The Nasal Region PDF

The Nasal region Lecture 4 The Nose The nose consists of the external nose and the nasal cavity, both of which are divided by a septum into right and left halves. External Nose Th...

The Nasal region Lecture 4 The Nose The nose consists of the external nose and the nasal cavity, both of which are divided by a septum into right and left halves. External Nose The external nose has two elliptical orifices called the nostrils, which are separated from each other by the nasal septum. The lateral margin, the ala nasi, is rounded and mobile. The framework of the external nose is made up above by the nasal bones, the frontal processes of the maxillae, and the nasal part of the frontal bone. Below, the framework is formed of plates of hyaline cartilage Nerve Supply of the External Nose The infratrochlear and external nasal branches of the ophthalmic nerve (CN V) and the infraorbital branch of the maxillary nerve Blood Supply and Venous Drainage of the External Nose The skin of the external nose is supplied by branches of the ophthalmic and the maxillary arteries. The skin of the ala and the lower part of the septum are supplied by branches from the facial artery. Nasal Cavity The nasal cavity extends from the nostrils in front to the posterior nasal apertures or choanae behind, where the nose opens into the nasopharynx. The nasal vestibule is the area of the nasal cavity lying just inside the nostril. The nasal cavity is divided into right and left halves by the nasal septum. The septum is made up of the septal cartilage, the vertical plate of the ethmoid, and the vomer. Walls of the Nasal Cavity Each half of the nasal cavity has a floor, a roof, a lateral wall & a medial or septal wall. Floor The palatine process of the maxilla and the horizontal plate of the palatine bone. Roof The roof is narrow and is formed anteriorly beneath the bridge of the nose by the nasal and frontal bones, in the middle by the cribriform plate of the ethmoid, located beneath the anterior cranial fossa, and posteriorly by the downward sloping body of the sphenoid. Lateral Wall The lateral wall has three projections of bone called the superior, middle, and inferior nasal conchae. The space below each concha is called a meatus. Sphenoethmoidal Recess The sphenoethmoidal recess is a small area above the superior concha. It receives the opening of the sphenoid air sinus. Superior Meatus The superior meatus lies below the superior concha. It receives the openings of the posterior ethmoid sinuses. Middle Meatus The middle meatus lies below the middle concha. It has a rounded swelling called the bulla ethmoidalis that is formed by the middle ethmoidal air sinuses, which open on its upper border. A curved opening, the hiatus semilunaris, lies just below the bulla. The anterior end of the hiatus leads into a funnel-shaped channel called the infundibulum, which is continuous with the frontal sinus. The maxillary sinus opens into the middle meatus through the hiatus semilunaris. Inferior Meatus The inferior meatus lies below the inferior concha and receives the opening of the lower end of the nasolacrimal duct, which is guarded by a fold of mucous membrane. Medial Wall The medial wall is formed by the nasal septum. The upper part is formed by the vertical plate of the ethmoid and the vomer. The anterior part is formed by the septal cartilage. The septum rarely lies in the midline, thus increasing the size of one half of the nasal cavity and decreasing the size of the other. Mucous Membrane of the Nasal Cavity The vestibule is lined with modified skin and has coarse hairs. The area above the superior concha is lined with olfactory mucous membrane and contains nerve endings sensitive to the reception of smell. The lower part of the nasal cavity is lined with respiratory mucous membrane. A large plexus of veins in the submucous connective tissue is present in the respiratory region. Function of Warm Blood and Mucus of Mucous Membrane The presence of warm blood in the venous plexuses serves to heat up the inspired air as it enters the respiratory system. The presence of mucus on the surfaces of the conchae traps foreign particles and organisms in the inspired air, which are then swallowed and destroyed by gastric acid. Nerve Supply of the Nasal Cavity. The olfactory nerves from the olfactory mucous membrane ascend through the cribriform plate of the ethmoid bone to the olfactory bulb. The nerves of ordinary sensation are branches of the ophthalmic division (V1) and the maxillary division (V2) of the trigeminal nerve. Blood Supply to the Nasal Cavity The arterial supply to the nasal cavity is from branches of the maxillary artery, one of the terminal branches of the external carotid artery. The most important branch is the sphenopalatine artery. The sphenopalatine artery anastomoses with the septal branch of the superior labial branch of the facial artery in the region of the vestibule. The submucous venous plexus is drained by veins that accompany the arteries. Lymph Drainage of the Nasal Cavity The lymph vessels draining the vestibule end in the submandibular nodes. The remainder of the nasal cavity is drained by vessels that pass to the upper deep cervical nodes.  The Paranasal Sinuses The paranasal sinuses are cavities found in the interior of the maxilla, frontal, sphenoid, and ethmoid bones. They are lined with mucoperiosteum and filled with air; they communicate with the nasal cavity through relatively small apertures. The maxillary and sphenoidal sinuses are present in a rudimentary form at birth; they enlarge appreciably after the eighth year and become fully formed in adolescence. Maxillary Sinus The maxillary sinus is pyramidal in shape and located within the body of the maxilla behind the skin of the cheek. The roof is formed by the floor of the orbit, and the floor is related to the roots of the premolars and molar teeth. The maxillary sinus opens into the middle meatus of the nose through the hiatus semilunaris. Frontal Sinuses The two frontal sinuses are contained within the frontal bone. They are separated from each other by a bony septum. Each sinus is roughly triangular, extending upward above the medial end of the eyebrow and backward into the medial part of the roof of the orbit. Each frontal sinus opens into the middle meatus of the nose through the infundibulum. Sphenoidal Sinuses The two sphenoidal sinuses lie within the body of the sphenoid bone. Each sinus opens into the sphenoethmoidal recess above the superior concha. Ethmoid Sinuses The ethmoidal sinuses are anterior, middle, and posterior and they are contained within the ethmoid bone, between the nose and the orbit. They are separated from the latter by a thin plate of bone so that infection can readily spread from the sinuses into the orbit. The anterior sinuses open into the infundibulum; the middle sinuses open into the middle meatus, on or above the bulla ethmoidalis; and the posterior sinuses open into the superior meatus.  