Cranial nerves


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Cranial nerves

  1. 1. INTRODUCTION The face and the dental apparatus receive innervation from sensory fibers, motor fibers, fibers of the special sense and parasymphatalie fibers, the four modalities are carried by different cranial nerves. The face and the dental structures also receive rich and extensive blood supply through various blood vessels. Apart from this 15% of the lymph nodes of the body are situated in the head and neck region. THE CRANIAL NERVES The nerves of the body may be classified also by their functions. Those nerves that supply muscles and structures of the body wall are called somatic. Nerves to the internal organs (viscera) are termed visceral. Sensory fibers that carry impulses toward the brain are designated as afferent. Motor fibers are termed efferent. They carry impulses away from the brain to the effector. Cranial nerves are comprised of afferent fibers (taste, pain, proprioception), as well as efferent fibers to the muscles, glands, and blood vessels. Some nerves are highly specialized and do not carry all the components. The cranial nerves are released from the base of the brain, and exit from the cranial cavity through various openings and foramina. They are designated by Roman numerals, and all paired. There are 12 pairs of cranial nerve. They are. I Olfactory II Optic III Oculomotor IV Trochlear
  2. 2. V Trigeminal VI Abducent VII Facial VIII Vestibulocochlear IX Glossopharyngeal X Vagus XI Accessory XII Hypoglossal. The cranial nerves involved in the innervation of dental apparatus are TRIGEMINAL NERVE (V) Not only in the fifth cranial nerve the largest of the cranial nerves, but also is the single most important nerve to the members of the dental profession. It supplies almost all the pain and proprioception fibers to the face, jaws and scalp. The trigeminal nerve also innervates muscles and carries parasympathetic fibers to the salivary and the lacrimal glands. The trigeminal nerve arises from the ventral surface of the cerebral pons by a short trunk composed of too closely adapted roots; a thin motor root and a thick sensory root. The two roots pass anteriorly together for a short distance within the cranial cavity, a swelling or bulging of this structure is then noted. This is the semilunar (gasserian) ganglion. In this ganglion lie the cell bodies of the sensory fibers of the fifth cranial nerve. The nerve divides into three branches; the ophthalmic, the maxillary and the mandibular. The ophthalmic nerve : The ophthalmic nerve is the first division of the trigeminal nerve. It exists from the brain case and enters the orbit through the superior orbital fissure. It supplies sensory fibers to the bulb of the eye,
  3. 3. the conjunctiva, the lacrimal gland, inside of the nose, and skin of the eyelids, forehead and nose. It divides into three branches – the lacrimal, frontal and nasocilliary. The lacrimal nerve : This branch supplies the lacrimal gland with sensory fibers. In its course towards the lacrimal gland, it receives a branch from the zygomatic nerve of the second division. This connecting branch contains postganglionic parasympathetic fibers from the pterygopalatine ganglion, which reach the lacrimal gland via the lacrimal nerve. After passing through or along the lacrimal gland, the lacrimal nerve reaches the upper eyelid near the outer corner of the eye and supplies the lateral part of the upper eyelid and a small adjacent area of the skin. The frontal nerve : This is the largest of the three terminal branches of the ophthalmic nerve. At the middle of the orbit it divides into a small supratrochlear branch and a large supraorbital branch. The supratrochlear nerve emerges from the orbit above the trochlea. It supplies the conjunctiva, the upper eyelid, and a small area of the skin of the forehead above the root of the nose. The supraorbital nerve emerges from the orbit through the supraorbital notch or foramen. It divides into medial and lateral branches which run upwards over the forehead and scalp. It supplies the conjunctiva, the central part of the upper eyelid, the frontal air sinus and the skin of the forehead and scalp up to the vertex. Nasocilliary nerve : This is one of the terminal branches of the ophthalmic division of the trigeminal nerve. It runs along the medial wall of the orbit and ends at the anterior ethmoidal foramen by dividing into infratrochlear and anterior ethmoidal nerves. Its branches are: - It sends a communicating branch through the cilliary ganglion, its fibers continue through the ganglion into the eyeball.
  4. 4. - The next branches of the nasocilliary nerves are the two or three long cilliary nerves that run directly into the orbit, pierce the sclera and supply sensory nerves to the cornea, the iris and the cilliary body. - The infratrochlear nerve is the smallest terminal branch of the nasocilliary nerve. It emerges from the orbit below the trochlea. It supplies the conjunctiva, the lacrimal sac, the medial ends of the eyelids and upper half of the external nose. - The anterior ethmoidal nerve is the larger terminal branch of the nasocilliary nerve. It leaves the orbit by passing through the anterior ethmoidal foramen. It descends to into the nose through a slit at the side of the crista galli. In the nasal it gives off two internal nasal branches (medial and lateral) to the mucosa of the nose. Finally it emerges at the lower border of the nasal bone as the external nasal nerve which supplies the skin of the lower half of the nose. THE MAXILLARY NERVE : The maxillary nerve is the second division of the trigeminal nerve, it leaves the skull through the foramen rotandum. It passes into the pterygopalatine fossa, where it splits into three major branches : The pterygopalatine nerve, the infraorbital nerve and the zygomatic nerve. Pterygopalatine nerve : This nerve turn straight downward after it has left the trunk of the second division. The pterygopalatine ganglion is attached to the medial side of the nerve. The pterygopalatine nerve seem to enter the ganglion. The fibers of the pterygopalatine nerve have, however only a topographic connection with the pterygopalatine ganglion and do not enter into a synapse with its cell. The superior posterior nasal branches are given off at the level of the ganglion. They enter the nasal cavity through the sphenopalatine foramen. The lateral braches of the superior posterior nasal nerves supply the upper and middle conchae. Medial branches pass over the
  5. 5. roof of the nasal cavity to the nasal septum. One long medial fibre, course downward and forward along the nasal septum, it is the nasopalatine nerve. The nasopalatine nerve supplies the septal mucosa and passes through the incisive cannal into the oral cavity. It supplies the oral mucosa and minor salivary glands behind the maxillary teeth and may participate in the innervation of upper central incisors. The main part of the pterygopalatine nerve continues below the pterygopalatine ganglion in a straight downward course through the entire height of the pterygopalatine fossa and then through the pterygopalatine canal. These descending nerves are called Palatine nerves. Two or three branches leave the palatine nerve enter the nasal cavity and supply the inferior conchae and are known as inferior or posterior nasal nerves. Before reaching the lower, oral end of the pterygopalatine canal, the palatine nerve divides into one larger and two smaller terminal branches. The large branch, the anterior palatine nerve, enters the oral cavity through the major palatine foramen and turn anteriorly and soon splits into numerous branches and supply the mucosa of the hard palate. The smaller middle and posterior palatine nerves emerge into the oral cavity through the lesser palatine foramina and oral cavity through the lesser palatine foramina and supply the tonsil and soft palate with sensory twigs. Infraorbital nerve : It is the continuation of the maxillary nerve. It enters the orbit through the inferior orbital fissure. It then runs forward on the floor of the orbit, at first in the infraorbital groove and then in the infraorbital canal. It emerges on the face through the infraorbital foramen and terminates by dividing into palpebral, nasal and labial branches. The infraorbital nerve releases three sets of branches, before it emerges at the infraorbital foramen. These branches are the superior
