1. Structure of a peripheral nerve Myelinated axons (diam. 1-15 um)are wrapped in a myelin sheath; nonmyelinated axons also exist. They are the elementary units for conduction of electric signals in the body. Myelin formed by wrapping a Schwann cell membrane many times around axon perimeter. No ECM inside nerve fibers Myelin sheath is a wrapping of Schwann cell membranes around certain axons
1. Structure of a peripheral nerve. II Myelinated axons (diam. 1-15 µm) are wrapped in a myelin sheath; nonmyelinated axons also exist. They are the elementary units for conduction of electric signals in the body. Myelin formed by wrapping a Schwann cell membrane many times around axon perimeter. No ECM inside nerve fibers. Myelin sheath is a wrapping of Schwann cell membranes around certain axons
1. Structure of a peripheral nerve Nonmyelinated axons(diam. <1 um) function in small pain nerves. Although surrounded by Schwann cells, they lack myelin sheath: Schwann cells are around them but have retained their cytoplasm Basement membrane(tubular) encases the myelin sheath Structure similar to that of skin bM
1. Structure of a peripheral nerve. III Nonmyelinated axons (diam. <1 µm) function in small pain nerves. Although surrounded by Schwann cells, they lack myelin sheath; Schwann cells are around them but have retained their cytoplasm. Basement membrane (tubular) encases the myelin sheath. Structure similar to that of skin BM
1. Structure of a peripheral nerve Nerve fibers are embedded in endoneurium a delicate packing of loose vascular supporting tissue that is rich in collagen fibers. Definitely ECM! Many nerve fibers with their associated endoneurium are packed in a collagenous layer, the perineurium, This forms a fascicle Multifascicular nerves encased in a collagenous layer, the epineurium
1. Structure of a peripheral nerve. IV Nerve fibers are embedded in endoneurium: a delicate packing of loose vascular supporting tissue that is rich in collagen fibers. Definitely ECM! Many nerve fibers with their associated endoneurium are packed in a collagenous layer, the perineurium. This forms a fascicle. Multifascicular nerves encased in a collagenous layer, the epineurium
Cylindrical symmetry of peripheral nerve structure Summary of nerve trunk structure proceeding radially from the center out axon-myelin sheath-BM] endoneurium- perineurium epineurium. [….]=“ nerve fiber
Cylindrical symmetry of peripheral nerve structure Summary of nerve trunk structure proceeding radially from the center out: [axon ⎯ myelin sheath ⎯ BM ] ⎯ endoneurium ⎯ perineurium ⎯ epineurium. [ …. ] = “nerve fiber
Rat sciatic nerve nerve trunk One fascicle Several thousand Image removed due to copyright considerations axons See Figure 10.7(upper left) in Yannas, I. V. Tissue and Organ Regeneration in Adults. New York: Springer-Verlag, 2001
Rat sciatic nerve (nerve trunk). One fascicle. Several thousand axons. Image removed due to copyright considerations. See Figure 10.7 (upper left) in Yannas, I. V. Tissue and Organ Regeneration in Adults. New York: Springer-Verlag, 2001. Image removed due to copyright considerations. See Figure 10.7 (upper left) in Yannas, I. V. Tissue and Organ Regeneration in Adults. New York: Springer-Verlag, 2001