Basic Anatomy and Physiology of the Lips and Oral Cavity Dr. Faghih
It is divided into seven specific subsites : 1. Lips 2. dentoalveolar ridges 3. oral tongue 4. retromolar trigone 5. floor of mouth 6. buccal mucosa 7. hard palate
the lips and oral cavity comprise the initial part of the upper digestive tract and thus play a key role in food ingestion Speech production additionally developed during the course of phylogenesis. large percentage of the taste receptors are located in the oral cavity
Anatomy
Oral Vestibule is bounded : externally by the lips and cheeks internally by the alveolar processes and teeth
When the teeth are in occlusion, the oral vestibule communicates with the oral cavity via a space behind the last molar.
Lips and Cheeks formed largely by the mimetic muscles, are lined on their mucosal side by nonkeratinized squamous epithelium
Lips longer upper lip shorter lower lip labial commissures nasolabial fold lamina propria orbicularis oris muscle
blood supply : Superior and inferior labial arteries drained primarily facial vein
With inflammatory lesions of the lip, infectious organisms can spread into the cranial cavity via connections between the orbital veins and cavernous plexus
lymphatic drainage : The submandibular and submental lymph nodes sensory innervation The infraorbital nerve, mental nerve
Cheeks form the lateral boundaries of the oral vestibule contain small salivary glands The buccinator forms the muscular framework its motor innervation from branches of the facial nerve
The Bichat fat pad (buccal fat pad) is located between the buccinator muscle and the overlying masseter Muscle The excretory duct of the parotid gland opens opposite the upper second molar
Masticatory Muscles masseter muscle Temporalis muscle Medial pterygoid muscles lateral pterygoid muscles all supplied by the mandibular nerv
Teeth Two incisors One canine Two premolars Three molars
Each tooth consists of Crown root apex neck (cervix) Enamel pulp chamber The teeth are anchored in the alveoli by the cementum, the bony alveolarwall itself, and the gingiva. These anchoring and supporting structures are known collectively as the periodontium
The alveolar processes in the maxilla also form the floor of the maxillary Normally, the roots of the second premolar and first molar are very closely related to the maxillary sinus
The arteries that supply the maxilla and mandible: Inferior alveolar artery anterior superior alveolar arteries posterior superior alveolar arteries their innervation from : branches of the maxillary nerve branches of the mandibular nerve
Oral Cavity is bounded : anteriorly and laterally by the alveolar ridge and teeth superiorly by the hard and soft palate posteriorly by the faucial isthmus This narrow opening between the oral cavity and pharynx is bordered by the soft palate with the uvula dorsum of the tongue
Palate The hard palate is formed by Anteriorly palatine processes of the maxilla Posteriorly the incisive bone, and the horizontal plates of the palatine bones The palatal muscles are tensor veli palatini levator veli palatini Palatoglossus Muscle of the uvula
The palatal mucosa, contains numerous salivary glands The palatal mucosa receives its sensory innervation from greater and lesser palatine nerves The blood supply to the palate is derived from the ascending palatine branch of the facial artery
Developmentally, the individual muscular components of the soft palate are derived from different structures and are therefore supplied by different cranial nerve IX X V
Tongue The main anatomical subdivisions Apex Body base or root The body of the tongue is separated from the base by a V-shaped groove called the terminal sulcus
four extrinsic muscles 1. Genioglossus 2. Hyoglossus 3. Styloglossus 4. Palatoglossus four intrinsic muscles 1. superior-inferior longitudinal 2. Transverse 3. vertical
Numerous papillae, project from the surface of the tongue and give it its characteristic roughness Four types of papillae are distinguished: 1. Filiform 2. Fungiform 3. vallate, 4. Foliate The microscopic taste are most numerous on the vallate and foliate papillae
blood supply from lingual and sublingual arteries Homonymous accompanying veins provide for drainage via the facial vein Lymphatic drainage submandibular and submental lymph nodes
All of the musculature of the tongue derives its innervation via the hypoglossal nerve with the exception of the palatoglossus, which is supplied by a pharyngeal branch of the vagus nerve.
The general sensory innervation of the anterior two thirds of the tongue is provided by the lingual nerve The special sensory innervation of the oral tongue for taste is provided by the chorda tympani nerve (CN VII) both functions are performed by the glossopharyngeal nerve for the base of tongue.
Floor of Mouth The floor of mouth is a mucosal surface bordered by the oral tongue and alveolar ridge laterally and anteriorly. The posterior margin is the anterior tonsillar pillar The mylohyoid and hyoglossus muscles provide the structural support for contents of the space.
A branch of the lingual nerve provides sensation for the floor of mouth The lymphatic drainage of the anterior aspect of this space may cross to contralateral submental-submandibular nodes The posterior portion of the space tends to drain to ipsilateral upper cervical lymph nodes.
Physiology
Importance for Food Intake Lips sealing the oral cavity during chewing and swallowing Tongue multifunction organ with both motor and sensory properties Molars greatest importance in chewing
Taste There are only four basic taste sensations: 1) Sweet 2) Sour 3) Salty 4) Bitter The sensory experience of taste is a much more complex phenomeno Results from a combination of olfactory, thermal, mechanical, and sensory impressions.
Importance in Phonation and Articulation The musculature of the lips has an essential role in phonation lingual articulation joins with the pharynx, nose, and paranasal sinuses
Methods of Examining the Lips and Oral Cavity
Inspection of the lips and oral cavity additional diagnostic procedures
Visual Inspection
With hypoglossal nerve palsy, the tongue will deviate toward the affected side With Glossopharyngeal nerve palsy, in which the uvula and palatal arches deviate toward the healthy side
Palpation better assess the consistency and depth of the suspicious Finding The cervical lymph nodes should also be palpated.
Taste Testing Abnormalities of taste are classified as : 1) hypogeusia 2) hypergeusia 3) Ageusia
Subjective Taste Testing Chemogustometry Electrogustometry Objective Taste Testing
Imaging Procedures Ultrasound Computed Tomography Magnetic Resonance Imaging