PERIPHERAL NERVOUS SYSTEM
NERVES – 3
The upper image shows a cross-section of a large nerve formed by at least four fascicles, identified as 1 to 4. Next to this nerve is a thin nerve indicated by the arrow. The white, unstained spaces inside the nerve are due to the histological preparation of the tissue.
The epineurium is highlighted in light green when you hover the cursor over or click on the image. Observe that, as it is a large nerve, in addition to covering the nerve externally, the epineurium surrounds its various fascicles.
The perineurium (highlighted in dark green) surrounds each fascicle and, in the case of thin nerves as the one indicated by the arrow, it acts as the nerve’s outer covering. In this case the perineurium consists of a thin, compact layer of flattened cells.
The lower image shows a cross-section of a nerve that is thinner than the one seen above. Observe a thick epineurium and a very well-defined perineurium.
Nerve (cross section). Staining: HE. Small magnification.
Nerve (cross section). Staining: HE. Medium magnification.