HISTOLOGY OF THE
SPINAL CORD
DR SAM CHIME
SPINAL CORD
FUNCTIONS
Pathway between the body and the brain
Contains ascending and descending nerve tracts of CNS
Initiates basic reflexes independent of the brain
SPINAL CORD
• The spinal cord is a bundle of nerve fibers that extend from the brain
stem down the spinal column to the lower back. A component of the
central nervous system, it sends and receives information between
the brain and the rest of the body.
• The spinal cord is composed of neurons that send and receive signals
along tracts towards and away from the brain.
SPINAL CORD SEGMENTS
• The spinal cord is also organized into segments and named and numbered from top to
bottom. Each segment marks where spinal nerves emerge from the cord to connect to
specific regions of the body. Locations of spinal cord segments do not correspond exactly to
vertebral locations, but they are roughly equivalent.
• Cervical spinal nerves (C1 to C8) control signals to the back of the head, the neck and
shoulders, the arms and hands, and the diaphragm.
• Thoracic spinal nerves (T1 to T12) control signals to the chest muscles, some muscles of the
back, and parts of the abdomen.
• Lumbar spinal nerves (L1 to L5) control signals to the lower parts of the abdomen and the
back, the buttocks, some parts of the external genital organs, and parts of the leg.
• Sacral spinal nerves (S1 to S5) control signals to the thighs and lower parts of the legs, the
feet, most of the external genital organs, and the area around the anus.
• The single coccygeal nerve carries sensory information from the skin of the lower back.
• The spinal cord is composed of two discrete parts; the white matter,
which is the outer part of the cord and the grey matter, which is the
inner portion of the cord. The white matter is given this name due to
its appearance in unfixed histological specimens in which the white
nature of the tissue is caused by the myelination of ascending and
descending nerve fibres. The grey matter is also named after its
unfixed histological appearance and contains the cell bodies of
neurons as well as nerve fibres.
• Within the spinal cord the grey matter forms an H-shape where the
ventral horns of the H are broader than the dorsal horns.
• The grey matter shape has also been likened to that of a butterfly.
• The grey matter also has a histologically visible central canal running
through it.
• The ventral horns of the grey matter contain the cell bodies of motor
neurones whilst the dorsal horns contain sensory neurons where the
cell bodies are found in the dorsal root ganglia.
• The relative size of the grey matter is dependent on the number of
motor cells related to controlling limbs and therefore the size varies
along the length of the spine.
• Around the areas of the fore and hind limbs, the grey matter is
considerably larger.
• The above image shows a higher magnification view of the grey
matter of the spinal cord which is clearly surrounded by white matter.
• The ventral horn has a number of processes which extend into the
white mater.
• The image displays a number of multipolar cells that are relatively
large likely that they are cell bodies of neurons.
• The surrounding nerve fibers are neuroglia cells, although the
cytoplasm of these cells is not visible.
• The seemingly poor organization of the tissues surrounding these
neurons is often referred to as neuropil.
• The image above shows a further magnified view which displays the
central canal and ependymal cell layers.
• The surrounding tissue is similar to that of the grey matter neuropil
seen in the previous image above.
• Within the central canal vessel some remnants of CSF can be seen.
• Within the neuropil tissues, some cell bodies can be seen.
SPINAL CORD INJURY
• The consequences of a spinal cord injury vary depending on the size
and severity of the injury. A spinal cord injury may cut off normal
communication with the brain that can result in a complete or
incomplete injury. A complete injury results in a total lack of sensory
and motor function below the level of injury. In the case of an
incomplete injury, the ability of the spinal cord to convey messages to
or from the brain is not completely lost. This type of injury enables a
person to maintain some motor or sensory function below the injury.