  6. 6. alveolar nerve, which supply the upper teeth, their periodontal membrane and the gingiva on the outer surface of the upper jaw. The posterior superior alveolar nerves arises from the infraorbital nerve in the infratemporal fossa and enters the maxillary tuberosity through posterior superior alveolar canal. The middle superior alveolar nerves which is frequently absent run down in the lateral wall of the sinus to enter the maxilla just before the infraorbital nerve exists from the infraorbital canal through the infraorbital foramen releases the anterior superior alveolar nerve, this nerve drops to the alveolar process through the canal situated in the anterior wall of the maxillary sinus. In the base of the alveolar process the superior alveolar nerves exchange fibers and form a loose plexus, the superior alveolar or the superior dental plexus. The terminal branches of the superior alveolar nerves emerge from this plexus in two sets that accompany the corresponding arteries. The first group are the dental nerves. Their number corresponds to the number of roots of the superior teeth. Each dental nerve enters the apical foramen of one of the roots and branches in the dental pulp. The second group of the terminal branches of the superior alveolar nerves are the interdental and interradicular nerves. Each interdental branch run through the entire height of an interalveolar septum between two adjacent teeth and supplies, during this part of its course, numerous branches to the periodontal ligaments of the adjacent teeth through the alveolar bone proper. At the crest of the interalveolar septum, the interdental nerves emerge into the gingiva and supply the interdental papilla and the labial and buccal gingiva. The interradicular nerves end in the periodontal ligament at the furcation of the roots. The terminal branches of the infraorbital nerve itself spread fanwise from the intraorbital foramen towards the lower eyelid, nose, and upper lip. The palpabral branches turn upward into the eyelid, the nasal branches
  7. 7. supply the lateral slope of the nose and the nasal wing. The superior labial branches enter the upper lip and supply the mucous membrane, skin and orbicularis Orin muscle. Zygomatic nerve : It is the branch of the maxillary nerve given off in the pterygopalatine fossa, it enter the orbit through the inferior orbital tissues, and runs in the lateral wall to enter the zygomatic bone (through zygomatic orbital foramen in the orbital surface of temporal bone. The zygomatic nerve sends a branch upward to the lacrimal nerve; this communicating branch consists of the postganglionic parasympathetic fibers, which arise from the cells of the pterygopalatine ganglion. At first incorporated in the zygomatic nerve, these visceral efferent fibers are shunted to the lacrimal nerve and thus reach the lacrimal gland. In the zygomatic bone the nerve divides into two branches. One branch the zygomaticofacial nerve, emerges at the anterior or molar, surface of the zygomatic bone and supplies the skin once the height of the right cheek. The second branch, the zygomaticotemporal nerve emerges at the posterior or temporal surface of the frontal process in the temporal fossa ; it supplies a small anterior area of the skin in the temporal region. MANDIBULAR NERVE : The mandibular nerve is the third and the largest division of the trigemenal nerve. It is also the only division to carry fibers from the motor root to the skeletal muscle. Both the roots. The large sensory and a small motor root, leave the skull through the foramen ovale and enters the infratemporal fossa. The nerve then ramifies as it lies in the infratemporal fossa, deep to the lateral pterygoid muscle. Most of the motor nerves to the muscles of mastication are released here. Masseteric nerve : It emerges at the upper border of the lateral pterygoid, just in front of the temporomandibular point, passes laterally through the
  8. 8. mandibular notch and enters the deep surface of the masseter. It also supplies the TMJ. Deep Temporal nerves : There are two deep temporal nerves, anterior and posterior. They pass between the skull and the lateral pterygoid and enter the deep surface of the temporalis. The anterior nerve is often a branch of the buccal nerve. The posterior nerve may arise in common with the masseteric nerve. Nerve to the medial pterygoid : It arises close to the otic ganglion and supplies the medial pterygoid and also the tensor palati and tensor tympani muscle. Nerve to the lateral pterygoid : This nerve arises with the other nerves to the muscles of mastication and enters the deep surface of the muscle. Buccal nerve (Long Buccal Nerve ) : This is primarily a sensory nerve, but it may carry a few motor fibers to the temporalis and lateral pterygoid muscles (the buccinator receives motor fibers from the facial nerve) After releasing the motor fibers, the buccal nerve passes laterally, between the heads of the lateral pterygoid muscles and passes down and forward. It crosses the anterior border of the vertical ramus of the mandible. When it reaches the buccinator muscle, it turns forward and lies on the lateral surface. The buccal nerve then ramifies, and the branches pierce the buccinators muscle and supply the buccal mucosa of the cheek, buccal gingiva of the mandibular molars, and sometimes a portion of the lip mucosa breathes supply the skin of the cheek. The lingual nerve : It is one of the two terminal branches of the posterior division of the mandibular nerve. Below the foramen ovale, this nerve united closely with the inferior alveolar nerve. The lingual nerve descends between the lateral and medial pterygoid muscles and may be separated from the inferior alveolar nerve by the pterygospinous ligament. At the lower border of the lateral pterygoid the lingual nerve receives the chorda
  9. 9. tympani, the chorda tympani carries visceral efferent and taste fibers from the facial nerve. Below the lateral pterygoid muscle the lingual nerve courses downwards and follows the lateral surface of the medial pterygoid muscle. At the level of the upper end of the mylohyoid line the nerve turns in a sharp curve anteriorly to continue horizontally on the superior surface of the mylohyoid muscle into the oral cavity. At this point it releases fibers to the submandibular ganglion. At the posterior part of the oral cavity, above the mylohyoid line, at the level of the third and the second lower molars, gives off gingival branches that supply the mucous membrane on the inner side of the mandible and the gingiva on the lingual surface of the teeth. Farther anteriorly the lingual nerve is in close relation to the posterior part of the sublingual gland, which receives several fine branches. When it enters the substance of the tongue, the branches of the lingual nerve perforate the muscles of the tongue lateral to the genioglossus muscle and end in the mucous membrane of the lower and upper mucous membrane of the body of the tongue. Posteriorly circumvallat papillae. At its origin the lingual nerve carries only the fibers of general sense, that is fibers for the perception of touch, pressure, pain and temperature. The taste fibers for the anterior two thirds of the tongue, derived from the facial nerve, are carried to the lingual nerve by the chorda tympani nerve and are distributed to the taste buds in the branches of the lingual nerve. Inferior alveolar nerve : It is the larger branch of the posterior division of the mandibular nerve. This nerve descends with the lingual nerve in the pterygomandibular space between the two pterygoid muscles. It winds around the lower border of the lateral pterygoid muscle, which separates the alveolar nerve from the mandibular ramus and then turns sharply outward