Paranasal Sinuses and Their Site of Drainage Into the Nosea Sinus Site of Drainage Maxillary sinus Middle meatus through hiatus semilunaris Frontal sinuses Middle meatus via infundibulum Sphenoidal sinuses Sphenoethmoidal recess Ethmoidal sinuses Anterior group Infundibulum and into middle meatus Middle group Middle meatus on or above bulla ethmoidalis Posterior group Superior meatus Drainage of Mucus and Functions of Paranasal Sinuses The mucus produced by the mucous membrane is moved into the nose by ciliary action of the columnar cells. Drainage of the mucus is also achieved by the siphon action created during the blowing of the nose. The function of the sinuses is to act as resonators to the voice; they also reduce the weight of the skull. When the apertures of the sinuses are blocked or they become filled with fluid, the quality of the voice is markedly changed. Clinical Notes Sinusitis and the Examination of the Paranasal Sinuses Infection of the paranasal sinuses is a common complication of nasal infections. Rarely, the cause of maxillary sinusitis is extension from an apical dental abscess. The frontal, ethmoidal, and maxillary sinuses can be palpated clinically for areas of tenderness. The frontal sinus can be examined by pressing the finger upward beneath the medial end of the superior orbital margin. Here the floor of the frontal sinus is closest to the surface. The ethmoidal sinuses can be palpated by pressing the finger medially against the medial wall of the orbit. The maxillary sinus can be examined for tenderness by pressing the finger against the anterior wall of the maxilla below the inferior orbital margin; pressure over the infraorbital nerve may reveal increased sensitivity. Directing the beam of a flashlight either through the roof of the mouth or through the cheek in a darkened room will often enable a physician to determine whether the maxillary sinus is full of inflammatory fluid rather than air. This method of transillumination is simple and effective. Radiologic examination of the sinuses is also most helpful in making a diagnosis. One should always compare the clinical findings of each sinus on the two sides of the body. The frontal sinus is innervated by the supraorbital nerve, which also supplies the skin of the forehead and scalp as far back as the vertex. It is, therefore, not surprising that patients with frontal sinusitis have pain referred over this area. The maxillary sinus is innervated by the infraorbital nerve and, in this case, pain is referred to the upper jaw, including the teeth. The frontal sinus drains into the hiatus semilunaris, via the infundibulum, close to the orifice of the maxillary sinus on the lateral wall of the nose. It is thus not unexpected to find that a patient with frontal sinusitis nearly always has a maxillary sinusitis. The maxillary sinus is particularly prone to infection because its drainage orifice through the hiatus semilunaris is badly placed near the roof of the sinus. In other words, the sinus has to fill up with fluid before it can effectively drain with the person in the upright position. The relation of the apices of the roots of the teeth in the maxilla to the floor of the maxillary sinus was already emphasized.  MANDIBULAR NERVE Lecture 6 The mandibular nerve is mixed nerve with both motor and sensory. The sensory root leaves the trigeminal ganglion and passes out of the skull through the foramen ovale to enter the infratemporal fossa. The motor root of the trigeminal nerve also leaves the skull through the foramen ovale and joins the sensory root to form the trunk of the mandibular nerve and then divides into a small anterior and a large posterior divisions. Branches From the Main Trunk of the Mandibular Nerve 1- Meningeal branch 2- Nerve to the medial pterygoid muscle, which supplies the medial pterygoid muscle & the tensor veli palatini muscle. Branches From the Anterior Division of the Mandibular Nerve 1- Masseteric nerve to the masseter muscle 2- Deep temporal nerves to the temporalis muscle 3- Nerve to the lateral pterygoid muscle 4- Buccal nerve to the skin and the mucous membrane of the cheek. The buccal nerve does not supply the buccinator muscle (which is supplied by the facial nerve) and it is the only sensory branch of the anterior division of the mandibular nerve. Branches From the Posterior Division of the Mandibular Nerve 1- Auriculotemporal nerve which supplies a-the skin of the auricle. b-the external auditory meatus. c-the temporomandibular joint and d- the scalp. e- it conveys postganglionic parasympathetic secretomotor fibers from the otic ganglion to the parotid salivary gland. 2- Lingual nerve which descends in front of the inferior alveolar nerve and enters the mouth to run forward on the side of the tongue and crosses the submandibular duct. In its course, a- it is joined by the chorda tympani nerve and it supplies the mucous membrane of the anterior two thirds of the tongue and the floor of the mouth. b- it gives off preganglionic parasympathetic secretomotor fibers to the submandibular ganglion. 