Functional integration of the bony orbits and piriform aperture during facial growth in humans

This study tested two hypotheses related to facial ontogeny within humans: 1) the orbits reach adult size early in development; 2) the dimensions of the piriform aperture will change over development, growing taller and narrower in response to the functional demands of respiration (i.e., maximizing surface area for mucosa). Three‐dimensional landmark coordinate data were collected on a growth series of dry human crania (n=260). Ages were assigned based on patterns of dental eruption and divided into Stage 1 (newborns), Stage 2 (eruption of deciduous dentition), Stage 3 (eruption of M 1 ), Stage 4 (eruption of M 2 ), and Stage 5 (eruption of M 3 ). Coordinate data underwent Procrustes correction, which optimally scales and superimposes all individuals, allowing for direct comparison of their dimensions. Each growth stage was compared via pairwise T‐tests (Bonferroni‐adjusted). Results show that nasal width increased only between stages 1–2 but that nasal height continued growing until Stage 3. The width and area of the orbital rim also exclusively increased between Stages 1–2. Orbital depth, however, increased between Stages 1–2 and decreased after Stage 3. Thus the eyes are more deeply retracted under the forebrain between Stages 2–3 as adult size is achieved earlier by the brain than the face. The results suggest that facial growth is related to the functional stresses of respiration and encephalization. Grant Funding Source : Center for Anatomy and Functional Morphology