  10. 10. and downward to reach the inner surface of the mandible at the mandibular foramen. Before the nerve disappears into the canal of the mandible, it releases the mylohyoid nerve (contain motor fibers also) it pierces the sphenomandibular ligament runs in the mylohyoid groove, and supplies the mylohyoid muscle and the anterior belly of the diagnostic. The inferior alveolar nerve passes through the length of the mandibular canal and divides in the premolar region into two unequal terminal branches the incisive and mental nerves. The mental nerve leaves the body of the mandible through the mental canal; emerging at the mental foramen, the nerve usually divides into three branches. One branch turn forward and downward to the skin of the chin. The other two branches course anteriorly and upward into the lower lip and mucosa on the labial alveolar surface. The incisive branch in one of the dental branches of the inferior alveolar nerve. The dental branches of the inferior alveolar nerve vary in number and are arbitrarily divided into posterior, middle and anterior sets. The posterior dental branch leaves the alveolar nerve in the most posterior part of the mandibular canal ; the middle branches separate from the nerve trunk below the first molar on the second premolar the anterior dental nerve is the incisive nerve. Before the lower dental nerves send out their terminal branches they exchange fibers and form a loose inferior alveolar plexus and are arranged divided and supplied in a similar way as in the upper jaw. Auriculotemporal nerve : This nerve turns backwards from the trunk of the mandibular nerve, arising shortly after the mandibular nerve exits from the foramen ovale. It splits encircling the middle meningial artery, fuses, and rums posteriorly. When it reaches the rear of the neck of the mandible, it turns upwards and accompanies the superficial temporal artery, it then
  11. 11. passes under the parotid gland and over the root of the zygomatic arch. The auriculotemporal nerve supplies the skin of the car and the temporal region with sensory fibers. It also supplies sensation to the temporamandibular joint, sends a few fibers to the zygomatic portion of the cheek, and carries postgangliomic secretory fibers from the glossophragneeal nerve to the parotid gland. Applied anatomy : 1) The sensory distribution of the trigeminal nerve explain why headache is a uniformly common symptom in involvements of the nose (common cold, boils), the paranasal air sinuses (Sinusitis), the teeth and gums (infections C inflammation), eyes (refractive errors, glaucoma etc), the meanings (meningitis) and so on. 2) Trigeminal neuralgia : May involve or more of the three division of the trigeminal nerve. It causes attacks of very severe, burning and scalding pain along the distribution of the affected nerve. Pain is relieved either a) by injecting 90% alcohol into the affected division of the trigeminal ganglion b) by sectioning the affected nerve, the main, sensory root, or the spinal tract of the trigeminal (medullary tractotomy) FACIAL NERVE (VII) The facial nerve is an interesting and complex structure. The facial nerve in reality consists of two nerves, the facial nerve proper and the intermediate nerve. The facial nerve proper consists of the somatized motor fibers, which are destined for the muscles of facial expression, the occipital, auricular, platsyma and stepedius, the posterior belly of diagastric, and the stylohyoid muscle. The intermediate nerve contain propioceptive sensory fibers. Which serve the deep sensitivity of the face, and special sensory fibers mediating
  12. 12. the taste sensation to the anterior 2/3rd of the tongue and the palate, and afferent parasympathetic preganglionic fibers to the mucous glands of the nose and salivary glands of the mouth. Both roots fuse and pass into the internal auditory meatus and enter the substance of the petrous portion of the temporal bone. While still in the temporal bone, the facial nerve enters the facial canal. It takes a tortuous course within the bone in the facial canal, a channel inside the temporal bone. While still inside the one, the nerve encounters the sensory ganglion of the facial nerve, the geniculate ganglion. Also while in the facial canal of the temporal bone, the facial nerve releases several branches. The first important branch of the facial nerve leaves at the knee of the facial nerve. It is the Greater petrosal nerve : This nerve contain taste some fibers for the palate, but mainly it contain the preganglionic parasympathetic ganglion, whence they are relayed to the lacrimal gland and some nasal and palatine glands this nerve leaves the cranial cavity by a complex route, after joining the deep petrosal nerve from the sympathetic plexus of the internal carotid artery, the greater petrosal nerve and the deep petrosal nerve form the nerve of the pterygoid canal, which passes through the pterygoid canal into the pteygopalatine fossa to the pterygopalatine ganglion. The next branch of the facial nerve given off in the descending part of the facial canal is a small motor nerve for the stapedius muscle, called the nerve to the stapedius muscle. One more branch leaves the facial nerve in its canal above the stylomostoid foramen, that is the Chorda tympani nerve : After arising from the facial nerve, and taking a tortuous course, the chorda tympani nerve exists from the skill from the base of the sphenoid bone near the angle of the spine. It then courses downward
  13. 13. and joins the lingual nerve where the lingual nerve passes between the pterygoid muscles. The chorda tympani continues with the lingual nerve, when the lingual nerve lies close to the upper pole of the submandibular gland, the preganglionic parasympathetic secretory fibers contained in the chorda tympani, leave the lingual nerve and enter the submandibular ganglion. The taste fibers of the chorda tympani follow the lingual nerve into the substance of the tongue and are distributed to the taste buds on the anterior 2/3rd of the tongue. Taste buds signal sweet and salt from the tip of the tongue, sour (acid) from the sides, and bitter from the base. The dorsum is silent. Immediately after emerging from the stylomastoid foramen, the facial nerve gives of two branches. One of these, the posterior auricular branch, turns backwards and upwards between the mastoid process and the auricle and supplies the posterior auricular and occipital muscles. The other branch, the diagastric branch turns downwards and supply the posterior belly of the diagastic muscle. At the stylomastoid foramen the main trunk of the facial nerve enters the substance of the parotid gland, in which its ramification takes place. It enters the posteromedial surface of the parotid gland, runs through the gland crossing the retromandibular vein and the external carotid artery. Behind the neck of the mandible it divides into its five terminal branches. From above downwards these branches are the temporal, zygomatic, buccal, mandibular and cervical branches. The temporal branches : emerge from the parotid grand, cross the zygomatic arch, and supply the auricularis muscles, frontalis, orbicularis occuli and corrugator muscles. The zygomatic branches of the facial nerve supply the inferior part of the orbicularis oculi muscle.
