The Digestive System in the Head and Neck

The Digestive System in the Head and Neck • The Gastrointestinal system is an organ system, it is divided into: A. The Alimentary canal (also known as the GI (digestive) tract): a tube that begins by the mouth and ends in the anal canal. It contains the oral cavity, pharynx, esophagus, stomach, duodenum, small intestines (jejunum and ileum), large intestines (colon with appendix), rectum and the anus. B. Accessory (association) digestive organs: ✓ The tongue and teeth. ✓ The salivary glands. ✓ The liver and gallbladder (they have a duct connecting them with the duodenum). ✓ The pancreas. The Mouth (Oral cavity( : • The oral cavity has 2 openings: ✓ Anterior opening (the mouth). ✓ Posterior opening (Oropharyngeal Isthmus). The Anterior opening (the mouth): • • It lies between the upper lip and the lower lip. The lips are two fleshy folds (muscular organs as they contain Orbicularis oris muscle) that surround the oral orifice. A bridge to histology: The lip is covered by three different zones: • • • The skin of the lip which Consists of stratified squamous keratinized epithelium. It has hair follicles, sebaceous glands and sweat glands. Transitional zone (Vermilion zone): it is the reddish part of the lip which consists of a modified squamous epithelium. It contains a large number of vessels and nerve terminals that make it red and very sensitive, but It has no hair follicles, sebaceous glands or sweat glands. The mucosa (from inside) of the lip Consists of stratified squamous non-keratinized epithelium. And it has labial glands 1|Page • • The philtrum is the shallow vertical groove seen in the midline on the outer surface of the upper lip only. It is formed in the embryo by the lateral to medial maxillary prominence growth (where the maxillary prominence meets with the nasomedial prominence ➔ doctor didn’t mention the nasomedial prominence). Median folds of mucous membrane” the labial frenulum” connects the inner surface of the lips to the gums. the substance of the lips is made up by the orbicularis oris muscle and the muscles that radiate from the lips into the face: orbicularis oris muscle: ✓ ✓ ✓ ✓ • is a striated muscle. it has a circular fiber. it is innervated by the facial nerve. it acts as a sphincter to close the lips and it is important in the whistling action. (the inability to whistle and the drooping of saliva on one side is a sign of facial nerve paralysis on one side). Also included are the labial blood vessels and nerves, connective tissue, and many small salivary glands. Posterior opening (Oropharyngeal Isthmus or Isthmus of the Fauces): • • • • It is the posterior orifice and the entrance into the pharynx. At the two sides of the Oropharyngeal Isthmus there are palatine tonsils. The Roof: The Uvula which is an extension of the soft palate. The Floor: posterior third of the tongue. Palatine tonsils: Palatine tonsils are found between 2 folds (arches): ✓ The palatoglossal fold (anterior one): extends from the palate to the tongue (glossal refers to the tongue). ✓ The palatopharyngeal fold (posterior one): extends from the palate to the pharynx. 2|Page The mouth cavity is divided into: A) The vestibule B) Mouth proper. The Vestibule: • • • • • The vestibule lies between: ✓ externally: the lips anteriorly and the cheeks on the sides. ✓ Internally: the (closed) teeth and gum. This slit-like space communicates with the exterior through the oral fissure between the lips. It is where you move the tooth brush to brush your teeth when the upper and the lower jaw are closed. when the jaws are closed, it communicates with the mouth proper behind the third molar tooth on each side. The lateral wall of the vestibule is formed by the cheek, which is made up by the buccinator muscle. Remember: buccinator muscle is used for blowing and it is supplied by the motor facial nerve. • • • • The cheeks (buccinator muscle) is lined form the outside by skin (keratinized stratified squamous epithelium) and from the inside by mucous membrane (Non-keratinized stratified squamous epithelium). 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 which is found over the ramus of mandible opens on a small papilla into the vestibule opposite the upper second molar tooth, it also contains minor glands. The vestibule is limited above and below by the reflection of the mucous membrane from the lips and cheeks to the gums. Buccinator muscle Connection between vestibule and mouth proper. 