University:
Kentucky State University
Course:
BIO 301 | Human Anatomy
Academic year:

2021
Views:

388

Pages:

43
Author:

suzshikn5

Oral cavity Learning Objectives At the end of the lecture, students should be able to: • Understand the regions and boundaries of the oral cavity. • Describe parts of the mouth, the oral cavity proper. • Understand the anatomy of the hard and soft palate. • Identify the location and the anatomy of palatine tonsils. • List the primary and permanent teeth. • Identify the innervation, blood supply and lymphatic drainage of the mouth cavity. • Explain the anatomy of the tongue, including muscles, blood supply, lymphatic drainage, and innervation. • Understand different clinical correlation related to different structures in the oral cavity. Oral Cavity (Mouth) The mouth divided into: 1. Oral Vestibule: Which lies between teeth & gums internally and cheeks & lips externally. The parotid duct opens opposite the upper second molar. 2. Oral cavity proper: Which lies within the alveolar arches, teeth and gums. Oral Vestibule • Slitlike space between the cheeks and the gums • Communicates with the exterior through the oral fissure • When the jaws are closed, communicates with the oral cavity proper behind the 3rd molar tooth on each side • Superiorly and inferiorly limited by the reflection of mucous membrane from lips and cheek onto the gums. Oral Vestibule cont’d • The lateral wall of the vestibule is formed by the cheek • The cheek is composed of Buccinator muscle, covered laterally by the skin & medially by the mucous membrane • A small papilla on the mucosa opposite the upper 2nd molar tooth marks the opening of the duct of the parotid gland. Mouth Tongue • Mouth proper: has a roof, which is formed by hard & soft palate. • The floor is formed by the anterior 2/3 of the tongue and mylohyoid muscle. Palate The palate is a wall or septum that separates the oral cavity from nasal cavity, and forms the roof of the mouth. § The hard palate—the anterior bony por:on of the roof of the mouth. § The so- palate: the muscular posterior por:on of the roof of the mouth. § Uvula: a muscular structure hanging from the free border of the so= palate. During swallowing, the so2 palate and uvula are drawn superiorly, closing oﬀ the nasopharynx and preven9ng swallowed foods and liquids from entering the nasal cavity. Palate The palate forms the roof of the mouth. It is divided into two parts: 1. The hard (Bony) palate in front 2. The soft palate behind. Hard Palate The hard palate is formed by (4 bones): - Palatine processes of the maxillae and - Horizontal plates of palatine bones. It forms the floor of nasal cavities and the roof of mouth cavity. Soft Palate • It is a mobile fold of mucous membrane filled with striated muscles. • It is attached to the posterior border of the hard palate. • Its free posterior end is a conical projection called the uvula. The mucosa of the hard palate in the oral cavity possesses numerous transverse palatine folds (palatine rugae) and a median longitudinal ridge (palatine raphe), which ends anteriorly in a small oval elevation (incisive papilla). The incisive papilla overlies the incisive fossa formed between the horizontal plates of the maxillae immediately behind the incisor teeth. Soft palate attaches to the posterior border of the hard palate Covered on its upper and lower surfaces by mucous membrane Composed of: • Muscle fibers • An aponeurosis • Lymphoid tissue • Glands • Blood vessels • Nerves Palatine Aponeurosis § Fibrous sheath § Attached to posterior border of hard palate § Is expanded tendon of tensor veli palatini § Splits to enclose musculus uvulae § Gives origin & insertion to palatine muscles Muscles of the Soft Palate 5 pairs of muscles: 1. Tensor veli palatini, 2. Levator veli palatini, 3. Palatoglossus, 4. Palatopharyngeus, 5. Musculus uvulae Muscles Tensor veli palatini • Origin: spine of sphenoid; auditory tube • Insertion: forms palatine aponeurosis • Action: Tenses soft palate Levator veli palatini • Origin: petrous part of temporal bone, auditory tube • Insertion: palatine aponeurosis • Action: the only muscle to elevate soft palate Muscles Musculus uvulae • Origin: posterior nasal spine of hard palate • InserBon: connecBve Bssue of uvula • AcBon: Elevates and retract uvula Muscles Palatoglossus • Origin: palatine aponeurosis • Insertion: lateral margin of tongue • Action: elevates back of the tongue upward, narrowing oropharyngeal isthmus by moving palatoglossal arch toward midline. Palatopharyngeus • Origin: palatine aponeurosis • Insertion: Lateral wall of pharynx • Action: Elevates pharynx, moves palatopharyngeal arch toward midline. Sensory innervation of Hard & Soft Palate The greater and lesser palatine nerves from the maxillary nerve. The nasopalatine nerve, from the maxillary nerve. Motor Innervation of Soft Palate All muscles of the palate are innervated by the vagus nerve* [X], except for the tensor veli palatini, which is innervated by the mandibular nerve [V3] (via the nerve to the medial pterygoid). * Pharyngeal branch of vagus nerve [X] via pharyngeal plexus. Pharyngeal plexus ØIt is a network of nerve fibers innervating most of the palate, pharynx and larynx. ØIt lies on the outer wall of pharynx, mostly on the middle constrictor. ØIt is formed of pharyngeal branches of glossopharyngeal N., vagus N. including fibers of cranial root of accessory and superior cervical sympathetic ganglion. Blood Supply of the Palate Greater & lesser palatine branches of the maxillary artery. Ascending palatine branch of the facial artery. Palatine branch of ascending pharyngeal artery of the external carotid artery. Testing the Motor innervation of Soft Palate Motor innervation of soft palate • Can be tested by saying ‘ah’, Normally soft palate rises and uvula moves backward in the middle. Pharyngeal isthmus, the communication between nasal and oral parts of the pharynx, is closed by raising the soft palate via contraction of levator veli palatini. • Closure