Oral cavity.pdf

ORAL CAVITY - Oral cavity or the mouth, it represents the first part of the digestive system, the main functions of this part are: 1- Mastication. 2- Salvation. 3- Swallowing. 4- Tasting. 5- Speech. - The oral cavity opens anteriorly through the t...

ORAL CAVITY - Oral cavity or the mouth, it represents the first part of the digestive system, the main functions of this part are: 1- Mastication. 2- Salvation. 3- Swallowing. 4- Tasting. 5- Speech. - The oral cavity opens anteriorly through the transverse oral fissure (which is guarded by upper and lower lip). - Posteriorly, the oral cavity is connected with the oropharynx through the isthmus of the fauces(oropharyngeal isthmus), it is bounded by the soft palate superiorly, by the surface of the posterior one third of the tongue inferiorly and by the palatoglossal archs laterally.  Boundaries of the oral cavity: - Anterolaterally, or the anterior lateral wall is formed by the lips and cheeks. - The roof is formed by the upper jaw (maxilla, hard and soft palate). - The floor is formed by the lower jaw (mandible, mylohyoid muscle which forms the muscular diaphragm. The oral cavity is divided into two parts: 1) The vestibule: which is a narrow space located between the teeth and the mucosa (which lines the lips and cheeks). 2) The oral cavity proper: which is the space between the upper and lower dental arches. The roof (palate): - The palate separates the nasal cavity above from the oral cavity below. - The anterior two thirds of the palate contain a bony skeleton called the hard palate. - The posterior third is formed by a movable portion which consists no bony skeleton and called the soft palate. - The mouth is one of the important areas of the body that must be examined, to recognize all the structures visible in the mouth and be familiar with the normal variations in the color of the mucous membrane covering underlying structures. The sensory nerve supply and lymph drainage of the mouth cavity should be known. -  HARD PALATE  The hard palate: it’s formed by two bones: - Anteriorly: palatine process of the maxilla which forms the anterior two thirds of the hard palate. - Posteriorly: formed by horizontal plate of the palatine bone. There are 3 foramina open in the hard palate: 1- Anteriorly, incisive foramen (or fossa), opens behind the maxillary central incisors in the midline, and transmits the nasopalatine nerves and vessels. 2- The greater palatine foramen, located medial to the root of the third molar and transmits the greater palatine nerves and vessels. 3- The lesser palatine foramen, located posterior to the greater palatine and medial to the maxillary tuberosity, transmits the lesser palatine nerves and vessels. The mucosa of the hard palate is tightly bound to the underlying bones. Behind the maxillary central incisors, the incisive papilla, which the incisive foramen is located beneath it. Number of parallel transverse ridges known as rugae, radiate laterally from the incisive papilla. The midline palatine raphe runs posteriorly from the incisive papilla. There are also numerous glands open into the mucosa as small pits.  SOFT PALATE  The soft palate: (it has no bony parts) - It is a movable portion, attached anteriorly to the posterior border of the hard palate, while posteriorly, it ends as a free edge with a small projection called uvula. - The soft palate separates the oropharynx from the nasopharynx above.The superior surface is covered with respiratory mucosa while the inferior surface is covered with oral mucosa. - - It’s composed of: 1- Palatine aponeurosis. 2- Five pairs of muscles. Muscles of the soft palate: 1) Palatopharyngeal (Palatopharyngeus) muscle: (PPM) - It originates from the palatine aponeurosis and inserts in the lateral wall of pharynx. - This muscle is covered by mucous membrane, that’s why it’s called “posterior pillar” or “palatopharyngeal arch”. 2) Palatoglossus muscle: (PGM) - Originates from the palatine aponeurosis and inserts in the side of the tongue. - It’s covered by mucous membrane to form the “anterior pillar” or “palatoglossus arch”. Isthmus of fauces is present in the space between the right and left palatoglossus arch. 3) Levator (vell) palatini muscle: - Originates from the medial aspect of the auditory tube, it passes downward, medialward and inserts in the palatine aponeurosis. 4) Tensor(vell) palatini muscle: - Originates from the lateral surface of the auditory tube and inserts in the upper surface of the palatine aponeurosis. 5) Uvular muscle: - Arises from the posterior nasal spine, directs posteriorly and inserts in the uvula. Actions of these muscles: - Palatopharyngeus M. + Palatoglossus M. (with the help of the uvular M.), they seal the oropharynx from the oral cavity by approximate the soft palate with the posterior third of the tongue. - Levator palatini M.: it acts to elevate the soft palate in order to seal the nasopharynx from the oropharynx. - Tensor palatini M.: it makes the soft palate rigid or tense in order to let the other muscles act. Nerve supply of the palate: - The nerve supply is from the pterygopalatine ganglion associated with the maxillary nerve. 1- Nasopalatine nerve: arises from the pterygopalatine ganglion and passes to the nasal cavity along the nasal septum, it appears in the oral cavity by passing through the incisive foramen. - It supplies the mucous membrane of the lingual mucosa and palatal mucosa anterior to the maxillary canines. 