3|Page The Mouth Proper: • • Found inside the closed teeth. The mouth proper boundaries: ✓ Roof: the hard palate in front and the soft palate in the back. ✓ Floor: formed largely by the anterior two thirds of the tongue (dorsum aspect) and by the reflection of the mucous membrane from the sides of the tongue to the gum of the mandible. ✓ Sides: the teeth and cheeks (buccinator muscle lined by mucous membrane). ✓ Posteriorly: Oropharyngeal isthmus with its folds and tonsils. • Mucous Membrane of the Mouth: ✓ Stratified squamous Non-keratinized epithelium. ✓ Rich in minor salivary glands. ✓ fold of mucous membrane called the frenulum of the tongue connects the undersurface of the tongue in the midline to the floor of the mouth. ✓ Also, there are the Superior labial frenulum which connects the inner surface of upper lip to the mouth. And the Inferior labial frenulum which connects the inner surface of lower lip to 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 (Numerous ducts of the gland open on the summit of the fold). ✓ The mucous membrane is hard (tough) over the gingiva (the gum) and it is strongly attached to the alveolar periosteum (found on the border of the alveolar socket). ✓ In the vestibule the mucous membrane is tethered to the buccinator muscle by elastic fibers in the submucosa and this prevents redundant folds of mucous membrane from being bitten between the teeth when the jaws are closed. • Salivary glands: ✓ Secretion of saliva. ✓ Either minor glands prevalent in the oral cavity. ✓ Or 3 major glands: A) Parotid gland B) submandibular gland C) sub lingual gland ✓ They are important because the oral cavity must be moist ➔ the dryness of the oral cavity permits the bacteria to grow and cause infection. 4|Page **Titles are labeled with green colors: Soft palate Hard palate inferior labial frenulum Frenulum of the tongue Superior labial frenulum Gum 5|Page Submandibular gland Sublingual fold Sublingual gland Submandibular duct Opening of submandibular duct 6|Page Sensory Innervation of the Mouth: Remember: trigeminal nerve is the 5th cranial nerve which gives 3 divisions: ophthalmic (sensory to the eye), maxillary (supplies the maxilla and the upper teeth) and the mandibular (supplies the mandible and the lower teeth). • • • • Roof: The greater palatine and nasopalatine nerves from the maxillary division of the trigeminal nerve. Floor: The lingual nerve (general (common) sensation ➔ touch, pain and temperature), a branch of the mandibular division of the trigeminal nerve. The taste (special sensation) fibers travel in the chorda tympani nerve, a branch of the facial nerve. Cheek: The buccal nerve (sensory), a branch of the mandibular division of the trigeminal nerve (the buccinator muscle is innervated by the buccal branch of the facial nerve (motor)). 7|Page Lingual nerve 8|Page The Teeth: • • • • Found within the alveolar sockets of the upper and lower jaw (maxilla and mandible). The gingivae (gums) are specialized regions of the oral mucosa that surround the teeth and cover adjacent regions of the alveolar bone. Deciduous Teeth (Milk teeth): ✓ There are 20 deciduous teeth (10 at each jaw): four incisors, two canines, and four molars in each jaw. ✓ They begin to erupt about 6 months after birth and have all erupted by the end of 2 years. ✓ The teeth of the lower jaw usually appear before those of the upper jaw (specifically the incisors). Permanent Teeth: ✓ There are 32 permanent teeth (16 at each jaw): four incisors, two canines, four premolars, and six molars (including wisdom teeth) in each jaw. ✓ They begin to erupt at 6 years of age and have all erupted by the age of 12. Except for the third molar (wisdom teeth) which may happen between the ages of 17 and 30 (they may erupt normally but, some cause an infection, or they do not erupt at all). ✓ The teeth of the lower jaw appear before those of the upper jaw. 9|Page The Tongue: • • • • • • • • • The tongue is a mass of striated muscle covered with mucous membrane (has no bones). The dorsum surface of the tongue is covered by taste buds (lingual papillae). The epithelium type of the dorsum surface is stratified squamous para-keratinized (subjected to injuries which induces changes, but it is still keratinized) epithelium. And for the lower surface is stratified squamous non keratinized epithelium. Muscles attach the tongue to the styloid process and the soft palate above and to the mandible and the hyoid bone below. The tongue is divided into right and left halves by a median fibrous septum. The mucous membrane of the upper surface of the tongue can be divided into anterior 2/3 (apparent part) and posterior 1/3 (pharyngeal part) by a V-shaped sulcus, the sulcus terminalis. The apex of the sulcus projects backward and is marked by a small pit, the foramen cecum. the foramen cecum is an embryologic remnant and marks the site of the upper end of the thyroglossal duct. The posterior third contains the lingual tonsils. Sulcus terminalis Epiglottis (of larynx) Lingual tonsils Foramen cecum Palatine tonsils 10 | P a g e Taste buds (papillae): • four types of papillae are present on the upper surface of the anterior two thirds of the tongue: the filiform papillae, the fungiform papillae, the vallate (12 -18 Circumvallate papillae for bitter taste) papillae and the foliate papillae. the vallate papillae • • • • The mucous membrane covering the posterior third of the tongue is devoid of papillae but has an irregular surface caused by the presence of underlying lymph nodules, the lingual tonsil. The mucous membrane on the inferior surface of the tongue is reflected from the tongue to the floor of the mouth. In the midline anteriorly, the undersurface of the tongue is connected to the floor of the mouth by a fold of mucous membrane, the frenulum of the tongue. On the lateral side of the frenulum, the deep lingual vein can be seen through the mucous membrane. Lateral to the lingual vein, the mucous membrane forms a fringed fold called the plica fimbriata. 