1School of Physical Therapy, Slippery Rock University, 2Division of Anatomy, The Ohio State University, 3Department of Biology, Slippery Rock University, 4Department of Public Health and Social Work, Slippery Rock University, 5Department of Anatomy and Neurobiology, NEOMED, 6University of Florida, University of Florida, 7Department of Anthropology, Pennsylvania State University
April 18, 2020 , Platinum Ballroom
Five synchondroses have been described in the midline of the mammalian basicranium. They exist at interfaces between basicranial bones (spheno-occipital, intrasphenoidal, and spheno-ethmoidal) and between basicranial bones and the unossified septal cartilage (prespheno-septal, and ethmo-septal). Midline synchondroses have been implicated as having a potential role in the angularity observed in the adult primate bascranium. However, few studies have examined them histologically. Using histological and immunohistochemical methods, we studied these basicranial joints in serial sagittal sections of newborn heads from ten genera of primates (seven anthropoids, three strepsirrhines). Each synchondrosis was examined for characteristics of active growth plates, including the zones of chondrocyte proliferation and hypertrophy, as well as corresponding changes in matrix characteristic (i.e., density and organization of type II collagen). Results reveal three synchondroses (spheno-occipital, intrasphenoidal, and prespheno-septal) possess attributes of active growth centers in all species. One additional synchondrosis (ethmo-septal) was present with growth center characteristics in newborn Papio anubis and Galago moholi, but not in the other species. The sphenoethmoidal synchondrosis (SES) varies at birth. In the catarrhines and Galago, it is a suture-like joint at birth (collagenous tissue between the two bones). But in most species, the jugum sphenoidale is ossified while the ethmoid remains cartilaginous. No species possesses a SES that has the organization of a growth plate. Thus, only four midline synchondroses have the potential to actively affect basicranial angularity and facial orientation during the perinatal timeframe. In contrast, we hypothesize the SES essentially transitions toward a “suture-like” function, permitting passive growth postnatally.
This study was funded by NSF grant numbers BCS-1830894, BCS-1830919 and BCS-0959438