Histologic examination of a biopsy specimen shows a structure of the oral cavity composed of the bone tissue which is covered by stratified squamous non keratinized epithelium and lamina propria. The specimen has also minor mucous salivary glands.In all parts of the lamina propria the collagenous fibres from thick bundles that bind the mucous to the periosteum.Based on these findings, which of the following is the most likely structure?