Final answer:
The lamina propria is the tissue that lies between the epithelia and connective tissues in the oral mucosa, providing support and facilitating functions such as protection, absorption, and mucus production.
Step-by-step explanation:
Between the epithelia and connective tissues in the oral mucosa lies the lamina propria. The lamina propria is a layer of connective tissue that provides support to the fragile epithelial layer. An important characteristic of the epithelial membranes, like the mucosa, is their mucus production, which is essential for protecting the interior of the gut by lubricating and facilitating the passage of food. In addition, the mucosa contains a thin smooth muscle layer known as the muscularis mucosae, which is distinct from the muscularis layer, and contributes to the movement and continued support of the mucosal structure.
The epithelial layer, which includes the mucosal epithelium, covers microvilli-enhanced structures known as villi, which are also embedded within the lamina propria. These increase the surface area for absorption substantially. Each villus is equipped with its own capillary and lymphatic networks, important for the transport of nutrients into the bloodstream. This finely structured arrangement serves multiple functions, including protection, absorption, transport, and secretion.