In the next few slides we’ll study the organization of peripheral nerves. Examine sections of small autonomic ganglia and small peripheral nerves in loose CT and in this section of the spermatic cord. Identify the nerve fibers, Schwann cells, and surrounding CT layer.

Examine the images below and these two sections of peripheral nerve (sample 1, sample 2). Sample 2 has been prepared with osmium, which stains myelin black. The perineurium, along with the nature of the capillaries in the endoneurium, make up a “blood-nerve barrier” that helps protect the myelin sheaths of peripheral nerves from viral or immunological agents. In these specimens identify:

• Epineurium (Ep)- thick dense irregular CT surrounding several nerves
• Perineurium (P)- CT layer surrounding a group of nerve fibers
• Endoneurium (En)- very thin CT layer surrounding Schwann cells in nerves
• Myelinated fibers
• Non-myelinated fibers

Next are synapses and sensory receptors.