  14. 14. The buccal branches of the facial nerve are often divided into upper and lower group. The upper buccal branches supply the muscle of the upper lip and muscles of the nose. The lower buccal branches supply the buccinator muscle and risorius muscle as well as orbicularis oris. The mandibular branch passes forward and downward and curves anteriorly at the level of the inferior border of the mandible. It supplies the muscles of the lower lip and chin. The cervical branch emerges from the apex of the parotid gland, and runs downwards and forwards in the neck, to supply the platysma. The branches of the facial nerve exchange fibers with almost all the sensory cutaneous branches of the trigeminal nerve. The connection between the facial and trigeminal branches results in the formation of small mixed terminal nerves, which carry motor and sensory fibers to the limited area of the face. Applied anatomy : • In the infranuclear lesion of the facial nerve (ex : Bell’s palsy) the whole of the face is paralysed. The face becomes asymmetrical and is drawn towards the normal side. The affected side is motionless. wrinkles disappear from the forehead, the eye cannot be closed, any attempt to smile draws the face to the normal side. During mastication, food accumulated between the teeth and the cheek. Articulation of labials is impaired. • In supranuclear lesions of facial nerve (usually a part of hemiplegia) only the lower part of the face is paralysed.
  15. 15. GLOSSOPHARYNGEAL NERVE (IX) The glossophryngeal nerve emerges from the brain on the lateral surface of the medulla oblongata. The glossophryngeal nerve supplies the tongue and the pharynx, it is composed of variety of fibers, both afferent and efferent. It leaves the skill through the jugular foramen, at which point its two sensory ganglion are locate. Those ganglia are known as the superior petrosal and inferior petrosal ganglia. The glossophryngeal nerve has several branches. The tympanic nerves : The tympanic nerve leaves the inferior sensory ganglion. It carries preganglionic parasympathetic secretory fibers and sensory fibers to the mucosa of the middle ear. After leaving the sensory ganglion, it enters the tympanic cavity. The tympanic nerve them perforates the root of the cavity and having lost its sensory fibers, is known as the lesser petrosal nerve. Its preganglionic parasympathetic secretory fibers then synapse at the otic ganglion second order neurons then go to the parotid salivary gland after joining the auriculotemporal nerve. Carotid branch : At a variable level below the jugular foramen, the carotid branch in released. It supplies afferent fibers to the carotid sinus and carotid bodies. These two tiny organs are blood pressure regulatory mechanisms that are located close to the bifurcation of the common carotid artery the carotid nerve plays an important role in the reflex regulation of respiration, heart action and blood pressure. Stylopharyngeal nerve : With the stylopharygeal branch the glossophragnogeal nerve supplies the motor fibers to the stylophrayngeas muscle. Pharyngeal branches : On the lateral wall of the pharynx and above the stylopharyngeas muscle the pharyngeal branch are released. Some of which join the branches of the vagus nerve to from the pharyngeal plexus. And
  16. 16. other of which perforate the middle constrictor of the pharynx to supply its mucous membrane. The glossopharyngeal nerve itself enter the base of the tongue below the styloglossus muscle and deep to the hyoglossus muscle. Its terminal branches supply the base of the tongue (posterior 1/3), including the vallate and foliate papillae, with fibers of general sense and taste fibers. Branches are also sent to the palatine tonsils; which are called the tonsillar branches that supply the tonsil and join the lesser palatine nerves to form a plexus from which fibers are distributed to the soft palate and to the palatoglossal arches. Applied Anatomy : Taste sensation in posterior 1/3rd of the tongue is lost in the IX nerve lesion. HYPOGLOSSAL NERVE (XII) The twelfth cranial nerve supplies motor fibers to all the intrinsic and extrinsic muscles of the tongue. No other nerve supplies these muscles with motor fibers. In addition, the hypoglossal nerve carries proprioceptive impulses from the muscles of the tongue to the brain. The hypoglossal nerve arises from the anterior surface of the medulla oblongata in the form of rootlets. These rootlets merge into a trunk, which passes out from the brain case via the hypoglossal canal. At the level of the mandibular foramen, as the nerve is passing downward, it turns anteriorly and superficially, it courses forward and is almost horizontal as it reaches a deep level to the angle of the mandible. Passing deep to the posterior belly of the diagastric and stylohyodius muscle it ramifies to supply the muscles of the tongue. Intrinsic muscles – longitudinal, transverse and vertical Extrinsic muscles – styloglossus, hyglossurs and genioglossus
  17. 17. As the nerve descends from the hypoglossal canal, it picks up fibers from the first cervical nerve. It carries these fibers to a short distance and then drops them off to the geniohyoid and thyrohyoid muscles. Applied anatomy : A lesion of the hypoglossal nerve produces paralysis of the tongue on that side. It will not be able to move the tongue on that side. When the patient attempts to protrude the tongue, the tongue will deviate towards the affected side. All the muscles of the palate – palatophargngeus, leveator palati, palatoglossus supplied by phargngeal plexus. The fibres of this plexus are derived from cranial part of accessory nerve (XI), through the vagus nerve (X) except tensor palati which is supplied by mandibular division of the trigeminal nerve (V3). Applied Anatomy : Lesions in the vagus and cranial part of the accessory nerve produce - Nasal regurgitation of liquids - Flattening of the palatal arch - Nasal twang in the voice
  18. 18. BLOOD SUPPLY The nutrients and oxygen necessary to sustain life are carried to all the cells of all the tissues by the arteries. Vein and lymphatics pick up the waste products of cell metabolism and together with deoxygenated red blood cells, return them to various arras. The blood is then rejuvenated and returns to the tissues for continued cell nutrition. ARTERIAL SUPPLY The arteries of the oral apparatus and adjacent regions are, with a few exception, branches of the external carotid artery. Only parts of the nasal cavity and upper parts of the face receive branches from the internal carotid artery. The common carotid as a rule is branches, runs lateral to the trachea and the larynx to the level of the upper border of the thyroid cartilage, here it gives side to internal carotid artery, situated posteromedially and external carotid artery, situated posteromedially and external carotid situated anterolaterally. At the division, of the internal carotid artery is slightly widened to form a carotid sinus which is important for the reflex regulation of blood pressure. INTERNAL CAROTID ARTERY The internal carotid artery ascends from its origin along the lateral wall of the pharynx to the base of the skill, where the internal carotid artery reaches the lateral wall of the pharynx, it is separated from the external carotid artery by the styloglossal and stylopharyngeus muscles. At the base of the skill, the internal carotid artery enters the carotid canal and passes through it into the cranial cavity.
