ABSTRACT
The oral cavity forms the first part of the alimentary system, with the lips forming its entrance. The oral cavity is lined by stratified squamous epithelium, and numerous salivary glands open onto the mucosal surface. The oral cavity is functionally responsible for mastication, which is the initial phase of digestion. Food is broken into smaller particles and mixed with saliva so as to soften and form a bolus for swallowing. Saliva is important in lubricating food to enable swallowing and also moistens the mouth to aid speech. It is important in dissolving food to stimulate taste, and it contains bactericidal substances, for example, thiocyanate and lysozyme, which maintain oral hygiene. The pharynx is an incomplete tube enclosed by three constrictor muscles. The cricopharyngeus muscle is an important component of the inferior constrictor and acts as an upper oesophageal sphincter that keeps the oesophageal inlet closed, except during swallowing.
