Anatomy of Oral Region PDF

ORAL REGION (gums) and the lips and cheeks.The vestibule communicates...

ORAL REGION (gums) and the lips and cheeks.The vestibule communicates with the exterior through the oral fissure (opening).The size of the fissure iscontrolled by the peri-oral muscles, such The oral region includes the oral cavity, teeth, gingivae, as the orbicularis oris (the sphincter of the oral fissure), the tongue, palate, and the region of the palatine tonsils. The buccinator, risorius, and depressors and elevators the lips of oral cavity where food is ingested and prepared for diges of the is (dilators fissure). tion in the stomach and small intestine. Food chewed by is The oral cavity proper is the space between the upper the teeth, and saliva from the salivary glands facilitates the and lower dental arches or arcades (maxillary and man the formation of a manageable food bolus (L.lump). Deglutition dibular alveolar arches and the teeth they bear). The oral cav (swallowing) isvoluntarily initiated in the oral cavity. The vol ity limited laterally and anteriorly by the dental arches. The is untary phase of the process pushes the bolus from the oral roof the oral cavity is formed bythe palate. Posteriorly, the of cavity into the pharynx, the expanded part of the alimentary oral cavity communicates with the oropharynx (oral part of (digestive) system, where the involuntary (automatic) phase the pharynx). When the mouth isclosed and at rest, the oral of swallowing occurs. cavity fully occupied by the tongue. is Oral Cavity Lips, Cheeks,and Gingivae The oral cavity (mouth) consists of two parts: the oral ves LIPS AND CHEEKS tibule and the oral cavity proper (Fig,7.76). It is in the oral cavity that food and drinks are tasted and where mastication The lips are mobile, musculofbrous folds surrounding the (chewing) and lingual manipulation of food occur.The oral mouth, extending from the nasolabial sulci and nares lat vestibule is the slit-likespace between the teeth and gingivae erally, and superiorly to the mentolabial sulcus inferiorly 958/1170 Chapter 7 Head 929 Oral cavity proper Molar tooth -Palatine Alveolar mucosa* mucosa -Superior lingual Gingiva proper gingiva (superiorbuccal (proper) gingiva) Oral Tongue Plane of section vestibule C Buccal C Crown mucosa* - Inferior N Neck -oftooth lingual Buccinator R Root gingiva Bolus of food (proper) FIGURE 7.76. Coronal section of Inferior -Oral mucOsa* R mouth region.The orientationdrawing buccal of floorof shows the plane ofthe section.During gingiva mouth chewing, the tongue buc (centrally), cinator and orbicularis oris Mandible (laterally), *Mucous (anteriorly)work together to retain the Anterior view of membrane bolus offood between the occlusivesur coronal section of mouth faces ofthe molar teeth. (Fig. 7.77). They contain the orbicularis oris and superior The labial frenula are free-edged folds of mucous mem and inferior labial muscles, vessels, and nerves (Fig.7.16). brane in the midline, extending from the vestibular gingiva The lips are covered externally by skin and internally by to the mucosa of the upper and lower lips;the one extending mucous membrane. The lips function as the valves of the to the upper lip is larger. Other smaller frenula sometimes oral fissure, containing the sphincter (orbicularis oris) that appear laterally in the premolar vestibular regions. controls entry and exit from the mouth and upper alimentary The superior and inferior labial arteries, branches of and respiratory tracts. The lips are used for grasping food, the facial arteries, anastomose with each other in the lips to sucking liquids, keeping food out of the vestibule, forming form an arterial ring (Fig. 7.24; Table 7.5). The pulse of these speech, and osculation (kising). arteries may be palpated by grasping the upper or lowver lip The transitional zone of the lips (commonly considered lightly between the first two digits. The upper lip is supplied by itself to be the lip),ranging from brown to red, continues by superior labial branches of the facial and infra-orbital into the oral cavity where it is continuous with the mucous arteries. The lower lip supplied by inferior labial branches is membrane of the mouth (labial mucosa). This membrane of the facialand mental arteries. covers the intra-oral, vestibular part of the lips (Fig.7.78). The upper lip is supplied by the superior labial branches of the infra-orbital nerees (of CN V), and the lower lip is supplied by the inferior labial branches of the mental nerves (of CN V). Lymph from the upper lip and lateral parts of the Philtrum lower lip passes primarily to the submandibular lymph nodes Transitional zone -Nasolabial , (Fig. 7.77. whereas lymph from the medial part of the lower sulcus lip passes initiallyto the submental lymph nodes. Vermilion border -Lips The cheeks (L.buccae) have essentially the same struc Mentolabial ture as the lips with which they are continuous. The cheeks sulcus form the movable walls of the oral cavity. Anatomically, the external aspect of the cheeks constitutes the buccal region, bounded anteriorly by the oral and mental regions (lips and Submental -Submandibular chin), superiorly by the zygomatic region, posteriorly by the lymph nodes lymph nodes parotid region, and inferiorly by the inferior border of the mandible (Fig. 7.14). The prominence of the cheek occurs at the junction of the zygomatic and buccal regions. The zygo Anterior view matic bone underlying the prominence and the zygomatic arch, which continues posteriorly, are commonly referred FIGURE 1.77. Lymphatic drainage of Lymph from the upper lips. lip and partsofthe lower drainsto the submandibular nodes. to as the "cheek bone" (Fig. 