  19. 19. The internal carotid artery now enters the cavernous sinus, through which it passes in a tight s-shaped curve – perforating the dura mater at the roof of the cavernous sinus, the internal carotid artery reaches the intradural space and the brain. After emerging through the roof of the cavernous sinus, the internal carotid artery releases the ophthalmic artery, which follows the optic nerve into the orbit, then emits its cerebral branches. The anterior cerebral artery turns medially and then anteriorly ; where it bends it is connected with the anterior cerebral artery of the other side by the anterior communicating artery. The middle cerebral artery leaves the internal carotid at its lateral circumference to enter the deep lateral, or syluian fissures between the frontal and temporal lobes of the brain. The posterior communicating artery is given at the posterior circumference of the internal carotid artery together with the anterior choroid artery. The right and left posterior communicating arteries jein the posterior cerebral arteries, which are the terminal braches of the unpaired basilar artery. Thus an irregular hexagonal chain of anastomasing arteries, the Circle of Willis, is around the optic chiasm and the stalk of the hypophysis. Thus an elaborate, anastomotic, well – designed network of arterial. Supply is available to the brain. Ophthalmic artery : This branch of the internal carotid artery supplies the eyeball, its muscles and the lacrimal gland and sends branches into the eyelids and into the upper part of the face. The central artery of the retina and the cilliary arteries are destined for the eyeball. The lacrimal gland and the muscles of the eyeball are supplied by the lacrimal artery and muscular branches. Posterior and anterior ethmoid branches enter the nasal cavity through the ethmoid foramina.
  20. 20. Medial and lateral palpebeal branches ; the latter arising from the lacrimal artery, ramify in the eyelids. The superaorbital branch passing through the superorbital foramen supplies the frontal muscle and the skin of the forehead. A frontal or supratrochlear branch leaves the orbit at the medial corner of the eye and sends branches to the soft tissues of the forehead. The supraorbital and frontal branches anastamose with each other and with the branch of the superficial temporal artery. The last facial branch of the ophthalmic artery in the nasal branch, which courses downward on the lateral surface of the nose and anastomoses with the angular artery, the terminal part of the facial artery, it also anastamoses with the infraorbital artery. EXTERNAL CAROTID ARTERY The external carotid artery is the branch of the common carotid artery that supplies the face, jaws and the scalp. It lies superficial to the internal carotid artery. The external carotid artery runs straight upwards, the artery transverses the most posterior part of the submandibular triangle to enter the retromandibular fossa. Here the external carotid artery changes its course and ascends, embedded in the substance of the parotid gland, at the level of the mandibular neck, the artery splits into two terminal branches the superficial temporal artery and the maxillary artery. According to the location of their origin, the branches of the external artery can be divided into : anterior, posterior and medial branches, to which the terminal branches of the artery have to be added.
  21. 21. Anterior branches of external carotid artery Three arteries arise from the anterior wall of the external carotid artery ; the superior thyroid artery, the lingual artery and the facial artery. Superior thyroid artery : The bifurcation of the common carotid artery is also the location for the origin of the superior thyroid artery, it curves anteriorly and downward to supply the thyroid gland. The mucous membrane and the muscles of the larges also receive blood from the superior thyroid artery. Lingual artery : Destined for the tip of the tongue via a tortuous course, the lingual artery arises from the external carotid artery at the level of the hyoid bone. Often in arises in common with the facial artery via the lingual – facial trunk from its origin the lingual artery courses anteriorly to the posterior border of the hyoglossus muscle. It passes deep to this muscle and turns upwards to the mouth where it enter the base of the tongue. It terminates at the tip of the tongue. The lingual artery gives of sublingual artery to the floor of the mouth, prior to entering the substance of the tongue. The sublingual artery supplies the sublingual gland, mucosa of the floor of the mouth, the mylohyoid muscle and the lingual gingiva. It anastamoses with the submental branch of the facial artery. After giving off the sublingual artery, the lingual artery, now in the body of the tongue, is termed the deep lingual artery. Facial artery : The facial artery supplies, for the most part the superficial structure of the face. It arises from the external carotid artery just above the origin of the lingual artery at about the level of the angle of the mandible. It may arise from the lingual – facial trunk. Passing forward and upward, it pass deep to the diagastric muscle and enters the submandibular triangle. It then enters
  22. 22. the substance of the submandibular salivary gland. After it reaches superior border of the gland, it arches upwards towards the floor of the mouth and then turns downwards and laterally to pass below the inferior border of the mandible. The artery then turns sharply upward on the lateral surface of the mandible and crosses it in front of the anterior border of the masseter muscle to enter the face. The facial part of this artery is characterized by the course of the vessel, an adaptation to the varying expansion of the lip and check. From the point where the artery crosses the lower border of the mandible, it is directed towards the corner of the mouth and then follows the lateral border of the nose to the inner corner of the eye. Here it ends as the angular artery, anastamosing with branches of the ophthalmic artery of the internal carotid artery. The two most important branches of the facial artery under the jaws are the ascending palatine and submental arteries. The ascending palatine arises close to the origin of the facial artery and supplies the soft palate, pharynx and the tonsils. The submental artery originates from the facial artery before it turns into the face. It supplies the submandibular region and anastamoses with the sublingual artery. The facial part of the artery gives off the inferior labial and superior labial arteries, at the corner of the mouth. The inferior labial artery anastomes with the mental artery to supply chin and lower lip. The superior labial artery anastamoses with the terminal branches of the ophthalmic artery and with the infraorbital arteries. The facial artery then courses superiorly, giving branches to the side of the nose and check to end at the medial cantus of the eye as the angular artery.
