Properties of the stellar subclusters around massive stars

- CN V, VII, IX, X are branchiomeric (nonsomitic) in origin because they originate from the branchial arches - Olfactory (CN I)

o Exits Cribiform plate of ethmoid bone o Enters nasal canal for smell

o Fracture of the cribiform plate typically results in loss of sense of smell - Optic nerves (CN II)

o Arise from axons of the ganglion cells of the retina which converge at the optic disk o Optic foramen (optic canal):

 Area where nerve enters the cranial cavity through the sphenoid bone o Optic disc (aka optic papilla):

 Area where optic nerve exits eye

 Made up of nerve cells

 Small blind spot on surface of the retina – no rods or cones

 Located ~3mm to nasal side of the macula

 Only part of retina which contains no photoreceptors

 Optic tracts consists of axons from ganglion cells

 Consists of axons of ganglion cells exiting the retina to form the optic nerve

• The axons are accompanied by the central artery & vein of the retina

o After exiting eyes, optic nerves meet at the optic chiasm (in the floor of the diencephalon) o From optic chiasm, axons that perceive the left visual field form the right optic tract & vice-versa

 Fibers that arise from the nasal hemiretinas decussate & contribute to the contralateral optic tract

o Optic nerve fibers from the nasal side cross the midline and enter the optic tract of the other side by way of the optic chiasma

 Fibers arising from the temporal hemiretinas remain ipsilateral

 Optic tract fibers synapse in the lateral geniculate nuclei w/ geniculocalcarine fibers (optic radiations) that terminate on the banks of the calcarine sulcus in the primary visual cortex (Brodmann’s area 17) of the occipital lobe

 So, the right visual field is interpreted in the left hemisphere of the brain & vice versa

o Central artery of the retina (branch of ophthalmic artery), pierces the optic nerve & gains access to the retina by emerging from the center of the optic disc

- Oculomotor nerve (CN III)

o Supplies: medial, superior, & inferior recti; inferior oblique; & levator palpebrae superioris o Sends pregangl fibers to ciliary ganglion

o Post gang fibers leave the ganglion in the short ciliary nerves to supply the sphincter pupillae & the ciliary muscle

- Oculomotor nerve (CN III), trochlear nerve (CN IV) & abducens nerve (CN VI) and ophthalmic (V div 1) all exit the cranium through the superior orbital fissure. They innervate the extrinsic ocular muscles, resulting in movement of the eyeball

- Trochlear nerve (CN IV):

o Supplies the superior oblique muscle o Smallest cranial nerve

o Only cranial nerve that emerges from dorsal aspect of the brainstem - Trigeminal nerve (CN V):

o Exits inferolateral PONS as a sensory & motor root o Largest of 12 cranial nerves

o Larger sensory root enters the trigeminal (semilunar, gasserian) ganglion in the middle cranial foss, Embeds in Meckel’s CAVE o Three sensory divisions of the nerve arise from the ganglion & leave the cranial cavity through foramina in the sphenoid bone o Smaller motor root passes under the ganglion & joins the mandibular division as it exists through the foramen ovale - Semilunar ganglion (aka trigeminal or gasserian ganglion)

o Large, flattened, sensory ganglion of the trigeminal nerve o Lies close to cavernous sinus in the middle cranial fossa o Ophthalmic division (V1):

 Enters orbit through superior orbital fissure

 Sensory innervation to eyeball, tip of nose, skin on face above eyes

 Three branches: lacrimal, frontal, & nasociliary o Maxillary division (V2):

 Passes through foramen rotundum

 Sensory innervation to midface (below eyes & above upper lip), palate, paranasal sinuses, & maxillary teeth o Mandibular division (V3):

 Exits cranial cavity through foramen ovale

 Motor innervation to tensor veli palatine, tensor tympani, muscles of mastication, and anterior belly of digastric & mylohyoid

 Has no PS component at its origin:

 Sensory innervation to:

• Skin on Lower face, skin of mandible, lower lip & side of the head

• TMJ (Auriculotemporal, and Masseteric and Posterior Deep Temporal), mandibular teeth, mucous MBs of cheek, floor of mouth, & anterior part of the tongue

 Lingual nerve –branch of V3:

• Descends deep to lateral pterygoid muscle, where it is joined by chorda tympani (branch of CN VII) which conveys pregang PS fibers to submandibular ganglion & taste fibers from anterior 2/3 of tongue

