Heartbeat, digestion, respiration, and elimination of wastes are carried out by organ systems close to the central axis. These functions, close to the center of the body, operate or are ready to operate when the child is born. What principle of development does this represent?

This is the principle of proximodistal development that additionally depicts the bearing of advancement. This implies that the spinal string creates before external parts of the body.
The child arms create before the hands also, the hands and feet create before the fingers and toes. Finger and toe muscles (utilized in fine engine ability) are the last to create in physical development.
Proximodistal development is the changes of growth in child to operate the body when the child ready to operate after birth.
Hence, the proximodistal development represent the changes in these functions.

​Heartbeat, digestion, respiration, and elimination of wastes are carried out by organ systems close to the central axis. These functions, close to the center of the body, operate or are ready to operate when the child is born. What principle of development does this represent?