The Oral Cavity (الفم) PDF

1 The oral cavity ‫حيدر كامل الجبوري‬.‫د‬ The Lips The lips are two fleshy folds that surround the oral orifice. They are covered on the outside by skin and are lined on the inside by mucous membrane. The substance of the lips is made up of...

1 The oral cavity ‫حيدر كامل الجبوري‬.‫د‬ The Lips The lips are two fleshy folds that surround the oral orifice. They are covered on the outside by skin and are lined on the inside by mucous membrane. The substance of the lips is made up of the orbicularis oris muscle and the muscles that radiate from the lips into the face. Also included are the labial blood vessels (facial artery branches which are the superior labial artery for the upper lip, submental artery, and inferior labial artery for the lower lip) Nerves (upper lip: infraorbital nerve from maxillary division, lower lip: mental nerve from mandibular division), connective tissue, and many small salivary glands. The philtrum is the shallow vertical groove seen in the midline on the outer surface of the upper lip. The lips bound the oral fissure. They meet laterally at the angles of the mouth. The inner surface of each lip is supported by a frenulum(labial frenulum) which ties it to the gum. 1  2 The oral Cavity The oral cavity extends from the lips to the pharynx. The paired palatoglossal folds form the oropharyngeal isthmus, which is the entrance into the pharynx. The oral cavity has two components: the vestibule and the oral cavity proper. Vestibule The vestibule lies between the lips and the cheeks externally and the gums and the teeth internally. This slitlike space communicates with the exterior through the oral fissure between the lips. When the jaws are closed, it communicates with the mouth proper behind the third molar tooth on each side. The vestibule is a slitlike space that lies between the lips and the cheeks externally and the gums and the teeth internally. It communicates with the exterior through the oral fissure between the lips. When the jaws are closed, it communicates with the oral cavity proper behind the third molar tooth on each side. The vestibule is limited above and below by the reflection of the mucous membrane from the lips and cheeks onto the gums. The lateral wall of the vestibule is formed by the cheek, which is made up by the buccinator muscle and is lined with mucous membrane. The mucous membrane is tethered (tied) to the buccinator muscle by elastic fibers in the submucosa that prevent redundant folds of mucous membrane from being bitten between the teeth when the jaws are closed. The mucous membrane of the gingiva, or gum, is strongly attached to the alveolar periosteum. The tone of the buccinator muscle and that of the muscles of the lips keeps the walls of the vestibule in contact with one another. The duct of the parotid salivary gland opens on a small papilla into the vestibule opposite the upper second molar tooth. ❖ Note: The entire vestibule is lined by mucous membrane. The mucous membrane forms median folds that pass from the lips to the gums, and are called the frenula of the lips. 2  3 Cheeks (Buccae) 1. The cheeks are fleshy flaps, forming a large part of each side of the face. They are continuous in front of the lips, and the junction is indicated by the nasolabial sulcus (furrow), which extends from the nose's side to the mouth's angle. 2. Each cheek is composed of: a. Skin b. Superficial fascia containing some facial muscles, the parotid duct, mucous molar glands, vessels and nerves. (Maxillary division: infraorbital nerve and zygomaticofacial nerve…. Mandibular division: buccal nerve) c. The buccinator is covered by buccopharyngeal fascia and pierced by the parotid duct. d. Submucosa, with mucous buccal glands. e. Mucous membrane. 3. The buccal pad of fat is best developed in infants. It lies on the buccinator partly deep to the masseter and partly in front of it. 4. The lymphatics of the cheek drain chiefly into the submandibular and preauricular nodes, and partly also to the buccal and mandibular nodes. 3  4 Gums (Gingivae) 1. The gums are the soft tissues which envelop the alveolar processes of the upper and lower jaws and surround the necks of the teeth. These are composed of dense fibrous tissue covered by stratified squamous epithelium. 2. Each gum has two parts: a. The free part surrounds the neck of the tooth like a collar. b. The attached part is firmly fixed to the alveolar arch of the jaw. The fibrous tissue of the gum is continuous with the periosteum lining the alveoli (periodontal membrane). Nerve supply of gums Gums Nerve supply Upper gums Labial side Posterior, middle and anterior superior alveolar nerves) (maxillary nerve (V2)) Lingual side (palatal side) palatine and nasopalatine nerves (from pterygopalatine ganglion) ( maxillary nerve (V2)) Lower gums Labial side (buccal side) Buccal branch of mandibular and incisive branch of mental nerve (V3) Lingual side Lingual nerve (V3) Note: The buccal nerve (long buccal nerve) is a nerve in the face. It is a branch of the mandibular nerve (which is itself a branch of the trigeminal nerve) The buccal branches of the facial nerve. The facial nerve innervates the muscles of facial expression 4  5 Lymphatics Lymphatics of