histology: nerves
DESCRIPTION
A PowerPoint review of photomicrographs depicting the various histological features of nervous tissue. By Timothy Ballard, UNC Wilmington. Licensed under a Creative Commons License: Attribution Non-Commercial-NoDerivs. From http://www.lifescitrc.org/resource.cfm?submissionID=8993.TRANSCRIPT
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