• Supplies general sensation for anterior 2/3 of tongue, floor of mouth, & mandibular lingual gingiva

• Submandibular duct has an intimate relation to the lingual nerve, which crosses it twice

• Is directly on the lateral surface of the medial pterygoid muscle

• If you cut lingual nerve after its junction w/ chorda tympani, pt loses taste & tactile sense to anterior 2/3 of tongue

 Nerve to Masseter:

• Passes through mandibular notch to enter muscle on medial surface

• Also a branch of V₃

• Carries a few sensory fibers to the anterior portion of the TMJ

• Anterior portion of TMJ also supplied by branches of the posterior deep temporal nerve (branch of V3)

 Auriculotemporal nerve:

• Arises from posterior division of V₃

• Provides posterior sensory innervation to TMJ

o Pain (TMJ pt) is transmitted in the capsule & periphery of the disk by the auriculotemporal nerve

• Pain from a fractured mandible

• The joint only sends sensory information – it does not receive motor innervation (the muscles do, duh!)

• Carries some secretory fibers from the otic ganglion to the parotid gland (from CN IX)

• Referred pain from the TMJ to skin over the parotid region & side of head is based on the distribution of the auriculotemporal n.

- TMJ

o Innervated by: (Think of the nerves as a MAP of the TMJ)

 Nerve to the masseter (anterior portion) V3

 Auriculotemporal (Primary) V3

 Posterior deep temporal nerve (anterior portion) V3

- CN III, VII, IX use branches of CN V to distribute their preganglionic PS to the PS head ganglia - Abducens (CN VI):

o Supplies the lateral rectus of the eye

o NOT found within the walls of the cavernous sinus (III, IV, V1, and V₂ are) – actually within the C sinus itself.

- Facial nerve (CN VII):

o Contains sensory neurons that originate from taste buds on anterior 2/3 of tongue

 The cell bodies are located in the geniculate ganglion, which lie in the facial canal, in the inner ear o Associated with the second pharyngeal arch

o Innervates the facial muscles w/ motor fibers

o Supplies the Mimetic muscles (LIKE a MIME, facial expression) o Lacrimal gland & salivary glands w/ PS fibers

o Anterior tongue w/ taste fibers o Originates in the pons

o Traverses the facial canal of the temporal bone & exits the stylomastoid foramen

o Also contains PS fibers to sublingual & submandibular glands (via submandibular ganglion) o Facial nerve function:

 Motor innervation:

• Muscles of facial expression

• Posterior belly of digastric muscle & stylohyoid muscle – after CN VII emerges from stylomastoid foramen

• Stapedius muscle w/in the middle ear

• Damage just after it left stylomastoid foramen would cause loss of innervation to facial muscles (orbicularis oculi m.)

• Which structure innervates the orbicularis oculi?  Temporal and zygomatic branches of CN VII

 Sensory: proprioceptive innervation: from the same muscles listed for motor innervation

 Secretomotor: PS innervation. Secretion of tears from the lacrimal gland & salivation from the sublingual & submandibular glands

 Special sensory: taste impulses (sweet sensation) from the taste buds on the anterior 2/3 of tongue, floor of mouth, & palate o Bell’s Palsy

 Damage to the facial nerve or its branches may cause weakness or paralysis of facial muscles

 Peripheral ipsilateral facial paralysis

 Inability to close eye on affected side

 Complete destruction of the facial nucleus itself OR its branchial efferent fibers (facial nerve proper) paralyzes all ipsilateral facial muscles

 Upper motor neuron  Can wrinkle forehead (Inability to smile – he can still wrinkle forehead because upper face gets innervation from the BOTH sides of the brain (See Pic)

 Lower motor neuron lesion (i.e. Facial Nucleus Destruction)

Complete facial paralysis (Inability to smile OR wrinkle forehead)

- PS innervation controlling salivation originate in facial

& glossopharyngeal nerves - Chorda tympani

o Emerges from a small canal in posterior wall of tympanic cavity & crosses medial surface of tympanic MB

o Joins lingual nerve in the infratemporal fossa - Geniculate ganglion:

o Located w/in the facial canal (petrous portion of temporal bones)

o Contains sensory neurons via chorda tympani of CN VII (innervates taste buds on anterior 2/3 of tongue) o Greater petrosal nerve:

