The buccal cavity, otherwise known as the mouth, marks the beginning of the digestive system. Starting at the lips, it consists of the oral cavity, tongue, jaw, and throat. While digestion is its primary function, it also plays an equally important role in communication, through the development of sounds and speech.
The lips, which are made up of upper and lower parts, are soft and fleshy folds of skin lined with mucous membranes, and they shape the opening of the buccal cavity. The skin of the lips is thinner than in other parts of the body and does not contain hair, sweat glands, or sebaceous glands. Lips assist the intake of food as it passes into the mouth. Closed lips provide a relatively tight chamber, keeping food and drink locked firmly inside, preventing spillage or leakage from the mouth. Because they have a large number of nerve endings, the lips are considered a tactile organ, sensitive to touch and temperature.
There are two sections in the oral cavity of the mouth: the vestibule and the buccal cavity proper. Located just outside of the oral cavity, the vestibule is a tiny gap between the teeth and cheeks that receives the secretion of saliva and transfers this to the main cavity. The buccal cavity proper is defined as the main area where digestion begins. This area is surrounded by the upper and lower teeth, roofed by the hard and soft palates, and floored by the tongue, all of which aid in the chewing and eventual swallowing of food and drink.
The tongue, which covers the entire bottom part of the mouth, is one of the sensory organs of the human body. Structured with small pimple-like bumps called taste buds, the tongue is able to distinguish five different flavors: sweet, bitter, salty, sour, and umami. Aside from this, the tongue helps with the chewing and swallowing of food by keeping it moist and manipulating it from one section of the cavity to the other. The tongue also influences the projection of sounds and speech.
The jaw is a part of the buccal cavity that is critical to the chewing of food. Made up of a fixed upper jaw bone — the maxala — and a mobile lower jaw bone — the mandible — the jaw moves back and forth to facilitate the tearing and chewing of food by the teeth. Similar to the tongue, movements of the jaw influence speech and communication of sounds.
The throat is where the first section of the digestive system ends and the second section begins. It is found at the end of the buccal cavity proper and is made up of the pharynx, larynx, trachea, and esophagus. The throat has multiple functions, the first of which is to enable swallowing in order to control the buildup of excess secretions in the mouth such as saliva and mucus. In the digestive system, the throat moves masticated food from the mouth through the esophagus and into the stomach. Its secondary role is carried out by the larynx, which houses the vocal cords crucial for the production of sounds.