Spinal cord, dog (LM, Low)

Structure List Dorsal white columns Lateral white columns Ventral white columns Dorsal roots Ventral roots Dorsal horn Ventral horn Intermediate horn

Spinal cord of both birds and mammals is divided into regions depending upon which portion of the body is served by the spinal nerve attached to it. The neuron cell bodies for interneurons receiving sensory information from the dorsal roots and motor neurons which project through the ventral roots are found in the H-shaped gray matter of the spinal cord. The gray matter of the spinal cord consists of three major zones or "horns" The white matter contains the myelinated axons which project to and from the various parts of the brain. The axons from neurons in the dorsal (or posterior) horns which carry information regarding touch, pressure and body sense are carried in the dorsal white columns which are located between the two dorsal horns. The axons from dorsal horn interneurons, which carry information regarding pressure and temperature, are carried in the lateral and ventral portions of the white columns outside the H-shaped gray matter. Axons from various portions of the brain which carry information to stimulate motor neurons in the ventral (or anterior) horn are carried in the white columns immediately next to the gray matter on the lateral and ventral sides. On these slides, compare the size of the various parts of the gray and white matter in the three general regions: cervical, thoracic, lumbar and sacral regions. Compare the gray and white matter sizes in the same region for birds and mammals. Why is the ventral horn larger in the distal cervical and lumbar and sacral regions than it is in the thoracic region? Why are the dorsal white columns larger in the cervical and thoracic regions than they are in the lumbar and sacral regions? Why are the lateral white columns largest in the sacral regions? Are the gray and white matter sizes the same in the cervical, thoracic, lumbar and sacral regions for both the dog and the bird?