# 59 - Spinal cord, human, thoracic, c.s., Luxol Fast Blue B-PAS

# 58 - Spinal cord, silver

Slide 59 is stained with Luxol Fast Blue B-PAS. Fast Blue stains the myelin sheath blue-purplish; it also stains elastic tissue, cartilage and nuclei. This slide visualizes well the "butterfly" of gray matter (this cell-rich gray matter appears pink with this stain).

Slide 58 is a silver preparation useful in showing the fibroarchitecture of the spinal cord. It stains the cell bodies of neurons darkand shows the neuropil (nerve processes) better than H&E. Silver staining, however, is not useful for showing intracellular details.

The spinal cord is enclosed in the connective tissue of the meninges. The innermost layer of the meninges, the pia, extends in at the dorsal septum and the ventral fissure. In these cross sections through the cervical or thoracic spinal cord, find the central canal. The central canal is lined with ependymal cells. Surrounding this central canal is the butterfly-shaped gray matter [formed by two dorsal (posterior) horns and two ventral (anterior) horns].

The large multipolar nerve cell bodies are grouped together in nuclei (nucleus = a cluster of nerve cell bodies in the CNS) with their fiber processes entering and leaving the gray matter. The largest neurons in the cord, motor neurons, are in the ventral (anterior) horn. The outer white matter of the cord is composed of nerve fibers, many thickly myelinated, as well as glial cells. The myelinated axons of the CNS are covered with the processes of oligodendrocytes (but in the PNS, Schwann cells provide the myelin for axons).

Those nerve fibers which ascend and descend the cord will be seen in cross section. With silver staining, axons appear as black dots in the center of circular clear zones . These clear zones show where myelin has been extracted during fixation and the perimeter of these zones is outlined with the pink-staining remnants . Generally fibers to and from a particular brain region run together in a tract. You will see such a tract (called a commissure in this case) crossing from one side of the cord to the other just beneath the central canal. Identify the ependymal cells lining the central canal. They are cuboidal or low columnar and may be ciliated.

Identify the roots of fibers entering the cord on the dorsal (posterior) side and other fibers which leave on the ventral (anterior) side. Which of these fibers are motor and which are sensory? In # 58, identify the dense black glial cell nuclei and the blood vessels in both the white and gray matter. This silver stain also blackens the blood cells seen within vessels.

The gray matter changes in shape in the thoracic, lumbar and sacral spinal cord. Why are the ventral horns of the lumbar section so much greater in size than those in the thoracic area? Find the central canal. What type of cell lines this structure?

Identify the gray matter and the white matter. The white matter has a vacuolated appearance. Can you explain this observation? Identify longitudinal and cross sections of nerve fibers outside the cord near its dorsal surface. Compare this slide to the previous one. Why is the shape of the ventral horns in the cervical spinal cord so different in # 57 in comparison to the previous slide (thoracic cord)?

Spinal Cord References: Gartner, p. 134 - 135 Ross, p. 272, Fig. 11.17 (central canal and ependymal cells) p. 300 - 30, fig. 1, 2, 3 Wheater, p. 133, Fig. 7.24 (ependymal cells) p. 367, Fig. 20 (different regions of spinal cord)

Spinal Chord ( Silver Stain & H + E stain)

White dotted line - Dorsal Root / Blue dotted line - Dorsal Horn / Red dotted Line - Ventral Horn / Green Dotted Line - Commisure / Blue arrow - Dorsal Spetum / Red arrow - Ventral Fissure / Black arrow - Central Canal

These are images of both halves of the Spinal Chord. For orientation the top of the picture is the posterior aspect, or dorsal aspect of the spinal chord. All the tissue surrounded by any colored dotted line is what is known as GRAY MATTER, looks like an H or a butterfly. Which consists of all the cell bodies in the spinal chord. All the tissue out side of the dotted lines is what is known as White Matter, which consists of all the tracts, or bundles of axons of the spinal chord. Named "White" because of the Myelin sheath around axons that stains white.

The Blue arrows are pointing to the Ventral Septum, while the Red arrows are pointing to the Dorsal Fissure. The black arrow is pointing to the Central Canal, in which the CSF courses. The Green dotted line is surrounding the portion of the grey matter that crosses the midline known as the Commisure. The blue dotted line is outlining the portion of the grey matter known as the Dorsal Horn. Here is the sensory side of the grey matter where Nerve fibers are coming IN to the spinal chord. The red dotted line is pointing to the portion of the grey matter known as the Ventral Horn, which is the Motor side of the spinal chord where Large Multipolar Motor Neuron that innervated body musculature are located.

This is a High Power shot of the Vetral Horn (blue dotted lines) of the spinal chord. What is showed is the Multipolar Motor Neurons (Red arrows) that are located there. These neurons are very noticable because they are very LARGE and are ONLY FOUND IN THE VENTRAL HORN.

Blue dotted line - Ventral Horn

Red arrow - MultiPolar Motor

This is a high power shot of the Central canal, the lumen of which is shown by the Red arrow. The central canal is where the CSF is flowing. It is also lined by cuboidal cells called Ependymal Cells, (Blue arrow).

Blue arrow - Ependymal Cells

Red arrow - Central Canal Lumen

Ventral Horn (spinal chord)

Central Canal