2- Greater palatine nerve: arises from the pterygopalatine ganglion and passes inferiorly through the greater palatine canal to appear in the oral cavity by passing through the greater palatine foramen. - It supplies the remainder part of the mucous membrane of the hard palate. 3- Lesser palatine nerve: arises from the pterygopalatine ganglion and passes inferiorly through the lesser palatine canal, it appears in the oral cavity by passing through the lesser palatine foramen - It supplies the mucous membrane of the soft palate. Blood supply: - The arterial supply is closely parallel to the nerve supply. - Arising from the 3rd part of the maxillary artery as: 1- Nasopalatine artery. 2- Greater palatine artery. 3- Lesser palatine artery.  Clinical Notes (palate) a) Paralysis of the muscles of soft palate (because of the damage of vagus nerve or the cranial part of accessory nerve) is characterized by: 1- Nasal regurgitation of liquid. 2- Nasal twang in voice. 3- Flattening of palatal arches on the side of lesion and deviation of uvula to opposite side. b) Osseous protrusions, palatal tori (is a bony protrusion on the palate). may be observed on the hard palate. These tori, usually bilateral, they can interfere with fitting of maxillary dentures. They may need to be removed surgically before the taking of impressions. c) The soft palate is a movable structure and must be avoided by the posterior aspect of the maxillary denture because its muscular action will break the palatal seal and dislodge the prosthesis. d) A cleft refers to a gap/split in the palate. It results from a defect during development when the palatal parts fail to fuse with each other. It may combine with cleft lip  Unilateral cleft palate  Bilateral cleft palate  Incomplete or partial cleft  Bifid uvula-cleft affecting only uvula  Cleft of soft palate-affecting uvula and soft palate  Cleft of soft palate-extending into the hard palate THE TONGUE  The tongue is a muscular organ covered by mucous membrane. It is located in two regions: 1- In the oral cavity (in the floor of the mouth). 2- In the oropharynx (ventral wall). - It’s an important organ in: a) Mastication. b) Swallowing. c) Tasting. d) Speech. Parts of the tongue 1- Body of the tongue: it’s the anterior two thirds of the tongue which is located in the oral cavity. 2- The root of the tongue: it’s the posterior one third of the tongue, located in the oropharynx.It consist of numerous lymphoid aggregates known as the lingual tonsils. 3- The sulcus terminalis: a V- shaped groove, the apex of this groove is directed posteriorly. It divides the tongue into anterior two thirds and posterior one third. 4- The foramen cecum: a small pit at the apex of the sulcus terminalis. 5- The dorsum: it’s the superior surface of the body which is characterized by rough appearance because of small numerous projections called “Lingual papillae” which are of 3 types: a- Filiform. b- Fungiform. c- Vallate papilla. Within the wall of some papillae (especially the vallate), there are receptor organs for special sensation of taste called “taste buds”. The dorsum of the body possesses the median sulcus, a shallow groove.Deep to this sulcus there is a vertical fibrous tissue called median lingual septum which partly dividing the tongue longitudinally in the midline into right and left halves. This septum united posteriorly to hyoid bone and some muscle fibers of intrinsic muscles attach to it. 6- Inferior surface of the body: is covered by a thin mucous membrane without papillae. In the median part, there’s a prominent fold known as “Lingual frenulum” which connects the tongue with the mandible and the floor of the mouth. On each side of the inferior surface, there’s an irregular fold called “fimbriate fold”, between the frenulum and the fold, there are deep lingual veins. Muscles of the tongue - The tongue is composed of voluntary striated skeletal muscle. - A thin median fibrous septum divides the tongue into right and left halves. - There are 2 types of muscles found within the tongue: 1) Intrinsic muscles: originate and insert within the tongue. Action: change the tongue’s shape. 2) Extrinsic muscles: originate from structures adjacent to the tongue and insert into the tongue. Action: move the body of the tongue. Extrinsic muscles There are 3 muscles: 1- Genioglossus muscle: it has a fan shape. Originates from the superior mental spine of the mandible and it is directed upward. - Inserts into the posterior aspect of the tongue (along the entire length of the dorsum). - Its action is to pull the dorsum of the tongue forward (protrude the tongue). 2- Hyoglossus muscle: it’s quadrant in shape. - Originates from the hyoid bone, directed upward and anteriorly. - Inserts into the lateral aspect of the tongue. - Its action is to pull the sides of the tongue downward, depress the dorsum and also help in the retraction of the tongue. 3- Styloglossus muscle: - Originates from the anterior aspect of the styloid process, passes downward and forward. - Inserts into the lateral aspect of the tongue. - It acts to draw up the sides of the tongue which helps for the swallowing, also helps in retraction of the tongue. Intrinsic muscles 1- Longitudinal fibers: they are distributed as superior and inferior bundles. Their action is to shorten the length of the tongue. 2- Transverse fibers: run horizontally at the right angles just below the superior longitudinal bundle. They act to narrow or broaden the tongue. 