RD 060 Peripheral Nerves

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Peripheral Nerve

Transmission electron micrograph (TEM) of peripheral nerves in the exocrine pancreas.

Unmyelinated Nerve Fibers (,; yellow)
- Contain synaptic vesicles, mitochondria (red), and smooth endoplasmic reticulum (cyan)
- Cytoskeleton - microtubules (dark blue) and neurofilaments
(green) - glial cells that cover axons in peripheral nerves
- Completely (or partially) ensheath multiple unmyelinated axons in cytoplasmic invaginations
- (purple) - covers the outer surface
- inner layer of connective tissue that surrounds nerve fibers
- Collagen Fibrils (light blue) - cross-sections of longitudinal fibers that structurally support the nerve
(tan) - outer layer of connective tissue that surrounds bundles (or fascicles) of nerve fibers
- One or more concentric layers of flattened cells
  - Usually does not continue to single nerve fibers as seen here
- Tight junctions between cells form a diffusion barrier that maintains the environment of ensheathed nerve fibers

Subcellular Structures:

Courtesy of Ronald W. Dudek, Department of Anatomy & Cell Biology, East Carolina University, Greenville, North Carolina

Several other types of cells found in the exocrine pancreas are visible.

Acinar Cells (blue) - exocrine cells that produce digestive enzymes
- Rough Endoplasmic Reticulum (RER; cyan) - large amounts of RER fill the base of acinar cells
Capillary (red) - small blood vessel with a single layer of cells, the endothelium
Lymphocyte (purple) - migrate from blood into connective tissue
- Perform immune surveillance for potential threats, such as pathogens or damaged cells
Parasympathetic Ganglion (grayscale) - the edge of a ganglion cell covered by satellite cells surrounded by some nerve fibers is visible in the lower-left corner