11 | P a g e Muscles of the Tongue: • • • The muscles of the tongue are divided into two types: intrinsic and extrinsic. Intrinsic Muscles: ✓ These muscles are confined to the tongue and are not attached to bone. ✓ They consist of longitudinal, transverse, and vertical fibers. ✓ Nerve supply: Hypoglossal nerve (motor). ✓ Action: Alter the shape of the tongue. Extrinsic Muscles: ✓ These muscles are attached to bones and the soft palate and they end by attaching to the tongue. ✓ Nerve supply: Hypoglossal nerve. Except palatoglossus by pharyngeal plexus through the vagus nerve. ✓ Insertion: Blends with each other, the palatoglossus inserts at Side of tongue ✓ the palatoglossus (origin: Palatine aponeurosis) ➔ Pulls roots of tongue upward and backward, narrows oropharyngeal isthmus. ✓ the styloglossus (O: Styloid process of temporal bone) ➔ Draws tongue upward and backward. ✓ the hyoglossus (O: Body and greater cornu (horn) of hyoid bone)➔ Depresses tongue. ✓ genioglossus (O: Superior genial spine of mandible)➔ Protrudes apex of tongue through mouth (it pulls the tongue from the posterior part outwards). So, for example if there is a patient with an injured right hypoglossal nerve and we ask him to bring out his tongue, it will be deviated toward the same paralyzed side (right side). Summary of muscle movements: • • • • • Protrusion: The genioglossus muscles on both sides acting together. Retraction: Styloglossus and hyoglossus muscles on both sides acting together. Depression: Hyoglossus muscles on both sides acting together. Retraction and elevation of the posterior third: Styloglossus and palatoglossus muscles on both sides acting together. Shape changes: Intrinsic muscles. 12 | P a g e Innervation, blood supply and lymphatic drainage of the tongue: • Sensory and taste innervation: ✓ Posterior 1/3: Glossopharyngeal for both. ✓ Anterior 2/3: sensory (lingual nerve), taste (chorda tympani). • Blood Supply: ✓ The lingual artery, the tonsillar branch of the facial artery, and the ascending pharyngeal artery supply the tongue (all branches from external carotid artery). • Venous drainage (lingual veins): ✓ The veins drain into the internal jugular vein. • Lymph Drainage: ✓ Tip of the tongue: Submental lymph nodes. ✓ Sides of the anterior two thirds: Submandibular and deep cervical lymph nodes. ✓ Posterior third: Deep cervical lymph nodes. Facial artery ascending pharyngeal artery Lingual artery 13 | P a g e Submental lymph nodes The Palate: • • • • • • • • The palate forms the roof of the mouth and the floor of the nasal cavity. is divided into two parts: the hard palate in front and the soft palate behind. Hard Palate: ✓ The hard palate is formed by the palatine processes of the maxillae (anterior part) and the horizontal plates of the palatine bones (posterior part). ✓ It is continuous behind with the soft palate. 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. 14 | P a g e • • • The mucous membrane covers the upper and lower surfaces of the soft palate. 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 which tenses the soft palate. Muscles of the soft palate: ✓ tensor veli palatini and its continuation musculus uvulae. Sometimes the uvula muscle may be divided into 2 parts by a fissure which is a defect in embryo development. ✓ the levator veli palatini which elevates the soft palate. ✓ the palatoglossus. ✓ the palatopharyngeus (from the palate to the wall of the pharynx). ✓ All are innervated by pharyngeal plexus. **doctor did not mention their origin or insertion, but you can check them from slides 20,21. 15 | P a g e Movements of the Soft Palate: • • • • • • • • If the soft palate is relaxed, the oropharyngeal isthmus would be opened with the nasopharynx, so the air can enter from the nasal cavity or from the oral cavity and both lead to the pharynx. Soft palate is opened during deglutition (swallowing). In the case of vomiting, soft palate closes the nasopharynx so the vomit can exit from the mouth. Closure occurs during the production of explosive consonants in speech. The soft palate is raised by the contraction of the levator veli palatini on each side. 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. By this means the nasal part of the pharynx is closed off from the oral part. 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 nasopalatine nerve, also a branch of the maxillary nerve, enters the front of the hard palate through the incisive foramen. The glossopharyngeal nerve 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. 16 | P a g e