occurs during the production of explosive acts in speech & in swallowing. The Palatine Tonsils The palatine tonsils are collections of lymphoid tissue on each side of the oropharynx in the interval between the palatine arches. • • The palatine tonsils are the common site of infection, producing the characteristic tonsilitis. The deep cervical lymph node, which situated below and behind the angle of mandible is usually enlarged and tender. • Recurrent attacks of tonsilitis are treated by tonsillectomy. • Clinically, the external palatine vein, which lies lateral to the tonsil, may be the source of postoperative bleeding. Clinical Notes • Cleft palate: • Unilateral • Bilateral • Median • Paralysis of the soft palate • The pharyngeal isthmus can not be closed during swallowing and speech Pharyngeal isthmus Teeth • Teeth live in sockets (alveoli) in the gum-covered margins of the mandible and maxilla. • Chewing: raising and lowering the mandible and moving it from side to side while tongue positions food between teeth. • Two sets Primary or deciduous • • • • “Baby” teeth Start at 6 months 20 are out by about 2 years Fall out between 2-6 years Permanent: 32 total All but 3rd set of molars by end of adolescence Tongue The tongue is a mass of striated muscles covered with mucous membrane. Its anterior 2/3 lies in the mouth, and its posterior 1/3 lies in the pharynx. The tongue has a root, a body, and an apex. It has several funcLons: o Manipula)on of food and swallowing. o Produc)on of normal speech. The upper surface (Dorsum)of the tongue can be divided by a V-shaped sulcus (sulcus terminalis) into: - Oral part (Anterior 2/3) - Pharyngeal part (posterior 1/3) • • The apex of the sulcus is marked by a small pit, the foramen cecum. It is Embryologic remnant of the upper end of the thyroglossal duct. Mucous Membrane of tongue Three types of papillae are present on the upper surface of the anterior two thirds of the tongue: the fungiform papillae, the filiform papillae, and the vallate papillae. The mucous membrane covering the posterior third of the tongue is devoid of papillae but has a nodular irregular surface caused by the presence of underlying lymph nodules, the lingual tonsils. •Changes in the mucosa lining the tongue indicate the systemic diseases, such as diabetes or vitamin deficiency, or the local effects of chronic tobacco or alcohol use. Floor of the Mouth Mucous membrane on the under surface of the tongue is smooth. In the midline, the undersurface of the tongue is connected to the floor of the mouth by a fold of mucous membrane, the frenulum of tongue. Ø The submandibular duct opens into the floor of mouth on each side of frenulum of tongue. Ø The sublingual ducts also open by many openings (8-20) into the floor of mouth on the summit of sublingual fold on lateral side of submandibular duct opening. Smooth (no papillae) Lateral to frenulum, deep lingual vein can be seen through the mucosa. Lateral to lingual vein, a fold of mucosa forms the plica fimbriata. Clinical Anatomy of Submandibular Duct • Calculus formation: • It is a tense swelling below the body of the mandible, which is greatest during a meal and is reduced in size or absent between meals (diagnostic of the case). Clinically: • by examination of floor of mouth, reveals absence of ejection of saliva from the orifice of duct & stone can be palpated in the duct, which lies below m.m. of the floor of mouth. • During the operation, we should remember that the duct is crossed by the lingual nerve. Muscles of Tongue The muscles of the tongue are divided into two types: Intrinsic and extrinsic. The intrinsic muscles are restricted to the tongue and are not attached to bone. They consist of longitudinal, transverse, and vertical fibers. Nerve supply: Hypoglossal nerve. Action: Alter the shape of the tongue while it lies in the mouth cavity. Extrinsic Muscles of Tongue § The extrinsic muscles are 4 pairs attached to bones and the soft palate. § They are: § Palatoglossus § Styloglossus § Genioglossus § Hyoglossus All muscles of the tongue are supplied by the hypoglossal nerve EXCEPT palatoglossus which is supplied by pharyngeal plexus which contains ﬁbers from vagus nerve. Muscles of the Head: Moving the Tongue Sensory Innervation of Tongue General sensations from the anterior 2/3 of the tongue are carried by the lingual nerve (V3). Taste fibers from the anterior 2/3, excluding the vallate papillae, are carried by the chorda tympani of the facial nerve. General & taste sensations from the posterior 1/3, including the vallate papillae, are carried by the glossopharyngeal nerve. General & taste sensations from root of the tongue and epiglottis are carried by the vagus nerve. Injury to Lingual nerve • The dangerous area during tooth extraction. • Here, Lingual nerve is closely related to the lower last molar tooth and is liable to be damaged in cases of clumsy extraction on an impacted 3rd molar. Blood Supply The main artery is the lingual artery: the lingual artery passes deep to the hyoglossus muscle. • The dorsal lingual arteries supply the root of the tongue; • The deep lingual arteries supply the body. The veins drain into the internal jugular vein. Lympha+c Drainage The tip of the tongue drains into the submental lymph nodes. The remainder of the anterior 2/3 of the tongue drains into the submandibular & deep cervical lymph nodes. Lymph from the posterior 1/3 of the tongue drains into the deep cervical lymph nodes. The lymphatic drainage is important in the early spread of carcinoma of the tongue. Clinical Estimation of the Hypoglossal Nerve §Ask the patient to protrude his tongue : § Normally, Rt.&Lt. genioglossus muscles contract together protruding the tip of tongue anteriorly in the middle line. § Lesion of hypoglossal N. on Rt. side leads to atrophy & wrinkling of the tongue on the same side of lesion. § Asking patient to protrude the tongue, the tip deviates to side of the lesion.

Oral Сavity

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