Dynamics of spinal cord and vertebral column development during the postnatal ontogenesis of the cat.

Data on the structure and postnatal ontogenesis of the vertebral column and spinal cord are of great importance for neurobiology. The present study is devoted to a morphometric analysis of the spinal cord and vertebral column of the cat during the period from birth to adulthood. A complex pattern of postnatal development of both structures was revealed. It was established that the growth rate of vertebral length depends on the rostrocaudal position of the vertebrae: it is similar in VC3-VT10 and increases in the caudal direction, reaching a maximum in VL5. The growth rate of segment length demonstrates a more complex pattern: it decreases in the rostrocaudal direction (between segments C2-C3 and T2), then increases (up to T13), and decreases again (up to S3). At the same time, the growth rate of segments C7-T2 and L2-L7 is lower, whereas that of segments T4-T13 is higher than the growth rate of the corresponding vertebrae. As a result of this relationship between the growth rates of segment and vertebral lengths, a rostral displacement of the cervical and upper lumbar segments and a caudal displacement of the lower lumbar spinal cord relative to the corresponding vertebrae occurs. The growth rate of the spinal cord gray matter area is inversely proportional to the growth rate of segment length. We suggest that the divergent growth processes observed in different spinal cord segments underlie the postnatal formation of the cervical and lumbar enlargements, which contain the principal neuronal networks controlling body and limb motor functions.