There are many hormonal influences on the digestive process. The stomach, for example, produces gastrin in response to food ingestion. This stimulates hydrochloride acid production in the stomach. Secretin is made by the duodenum, which stimulates bicarbonate production by the pancreas. Other hormones include cholecystokinin and gastric inhibitory peptide. These are hormones released into the bloodstream that all have GI effects.
MOUTH ANATOMY AND PHYSIOLOGY The mouth or oral cavity is the entryway to the digestive system. The lips have skin covering them on the outside (but with a thin layer of keratin) and are red because of their increased vascularity. The inner layer is mucus membrane, like the rest of the mouth. The mouth is surround by the orbicularis muscle. Just inside the mouth is the labial frenulum that attaches the inner surface of the upper and lower lip to the gums. The side of the mouth is the buccal side or the cheek side. The mucous membrane is non-keratinized, stratified squamous epithelium. Figure 99 is the illustration of the mouth anatomy:
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