HISTOLOGY REVIEW
Nervous Tissue
Dr. Tim Ballard
Department of Biology and Marine Biology
Orientation to the spinal cord
Spinal cord – cross section – silver – 4x objective
dorsal horns of gray matter
gray
commissure
central
canal
ventral horns of gray matter
Silver stains nerve cells and unmyelinated fibers brownish-black. The white
matter is lightly stained because there is so much myelin around the fibers.
Ventral motor neurons
motor
neurons
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 neurons
Spinal cord – cross section – silver – 40x objective
These much smaller cells are
likely to be neuroglial cells.
neuronal cell body
neuronal cell body
dendrites
nucleus with
a nucleolus
Think in three dimensions. Where would the dendritic zone or the axon be
related to this two-dimensional section?
Ventral motor neurons
Spinal cord – cross section – silver – 40x objective
nucleus with
a nucleolus
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.
Seeing Nissl substance and neurofibrils
within cell bodies requires special stains.
With careful fine-focusing, you may get a
sense of these intracellular materials.
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 neurons
Spinal cord – cross section – Nissl’s stain – 40x objective
ventral motor neuron
neuroglial cells
Look at the differences in size between neuronal cell bodies and neuroglia.
Cerebellar cortex
Cerebellum – section – silver – 4x objective
Purkinje cell layer
gray matter
white matter
The Weigert-Weils technique stains nerve cells and unmyelinated fibers brownish. White matter is heavily stained due to the presence of myelinated fibers.
Cerebellar cortex
Cerebellum – section – silver – 10x objective
molecular cell layer
Purkinje cell layer
granular
cell layer
Look at the differences in neuronal sizes between the three layers of neurons
shown above.
Cerebellar cortex
Cerebellum – section – silver – 40x objective
molecular cell layer
granular cell layer
Purkinje cell layer
Look at the differences in neuronal sizes between the three layers of neurons
shown above.
Dorsal root ganglion
Spinal ganglion – section – silver – 4x objective
The dorsal root ganglion consists of nothing but the cell bodies of sensory
neurons.
Dorsal root ganglion
Spinal ganglion – section – silver – 40x objective
Sensory neurons are pseudounipolar, so it is hard to see dendrites, axons, and
central processes.
Features of nerve fibers
Nerve – longitudinal section – H&E – 4x objective
The nuclei you find in this section are those
of Schwann cells (neurolemmocytes).
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 fibers
Nerve – teased fibers – osmium – 20x objective
node of Ranvier
Osmium stains the lipid of myelin gray-black. The segments you see are
individual pieces of myelin. Between each would reside nodes of Ranvier.
Structures of a nerve in cross section
Artery, vein, and nerve – cross section – H&E – 4x objective
nerve
vein
artery
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 section
Artery, vein, and nerve – cross section – H&E – 10x objective
fascicles
This nerve is formed of 4 fascicles (individual bundles of fibers)
Structures of a nerve in cross section
Perineurium – invests an individual fascicle, holding
the nerve fibers together as a single fascicle
Epineurium – invests all the fascicles, holding them together as a single nerve
Endoneurium – extensions of the perineurium that
invest each individual nerve fiber within the fascicle
Artery, vein, and nerve – cross section – H&E – 10x objective
This nerve is formed of 4 fascicles (individual bundles of fibers)
end