3- Inferior alveolar nerve which enters the mandibular canal to supply a) the teeth of the lower jaw and emerges through the mental foramen (mental nerve) to supply the skin of the chin. Before entering the canal, b- it gives off the mylohyoid nerve, which supplies the mylohyoid muscle and the anterior belly of the digastric muscle. c- communicating branch which frequently runs from the inferior alveolar nerve to the lingual nerve. The branches of the posterior division of the mandibular nerve are sensory (except the nerve to the mylohyoid muscle). Clinical Notes Injury to the Lingual Nerve The lingual nerve passes forward into the submandibular region from the infratemporal fossa by running beneath the origin of the superior constrictor muscle, which is attached to the posterior border of the mylohyoid line on the mandible. Here, it is closely related to the last molar tooth and is liable to be damaged in cases of clumsy extraction of an impacted third molar. Otic Ganglion The otic ganglion is a parasympathetic ganglion that is located medial to the mandibular nerve just below the skull, and it is adherent to the nerve to the medial pterygoid muscle. The preganglionic fibers originate in the glossopharyngeal nerve and they reach the ganglion via the lesser petrosal nerve. The postganglionic secretomotor fibers reach the parotid salivary gland via the auriculotemporal nerve.  Oral cavity Lecture 9 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 by the orbicularis oris muscle and the muscles that radiate from the lips into the face. Also included are the labial blood vessels and nerves, 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. Median folds of mucous membrane (the labial frenulae) connect the inner surface of the lips to the gums. The Oral Cavity The mouth extends from the lips to the pharynx. The entrance into the pharynx, the oropharyngeal isthmus, is formed on each side by the palatoglossal fold. The mouth is divided into the vestibule and the mouth 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 limited above and below by the reflection of the mucous membrane from the lips and cheeks to 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 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. Mouth Proper The mouth proper has a roof and a floor. Roof of Mouth The roof of the mouth is formed by the hard palate in front and the soft palate behind. Floor of Mouth The floor is formed largely by the anterior two thirds of the tongue and by the reflection of the mucous membrane from the sides of the tongue to the gum of the mandible. A 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. Lateral to the frenulum, the mucous membrane forms a fringed fold, the plica fimbriata. 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. Mucous Membrane of the Mouth In the vestibule the mucous membrane is tethered 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. Sensory Innervation of the Mouth Roof: The greater palatine and nasopalatine nerves from the maxillary division of the trigeminal nerv Floor: The lingual nerve (common 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 (the buccinator muscle is innervated by the buccal branch of the facial nerve)  Oral cavity Lecture 10 The Palate The palate forms the roof of the mouth and the floor of the nasal cavity. It 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 and the horizontal plates of the palatine bones. 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. Muscles of the Soft Palate The muscles of the soft palate are 1-the tensor veli palatini, 2-the levator veli palatini, 3- the palatoglossus, 4-the palatopharyngeus, and 5-the musculus uvulae. 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. Muscle Origin Insertion Nerve Supply Action Tensor veli Spine of With muscle of Nerve to Tenses soft palate palatini sphenoid, other side, medial auditory tube forms palatine pterygoid from aponeurosis mandibular nerve Levator veli Petrous part of Palatine Pharyngeal Raises soft palate palatini temporal bone, aponeurosis plexus auditory tube Palatoglossus Palatine Side of tongue Pharyngeal Pulls root of tongue aponeurosis plexus upward and backward, narrows oropharyngeal isthmus Palatopharyngeus Palatine Posterior border Pharyngeal Elevates wall of aponeurosis of thyroid plexus pharynx, pulls cartilage palatopharyngeal folds medially Musculus uvulae Posterior Mucous Pharyngeal Elevates uvula border of hard membrane of plexus palate uvula 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.  Temporal fossa Lecture 12 The temporal fossa is a shallow depression on the temporal region of the skull located between the superior temporal line and the zygomatic arch. It is formed by the four skull bones that meet at their junction called the pterion. These bones include: 1- The posterior part of the frontal bone 2- The anteroinferior part of the parietal bone 3- The lateral aspect of the greater wing of the sphenoid bone 4- The squamous part of the temporal bone. The borders: Superior and posterior: Superior temporal line Anteriorly: Frontal process of the zygomatic bone, zygomatic process of frontal bone Inferiorly: Zygomatic arch, infratemporal crest of greater wing of sphenoid Laterally: Temporal fascia, zygomatic arch. Contents: 1- Muscles: Temporalis muscle 2- Vessels: Superficial temporal artery and vein, middle temporal artery and vein, deep temporal arteries and veins 3- Nerves: Deep temporal nerves, zygomaticotemporal nerve, auriculotemporal nerve and temporal branches of the facial nerve. Communication: Infratemporal fossa, zygomatic canal. The infratemporal fossa The infratemporal fossa is a complex wedge shape area located at the base of the skull, deep to the masseter muscle & zygomatic arch. It is closely associated with both the temporal and pterygopalatine fossae and acts as a conduit for neurovascular structures entering and leaving the cranial cavity. The fossa is closely associated with both the pterygopalatine fossa, via the pterygomaxillary fissure, and also communicates with the temporal fossa, which lies superiorly. The Boundaries: Lateral: is formed by condylar process and ramus of the mandible bone Medial: is formed by lateral pterygoid plate; tensor veli palatine, levator veli palatine and superior constrictor muscles Anterior: is formed by posterior border of the maxillary sinus Posterior: is formed by carotid sheath Roof: is formed by greater wing of the sphenoid bone provides an important passage for the neurovascular structures transmitted through the foramen ovale and spinosum. Among these are the mandibular branch of the trigeminal nerve and the middle meningeal artery. Floor: is formed by medial pterygoid muscle Contents: 1- Muscles The infratemporal fossa is associated with the muscles of mastication. The medial and lateral pterygoids are located within the fossa itself, whilst the masseter and temporalis muscles insert and originate into the borders of the fossa. 