Autoradiographic investigation of calvarial growth in the rat

Abstract

AbstractResults of autoradiographic investigations utilizing tritiated proline reveal an intricate mechanism of rat calvarial growth and reshaping from age two days through 75 days. Generalized intramembranous bone growth dominates the growth process from two through eight days; however, this simple bony enlargement is terminated early. At eight days a differential apposition‐resorption process begins dorsally in the calvarium and progresses rostrally within a ten day period. This process includes differential apposition on the ectocranial and endocranial periosteal surfaces accompanied by a differential apposition‐resorption pattern on the endosteal surfaces. The wave‐like process begins in the occipital bone and progresses ventrally to the frontal bone resulting in a flattening of the bony components. At 35 days bone accretion is again generalized on most calvarial surfacse. However, at 40 days another change in the growth process evolves on the occipital and frontal bones. These bones are now seemingly displaced in a superior direction as bone apposition continues on their superior surfaces, namely, the ectocranial periosteal and endocranial endosteal surfaces and resorption progresses on the two inferior surfaces. The magnitude and duration of the process described in this paper is sufficient to account for calvarial flattening in the absence of bony spatial reorientation due to bending at sutures. The findings described here when compared to proposed in vitro studies can help put the importance of the so‐called “functional matrix” related to bone growth into its proper perspective.