  23. 23. Posterior branches of the external carotid artery Two branches arise from the posterior wall of the external carotid artery : the occipital artery and posterior auricular artery. Occipital artery : The occipital artery arises dose to the origin of the facial artery. It, however runs upwards and backwards towards the occipital area of the scalp. After it crosses the mastoid process in the occipital groove of the temporal bone, it becomes more superficial, it supplies the scalp. Posterior auricular artery : The posterior auricular artery originates from the external carotid artery at a level just opposite the lobe of the ear. It then passes laterally and posteriorly to supply the outer ear and adjacent scalp behind the ear. The superior temporal and occipital artery both give branches that anastamose with the posterior auricular artery. Medial branch of external carotid artery Ascending pharyngeal artery : it usually arises immediately above the bifurcation of the common carotid artery. It ascends along the lateral pharyngeal wall to the skull. The blood supply to the pharynx and adjacent muscles is provided in part by this vessel. It is small and anastamoses with pharyngeal branches of other arteries. Terminal branches of the external carotid artery The terminal branches of the external carotid artery are the superficial temporal artery and maxillary artery. Superficial temporal artery : The superficially temporal artery is anatomically, but not embryologically, the continuation of the external carotid artery. It ascends vertically in front of the ear to the temporal region of the scalp. It passes through the substances of the parotid gland in the retromandibular fossa, releasing the transverse facial artery, which passes horizontally and ends near the lateral canthus of the eye. Also it sends
  24. 24. branches to the outer ear and a middle temporal branch to the temporalis muscle. In the scalp, the branches of the superficial temporal artery anastome with branches of the occipital artery, surpraorbital artery and across the midline with the arteries of the opposite side. Maxillary artery : The maxillary artery arises from the external carotid artery just below the level of the mandibular neck in the substance of the pacolid gland. Although superficial temporal continues the course of the external carotid artery upward, whereas the maxillary artery arises at a right angle, the maxillary artery in embryologically and physiologically the continuation of ECA, which applies the deep tissues of the face. The course is horizontal and anterior as it heads to the pterygopalatic fossa. It is close to the medial surface of the condylar neck when it first originates, and as it passes deeply, it runs between the condylar neck and the sphenomandibular ligament. Where, it lies either lateral or medial to the lateral pterygoid muscle. If it lies lateral, it must reach the pterygopalatine fossa by turning medially between the two heads of origin of the lateral pterygoid muscle. It is easy to understand the division of the maxillary artery if one classifies it into sections and organizes its distribution. The maxillary artery may arbitrarily be divided into four parts. The first, or mandibular, part is that short section which lies medial to the mandibular neck. The second part, the muscular, or pterygoid, part is the longest of the four and is in close relation to the lateral pterygoid muscle. The third part is the maxillary part, which is here in dose relation to the posterior surface of the maxilla. The fourth and terminal part in best termed as the pterygopatatine part, because the artery divides into its terminal branches in the pterygopalatine space, which it enters through the pterygopalatine gap.
  25. 25. Mandibular part The first, or mandibular segment of the maxillary artery gives off two small branches to the ear. The deep auricular artery supplies the external acoustic mantas the tympanic membrane and the TMJ. The anterior tympanic branch supplies the middle ear including the medial surface of tympanic membrane. Following these, the two main branches of this mandibular segment are released, the middle meningeal artery and the inferior alveolar artery. The middle meningral artery : Passes between the two roots of the auriculotemporal nerve, runs straight up to enter the foramen spinosum into the cranial cavity it supplies the dura mater and adjacent bones. The inferior alveolar artery : from the origin, the inferior alveolar artery turns almost vertically downward to reach the mandibular foramen, the entrance to the mandibular canal, before entering the canal, the inferior alveolar artery releases the mylohyoid artery which supplies the mylohyoid muscle and anastomes with the mental artery. In the mandibular canal, the inferior alveolar artery sends branches into the marrow spaces of the bone and to the teeth and the alveolar process. The mental artery, the larger of the two terminal branches is released through the mental canal, it supplies the soft tissues of the chin and anastamoses with inferior labial artery. The second smaller branch, the incisive artery continues its course inside the mandible to the midline, where it anastamoses with the artery of the other side. The blood vessels that turn from the inferior alveolar artery upward into the alveolar process are of two distinct types. One set of branches enter the root canals through the apical foramina and supplies the dental pulps.
  26. 26. They can be termed dental arteries. A second set of branches, alveolar or perforating, branches, enter the interdental and interradicular septa. Many small branches arising at right angle from the interdental arteries supply the periodontal ligaments of adjacent teeth. The interradicular alveolar arteries and in the periodontal ligament at the bifurcation of the molars. The interdental alveolar arteries perforate the alveolar crest in the interdental spaces and end in the gingival, supplying the interdental papilla and the adjacent areas of the buccal and lingual gingival. In the gingiva these branches anastamose with superficial branches of arteries, which supply the oral and vestibular mucosa, for instance, with branches of the lingual buccal, mental and palatine artery. Muscular or pterygoid part. This part supplies the muscles of mastication and buccinator. The temporalis receives the posterior and anterior deep temporal arteries. The messenteric artery passes laterally through the condylar notch to supply the masseter muscle. A variable number of small pterygoid branches. Are released to the pterygoid muscles. The last branch of this section is the buccal artery; which turns downward and forward between the inferior head of the lateral pterygoid and temporal muscle and reaches the space between the buccinator and the masseter. At the outer surface of the buccinator muscle, the buccal artery breaks up into terminal branches. They supply the buccinator muscle and the mucous lining of the check and anastaomose with branches of the facial artery and the transverse facial artery.