2- Nerves The infratemporal fossa forms an important passage for a number of nerves originating in the cranial cavity. a) Mandibular nerve – a branch of the trigeminal nerve (CN V). It enters the fossa via the foramen ovale, giving rise to motor and sensory branches. The sensory branches continue inferiorly to provide innervation to some of the cutaneous structures of the face. b) Auriculotemporal, buccal, lingual and inferior alveolar nerves – sensory branches of the trigeminal nerve. c) Chorda tympani – a branch of the facial nerve (CN VII). It follows the anatomical course of the lingual nerve and provides taste innervation to the anterior 2/3 of the tongue. d) Otic ganglion – a parasympathetic collection of neurone cell bodies. Nerve fibres leaving this ganglion ‘hitchhike’ along the auriculotemporal nerve to reach the parotid gland. 3- Vasculature The infratemporal fossa contains several vascular structures: a) Maxillary artery – the terminal branch of the external carotid artery. It travels through the infratemporal fossa. Within the fossa, it gives rise to the middle meningeal artery, which passes through the superior border via the foramen spinosum. b) Pterygoid venous plexus – drains the eye and is directly connected to the cavernous sinus. It provides a potential route by which infections of the face can spread intracranially. c) Maxillary vein d) Middle meningeal vein Muscles of mastication 1) Masseter 2) Temporalis 3) Medial pterygoid 4) Lateral pterygoid The muscles of mastication develop from the first pharyngeal arch. They are therefore innervated by a branch of the trigeminal nerve (CN V), the mandibular nerve. Masseter The masseter muscle is the most powerful muscle of mastication. It is quadrangular in shape and has two parts: deep and superficial. It lies superficial to the pterygoids and temporalis muscles. The origin: The superficial part originates from maxillary process of the zygomatic bone. The deep part originates from the zygomatic arch of the temporal bone. The insertion: Both parts attach to the ramus of the mandible. The Actions: Elevation of the mandible (closes the mouth). The Innervation: Mandibular nerve (V3). Temporalis It is lodgged within the temporal fossa. The muscle is covered by tough fascia which can be harvested surgically and used to repair a perforated tympanic membrane (an operation known as a myringoplasty). The origin: from the temporal fossa of the skull The insertion: onto the coronoid process of the mandible. The Actions: 1- Elevation of the mandible (closing the mouth). 2- performs retraction of the mandible (moving the jaw posteriorly). The Innervation: Mandibular nerve (V3). Medial Pterygoid It has a quadrangular shape with two heads: deep and superficial. It is located inferiorly to the lateral pterygoid. The origin: The superficial head from the maxillary tuberosity and the pyramidal process of palatine bone. The deep head from the medial aspect of the lateral pterygoid plate of the sphenoid bone. The insertion: to the ramus of the mandible near the angle of mandible. The actions: Elevation of the mandible (closing the mouth). The Innervation: Mandibular nerve (V3). Lateral Pterygoid It has a triangular shape with two heads: superior and inferior. It has horizontally orientated muscle fibres, and thus is the major protractor of the mandible. The origin: The superior head from the greater wing of the sphenoid. The inferior head from the lateral pterygoid plate of the sphenoid. The insertion: The two heads converge into a tendon which attaches to the neck of the mandible. The actions: Bilateral action – protraction of the mandible and depression of the chin. Unilateral action – ‘side to side’ movement of the jaw. The Innervation: Mandibular nerve (V3).  The parotid gland Lecture 13 The parotid gland is a bilateral salivary gland located in the face. It produces serous saliva (a watery solution rich in enzymes) which is then secreted into the oral cavity, where it lubricates and aids in the breakdown of food. Anatomical Position The parotid gland is a bilateral structure, which displays a lobular and irregular morphology. Anatomically, it can be divided into deep and superficial lobes, which are separated by the facial nerve. It lies within a deep hollow, known as the parotid region. The parotid region is bounded as follows: Superiorly: Zygomatic arch. Inferiorly: Inferior border of the mandible. Anteriorly: Masseter muscle. Posteriorly: External ear and sternocleidomastoid. The secretions of the parotid gland are transported to the oral cavity by the Stensen duct. It arises from the anterior surface of the gland, traversing the masseter muscle. The duct then pierces the buccinator, moving medially to enter the vestibule of the mouth upon a small papilla opposite the upper second molar tooth. Anatomical Relationships The anatomical relationships of the parotid gland are of great clinical importance – particularly during parotid gland surgery. Several important neurovascular structures pass through the gland: 1- Facial nerve (CN VII): gives rise to five terminal branches within the parotid gland. These branches innervate the muscles of facial expression. 2- External carotid artery: gives rise to the posterior auricular artery within the parotid gland. It then divides into its two terminal branches (the maxillary artery and superficial temporal artery). 