3- Vertical fibers: run from the dorsum of the tongue down to the inferior surface. They act to flatten and broaden the tongue.  Nerve supply of the tongue - Motor nerve supply: all muscles of the tongue (extrinsic + intrinsic) are supplied by the Hypoglossal N. (CN XII). - Sensory nerve supply: the mucous membrane of the tongue is supplied by two types of fibers; General sensation and special sensation (taste). 1) General sensation: a- The lingual N.: a branch of the mandibular nerve, it carries general sensation to the anterior two thirds of the tongue. b- The glossopharyngeal N. (CN IX): carries general sensation to the posterior third of the tongue. c- The vagus N. (CN X): carries general sensation to the area surrounding the epiglottis. 2) Special sensation: a- The facial N.: through the corda tympani, which conveys taste sensation to the anterior two thirds of the tongue. b- The glossopharyngeal N.: carries taste sensation to the posterior one third of the tongue. c- The vagus N.: carries taste sensation to the area surrounding the epiglottis. Blood supply Through the lingual artery (branch of the external carotid artery).It gives: 1 - Dorsal lingual artery : supply the root of the tongue. 2- Sublingual artery: supply the sublingual salivary gland and anastomosis with the submental artery of the facial artery. 3- Deep lingual artery: as the lingual artery terminates near the lingual frenulum on the ventral surface of the tongue, it is called as the deep lingual artery. Veins of the tongue: The veins of the tongue are named similarly to the arteries that they accompany. As the deep lingual vein forms adjacent to the apex of the tongue, it courses along the ventral surface of the tongue (deep to the mucosa). As the deep lingual vein anastomosis with the sublingual vein, they become the lingual vein , which is usually empty into the internal jugular vein. Lymphatic drainage of the tongue: The tip of the tongue drains to submental lymph nodes. The lateral aspect of the anterior two thirds drain into the submandibular lymph nodes. The medial portion of the anterior two thirds drain into the deep cervical lymph nodes. The posterior third drains posteriorly to the retropharyngeal lymph nodes.  Clinical notes for tongue:  The inflammation of the tongue is called “Glossitis”.  Any ulcer or lesion which fails to heal within one’s mouth should be considered to be malignant until proved innocent. - Injury to the hypoglossal nerve on one side results in paralysis of the tongue on that side and atrophy of its muscles. The tongue surface becomes wrinkled, and when protruded, it deviates to the injured side. - lingual nerve injury may be caused by: third molar removal, local anesthesia, implants. - Symptoms after an injury to the lingual nerve include the following: 1. Numbing of the tongue and loss of general sensation to the anterior 2/3 of tongue and the floor of mouth. 2. Loss of taste or altered taste of the anterior 2/3 of tongue. 3. Decreased secretion of saliva. 4. A tingling or burning sensation in the tongue. 5. Impaired speech. 6. Damage of chorda tympani: Injury to the chorda tympani nerve leads to the loss (ageusia) or the distortion of taste from anterior 2/3 of tongue, and a decreased salivation which results to dryness of mouth (xerostomia). Hypoglossal nerve injery: Difficult third molar extractions and/or fractures of the mandible may damage the hypoglossal nerve (cranial nerve XII), causing paralysis of the tongue on the affected side. When the mouth is opened and the tongue is protruded, the genioglossus of the unaffected side will cause the tongue to deviate to the affected side. If the damage is prolonged, the tongue muscles will atrophy. A wound of the tongue is often caused by the patient’s teeth following a blow on the chin when the tongue is partly protruded from the mouth. It can also occur when a patient accidentally bites the tongue while eating, during recovery from an anesthetic, or during an epileptic attack. Bleeding is stopped by grasping the tongue between the finger and thumb posterior to the laceration, thus occluding the branches of the lingual artery.  Congenital disorders - Complete absence of the tongue – Aglossia. - Short and incompletely formed tongue – Hypoglossia. - Ankyloglossia (tongue-tie): refers to a condition in which the lingual frenulum that attaches the ventral surface of the tongue to the floor of the mouth is too short. - The infant would be unable to protrude the tongue and some disorder may make breastfeeding. The frenulum tends to elongate over time. Some individuals may also present later in life with difficulties with articulation (disturbance of speech). - The defect can be surgically corrected with a frenulectomy (surgical division of the frenulum).  Lingual thyroid gland Ectopic thyroid glands at the base of the tongue have been classified as lingual thyroid glands. This is occurred  when a part of or all of the thyroid gland fails to descend. Patients may experience obstructive symptoms (i.e. difficult swallowing, problems with phonation, and difficult breathing). Some patients are fortunate to remain asymptomatic.  Lingual cancer: Cancer of the tongue is the most common cancer of the oral cavity (36.2%). About 95% of the cancers located on the tongue and floor of the mouth are squamous cell carcinomas that are related with a history of high use of alcohol and tobacco.