  27. 27. Maxillary part The third segment of the maxillary artery runs along the posterior surface of the maxilla near its upper border. Here it gives of the posterior superior alveolar and the infraorbital branches before entering the pterygomaxillary fissure. The posterior superior alveolar artery : crosses the maxillary tuberosity and here gives off posterior superior arteries that enter the posterior superior alveolar canals accompanied by posterior superior alveolar nerves. The terminal, or gingival extensions of the posterior superior alveolar artery continue to supply the mucosa covering the buccal surface of the alveolar process of the molar and premolars up to their gingival margin several branches extend into the checks. The infraorbital artery : enters the orbit through the inferior orbital tissue and runs anteriorly, fist in the infraorbital sulcus and then in the infraorbital canal. Emerging through the infraorbital foramen, the infraorbital artery supplies the anterior part of the check and the root of the upper lip and anastamoses with the branches of the superior labial artery of the facial artery and the angular artery. In the infraorbital canal, anterior superior alveolar artery is given off before. Leaving through the infraorbital foramen. The anterior superior alveolar artery follows the anterior superior alveolar nerves through the narrow canals in the anterior wall of the maxillary sinus to the alveolar process. There the anterior superior alveolar artery anastamoses with branches of the posterior superior alveolar artery. The branches that the superior alveolar artery release are, in principle arranged like those in the mandible.
  28. 28. Pterygopalatine part This part of the maxillary artery is short because the artery divides into its terminal branches immediately after entering the pterygopalatine fossa through the pterygomaxillary fissure, the gap between the maxilla and the pterygoid process of the sphenoid bone. The descending palatine artery : arises in the pterygopalatine fossa and passes inferiorly to enter the oral cavity through the greater palatine foramen. In the pterygopalatine canal it may give off small nasal branches to the lateral wall of the nasal cavity. Also it gives off lesser palatine branches which exit from the lesser palatine foramina and supply the soft palate and tonsil once it exists from the greater palatine foramen, the descending palatine artery is known as the major palatine artery which turns forwards in the substance of the palatal mucosa and passes anteriorly to the nasopalatine foramen. In its course it gives branches to the associated bone, glands and mucosa. Once it reaches the nasopalatine foramen, it turns upwards and passes through the nasopalatine canal into the nose and anastamoses with sphenopalatine artery on the septum. Sphenopalatine artery : also arises in the pterygopalatine fossa. It enters the nasal cavity through the sphenopalatine foramen there it divides into branches supplying the lateral wall of the nasal cavity and septum. On the septum it anastamoses with the septal branch of the anterior palatine artery.
  29. 29. VENOUS DRAINAGE The venous blood of the head and neck is drained almost entirely by the internal jugular vein. Veins usually accompany arteries and carry the same or similar names. Deep vein are united with the superficial vein by several anastamoses. There multiple anastamoses present a potential danger by increasing the number and availability of pathways for speed of infection. In addition, because the vein of the face have few, if any, valves, backflow of blood can easily occur deep veins prior to the advent of antibiotics, brain infection secondary to facial and dental infection was not uncommon. Once blood reaches the internal jugular vein, it drains inferiorly to the brachiocephalic vein. The brachiocephalic vein is formed by the confluence of the internal jugular vein and the subclavian vein, which drains the upper extremity. The right and left brachiochephalic vein then join to form the superior vena cava. The inferior vena cava, draining the lower portion of the body, join the superior of vena cava in an area known as the confluence of the cava, located at the right atrium. VENOUS SINUSES The sinuses of the duramater in the brain empty their contents into the internal jugular vein which commences at the jugular foramen. Blood from the eye and the brain is collected in the dural sinuses. Superior sagittal sinus The superior sagittal sinus begins in the area of the cribriform plate of the ethmoid bone and passes posteriorly in the middle along the inner plate of the frontal, parietal and occipital bones. It drains some of the vein of the brain as it runs posteriorly.
  30. 30. Inferior sagittal sinus The inferior sagittal sinus is enclosed in the lower for border of the vertical fold of the dura which separates the two halves of the cerebreum. Straight sinus The straight sinus join the inferior and superior sagittal sinus. It lies in a horizontal fold of dura, separating the cerebrum and cerebellum. Transverse sinus The transverse sinus begins where the straight sinus and superior sagittal sinuses join. It passes laterally in a horizontal plane to become a s- shaped sinus, the sigmoid sinus, and then into the internal jugular vein at the jugular foramen. Cavernous sinus The cavernous sinuses, which lie on either side of the sella turcica, are pools of venous blood, subdivided by thin trabacule of connective tissue. The right and left cavernous sinuses communicate with one another via anterior and posterior chambers known as intercavernous sinuses. The cavernous sinus drain associated parts of the brain. Also, the ophthalmic veins draining the eye empty posteriorly into the cavernous sinus. Clinically, its of great importance to know that the internal carolid artery, first two division o the trigeminal nerve, the abducent the occulomotor and the trochlear nerve all pass through the cavernous sinus. Retrograde infection into this sinus can lead to a grave clinical problem. Petrosal sinuses The blood in the cavernous sinus is drained posteriorly in the superior and inferior petrosal sinuses. The superior petrosal sinus ends in the sigmoid sinus. The inferior petrosal sinus empties more inferiorly, directly into the jugular vein near the foramen.