3- Retromandibular vein: formed within the parotid gland by the convergence of the superficial temporal and maxillary veins. It is one of the major structures responsible for venous drainage of the face. Arterial supply: by the posterior auricular and superficial temporal arteries. They are both branches of the external carotid artery, which arise within the parotid gland itself. Venous drainage: is achieved via the retromandibular vein. It is formed by unification of the superficial temporal and maxillary veins. Innervation: The parotid gland receives sensory and autonomic innervation. The autonomic innervation controls the rate of saliva production. Sensory innervation is supplied by the auriculotemporal nerve (gland) and the great auricular nerve (fascia). The parasympathetic innervation to the parotid gland has a complex path. It begins with the glossopharyngeal nerve then the nerves reach the gland via the lesser petrosal nerve to the otic ganglion. The auriculotemporal nerve then carries parasympathetic fibres from the otic ganglion to the parotid gland. Parasympathetic stimulation causes an increase in saliva production. Sympathetic innervation originates from the superior cervical ganglion (part of the paravertebral chain). Fibres from this ganglion travel along the external carotid artery to reach the parotid gland. Increased activity of the sympathetic nervous system inhibits saliva secretion, via vasoconstriction. Lymphatic drainage: There are numerous lymph nodes distributed throughout and around the substance of the parotid gland. This is an exception to the norm as all other salivary glands (both major and minor) do not have lymph nodes within the glandular tissue and have far fewer nodes surrounding them. The lymph nodes of the parotid gland are distributed throughout the superficial and deep lobes of the gland. The majority of the lymph nodes (about 90%) are found in the superficial node. The nodes themselves are situated close to the surface of the gland, between the capsule and glandular tissue. a) The superficial set of lymph nodes drains the external acoustic meatus, auricle (pinna), scalp, eyelids, and lacrimal glands in addition to the parotid gland. b) The deep set of lymph nodes drains other structures in addition to the parotid gland: external acoustic meatus, soft palate, middle ear, and nasopharynx.  The parotid gland Lecture 14 The buccal fat pad: It is one of several encapsulated fat masses in the cheek. It is a deep fat pad located on either side of the face between the buccinator muscle and several more superficial muscles (including the masseter, the zygomaticus major, and the zygomaticus minor). The inferior portion of the buccal fat pad is contained within the buccal space. It should not be confused with the malar fat pad, which is directly below the skin of the cheek. It should also not be confused with jowl fat pads. It is implicated in the formation of hollow cheeks and the nasolabial fold, but not in the formation of jowls. The buccal fat pad is composed of several parts, although exactly how many parts seems to be a point of disagreement and no single consistent nomenclature of these parts has been observed. It was described as being divided into three lobes, the anterior, intermediate, and posterior, "according to the structure of the lobar envelopes, the formation of ligaments, and the source of the nutritional vessels". Also, there are four extensions from the body of the buccal fat pad: the sublevator, the melolabial, the buccal, and the pterygoid. The nomenclature of these extensions derives from their location and proximal muscles. The anterior lobe of the buccal fat surrounds the parotid duct, which conveys saliva from the parotid gland to the mouth. It is a triangular mass with one vertex at the buccinators, one at the levator labii superioris alaeque nasi, and one at the orbicularis oris. The intermediate lobe lies between the anterior and posterior lobes over the maxilla. The intermediate lobe seems to lose a significant amount of volume between childhood and adulthood. The posterior lobe of the buccal fat pad runs from the infraorbital fissure and temporal muscle to the upper rim of the mandible and back to the mandibular ramus. Some people describe the buccal fat pad's primary function in relation to chewing and suckling, especially in infants. This theory derives some support from the loss of volume to the intermediate lobe, which would be most directly involved in chewing and sucking, from infancy to adulthood. Another proposed function is as gliding pads that facilitate the action of the muscles of mastication. The buccal fat pad may also function as a cushion to protect sensitive facial muscles from injury due to muscle action or exterior force. Clinical Relevance: Disorders of the Parotid Gland Parotid Gland Tumours The parotid gland is the most common site of a salivary gland tumour. These tumours are usually benign, such as an adenolymphoma. In contrast, tumours of the submandibular and sublingual glands are less common, but more likely to be malignant. Treatment usually involves surgical excision of the tumour and parotid gland, known as a parotidectomy. During this procedure, it is critical to identify and preserve the facial nerve and its branches. Damage to facial nerve or its branches will cause paralysis of the facial muscles. The affected muscles will lose tone, and the area will ‘sag’. The inferior eyelid can be particularly affected, falling away from the eyeball (known as ectropion). Parotitis Parotitis refers to inflammation of the parotid gland, usually as a result of an infection. The parotid gland is enclosed in a tough fibrous capsule. This limits swelling of the gland, producing pain. The pain produced can be referred to the external ear,why? This is because the auriculotemporal nerve provides sensory innervation to the parotid gland and the external ear. Parotid Duct Injury The parotid duct, which is a comparatively superficial structure on the face, may be damaged in injuries to the face or may be inadvertently cut during surgical operations on the face. The duct is about 2 in. (5 cm) long and passes forward across the masseter about a fingerbreadth below