HISTOLOGY REVIEWNervous Tissue

Dr. Tim BallardDepartment of Biology and Marine Biology

Spinal cord – cross section – silver – 4x objective

Silver stains nerve cells and unmyelinated fibers brownish-black. The white matter is lightly stained because there is so much myelin around the fibers.

Orientation to the spinal cordOrientation to the spinal cord

dorsal horns of gray matter

dorsalventral

ventral horns of gray matter

gray commissu

re

central

canal

Spinal cord – cross section – silver – 10x objective

In the ventral horn there are very large motor neurons. The brown fibers you see leaving the ventral horn are axons from these neurons.

Ventral motor neuronsVentral motor neurons

motor neurons

Spinal cord – cross section – silver – 40x objective

Think in three dimensions. Where would the dendritic zone or the axon be related to this two-dimensional section?

Ventral motor neuronsVentral motor neurons

neuronal cell body

neuronal cell body

nucleus with a

nucleolus

dendrites

These much smaller cells are likely to be neuroglial

cells.

Spinal cord – cross section – silver – 40x objective

Look at all of the cross-hatching brown-black fibers between the cell bodies. This is the “neuropil,” all of the axons of the gray matter connecting cells.

Ventral motor neuronsVentral motor neurons

This could be an axon hillock. Compared to the other branches here, this has a larger diameter, so it could be giving rise to an axon.

nucleus with a

nucleolus

Seeing Nissl substance and neurofibrils within cell bodies requires special stains. With careful fine-focusing, you may get a sense of these intracellular materials.

Spinal cord – cross section – Nissl’s stain – 40x objective

Look at the differences in size between neuronal cell bodies and neuroglia.

Ventral motor neuronsVentral motor neurons

neuroglial cells

ventral motor neuron

Cerebellum – section – silver – 4x objective

The Weigert-Weils technique stains nerve cells and unmyelinated fibers brown-ish. White matter is heavily stained due to the presence of myelinated fibers.

Cerebellar cortexCerebellar cortex

white matter

gray matter

Purkinje cell layer

Cerebellum – section – silver – 10x objective

Look at the differences in neuronal sizes between the three layers of neurons shown above.

Cerebellar cortexCerebellar cortex

granular cell layer

molecular cell layer

Purkinje cell layer

Cerebellum – section – silver – 40x objective

Look at the differences in neuronal sizes between the three layers of neurons shown above.

Cerebellar cortexCerebellar cortex

granular cell layer

molecular cell layer

Purkinje cell layer

Spinal ganglion – section – silver – 4x objective

The dorsal root ganglion consists of nothing but the cell bodies of sensory neurons.

Dorsal root ganglionDorsal root ganglion

Spinal ganglion – section – silver – 40x objective

Sensory neurons are pseudounipolar, so it is hard to see dendrites, axons, and central processes.

Dorsal root ganglionDorsal root ganglion

Nerve – longitudinal section – H&E – 4x objective

With the H&E stain, nerve fibers don’t stain, but the Schwann cells do. Nodes of Ranvier and the myelin are much more easily seen with an osmium stain.

Features of nerve fibersFeatures of nerve fibers

The nuclei you find in this section are those of Schwann cells (neurolemmocytes).

Nerve – teased fibers – osmium – 20x objective

Osmium stains the lipid of myelin gray-black. The segments you see are individual pieces of myelin. Between each would reside nodes of Ranvier.

Features of nerve fibersFeatures of nerve fibers

node of Ranvier

Artery, vein, and nerve – cross section – H&E – 4x objective

Oftentimes, an artery, its two companion veins, and a nerve will travel together bundled into a common connective tissue.

Structures of a nerve in cross sectionStructures of a nerve in cross section

nerve

artery

vein

Artery, vein, and nerve – cross section – H&E – 10x objective

This nerve is formed of 4 fascicles (individual bundles of fibers)

Structures of a nerve in cross sectionStructures of a nerve in cross section

fascicles

Artery, vein, and nerve – cross section – H&E – 10x objective

This nerve is formed of 4 fascicles (individual bundles of fibers)

Structures of a nerve in cross sectionStructures of a nerve in cross section

Epineurium – invests all the fascicles, holding them together as a single nerve

Perineurium – invests an individual fascicle, holding the nerve fibers together as a single

fascicle

Endoneurium – extensions of the perineurium that invest each individual nerve fiber within

the fascicle

end