  31. 31. INTERNAL JUGULAR VEIN The blood from the brain empties into the internal jugular vein which is formed by the confluence of various sinuses and exits the brain case through the jugular foramen. The vein descends in the neck to the brachiocephalic vein. Contributing vein include the inferior petrosal sinus, communication from the pharynx and tongue, common facial vein, veins of the larynx and the thyroid gland, the external jugular vein and the anterior jugular vein. Common facial vein The common facial vein is a short, thick vessel resulting from a merger of the anterior facial vein and retromandibular vein. It enters the internal jugular vein at the level of the hyoid nerve. Anterior facial vein The anterior facial vein follows a course similar to that of the facial artery. It originates from the vein of the forehead and nose. The frontal vein, supraorbital vein, and vein from the lids and nose all contribute to first part of the facial vein, the angular vein. The angular vein than becomes the facial vein as it drain inferiorly. A wide anastamosis takes place between the angular vein and the superior and inferior ophthalmic vein. As the facial vein descends it picks up communicating branches from the associated area. An anastamotic facial vein at the level of the upper lip. This communicating vein is the deep facial vein once the facial vein has picked up the superior and inferior labial vein, it reaches the inferior border of the mandible where it terns posteriorly and deep. Here it receives the submental and palatine veins and enters the common facial vein. Ophthalmic vein The inferior ophthalmic vein drains the floor and medical wall of the orbit and associated tissues it empties into either the pterygoid plexus, the
  32. 32. cavernous, the superior ophthalmic vein, or any combination of the three the superior ophthalmic vein drains the area supplied by the ophthalmic artery and empties into the cavernous sinus after passing through the superior portion of the orbit. Retromandibular vein The areas supplied by the maxillary artery and superficial temporal artery are drained by the retromandibular vein. It is formed by the union of the superficial temporal vein with the deep vein of the maxilla. It emerges from the substance of the parotid gland and courses vertically down to the common facial vein. Lingual vein The lingual vein, 3 to 4 in number, drain the tongue and floor of the mouth and empty into the anterior facial vein, the common facial vein or retromandibular vein. Pterygoid plexus The venous network known as the pterygoid plexus lies between the temporal and pterygoid muscles. It drains the muscles of mastication, the nasal cavity, the TMJ, the external ear and a small portion of the dura. It communicates with the facial vein by the way of the deep facial vein. Also, it drains the maxillae and the palate and communicates with the cavernous sinus. It empties posteroinferiorly joining the superficial temporal vein to form the retromandibular vein. External jugular vein The external jugular vein is formed by the junction of the posterior auricular vein with the occipital vein. It enters the internal jugular vein low in the neck near the junction of the external jugular vein with the subcalvian vein. It often anastamoses with the common facial vein or retromandibular vein.
  33. 33. Anterior Jugular vein Often absent, the anterior jugular vein may be a single midline vein or two midline vein. It empties into the internal jugular vein near the junction of the internal jugular vein with the subclavian vein. It drains the skin and superficial fascia of a narrow anterior part of the neck close to the midline. LYMPHATIC DRAINAGE The lymphatic system represents an accessory route by which fluid can flow from the interstitial spaces into the blood. The fluid passing through the lymphatic vessels is called lymph - It supplies nutrition and oxygen to those parts of the body where blood cannot reach - Drains away excess tissue fluid and metabolites - Lymphocytes and monocytes of lymph acts as defensive cell of the body. Lymph nodes small bean shaped bodies, usually in groups are positioned along the course of the lymph vessels. Their function is to filter the lymphatic fluid flowing through them. Also they produce and discharge lymphocytes. As in the other parts of the body lymph in the head and neck is carried by the very thin – walled lymph vessels to aggregation of nodes. From the nodes it drains to other areas and ultimately into the thoracic duct. The nodal system of the head and neck can be divided into groups of nodes according to location. Occipital nodes Located near the occipital protuberance, the occipital nodes drain the occipital portion of the scalp and empty into the cervical nodes.
  34. 34. Posterior auricular nodes The posterior auricular nodes drain the mastoid region. Anterior auricular nodes The anterior auricular group drain the temporal region and skin of the ear. Parotid nodes Several nodes are locate around and in parotid gland. They drain the nasal cavities, eyelids, frontotemporal region, posterior palate, anterior auricular nodes and parotid region. Facial nodes Several groups of nodes are located in the facial structures most of these drain into submandibular nodes. Sumandibular nodes The submandibular nodes lie near the inferior border of the mandible. They collect lymph from the submental region, upper and lower teeth, tongue, lips and jaws and drain into deep cervical nodes. Submental nodes The submental group lies in the submental triangle between the anterior bellies of diagastric muscle. These nodes drain the lower incisors and empty into the submandibular and deep cervical nodes. Cervical nodes Various groups of nodes are located along the internal and external jugular veins. They are divided into superficial and deep cervical nodes. The superficial nodes are usually found in the upper region of the neck. They receive lymph from the ear and adjacent region. The deep cervical nodes are further sub divided into superior and inferior deep cervical nodes. Lymph from the base of the tongue and posterior floor of the mouth drain directly into these nodes, from the auricular nodes, submandibular nodes, submental nodes, facial nodes,
  35. 35. occipital nodes and viscera of the neck, lymph drain into deep cervical nodes. On the right, lymph from the deep cervical nodes empties into the right lymphatic duct. The thoracic duct collects the lymph from the left deep cervical nodes. Clinical implication Knowledge of the lymph system and the geography of the various groups of nodes is important in diagnosis in the normal state lymph nodes are not palpable. Infection or cancer in an area drained by the vessels to these nodes causes the nodes to become very active, and they become quite firm and palpable. Palpable nodes are a most important sign of clinical disease. The cause of palpable lymph nodes should always be investigated pain and swelling of the submandibular nodes are clearly indicative of oral pathology. In addition we can predict the pathologic condition. If left untreated, will spread involve the cervical nodes. Malignancy is also common cause of palpable nodes cancer cells often spread to regional lymph nodes and produce seeding and growth of the tumor within the nodes. Identification of palpable lymph nodes can result in early diagnosis and thereby improve the prognosis. CONCLUSION As we being dentist dealing with the stomatognathic system, it is imperative for us to have a sound knowledge about the nerve supply, blood supply and the lymphatic drainage of the dental apparatus.
  36. 36. REFERENCES 1) Oral Anatomy - Lloyd Dubrul 8th Edition 2) Anatomy of the head, neck, face and Jaws – Lawrence A. Fried 2nd Edition 3) Grants Atlas of Anatomy 9th Edition 4) Grays Anatomy 38th Edition 5) Human Anatomy – B.D. Chaurasia 3rd Edition 6) The Anatomical Basics of Dentistry – Bernard Liebgott 2nd Eidtion
  37. 37. CRANIAL NERVES AND BLOOD SUPPLY RELATED TO DENTAL APPARATUS INCLUDING LYMPHATIC DRAINAGE  INTRODUCTION  CRANIAL NERVES – Trigeminal nerve – Facial nerve – Glossopharyngeal nerve – Hypoglossal nerve.  BLOOD SUPPLY – Arterial supply – Venous drainage  LYMPHATIC DRAINAGE  CONCLUSION  REFERENCES Internal carotid artery External carotid artery Internal jugular vein