Histology Photomicrographs

Human Anatomy and Physiology (BIOL& 241L-242L)
Karen Hart, Peninsula College

Nervous system: Nerve cross section

Slide: Nerve c.s. H 1580

Microscope at 40X

In the peripheral nervous system axons are bundled together in structures called nerves. The 40X image shows a cross section through four fascicles f that are part of a nerve. A layer of connective tissue called the perineurium pn surrounds each fascicle. A whole nerve is surrounded by connective tissue called the epineurium (not shown by this slide.)

Axons in a nerve are surrounded by Schwann cells. It takes many Schwann cells to enclose an axon along its whole length.

For some axons the Schwann cell plasma membrane wraps tightly around and around the axon forming a many-layered structure called a myelin sheath. The solvents used in typical slide preparation dissolve myelin leaving a white space where the myelin was.

ma = myelinated axon

m = space where myelin sheath was

Nonmyelinated axons are enclosed by Schwann cells but the Schwann cells do not form a myelin sheath. The nonmyelinated axons stain lavender on this slide.

nma = nonmyelinated axon

Most of the dark purple nuclei visible in the 400X image are Schwann cell nuclei.

Scn = Schwann cell nucleus

Some of the dark purple nuclei are those of fibroblasts that form the connective tissue (called endoneurium) between the Schwann cell-enclosed axons. Endoneurium and Schwann cell cytoplasm stain red on this slide.

Two small blood vessels bv are visible in the connective tissue between fascicles.

Slide: Nerve c.s. H 1580

Microscope at 400X

Slide: Nerve c.s. H 1580

Microscope at 400X

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Peninsula College