Masticatory Loading, Function, and Plasticity: A Microanatomical Analysis of Mammalian Circumorbital Soft-Tissue Structures

摘要: In contrast to experimental evidence regarding the postorbital bar, septum, and browridge, there is exceedingly little load-bearing nature of soft-tissue structures mammalian circumorbital region. This hinders our understanding pronounced transformations during primate origins, in which euprimates evolved a bar from an ancestor with primitive condition where only soft tissues spanned lateral orbital margin between frontal bone zygomatic arch. To address this significant gap, we investigated microanatomy rabbits subjected long-term variation diet-induced masticatory stresses. Rabbits exhibit complex feeding behaviors similar primates, yet retain more Three cohorts were obtained as weanlings raised on different diets until adult. Following euthanasia, dissected away, fixed, decalcified. These divided into inferior, intermediate, superior units then dehydrated, embedded, sectioned. H&E staining was used characterize overall architecture. Collagen orientation complexity evaluated via picrosirius-red staining. Safranin-O identified proteoglycan content additional immunostaining performed assess Type-II collagen expression. Surprisingly, ligament along wall composed elastic fibrocartilage. A degraded organization fibers fibrocartilage correlated increased forces due fracture-resistant diet. Furthermore, lack marked changes extracellular composition related tissue viscoelasticity suggests it unlikely that exposure elevated stresses underlies development bony bar.