the upper gums pass to the submandibular nodes. The anterior part of the lower gums drains into the submental nodes, whereas the posterior part drains into the submandibular nodes. Mouth Proper The oral cavity proper has a roof and a floor. The palate forms the roof; it consists of the hard palate in front and the soft palate behind. The anterior two thirds of the tongue and the reflection of the mucous membrane from the sides of the tongue to the gum of the mandible largely form the floor. A midline fold of mucous membrane, the frenulum of the tongue, connects the undersurface of the tongue to the floor of the mouth. The submandibular duct of the submandibular gland opens onto the floor of the mouth on the summit of a small papilla on either side of the frenulum of the tongue. The sublingual gland projects up into the mouth, producing a low fold of mucous membrane, the sublingual fold (plica semilunaris). Numerous ducts of the gland open on the summit of the fold. 5  6 Sensory innervation of the Mouth (Oral Cavity) Roof: The greater palatine and nasopalatine nerves from the maxillary division of the trigeminal nerve. Floor: The lingual nerve (general sensation), a branch of the mandibular division of the trigeminal nerve. The taste fibers travel in the chorda tympani nerve, a branch of the facial nerve. Cheek: The buccal nerve, a branch of the mandibular division of the trigeminal nerve. Note: the buccal branch of the facial nerve innervates the buccinator muscle, whereas the buccal nerve supplies sensory fibers to the cheek. 6  7 7  8 Palate The palate forms the roof of the oral cavity and the floor of the nasal cavity.It has two parts: 1-The hard palate in front and the soft palate behind. The palatine processes of the maxillae and the horizontal plates of the palatine bones form the hard palate. It is continuous behind with the soft palate. 8  9 2-Soft Palate The soft palate is a mobile fold attached to the posterior border of the hard palate. Its free posterior border presents in the midline a conical projection called the uvula. The soft palate is continuous at the sides with the lateral wall of the pharynx. The soft palate is composed of mucous membrane, palatine aponeurosis, and muscles. Mucous Membrane The mucous membrane covers the upper and lower surfaces of the soft palate. Palatine Aponeurosis The palatine aponeurosis is a fibrous sheet attached to the posterior border of the hard palate. It is the expanded tendon of the tensor veli palatini muscle. Muscles of the Soft Palate They are as follows: 1. Tensor palati (tensor veli palatini) 2. Levator palati (levator veli palatini) 3. Musculus uvulae 4. Palatoglossus 5. Palatopharyngeus. The muscle fibers of the tensor veli palatini converge as they descend from their origin to form a narrow tendon, which turns medially around the pterygoid hamulus. The tendon, together with the tendon of the opposite side, expands to form the palatine aponeurosis. When the muscles of the two sides contract, the soft palate is tightened so that the soft palate may be moved upward or downward as a tense sheet. 9  10 Nerve Supply of the Palate The greater and lesser palatine nerves from the maxillary division of the trigeminal nerve enter the palate through the greater and lesser palatine foramina. The greater palatine nerve runs forward and mainly supplies the hard palate. The lesser palatine nerve mainly passes posteriorly and supplies the soft palate. The nasopalatine nerve, also a branch of the maxillary nerve, enters the front of the hard palate through the incisive foramen. The glossopharyngeal nerve(ninth cranial nerve, cranial nerve IX) also supplies the soft palate. Blood Supply of the Palate The greater palatine branch of the maxillary artery, the ascending palatine branch of the facial artery, and the ascending pharyngeal artery Lymph Drainage of the Palate Deep Cervical Lymph Nodes 10  11 Palatoglossal Arch: The palatoglossal arch is a fold of mucous membrane containing the palatoglossus muscle, which extends from the soft palate to the side of the tongue. The palatoglossal arch marks where the mouth becomes the pharynx. Palatopharyngeal Arch: The palatopharyngeal arch is a fold of mucous membrane behind the palatoglossal arch that runs downward and laterally to join the pharyngeal wall. The muscle contained within the fold is the palatopharyngeus muscle. The palatine tonsils, which are masses of lymphoid tissue, are located between the palatoglossal and palatopharyngeal arches. Movements of the Soft Palate Raising the soft palate closes the pharyngeal isthmus (the communicating channel between the nasal and oral parts of the pharynx). Closure occurs during the production of explosive consonants in speech and during swallowing. Bilateral contraction of the levator veli palatini muscles raises the soft palate. At the same time, the upper fibers of the superior constrictor muscle contract and pull the posterior pharyngeal wall forward. The palatopharyngeus muscles on both sides also contract so that the palatopharyngeal arches are pulled medially, like side curtains. 11  12 Muscles of the soft palate Figure 12.75 Arrangement of the facial muscles around the lips and the sensory nerve supply of the lips. 12