Head Part 1 PDF

Nerve Supply of Muscles of Mastication All muscles of mastication are supplied by branches from the anterior division of mandibular nerve except the medial pterygoid supplied by branch from main trunk. Temporomandibular Joint Type and articular surfaces: It is a biaxial condylar synovial joint pr...

Nerve Supply of Muscles of Mastication All muscles of mastication are supplied by branches from the anterior division of mandibular nerve except the medial pterygoid supplied by branch from main trunk. Temporomandibular Joint Type and articular surfaces: It is a biaxial condylar synovial joint present between the head of mandible below, and mandibular fossa and articular tubercle above. The articular surfaces are covered by white fibrocartilage. Fibrous capsule: It is attached as follows: Above: To the margins of the mandibular fossa and articular tubercle. It is thickened laterally forming temporomandibular ligament. Below: It is attached around the neck of mandible. The capsule is also attached to the margins of the articular disc. Articular disc: An oval plate of dense fibrocartilagenous tissue which separates the joint cavity into an upper and lower compartments. Its upper surface is concavo-convex while its lower surface is concave. Its periphery is attached to the fibrous capsule all around and it receives the insertion of lateral pterygoid muscle. Ligaments: There are 3 ligaments: 1- Temporomandibular ligament: Triangular thickened band of the lateral part of the capsule. Above, it is attached to the articular tubercle. Below, it is attached to the lateral and posterior surfaces of the neck of mandible. It is the only proper ligament which supports the joint. 2- Stylomandibular ligament: From the adjacent anterior surface of the styloid process near its tip to the angle and posterior border of the ramus of mandible. 3- Sphenomandibular ligament: It lies on the medial side extending from spine of sphenoid to lingula of mandible. Movements of mandible (movements of TM joint): 1- Depression (opening the mouth): mainly by lateral pterygoid muscles assisted by gravity. Digastric, mylohyoid and geniohyoid muscles help lateral pterygoids if the movement occurs against resistance. 2- Elevation (closing the mouth, occlusal position): by medial pterygoid, temporalis and masseter muscles of both sides. 3- Protrusion (forward movement): by the lateral and medial pterygoids of both sides. The superficial fibers of masseter muscle has a small effect in protraction. 4- Retraction (backwards movement): by the posterior fibers of temporalis muscle. 5- Side to side movement (for grinding and chewing): by medial and lateral pterygoid muscles of both sides acting alternately. Nerve supply: Fine branches from the auriculo-temporal nerve and nerve to masseter. Blood supply: 1- Maxillary artery. 2- Superficial temporal artery Applied Anatomy: The mandible is dislocated only forwards. With the mouth open, the condyles are present below the articular tubercle and sudden violence, even muscular spasm (convulsive yawn) may displace one or both condyles into the infratemporal fossa infront of the articular tubercle. Trigeminal Nerve (5th Cranial Nerve) It arises from the lateral surface of the pons by 2 roots (sensory and motor roots) A- Sensory root: The largest root, it has a ganglion called trigeminal ganglion which lies in a special depression in the anterior surface of petrous bone inside the cranial cavity. The ganglion divides into 3 sensory branches (ophthalmic - maxillary and mandibular) supplying the skin of face, scalp and the anterior 2/3 of the tongue. B- Motor root: The smallest root which joins the mandibular nerve and supplies 8 muscles: 4 muscles of mastication, 2 tensor muscles (tensor palati and tensor tympani), and 2 other muscles: mylohyoid and anterior belly of digastric. Maxillary Nerve purely sensory nerve, Course: It passes forwards along the lower part of lateral wall of cavernous sinus, It leaves the middle cranial fossa through foramen rotundum to enter the pterygopalatine fossa. It enters the orbit through the inferior orbital fissure. It is now called infra-orbital nerve, which passes in the infra-orbital groove, infra-orbital canal and through the infraorbital foramen to reach the face and terminates by dividing into 3 branches: Palpebral, nasal and labial. So, the course of maxillary nerve is divided into 4 parts present in the following regions: A- Cranial cavity (middle cranial fossa). B- Pterygo-palatine fossa. C- Floor of