Allometric growth rate of the spinal cord in relation to the vertebral column during prenatal life in male and female goats (Capra hircus)

Total and regional allometric growth rates and termination sites of the spinal cord related to the respective vertebra were studied in 36 goat fetuses, from the Ahvaz slaughterhouse. These specimens were assigned to 3 groups, group 1 (CRL 10-20 cm), group 2 (CRL 21-30 cm), and group 3 (CRL 31-40 cm), each consisting of 6 male and 6 female fetuses. Observations in all 3 groups revealed that although the growth of the vertebral column was greater than that of the spinal cord, the difference in growth was not constant throughout the spine. While in cervical and thoracic regions the growth rate of the spinal cord in relation to the vertebral column was almost isometric, in the caudal part of the spine there was marked decline in growth of the spinal cord compared to the respective regions of the vertebral column. Craniocaudally, the allometric growth rate became drastically negative. There was no significant difference (P>0.05) between males and females. Except in thoracic region, all other regions showed significant differences (P<0.01) between similar regions in all 3 groups. In the lumbar region of group 2 no significant difference was found (P>0.05). As a consequence of the negative allometric growth of the spinal cord in relation to the vertebral column in the caudal part of the spine, the conus medullaris was displaced from S4-S5 in group 1 to S2 in group 3. No significant difference (P>0.05) between male and female fetuses concerning the termination of the spinal cord was found.