<Li> The bodies of these four vertebrae are small, and broader from side to side than from front to back . <Ul> <Li> The anterior and posterior surfaces are flattened and of equal depth; the former is placed on a lower level than the latter, and its inferior border is prolonged downward, so as to overlap the upper and forepart of the vertebra below . </Li> <Li> The upper surface is concave transversely, and presents a projecting lip on either side . </Li> <Li> The lower surface is concave from front to back, convex from side to side, and presents laterally shallow concavities that receive the corresponding projecting lips of the underlying vertebra . </Li> </Ul> </Li> <Ul> <Li> The anterior and posterior surfaces are flattened and of equal depth; the former is placed on a lower level than the latter, and its inferior border is prolonged downward, so as to overlap the upper and forepart of the vertebra below . </Li> <Li> The upper surface is concave transversely, and presents a projecting lip on either side . </Li> <Li> The lower surface is concave from front to back, convex from side to side, and presents laterally shallow concavities that receive the corresponding projecting lips of the underlying vertebra . </Li> </Ul> <Li> The anterior and posterior surfaces are flattened and of equal depth; the former is placed on a lower level than the latter, and its inferior border is prolonged downward, so as to overlap the upper and forepart of the vertebra below . </Li> <Li> The upper surface is concave transversely, and presents a projecting lip on either side . </Li>

What is the function of the cervical vertebrae