surface; white matter is blue. White matter is composed of axons from many of these cell bodies as well as axons coming into this cortex from elsewhere. The olfactory bulb stalk, on the orbital surface of the brain, is at the right margin of the section. Higher power magnification shows that nerve cell (neuron) bodies tend to be aligned at right angles to the tangent of the cortical surface. Myelinated fibers (axons) tend to parallel this vertical orientation in the cortex. Neurons have a vesicular nucleus with a prominent nucleolus and a variable rim of cytoplasm with Nissl substance. Oligodendroglia that make and maintain myelin are represented by round “ink dot” nuclei along the myelinated fibers. They are also in the cortex gray matter as satellite cells around the neurons. Astrocyte nuclei are usually larger. 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. A useful term for this matrix is neuropil (neuro + pil = hair, felt). Corpora amylacea, round basophilic bodies ~10 to 20 microns in diameter, accumulate as the years go by especially after the middle decades. This brain has them in subpial and subependymal regions, and in the olfactory bulb stalk.

 

NP002N. BASAL GANGLIA (Luxol)[WebScope] [ImageScope]:

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.

 

NP003N. STRIATUM (Luxol) [WebScope] [ImageScope]:

Striatum and adjoining insular cortex, internal capsule, anterior commissure, and anterior thalamus. The fornix is most medial in the section. Also note the optic chiasm, the external and extreme capsules, and the claustrum. 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. 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. There are also calcific “beads” in the adventitia of some small vessels.

 

NP004N. HIPPOCAMPAL REGION (Luxol) [WebScope] [ImageScope]:

This coronal section includes the hippocampus (hippocampus = sea horse) and adjacent temporal lobe gyrus (entorhinal cortex). Above the temporal (ventral or inferior) horn of the lateral ventricle the lateral geniculate nucleus is present. Lateral to this structure is the tail of the caudate. The medial surface of the section is the posterior portion of the thalamus and a small portion of the cerebral peduncle. Within the ventricle is the choroid plexus. 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. In the dentate gyrus portion of the hippocampus, granule cells (densely packed) are the characteristic neuron type. There are small beady calcific bodies in part of the hippocampus. Calcific bodies are present in the choroid plexus, another common site of accumulation as the years pass. In earlier years some degree of calcification in the choroid plexus may be classified as disease, but the beads (and calcification mentioned in the globus pallidus – NP003N) are usually regarded as “disease” because it is assumed that impaired blood supply is an accompaniment.

 

NP005N. MIDBRAIN (Luxol) [WebScope] [ImageScope]:


This coronal section is at the level of the exiting third nerve. Cerebral peduncle (basis pedunculus), substantia nigra, superior colliculus, medial lemniscus, aqueduct, and medial geniculate are landmarks telling you that you are in the midbrain. Large, somewhat round neurons in the ventral lateral margin of the central gray are from the mesencephalic nucleus of the trigeminal nerve. The big central zone of myelinated fibers is the superior cerebellar peduncles about to decussate caudal to the red nucleus. The broad ventral part is the basis pedunculus. The substantia nigra, just above it, is partly made up of pigmented (melanin) neurons in adults. The medial longitudinal fasciculus runs in the center of the tegmentum close to nuclei that run the eye muscles.

NP006N. PONS (Luxol) [WebScope] [ImageScope]:

From a 37-year-old man with chronic rheumatic heart disease and a fatal thrombotic embolus to his femoral artery. The corticospinal (pyramidal) tract is present here as a concentration of large longitudinal fiber bundles in the center of the base of the pons on each side. What effect would an extensive infarct involving the motor-sensory cortex or middle of the internal capsule, have on this tract? Identify the pontine nuclei and the crossing or transverse pontine fibers. Can you identify the locus coeruleus? It should be easy. Why?

 

NP007N. MEDULLA, CEREBELLUM (Luxol)[WebScope] [ImageScope]:

In this coronal section can you identify corticospinal (pyramidal) tracts (pyramids), medial lemniscus, 12th nerve nucleus and the inferior olivary nuclei? Purkinje cells in the cerebellum are actually flat cells, their dendrites extended in sagittal plane. Identify the three layers of the cerebellum, molecular, Purkinje cell, and granule cell.

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Questions or comments? Dr. Killen: pkillen@umich.edu

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