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Oral Cavity

Oral cavity

The oral cavity or mouth is part of the oral region. It lies inferior to the nasal cavities, and has a roof, floor, and lateral walls. It opens onto the face through the oral fissure and is continuous posteriorly with the cavity of the pharynx at the oropharyngeal isthmus. The oral cavity is an inlet for the digestive system. It is involved in food processing, which is aided by saliva secretions from the salivary glands. It contributes in articulation, where it manipulates the sounds produced by the larynx. The oral cavity also has a respiratory function, where it can be used for ventilation due to it opening into the pharynx, which is a common pathway for food and air.

Structure

The roof of the oral cavity includes both the hard and soft palates. The palates separate it from the nasal cavities. The floor is composed of the mylohyoid muscles and is mainly occupied by the tongue. The lateral walls of the oral cavity include the cheeks as well as the retromolar regions. The cheeks are formed of muscles that merge anteriorly with the lips surrounding the oral fissure. The oral cavity also contains three pairs of major salivary glands: the parotid, submandibular, and sublingual gland. As well as additional pairs of minor salivary glands: the labial, buccal, palatal and lingual glands. All of those glands open into the mouth and aid in mastication (chewing).

The oral cavity is divided into two parts: by the upper and lower dental arches. These arches consist of teeth and the alveolar bones that support them. The two parts are the oral vestibule and the oral cavity proper. The outer oral vestibule is a horse-shaped, slit-like space located between the dental arches and the deep surfaces of the lips, and cheeks. The oral fissure opens into it and it can be maneuvered by the muscles of facial expression and lower jaw movements. The inner oral cavity proper is the space enclosed by the upper and lower maxillary and mandibular dental alveolar arches. The level of separation between those two arches is established by the elevation or depression of the lower mandible at the temporomandibular joint.

Bones

The skeletal framework of the oral cavity consists of the paired maxillae, palatine and temporal bones; and the unpaired mandible, sphenoid, and hyoid bones. 

Muscles

The muscles of the oral cavity include that of the lips, cheeks, floor of the mouth and tongue. The tongue is a mobile structure formed by both extrinsic and intrinsic muscles. It is part of the floor of the oral cavity, and is involved in taste, mastication and oral cleansing.

Neurovasculature

The organs and structures within the oral cavity are supplied by numerous vessels originating from the external carotid artery to allow for adequate blood flow. The veins follow their associated arteries and bare their names. They drain into the pterygoid plexus and the internal jugular veins. The innervation of the oral cavity is complex and involves several nerves (sensory and motor), all of which originate directly or indirectly from the cranial nerves.

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