At the Cavanilles Institute of Biodiversity and Evolutionary Biology of the University of Valencia, researchers have been studying the anatomy of the human head in a unique way, revealing the modularity of the musculoskeletal system and its evolutionary origins. The quantitative technique is called anatomical network analysis (AnNA) and using a computer it maps all sorts of meeting points and interactions between different anatomical components of the head.
The team discovered that the head is broken down into ten different modules, each of which seems to have evolved mostly independently of the other ones.
As [lead researcher Diego Rasskin Gutman] explains, each skull “generated a network model in which each bone was represented as the network node and each physical articulation (contact), as a connection. Thus, each skull was modelled as a 0-1 matrix with each connection being a 1. This matrix served to analyse the network attributes, which could in turn be compared to other generic network properties”.
By using AnNa, which enables the analysis of bones and muscles at the same time, new cranial functional dependences have been uncovered, because muscles —associated to movements— link separate bones. For example, as the researcher points out, the lower jaw / inner ear module shows dependences between bones associated with masticatory muscles and which would not associate otherwise (jaw to parietal, temporal and occipital) as well as inner ear bones.
Moreover, muscle modules “show left/right independence of orofacial muscles (mouth and face) from the upper face muscles. This allows greater flexibility in facial expression for we are able to move facial muscles on either side separately”, he explains.
Study in Scientific Reports: Anatomical networks reveal the musculoskeletal modularity of the human head