| Lab 9 Central Nervous System: 1) Index 2) Introduction 3) Things To Identify 4) Spinal Chord 5)Ventral Horn Motor Neurons 6) Cerebrum 7) Cerebellum 8) Choroid Plexus 9) Practical |
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CEREBRUM
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# 47 - Cerebral cortex, human, h - e # 48 - Cerebral cortex, human, silver # 49 - Cerebral cortex, Golgi silver stain, pyramidal cells # 50 - Cerebral cortex, human fetus, silver (this slide has been discontinued; you may not have it) |
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Slide 47 was cut through a portion of a cerebral cortical gyrus. While there are six horizonal superimposed layers of cells in the cortex, each layer is not strikingly demarcated in your section. However, it should be possible to distinguish a few layers if you begin at the pial surface and work toward the interior of the gyrus. Just below the surface is the relatively cell free molecular layer (also called the plexiform layer) composed mostly of cell processes (neuropil); these unmyelinated fibers stain pink with H&E (eosinophilic). Further down you should begin to see the characteristic cell of the cortex, the pyramidal cell whose upper pointed end continues toward the surface of the brain as an apical dendrite. From the base of this cell emerge a number of short basal dendrites and an axon (generally larger diameter) which extends into the deep part of the cortex. Note the Nissl arrangement, large round nucleus and prominent nucleolus of the pyramidal cells. In this second layer (the outer granular layer) along with small pyramidal cells are stellate cells. The third layer (the pyramidal layer) contains larger pyramidal cells. The fourth layer is called the inner granular layer because of the densely packed stellate cells there. The largest pyramidal cells are found in layer V (the ganglionic layer). The last layer is the multiform layer consisting of many cell types. You do not have to differentiate each of these layers from the next; just be aware of their presence but know the top (molecular layer) as well as what cell types will be found in the layers from two to five. In silver and Golgi stained preparations, one can see the layering of the cell nuclei and the complex interlacing of fine black fibers (neuropil) of the cortex. Focus up and down to appreciate the orientation of cell processes and fiber tracts. Dark colored red blood cells fill the blood vessels running through this tissue. References: Gartner, p. 139, Fig. 1 - 4 Ross, p. 296 - 297 p. 281, Fig. 11.22 (diagram) DiFiore, p. 103, Fig. 7-23 - 7-24 Wheater, p. 372 - 373, Fig. 20.7 |
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Here is a low power slide of the Cerebrum. The White arrow is indicating the a-cellular layer just underneath the surface called the Molecular Layer. The red arrows is indicating where you would find the six levels of the Pyramidal Layer. Can you see the difference in amount of cells present in the pyramidal layer and the molecular layer? The pyramidal layer is full of Pyramidal Cells. The blue arrows are pointing to the innermost covering of the cerebrum called the Pia Matter. Blue arrow - Pia Matter White arrow - Molecular Layer Red arrow - Pyramidal Layer
Here is a closer look at the difference between the Molecular Layer (blue arrow) and the Pyramidal Layer (white arrow). Again notice how the cellular pyramidal layer makes a natural border between the two layers because the nuclei just stop at a certain level. The red arrows are again pointing to the Pia Matter, which will follow any vessels that will enter the cerebrum. Blue arrow - Molecular Layer White arrow - Pyramidal Layer Red arrow - Pia Matter
This is a closer look at the Pyramidal Layer, of the cerebrum. The blue arrow are pointing to the Pyramidal Cells located in the layer. Notice the characteristic shape that look like a pyramid. These are very unique in their shape so if you see cells with this kind of shape, you can safely call them Pyramidal Cells. Blue arrow - Pyramidal Cells
This is a close up of the Pyramidal cells, (white arrow). Observe the characteristic pyramidal shape of them which is very unique. The red arrow is pointing to another characteristic of these cells, which is their Apical Dendrite. They are called this because as you can see in the image, the dendrites extend from the cell body at the apex of the pyramid. Red arrow - Apical Dendrite White arrow - Pyramidal Cells
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Cerebrum
Cerebrum
Pyramidal Layer
Pyramidal Cells |
