Mouth Anatomy : The fascinating landscape of the human mouth! It's quite a complex

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Mouth Anatomy 

Author: Apostolos Christopoulos, MD, MSc, FRCSC; Chief Editor: Arlen D Meyers, MD, MBA more...

The fascinating landscape of the human mouth! It's quite a complex and dynamic region, playing crucial roles in everything from tasting our favorite foods to forming the words we speak. Let's explore its key components

Overview

The oral cavity represents the first part of the digestive tube. Its primary function is to serve as the entrance of the

alimentary tract and to initiate the digestive process by salivation and propulsion of the alimentary bolus into the

pharynx.

[1, 5] It also serves as a secondary respiratory conduit, a site of sound modification for the production of

speech, and a chemosensory organ.[5]

The mobility of the lips is also critical to speech production, whistling, singing, the playing of wind and brass

musical instruments, expectoration, and human behavioral communication (eg, kissing, smiling, pouting, baring of

teeth).[5] Even minor disruptions in the function of the oral cavity can seriously jeopardize an individual’s quality of

life.[5]

The oral cavity (see the image below) is oval shaped and is separated into the oral vestibule and the oral cavity

proper.[2] It is bound by the lips anteriorly, the cheeks laterally, the floor of the mouth inferiorly, the oropharynx

posteriorly, and the palate superiorly.[1] The oropharynx begins superiorly at the junction between the hard palate

and the soft palate, and inferiorly behind the circumvallate papillae of the tongue.[3] The bony base of the oral

cavity is represented by the maxillary and mandibular bones.[4]

Schematic representation of oral cavity and floor of mouth. A: philtrum; B: upper labial frenulum; C: opening of Stensen's duct; D: labial

commissure; E: hard palate; F: soft palate; G: intermaxillary commissure; H: base of tongue; I: lateral border of tongue, dorsal view; J:

tip of tongue, dorsal view; K: tip of tongue, ventral view; L: lateral border of tongue, ventral view; M: ventral surface of tongue; N: lingual

frenulum; O: floor of mouth; P: opening of Wharton's duct; Q: vestibular gingiva; R: vestibule. Teeth are numbered according to

international classification.

The oral cavity includes the lips, gingivae, retromolar trigone, teeth, hard palate, cheek mucosa, mobile tongue,

and floor of the mouth. The major salivary glands are in close relation with oral cavity structures, although they are

not part of the oral cavity. The tongue is part of the oral cavity; its anatomy is specifically described elsewhere (see

Tongue Anatomy). The palatine tonsils, soft palate, tongue base, and posterior pharyngeal walls are part of the

oropharynx; the oropharynx is not part of the oral cavity.

Gross Anatomy: Oral Vestibule

The oral vestibule is bounded externally by the lips and the cheek mucosa and internally by the alveolar processes

and the teeth. When the teeth are in occlusion, the vestibule communicates with the oral cavity proper via the

intermaxillary commissure behind the last molar teeth.

Lips

The longer upper lip and shorter lower lip are connected to each other by the labial commissures at the corners of

the mouth. The lips are separated from the cheeks by the nasolabial fold. The lip has an interior pale wet

vermilion and an outer darker dry vermilion, separated from each other by the red line; there is also a white line on

the outside that is the purely cutaneous part of the lip (see the image below).

Lips. Arrow indicates red line, which separates dry vermilion from wet vermilion.

Cheeks (mucosa)

The cheeks are a musculomembranous structure and are limited superiorly and inferiorly by the upper and lower

vestibules, anteriorly by the labial commissure, and posteriorly by the retromolar trigone and the intermaxillary

commissure. The inner surface of each lip is connected in the middle line to the corresponding gum by a fold of

mucous membrane, the labial frenulum. The upper labial frenulum (see the first image below) is larger than the

lower labial frenulum (see the second image below).

Upper vestibule (upper lip everted). Arrow indicates upper labial frenulum.

Lower vestibule (lower lip everted). Arrow indicates lower labial frenulum.

Gross Anatomy: Oral Cavity Proper

Hard palate

The palate is the horseshoe-shaped, domed roof of the oral cavity. It is divided into a hard portion and a soft

portion. The hard palate belongs to the oral cavity and separates it from the nasal cavities. The soft palate belongs

to the oropharynx and separates it from the nasopharynx.

The hard palate is concave, and this concavity is occupied mostly by the tongue when it is at rest. The hard palate

is subdivided into the primary and secondary palates. The primary palate is separated from the secondary palate

by a small depression behind the central incisors termed the incisive fossa, where the incisive foramen opens.

The anterior two thirds of the hard palate is formed by the incisive bone, or premaxilla, and the palatine processes

of the maxilla. The horizontal plates of the palatine bone form the posterior third. The secondary palate presents a

midline elevated suture line termed the median or palatine raphe. The hard palate also has transverse ridges (or

rugae) on the anterior third that serve to retain the food bolus.

Soft palate

The soft palate marks the beginning of the oropharynx and is the movable posterior third of the palate. It forms an

incomplete septum between the mouth and the pharynx. It is marked by a median raphe and is continuous with the

roof of the mouth and the mucous membrane of the nasal floor (see the image below).

Hard and soft palates. A: transverse rugae of hard palate; B: median raphe of hard palate; C: median raphe of soft palate.

When the soft palate is relaxed, its anterior surface is concave and its posterior surface is convex. The anterior

aponeurotic portion is attached to the posterior border of the hard palate, and the posterior muscular portion hangs

between the mouth and the pharynx and is termed the palatine velum (or velopharynx).

The velum is prolonged by a median free process termed the uvula and 2 bilateral processes termed the

palatoglossal and palatopharyngeal arches or pillars, which join the soft palate to the tongue and pharynx,

respectively. The fauces represent the space between the cavity of the mouth and the oropharynx. They are

bounded superiorly by the soft palate, inferiorly by the root of the tongue, and laterally by the pillars of the fauces.

The palatine tonsils are located in the tonsillar sinuses (or fossae) of the oropharynx, which is bounded by the

palatoglossal and palatopharyngeal arches and the tongue. They are thoroughly described elsewhere (see Tonsil

and Adenoid Anatomy).

During swallowing, the soft palate is initially tensed to squeeze the bolus of food between the tongue and pharynx

before elevation of the soft palate to block the nasal passages while the bolus is propelled into the pharynx.