SLIDES 60 - PERIPHERAL NERVE

Slide 60 - has both a cross-section and a long section of a nerve, such as you might dissect in gross anatomy.  The Masson stain shows the connective tissue sheaths clearly in blue.

Look first at the cross-section.  Note definite, round bundles of nerve processes.  Identify epineurium, perineurium and endoneurium in blue.  Where can you see nuclei of Schwann cells? fibroblasts? Individual axons may appear as dots in otherwise empty circles where myelin has been largely dissolved. (Figure 7-15a Wheater)

In long sections, again identify the C.T. coats in blue.  Notice also the waviness of the nerve processes; this is very typical of peripheral nerve as a tissue.  The paleness or foamyappearance of the myelin sheath is also characteristic.  Look for nodes of Ranvier.  Axons proper are thin, dark lines and continue straight through the nodes.  Where are Schwann cells? Endoneurial C.T. Cells? Some of the nerve processes are functionally dendrites; where do their cell bodies lie?  Some of the processes are functionally axons; where do their cell bodies lie?  These particular dendrites and axons are all heavily myelinated and look morphologically identical.  At the E M Level, concentric and alternating heavy and light lines can be observed.  What is the light line called?  What is the heavy line called?  What is the cellular origin of each line?