orbit. D- Face. N.B.: In parts C and D the maxillary nerve becomes the infra-orbital nerve. Branches of Maxillary Nerve A- In cranial cavity: it gives meningeal branch (1) to dura mater of middle cranial fossa. B- In the pterygo-palatine fossa: Gives 3 types of branches: Two ganglionic branches (2): Connect maxillary nerve to spheno-palatine ganglion. Posterior superior alveolar nerve (3): It leaves the pterygo-palatine fossa to enter a foramen present in the back of maxilla. It descends in this wall to reach and supply the upper molar teeth, gum and maxillary sinus. Zygomatic nerve (4): It enters the orbit through the inferior orbital fissure and divides into two branches (5): Zygomatico-temporal nerve: Emerges from zygomatico-temporal foramen to supply the skin of anterior part of temple. Zygomatico-facial nerve: Emerges from zygomatico-facial foramen to supply the skin over the body of zygomatic bone. C- In the orbit: (the branches here arise from infra-orbital nerve). They are: Middle superior alveolar nerve (6): Arises in the infra-orbital groove and descends in the lateral wall of maxilla (maxillary sinus) to supply the upper premolars and gum and maxillary sinus. Anterior superior alveolar nerve (7): Arises in middle of infra-orbital canal and descends in the anterior wall of maxilla (maxillary sinus) to supply the upper incisors and canine. It supplies also the gum and maxillary sinus. D- In the face: The infra-orbital nerve terminates by dividing into 3 branches (8): Palpebral (P): Supplies the skin of lower eyelid. Nasal (N): Supplies the skin of side of nose. Labial branch (L): Supplies the skin of upper lip. Mandibular Nerve Origin: by two roots (large sensory and small motor) 1- Motor: The motor root of the trigeminal nerve arises from pons. 2- Sensory: Arises from the trigeminal ganglion. Course: The two roots leave the skull through the foramen ovale where they unite together just beyond the foramen forming mandibular nerve trunk. Branches: I. From the trunk: (one motor and one sensory branches): They are: A- Motor: Nerve to medial pterygoid, it gives 3 branches for 3 muscles: a. Medial pterygoid muscle. b. Tensor palati muscle. c. Tensor tympani muscle. B- Sensory: Nervus spinosus: It reaches the middle cranial fossa through foramen spinosum to supply its dura mater. II. From the anterior division: All its branches are motor except one sensory branch, they are: 1. Motor branches: a. Two branches for temporalis, called deep temporal nerves. b. Branch for masseter, passes through mandibular notch. c. Branch for lateral pterygoid. 2. Sensory branch: (Buccal nerve): It is the continuation of the anterior division of the mandibular nerve. It supplies the skin covering and the mucosa lining the buccinator muscle. III.From the posterior division: The posterior division gives off auriculo-temporal nerve, then it divides into lingual and inferior alveolar nerves. A- Auriculotemporal nerve: It arises by 2 roots around the middle meningeal artery. It passes backwards deep to the neck of mandible, then it ascends behind TM joint within the parotid gland. It leaves the upper end of the gland crossing the zygomatic arch to reach the scalp where it divides into many branches. Branches: a. Sensory branches: To skin of posterior ½ of temple, upper 2/3 of lateral surface of auricle, external auditory meatus and ear drum. b. Parotid branches: It receives the postganglionic parasympathetic and sympathetic fibers from otic ganglion to the parotid gland. c. Articular branches: To the temporo-mandibular joint. B- Inferior alveolar nerve: It is the largest branch of posterior division of mandibular nerve. It passes vertically downwards on medial pterygoid muscle, posterior to the lingual nerve to enter the mandibular foramen. It runs in the mandibular canal giving the inferior dental branches and divides at the mental foramen into two terminal branches; mental and incisive. Branches: a. Nerve to mylohyoid: (motor nerve from posterior division). It arises near the mandibular foramen, runs in the mylohyoid groove supplying the mylohyoid and anterior belly of digastric muscles. b. Dental branches: They arise in the mandibular canal supplying the lower teeth, gums, and alveolar bone. Branches to the canine and incisor teeth arise from incisive nerve while branches to the remaining teeth arise from inferior alveolar nerve itself. c. Mental nerve: It comes out from the mental foramen to supply the skin of chin and lower lip. C- Lingual nerve (one of the two terminal branches of posterior division of mandibular nerve): Course and relations: It is related to 3 parts, in this order: 1. Deep to the ramus of mandible: It passes downwards on the medial pterygoid muscle in front of inferior alveolar nerve. 