Spinal cord, dog (LM, Medium)

Structure List Gray matter Dorsal horn Intermediate horn Ventral horn Motor neurons White matter Motor Neurons

The neurons located in the spinal cord are organized into an H-shaped structure called the gray matter. The gray matter is divided functionally into four zones: the two zones in the dorsal or posterior horn are the location of interneurons which receive sensory input either from the skin, striated muscles or joints (GSA) or from blood vessels and internal organs (GVA). The motor neurons which project to sympathetic ganglia to control the action of blood vessels or internal organs are located in the intermediate or lateral horns. The large motor neurons which control skeletal muscle movement are located in the ventral or anterior horn. Both of these types of motor information (GVE and GSE) are carried in axons which exit the spinal cord in the ventral or anterior root. Dorsal root ganglion cell processes carry the sensory information into the interneurons of the dorsal horn. Note change in the number of neurons that are there depending on the amount of motor control required for each spinal cord segment. Compare the number of neurons found in the ventral horns of gray matter in the cervical, lumbar and sacral portions of the spinal cord.