the zygomatic arch. It then pierces the buccinator muscle to enter the mouth opposite the upper second molar tooth. Parotid Salivary Gland and Lesions of the Facial Nerve The parotid salivary gland consists essentially of superficial and deep parts, and the important facial nerve lies in the interval between these parts. A benign parotid neoplasm rarely, if ever, causes facial palsy. A malignant tumor of the parotid is usually highly invasive and quickly involves the facial nerve, causing unilateral facial paralysis. The parotid gland may become acutely inflamed as a result of retrograde bacterial infection from the mouth via the parotid duct. The gland may also become infected via the bloodstream, as in mumps. In both cases the gland is swollen; it is painful because the fascial capsule derived from the investing layer of deep cervical fascia is strong and limits the swelling of the gland. The swollen glenoid process, which extends medially behind the temporomandibular joint, is responsible for the pain experienced in acute parotitis when eating. Frey's Syndrome Frey's syndrome is an interesting complication that sometimes develops after penetrating wounds of the parotid gland. When the patient eats, beads of perspiration appear on the skin covering the parotid. This condition is caused by damage to the auriculotemporal and great auricular nerves. During the process of healing, the parasympathetic secretomotor fibers in the auriculotemporal nerve grow out and join the distal end of the great auricular nerve. Eventually, these fibers reach the sweat glands in the facial skin. By this means, a stimulus intended for saliva production produces sweat secretion instead.  The Pterygopalatine fossa Lecture 15 The pterygopalatine fossa is an inverted pyramidal-shaped, fat-filled space located on the lateral side of the skull, between the infratemporal fossa and the nasopharynx. The contents of the pterygopalatine fossa:. 1- the maxillary nerve [V2] 2- the pterygopalatine ganglion 3- the terminal part of the maxillary artery 4- the veins, as well as their associated tributaries.. Boundaries: The walls of the pterygopalatine fossa are formed by three bones of the skull: 1-Maxilla 2-Palatine Bone 3-Sphenoid Bone The anterior wall is formed by the posterior surface of the maxilla. The medial wall is formed by the lateral surface of the palatine. The roof and the posterior wall are formed by the sphenoid, specifically the anterosuperior surface of its pterygoid process. Communications: The pterygopalatine fossa serves as a gateway for seven openings that communicate with 1- the orbit 2- the nasal cavity 3- the oral cavity 4- the middle cranial fossa 5- the infratemporal fossa 6- the nasopharynx Openings: These openings transmit branches of the maxillary nerve (V2), the pterygopalatine ganglion, and the maxillary vessels. The seven openings are the: 1-pterygomaxillary fissure 2-foramen rotundum 3-pterygoid canal 4-palatovaginal canal 5-inferior orbital fissure 6-palatine canal 7-sphenopalatine foramen Pterygomaxillary fissure The pterygomaxillary fissure is located between the anterior and posterior wall of the pterygopalatine fossa. It communicates with the infratemporal fossa and transmits the posterior superior alveolar nerve and the maxillary artery. Foramen rotundum The foramen rotundum is located on the posterior wall of the pterygopalatine fossa, superior to the pterygoid canal. It communicates with the middle cranial fossa and from there, it transmits the maxillary nerve (V2). Pterygoid canal The pterygoid canal is located on the posterior wall of the pterygopalatine fossa, between the foramen rotundum and the palatine canal. It communicates with the middle cranial fossa and from there, it transmits the nerve, artery, and vein of the pterygoid canal. Palatovaginal canal The palatovaginal canal is located on the posterior wall of the pterygopalatine fossa, inferior to the pterygoid canal. It communicates with the nasal cavity and transmits the pharyngeal branches of the maxillary nerve and artery. Inferior orbital fissure The inferior orbital fissure is located on the superior border of the pterygopalatine fossa. It communicates with the orbit and transmits the zygomatic nerve and the infraorbital artery and vein. Palatine canal The palatine canal is located inferiorly at the pterygopalatine fossa. It communicates with the oral cavity via the greater palatine and the lesser palatine canals, which transmit the greater palatine and lesser palatine nerves, respectively. The palatine canal also transmits the greater palatine artery. Sphenopalatine foramen The sphenopalatine foramen is located on the medial border of the pterygopalatine fossa. It communicates with the lateral wall of the nasal cavity and transmits nasal nerves and the sphenopalatine artery. Maxillary nerve The maxillary nerve arises from the trigeminal ganglion in the middle cranial fossa. It passes forward in the lateral wall of the cavernous sinus and leaves the skull through the foramen rotundum and crosses the pterygopalatine fossa to enter the orbit through the inferior orbital fissure. It then continues as the infraorbital nerve in the infraorbital groove, and it emerges on the face through the infraorbital foramen. It gives sensory fibers to the skin of the face and the side of the nose. Branches: 1-Meningeal branches 2-Zygomatic branch, which divides into the zygomaticotemporal and the zygomaticofacial nerves that supply the skin of the face. The zygomaticotemporal branch gives parasympathetic secretomotor fibers to the lacrimal gland via the lacrimal nerve. 3-Ganglionic branches, which are two short nerves that suspend the pterygopalatine ganglion in the pterygopalatine fossa. They contain sensory fibers that have passed through the ganglion from the nose, the palate, and the pharynx. They also contain postganglionic parasympathetic fibers that are going to the lacrimal gland. 