2. Deep to the body of mandible: It passes downwards and forwards in a faint groove below the last molar tooth, covered with oral mucosa. 3. At the side of the tongue: It crosses styloglossus muscle, upper part of hyoglossus muscle hooking around the submandibular duct, passes forwards deep to sublingual gland to reach the tongue. On hyoglossus muscle, the submandibular ganglion is suspended from lingual nerve by two roots. Near its origin it is joined by chorda tympani (branch of facial nerve) which distributed with some of its branches, to supply: a- General sensation: For the anterior 2/3 of tongue, mucosa of the floor of the mouth and gums and for submandibular and sublingual glands. b- Taste sensation of anterior 2/3 of tongue. c- Parasympathetic fibers: They relay in the submandibular ganglion and the postganglionic fibers to supply two glands: submandibular and sublingual glands. N.B.: (branches b and c from the chorda tympani nerve). Maxillary Artery Origin The larger of the two terminal branches of external carotid artery, it begins opposite the neck of the mandible inside the parotid gland. It enter the pterygomaxillary fissure to reach the pterygopalatine fossa where it ends by dividing into many branches. It has 3 parts: A- 1st part: It passes deep to the neck of mandible horizontally to the reach the lower border of lateral pterygoid muscle. B- 2nd part: It passes obliquely upwards and forwards superficial to the lateral pterygoid muscle, in some cases the artery may pass deep to it. C- 3rd part: It dips between the two heads of lateral pterygoid muscle, passes through the pterygomaxillary fissure to reach and end in the pterygopalatine fossa. Branches of 1st part: 1- Middle meningeal artery 2- Accessory meningeal artery: It ascends in front of the middle meningeal artery to enter the foramen ovale to reach the middle cranial fossa where it supplies the trigeminal ganglion and the dura mater. 3- Inferior alveolar artery: It descends with its nerve through the mandibular foramen and canal to supply the bone of mandible and the lower teeth. It terminates inside the mandibular canal opposite the mental foramen by dividing into 2 branches; incisive and mental. It gives the mylohyoid artery, which descends in its groove with its nerve. 4- Anterior tympanic artery: It supplies the middle ear and the tympanic membrane (ear drum). 5- Deep auricular artery: Supplies the external auditory meatus and ear drum. Branches of the 2nd part: The artery gives muscular branches for the muscles of mastication and buccal artery which accompanies the buccal nerve to reach the face. Branches of the 3rd part: 1- Greater palatine artery (GPA): Descends in greater palatine canal to reach and supply the hard palate. It passes forwards and ascends in the incisive canal to reach and supply the nasal septum. It gives 2 lesser palatine arteries for the soft palate and palatine tonsils. 2- Spheno-palatine artery: It passes through spheno-palatine foramen to enter the nasal cavity supplying it. 3- Posterior superior alveolar artery: Supplies the upper molars, premolars and maxillary sinus (like the corresponding nerve). 4- Infra orbital artery: It enters the orbit through the inferior orbital fissure, traverses the infra-orbital groove and canal. It emerges from the infra-orbital foramen to reach the face where it divides into 3 branches: palpebral, nasal and labial. In infra-orbital canal it gives off the anterior superior alveolar artery supplying the anterior teeth. 5- Pharyngeal artery 6- Artery of pterygoid canal: They supply the nasopharynx. Pterygoid Venous Plexus It is a rich plexus of veins, lying superficial and deep to the lateral pterygoid muscle. It receives the veins corresponding to the branches of the maxillary artery. It ends posteriorly by forming maxillary vein which passes backwards through the parotid gland to join the superficial temporal vein forming the retromandibular vein. Communications: 1- In front: It communicates with anterior facial vein by deep facial vein. 2- Above: It communicates with cavernous sinus by emissary veins passing through the foramen ovale and foramen lacerum. 3- In front and above: It communicates with inferior ophthalmic vein by a vein that passes through the inferior orbital fissure.