Oral Cavity 57n1z

DEPARTMENT OF ANATOMY

ORAL CAVITY

Dr. SREEKANTH THOTA

Pterion

Infratemporal fossa

Bounded by the inferior temporal line, frontal process of zygomatic bone & zygomatic arch.  Contains the temporalis muscle, deep temporal artery & nerve & zygomaticotemporal nerve.  Pterion is an important landmark. 

 The

mandible is the bone of the lower jaw.  It consists of a body of right and left parts, which are fused anteriorly in the midline, and two rami.  The site of fusion is visible on the external surface of the bone as a small vertical ridge in the midline (mandibular symphysis).

 The

upper surface of the body of mandible bears the alveolar arch, which anchors the lower teeth, and on its external surface on each side is a small mental foramen.

 The

ramus of mandible, one on each side, is quadrangular shaped and oriented in the sagittal plane. On the medial surface of the ramus is a large mandibular foramen for transmission of the inferior alveolar nerve and vessels.  Above the anterior one-third of the mylohyoid line is a shallow depression (the sublingual fossa), and below the posterior two-thirds of the mylohyoid line is another depression (the submandibular fossa).

 

1. 2.

3. 4. 5.

Area behind the maxilla. Communicates with the orbit via the inferior orbital fissure & the pterygopalatine fossa via the pterygomaxillary fissure. Contains: Mandibular nerve Chorda Tympani nerve Maxillary artery Medial & lateral pterygoids Lower part of temporalis

Synovial t (Gliding) between the:  Condyle of mandible  Mandibular fossa & articular tubercle of temporal bone Capsule:  Loose capsule surrounds the t & extends posteriorly to enclose part of the neck of the mandible.

 Fibrocartilage

that separates the t cavity into an upper & lower compartment.  The gliding movements of protrusion and retrusion (translation) occur in the superior compartment  Hinge movements of depression and elevation occur in the inferior compartment.

Slight opening of jaw = Hinge action.

Jaw opens widely = Hinge + sliding forward movement



 



Temporomandibular ligament: Reinforces t on the lateral surface. Sphenomandibular ligament: From the spine of sphenoid to the lingula of mandible. Lies on the medial side of the TMJ. Stylomandibular ligament: From the styloid process to the ramus of mandible above the angle.

Important muscles supplied by the mandibular nerve. 1. 2. 3. 4. 5. 6.

Temporalis Masseter Medial Pterygoid Lateral Pterygoid Anterior belly of Digastric Mylohyoid

 Extends

from the temporal fossa to the coronoid process & anterior border of the ramus.  Elevates & retracts the mandible.

 Extends

from the inferior surface of the zygomatic arch to the angle of the mandible.  Elevates the mandible.  Crossed superficially by the transverse facial artery, parotid duct & buccal branch of facial nerve.

 Arises

from the greater wing of sphenoid & lateral pterygoid plate.  Attaches to the neck of the mandible & the articular disc.  Protracts & depresses the mandible.  Deviates mandible to the other side.

 Arises

from the medial surface of the lateral pterygoid plate & maxillary tuberosity.  Attaches to the medial surface of the angle of the mandible.  Protracts & elevates the mandible.

Terminal branch of the external carotid artery given deep to the neck of the mandible.  Lies superficial (or in some cases deep) to the lateral pterygoid muscle.  Runs in the infratemporal fossa towards the pterygomaxillary fissure.  Divided into 3 parts. 

First part

Second Part

Third Part

Deep auricular

Deep Temporal

Posterior superior alveolar Artery of Pterygoid canal Infraorbital

Anterior Masseteric tympanic Middle Pterygoid meningeal Inferior alveolar Buccinator

Accessory Meningeal

Pharyngeal

Descending palatine Sphenopalatine

 Veins

that drain regions supplied by arteries branching from the maxillary artery in the infratemporal fossa and pterygopalatine fossa connect with the pterygoid plexus.  These tributary veins include those that drain the nasal cavity, roof and lateral wall of the oral cavity, all teeth, muscles of the infratemporal fossa, paranasal sinuses, and nasopharynx.  In addition, the inferior ophthalmic vein from the orbit drains through the inferior orbital fissure into the pterygoid plexus.

 The

mandibular nerve [V3] is the largest of the three divisions of the trigeminal nerve [V].  Unlike the ophthalmic [V1] and maxillary [V2] nerves, which are purely sensory, the mandibular nerve [V3] is both motor and sensory.  All branches of the mandibular nerve [V3] originate in the infratemporal fossa.