4-Posterior superior alveolar nerve, which supplies the maxillary sinus as well as the upper molar teeth and adjoining parts of the gum and the cheek 5-Middle superior alveolar nerve, which supplies the maxillary sinus as well as the upper premolar teeth, the gums, and the cheek 6-Anterior superior alveolar nerve , which supplies the maxillary sinus as well as the upper canine and the incisor teeth. THE PTERYGOPALATINE GANGLION The pterygopalatine ganglion gives rise to the following nerves: 1) the nasopalatine nerve 2) the lesser palatine nerve 3) the greater palatine nerve 4) the posterior superior lateral nasal nerve 5) the posterior inferior lateral nasal nerves 6) pharyngeal nerve The posterior inferior lateral nasal nerves branch off from the greater palatine nerve in the pterygopalatine canal to innervate the medial and inferior nasal meatuses, along with the inferior nasal concha. The posterior superior lateral nasal nerves directly project from the pterygopalatine ganglion to go through the sphenopalatine foramen to enter the nasal cavity posteriorly to innervate the middle and superior nasal conchae, the posterior aspect of the nasal septum, and the posterior ethmoidal air cells. The maxillary nerve, with its purely sensory axonal fibers, serves as a pathway for the post- ganglionic sympathetic and parasympathetic fibers of the pterygopalatine ganglion. The autonomic fibers of the pterygopalatine ganglion traverse with branches of the maxillary nerve that include the zygomatic, posterior superior alveolar, and infra-orbital nerves. The post-ganglionic sympathetic and parasympathetic fibers that travel with the zygomatic nerve are especially important because these nerves are what ultimately provide innervation to the lacrimal gland. The nasopalatine nerve exits the pterygopalatine fossa from the sphenopalatine foramen and emerges within the posterior aspect of the nasal cavity. It continues within the nasal cavity along the nasal septum in an anteroinferior direction, traversing a groove in the vomer and providing branches along its trajectory. It ultimately passes through the incisive canal and fossa to innervate the gingiva and mucosa of the anterior hard palate, just posterior to the maxillary incisors and canine teeth. The greater palatine nerve innervates the remaining portion of the hard palate’s gingiva and mucosa. The lesser palatine nerve is responsible for providing innervation to the soft palate, uvula, and tonsil. The soft palate communicates the sensation of taste from the lesser palatine nerve to the greater petrosal nerve. The pharyngeal nerve, which branches off of the pterygopalatine ganglion, exits the pterygopalatine fossa via the palatovaginal canal. It is responsible for providing innervation to the mucosa and glands of the nasopharynx. THE VEINS OF THE PTERYGOPALATINE FOSSA The veins of the pterygopalatine fossa are small and variable. The most consistent is the sphenopalatine vein. This vein drains the posterior aspect of the nose and passes into the pterygopalatine fossa through the sphenopalatine foramen. It drains into the pterygoid venous plexus via the pterygomaxillary fissure. The inferior ophthalmic vein in the floor of the orbit provides a connecting branch to the pterygoid venous plexus. This vein passes through the inferior orbital fissure in the region of the pterygopalatine fossa.  Temporomandibular joint Lecture 16  Introduction Articulation occurs between the articular tubercle and the anterior portion of the mandibular fossa of the temporal bone above and the head (condyloid process) of the mandible below. The articular surfaces are covered with fibrocartilage. Type of Joint The temporomandibular joint is synovial. The articular disc divides the joint into upper and lower cavities.  Capsule The capsule surrounds the joint and is attached above to the articular tubercle and the margins of the mandibular fossa and below to the neck of the mandible.  Ligaments 1-The lateral temporomandibular ligament: strengthens the lateral aspect of the capsule, and its fibers run downward and backward from the tubercle on the root of the zygoma to the lateral surface of the neck of the mandible. This ligament limits the movement of the mandible in a posterior direction and thus protects the external auditory meatus. 2-The sphenomandibular ligament: lies on the medial side of the join. It is a thin band that is attached above to the spine of the sphenoid bone and below to the lingula of the mandibular foramen. It represents the remains of the first pharyngeal arch in this region. 3-The stylomandibular ligament: lies behind and medial to the joint and some distance from it. It is merely a band of thickened deep cervical fascia that extends from the apex of the styloid process to the angle of the mandible.  The Articular Disk The articular disc divides the joint into upper and lower cavities. It is an oval plate of fibrocartilage that is attached circumferentially to the capsule. It is also attached in front to the tendon of the lateral pterygoid muscle and by fibrous bands to the head of the mandible. These bands ensure that the disc moves forward and backward with the head of the mandible during protraction and retraction of the mandible. The upper surface of the disc is concavoconvex from before backward to fit the shape of the articular tubercle and the mandibular fossa; the lower surface is concave to fit the head of the mandible.  Retrodiscal Tissue Retrodiscal tissue - Unlike the disc itself, the retrodiscal tissue is vascular and highly innervated. As a result, the retrodiscal tissue is often a major contributor to the pain of Temporomandibular Disorder (TMD), particularly when there is inflammation or compression within the joint The retrodiscal zone (bilaminar zone) of the TMJ is located between the posterior band of the articular disc and the posterior part of the articular capsule. It contains the two layers attaching the articular disc and vasculonervous structures: The superior retrodiscal layer of the TMJ joint is a lamina composed of connective tissue and elastic fibers that continues the posterior part of the articular disk and connects the disc to the tympanic plate of the temporal bone. The inferior retrodiscal layer of the TMJ joint is a lamina composed of collagen fibers that continues the posterior part of the articular disk and inserts into the condylar neck.  