ORAL CAVITY (MOUTH)

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ORAL CAVITY (MOUTH)
Is the first part of the digestive tract and only part involved in ingestion of food. It is bounded by:
Anteriorly – by the lips
Posteriorly - it is continuous with the oropharynx
Laterally – by the muscles of the cheeks
Superiorly – by the bony hard palate and muscular soft palate
Inferiorly – by the muscular tongue and the soft tissue of the floor of the mouth.
The walls of the mouth are lined with thick stratified squamous epithelium which can withstand considerable friction. The epithelium on the gum, hard palate, and dorsum of the tongue is slightly keratinized for extra protection against abrasion during eating.

The part of the mouth between the gums and cheeks is the vestibule and the remainder of the cavity is the oral cavity (area between the gums and the teeth.
 

LIPS (LABIA)
Lips are mobile, muscular folds surrounding the mouth. They are covered externally by skin and internally by mucous membrane. It extends from the inferior margin of the nose to the superior boundary of chin. It contains the orbicularis oris and superior and inferior labial muscles, vessels, and nerves. The reddened area where a person applies lip stick or land a kiss is called the red margin. This transitional zone, where keratinized skin meets the oral mucosa is poorly keratinized and translucent, allowing red color of blood in the underlying capillaries to show through. Because the red margin lacks sweat or sebaceous glands, it must be moistened with saliva periodically to prevent it from becoming dry and cracked. The labia frenulum is a median fold that joins the internal aspect of each lip to the gum. Lip is important for sucking liquids, manipulating and keeping food between the upper and lower teeth, forming speech, and osculation (kissing). 

CHEEKS
The cheeks form the lateral movable walls of the oral cavity. They are composed of outer layer of skin, subcutaneous fat, facial muscles (buccinators) and inner lining of sratified squamous epithelium.


GINGIVAE (GUM)
The gingivae are composed of fibrous tissue covered with mucous membrane.  They enveloped the alveolar processes of the jaw and the neck of the teeth and is continuous with the periosteal layer of the alveolar arch. The gingiva proper (“attached gingiva”) is firmly attached to the alveolar processes of the jaws and the necks of the teeth; it is normally pink and keratinizing. The alveolar mucosa (“loose gingiva”) is normally shiny red and nonkeratinizing.

THE PALATE
The palate forms the arched roof of the mouth and floor of the nasal cavities. It separates the oral cavity from the nasal cavities and it can be divided into anterior hard palate and posterior soft palate.

Hard palate
The hard palate is formed by the maxilla anteriorly and the palatine bones posteriorly. The anterolateral margins are continuous into the alveolar arches and gum while the posterior margins gives attachment to the soft palate.

Blood supply
Arteries – by greater palatine arteries
Veins – pterygoid plexus of veins
Nerve supply – maxillary nerve

Soft palate
Is the movable posterior 1/3 of the palate. It is muscular, so it has no bony skeleton and separates the nasopharynx from the oropharynx. The middle conical projection that hangs down the soft palate is called the uvula.

Laterally, the soft palate is anchored to the tongue by the palatoglossal arches and to the wall of the oropharynx by the more posterior palatopharyngeal arches. On each side, between the arches, is a collection of lymphoid tissue called the palatine tonsil. The muscle of the soft palate rises reflexively to close off the nasopharynx during swallowing.

Blood supply
• Lesser palatine arteries
• Ascending palatine arteries 
Veins – are tributaries of the pterygoid plexus

Nerve supply
• Greater palatine nerve
• Nasopalatine nerve
• Lesser palatine nerve.

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