7.3). Lay persons consider the lateral lip Lymph from the middle partof the lower drainsto the submental nodes. zygomatic and parotid regions also to be part of the cheek. lip 959/1170 930 Chapter 7 Head -Labial mucosa Vestibular (mucolabial) fold - Alveolar mucosa Labial frenulum Superior labial I1 gingiva 12 C PM M Vermilion border of lip (A) M C PMPM I1 12 Inferior labial gingiva (gingiva proper) Vestibular -Alveolar mucosa (mucolabial) fold (unattached gingiva) Labial mucosa (B) FIGURE7.78. Oral vestibule and gingivae. A. The vestibule and gingivae of themaxilla are shown. B. The vestibule and gingivae the mandible are of shown. As the alveolar mucosa approaches the necks ofthe teeth, changes in texture and color to become the gingiva proper. (Courtesy of Dr. B. Liebgott, it Professor, Division of Anatomy, Department of Surgery, University of Toronto, Toronto, Ontario, Canada.) The principal muscles of the cheeks are the buccinators pink, stippled, and keratinizing. The alveolar mucosa (Figs.7.76).Numeroussmall buccal glands lie between the (unattached gingiva) is normallyshiny red and non-keratin mucous membrane and the buccinators(Fig.7.74A). Super izing. The nerves and vessels supplying the gingiva, underly ficial to the buccinators are encapsulated collections of fat; ing alveolar bone, and periodontium (which surrounds the these buccal fat-pads are proportionately much larger in root[s]of a tooth, anchoring it to the tooth socket), are pre infants, presumably to reinforce the cheeks and keep them sented in Fig. 7.79A C. & from collapsing during sucking. The cheeks are supplied by buccal branches of the maxillary artery and innervated Teeth by buccal branches of the mandibular nerve. The chieffunctions of teeth are to: GINGIVAE Incise (cut), reduce, and mix food material with saliva during mastication (chewing). The gingivae (gums) are composed of fibrous tissue covered Help sustain themselves in the tooth sockets by assisting with mucous membrane. The gingiva proper (attached gin the development and protection of the tissues that sup giva) is firmly attached to the alveolar processesof the man port themn. dible and maxilla and the necks of the teeth (Figs. 7.76 and Participate in articulation (distinct connected speech). 7.78). The gingiva proper adjacent to the tongue the supe is rior and inferior lingual gingivae, and that adjacent to the The teeth are set in the tooth sockets and are used in mastica lips and cheeks is the maxillary and mandibular labial or tion and in assisting in articulation. A tooth is identified and buccal gingiva, respectively. The gingiva proper is normally desceribed on the basis of whether it is deciduous (primary) 960/1170 932 Chapter 7 Head or permanent (secondary), the type of tooth, and its prox in clinical (dental) practice,the mesial surfaceof a tooth is imity to the midline or front of the mouth (e.g., medial and directed toward the median plane of the facial part of the cra lateral incisors; the lst molar is anterior to the 2nd). nium. The distal surfaceis directed away from this plane; Children have 20 deciduous teeth; adults normally have both mesial and distal surfaces are contact surfaces-that is, 32 permanent teeth (Fig. 7.80A & C). The usual ages of surfaces that contact adjacent teeth. The masticatory surface the eruption ("cutting")of these teeth are demonstrated in is the occlusal surface. Figure 7.81 and listed in Table 7.13. Before eruption, the developing teeth reside in the alveolar arches as tooth buds PARTS AND STRUCTURE OF TEETH (Fig. 7.80B). The types of teeth are identified by their characteristics: A and root (Fig. 7.82). The crown tooth has a crown, neck, incisors, thin cutting edges; canines, single prominent projects from the gingiva. The neck is betweenthe crown cones: premolars (bicuspids),two cusps; and molars, three and root. The root is fixed in the tooth socket by the peri or more cusps (Fig. 7.80A & C). The vestibular surface odontium (connective tissue surrounding roots);the number (labial or buccal) of each tooth is directed outwardly, and the of roots varies. Most of the tooth is compoOsed of dentine lingual surfaceis directed inwardly (Fig. 7.79B). As used (L. dentinium), which is covered by enamelover the crowm Maxillary alveolar process PM M2 M1 PM PM PM M1 M3 M3 PM PM PM PM M2 M1 M1 M3 M2 C PM PMA M1 M2 M3 Mandibular alveolar process PM PMS MI (A) Right anterolateral view (B) Left anterolateral view M3 M2 23 456 78 M1 15 16 M3 M2 32 M1 PMPM c T9 10 11 12 13 14 18 31 30 20 19 PMPMCII 28 27 26 2524 22 21 (C) Panoramic view FIGURE7.80. Secondarydentition. A.The teeth are shown in occlusion. There is a supernumerary midline tooth (mesiodens) in this specimen ("). B. Maxillary and mandibular jawsof a child acquiring secondary dentition are shown.The alveolar processes are carved to reveal the roots of the teeth and tooth buds. C. A pantomographic radiograph of anadult mandible and maxilla is shown. The left lower 3rd molar is not present. I, incisor; C, canine; PM, premolar; M1, M2, and M3, 1st, 2nd, and 3rd molars. (Part C courtesy ofM.J. Pharoah, Associate Professor of Dental Radiology, Faculty Dentistry, of University of Toronto, Toronto, Ontario, Canada.) TABLE 7.13A. DECIDUOUS TEETH Deciduous Teeth Central Incisor Lateral Incisor Canine 1st Molar 2nd Molar Eruption (months) 6-8 8-10 16-20 12-16 20-24 Shedding (years) 6-7 7-8 10-12 9-11 10-12 Insome normal infants, the first teeth (medial incisors) may not erupt until 12-13 months of age. M1 M2 -Interradicular septa of tooth socket Socket for M1 Interalveolar septum Central and lateral incisors -C -M1 M2 M= Molar -M1 Pm = Premolar Permanent teeth M2 Deciduous teeth (A) (B) Primary dentition,