Synovial Membrane This lines the capsule in the upper and lower cavities of the joint).  Temporomandibular joint Lecture 17  Nerve Supply Auriculotemporal and masseteric branches of the mandibular nerve  Vascular Supply The TMJ is supplied mainly by three arteries. The main supply comes from 1-the deep auricular artery (from the maxillary artery) and 2-the superficial temporal artery (a terminal branch Of the external carotid artery). In addition, the joint is supplied by 3-the anterior tympanic artery (also a branch of the maxillary artery). The venous drainage of the TMJ is via the superficial temporal vein and the maxillary vein.  Movements The mandible can be depressed or elevated, protruded or retracted. Rotation can also occur, as in chewing. In the position of rest, the teeth of the upper and lower jaws are slightly apart. On closure of the jaws, the teeth come into contact. Depression of the Mandible As the mouth is opened, the head of the mandible rotates on the undersurface of the articular disc around a horizontal axis. To prevent the angle of the jaw impinging unnecessarily on the parotid gland and the sternocleidomastoid muscle, the mandible is pulled forward. This is accomplished by the contraction of the lateral pterygoid muscle, which pulls forward the neck of the mandible and the articular disc so that the latter moves onto the articular tubercle. The forward movement of the disc is limited by the tension of the fibroelastic tissue, which tethers the disc to the temporal bone posteriorly. Depression of the mandible is brought about by contraction of the digastrics, the geniohyoids, and the mylohyoids; the lateral pterygoids play an important role by pulling the mandible forward. Elevation of the Mandible The movements in depression of the mandible are reversed. First, the head of the mandible and the disc move backward, and then the head rotates on the lower surface of the disc. Elevation of the mandible is brought about by contraction of the temporalis, the masseter, and the medial pterygoids. The head of the mandible is pulled backward by the posterior fibers of the temporalis. The articular disc is pulled backward by the fibroelastic tissue, which tethers the disc to the temporal bone posteriorly. Protrusion of the Mandible The articular disc is pulled forward onto the anterior tubercle, carrying the head of the mandible with it. All movement thus takes place in the upper cavity of the joint. In protrusion, the lower teeth are drawn forward over the upper teeth, which is brought about by contraction of the lateral pterygoid muscles of both sides, assisted by both medial pterygoids. Retraction of the Mandible The articular disc and the head of the mandible are pulled backward into the mandibular fossa. Retraction is brought about by contraction of the posterior fibers of the temporalis. Lateral Chewing Movements These are accomplished by alternately protruding and retracting the mandible on each side. For this to take place, a certain amount of rotation occurs, and the muscles responsible on both sides work alternately and not in unison. Muscle Origin Insertion Nerve Supply Action Masseter Zygomatic arch Lateral surface ramus Mandibular Elevate mandible to occlude of mandible nerve teeth Temporalis Floor of temporal Coronoid process of Mandibular Anterior & superior fibers fossa mandible nerve elevate mandible while posterior fibers retract mandible Digastric Posterior Mastoid process of Intermediate tendon is Facial nerve Depresses mandible or belly temporal bone held to hyoid by fascial elevates hyoid bone sling Anterior Body of mandible Nerve to belly mylohyoid Mylohyoid Mylohyoid line of Body of hyoid bone and Inferior alveolar Depresses mandible or body of mandible fibrous raphe nerve elevates floor of mouth and hyoid bone Geniohyoid Inferior mental spine Body of hyoid bone First cervical depresses mandible or of mandible nerve Elevates hyoid bone lateral Greater wing of Neck of mandible & Ansa cervicalis; Depresses hyoid bone pterygoid sphenoid & lateral articular disc C1, 2, and 3 pterygoid plate Mandibular nerve Pull neck of mandible forward Medial Tuberosity of maxilla Oblique line on lamina Mandibular Elevate mandible pterygoid & & lateral pterygoid of thyroid cartilage nerve plate Important Relations of the Temporomandibular Joint Anteriorly: The mandibular notch and the masseteric nerve and artery. Posteriorly: The tympanic plate of the external auditory meatus and the glenoid process of the parotid gland. Laterally: The parotid gland, fascia, and skin. Medially: The maxillary artery and vein and the auriculotemporal nerve.  Clinical Notes Clinical Significance of the Temporomandibular Joint The temporomandibular joint lies immediately in front of the external auditory meatus. The great strength of the lateral temporomandibular ligament prevents the head of the mandible from passing backward and fracturing the tympanic plate when a severe blow falls on the chin. The articular disc of the temporomandibular joint may become partially detached from the capsule, and this results in its movement becoming noisy and producing an audible click during movements at the joint. Dislocation of the Temporomandibular Joint Dislocation sometimes occurs when the mandible is depressed. In this movement, the head of the mandible and the articular disc both move forward until they reach the summit of the articular tubercle. In this position, the joint is unstable, and a minor blow on the chin or a sudden contraction of the lateral pterygoid muscles, as in yawning, may be sufficient to pull the disc forward beyond the summit. In bilateral cases the mouth is fixed in an open position, and both heads of the mandible lie in front of the articular tubercles. Reduction of the dislocation is easily achieved by pressing the gloved thumbs downward on the lower molar teeth and pushing the jaw backward. The downward pressure overcomes the tension of the temporalis and masseter muscles, and the backward pressure overcomes the spasm of the lateral pterygoid muscles.