 Soon

after the sensory and motor roots , the mandibular nerve [V3] gives rise to a small meningeal branch and to the nerve to medial pterygoid, and then divides into anterior and posterior trunks  branches from the anterior trunk are the buccal, masseteric, and deep temporal nerves, and the nerve to lateral pterygoid, all of which, except the buccal nerve (which is predominantly sensory) are motor nerves

Figure 8.138 Mandibular nerve [V3]-meningeal nerve and nerve to medial pterygoid.

ed from: StudentConsult (on 10 December 2006 11:35 AM) © 2005 Elsevier

 auriculotemporal,

lingual, and inferior alveolar nerves, all of which, except a small nerve (nerve to mylohyoid) that branches from the inferior alveolar nerve, are sensory nerves.

 Anesthesia

of the inferior alveolar nerve is widely practiced by most dentists.  The inferior alveolar nerve es into the mandibular canal and runs within the medullary cavity of the mandible, piercing the anterior aspect of the mandible through the mental foramen.

 Branches

of two cranial nerves branches of the mandibular nerve [V3] in the infratemporal fossa  Chorda tympani branch of the facial nerve [VII] and the lesser petrosal nerve, a branch of the tympanic plexus in the middle ear, which had its origin from a branch of the glossopharyngeal nerve [IX].

 The

chorda tympani carries taste from the anterior two-thirds of the tongue and parasympathetic innervation to all salivary glands below the level of the oral fissure.

Lesser  The

petrosal nerve

lesser petrosal nerve carries mainly parasympathetic fibers destined for the parotid gland

 

Sweating and flushing of skin along distribution of auriculotemporal nerve Auriculotemporal branch of Mandibular nerve carries sympathetic fibers to sweat glands of scalp and parasympathetic fibers to parotid gland  

Causes Frey's syndrome often results as a side effect of parotid gland surgery or due to injury to auricotemporal nerve.

Symptoms of Frey's syndrome are redness and sweating on the cheek area adjacent to the ear.  They can appear when the affected person eats, sees, dreams, thinks about or talks about certain kinds of food which produce strong salivation.  Observing sweating in the region after eating a lemon wedge may be diagnostic. 

 Lymph

from the upper lip and lateral parts of the lower lip drains to the submandibular nodes.  Lymph from the middle part of the lower lip drains to the submental nodes.

 The

different types of teeth are distinguished on the basis of morphology, position, and function  The gingivae (gums) are specialized regions of the oral mucosa that surround the teeth and cover adjacent regions of the alveolar bone

 All

teeth are supplied by vessels that branch either directly or indirectly from the maxillary artery.  All lower teeth are supplied by the inferior alveolar artery  All upper teeth are supplied by anterior and posterior superior alveolar arteries.

 All

nerves that innervate the teeth and gingivae are branches of the trigeminal nerve [V]  The lower teeth are all innervated by branches from the inferior alveolar nerve  All upper teeth are innervated by the anterior, middle, and posterior superior alveolar nerves, which originate directly or indirectly from the maxillary nerve [V2].



The roof of the oral cavity consists of the palate, which has two parts-an anterior hard palate and a posterior soft palate

 The

soft palate is formed and moved by four muscles and is covered by mucosa that is continuous with the mucosa lining the pharynx and oral and nasal cavities.  The small tear-shaped muscular projection that hangs from the posterior free margin of the soft palate is the uvula.

 All

muscles of the palate are innervated by the vagus nerve [X] except for tensor veli palatini, which is innervated by the mandibular nerve [V3] (via the nerve to medial pterygoid).

 The

tongue is completely divided into a left and right half by a median sagittal septum composed of connective tissue.  This means that all muscles of the tongue are paired. There are intrinsic and extrinsic lingual muscles.  Except for the palatoglossus, which is innervated by the vagus nerve [X], all muscles of the tongue are innervated by the hypoglossal nerve [XII].

Superior longitudinal  Inferior longitudinal  Transverse  Vertical muscles  alter the shape of the tongue by: lengthening and shortening it; curling and uncurling its apex and edges; flattening and rounding its surface. 

 There

are four major extrinsic muscles on each side,  Genioglossus  Hyoglossus  Styloglossus  Palatoglossus.  These muscles protrude, retract, depress, and elevate the tongue.

 Lesion

of hypoglosal nerve: Ipsilateral tongue deviation.  Lesion of Corticobulbulbar fibers to Hypoglosal nerve: Contralateral tongue deviation