 Parasymp secretomotor branch of CN VII and general visceral afferent fibers

• No sympathetic fibers or general somatic efferents

 Also described as the parasympathetic root of the pterygopalatine ganglion

 Arises from the geniculate ganglion

 Carries PS preG fibers to pterygopalatine ganglion

• Exits cranial cavity through foramen lacerum

• Enters pterygoid canal after joining w/ deep petrosal nerve to form the nerve of the pterygoid canal o Deep petrosal nerve is carrying postG S from the superior cervical ganglion

o Both form the nerve of the pterygoid canal (Vidian’s)

• In pterygopalatine fossa, the nerve of the pterygoid canal terminates in the pterygopalatine ganglion

• PS pre-ganglionics from greater petrosal nerve synapse w/ post-ganglionics here

• S (already post-ganglionics) just pass on through the ganglion w/out synapsing

 Post-ganglionic autonomics – distributed to lacrimal gland & glands of mucous MB of nasal cavity, pharynx, & palate

 Also transmits taste centrally from palate through palatine nerves

• These taste fibers also necessarily pass through the pterygopalatine ganglion & nerve of the pterygoid canal to reach the greater petrosal nerve on their way to the tractus & nucleus solitarius in the pons

o Lesser petrosal nerve:

 Pregang PS to the otic ganglion  parotid gland (via auriculotemporal nerve V3)

• NOTE: the postG PS cell bodies to the parotid gland are found in the otic ganglion

• Stimulation of lesser petrosal nerve causes secretion by parotid gland

• Tympanic & lesser petrosal branches of CN IX supply preganglionic PS secretomotor fibers to the otic ganglion o Preganglionic fibers leave CN IX as the tympanic nerve (SEE MIDDLE PIC)

 Tympanic nerve enters middle ear cavity & participates in formation of the tympanic plexus (on the medial Wall), where chorda tympani runs from posterior wall across lateral wall (aka medial surface of Tympanic MB) o It reforms as the lesser petrosal nerve, leaves cranial cavity through foramen ovale, & enters otic ganglion

 Diminshed salivary gland production from the parotid due to MIDDLE EAR damage has most likely affected the Lesser Petrosal Nerve (NOT the auriculotemporal)

- Glossopharyngeal nerve (CN IX):

o Originates from anterior surface of the medulla oblongata along w/ CN X & CN XI o Passes laterally in posterior cranial fossa & leaves skull through the jugular foramen o Splits the Superior and Middle Constrictors to enter the oral cavity

o Supplies sensation (including pain) to pharynx & posterior 1/3 of tongue o Innervates derivatives of the 3^rd branchial arch

o Innervates stylopharyngeus muscle (the only muscle supplied by CN IX)

 Landmark for locating CN IX – as CN IX enters pharyngeal wall, it curves posterior around the lateral margin of the muscle

o Cell bodies of these sensory neurons are located in Superior & Inferior ganglia of this nerve

 Cell bodies of pain fibers in CN IX are found in the superior ganglion of CN IX o Descends through upper part of neck along w/ internal jugular vein & internal carotid artery

 Reaches posterior border of the stylopharyngeus muscle – supplies it w/ somatic motor fibers o Caries 1° afferent neurons that cause the gag reflex (innervates mucous MBs of the fauces) o ***NOTE: CN III, VII, IX, & X all carry pre-gang PS fibers

o Visceral sensory branches of CN IX:

 Lingual

• Terminal branch of CN IX to posterior 1/3 of tongue conveying general sensation & taste to circumvallate papillae

• Also carries some secretomotor fibers to the glands

 Pharyngeal

• Distributed to mucous MB of the pharynx – sensory limb of the gag reflex

 Carotid sinus nerve

• To carotid sinus (baroreceptor) & carotid body (chemoreceptor)

o Remember Sinus gets it from IX, but the whole BODY gets it from IX and X, aortic arch only from X - Otic ganglion:

o Pregang PS cell bodies originate in the Inferior Salivatory nucleus o Small PS ganglion, functionally associated w/ CN IX

o Situated below foramen ovale; medial to V3

o Tympanic & lesser petrosal branches of CN IX supply preganglionic PS secretomotor fibers to the otic ganglion

 Preganglionic fibers leave CN IX as the tympanic nerve

• Tympanic nerve enters middle ear cavity & participates in formation of the tympanic plexus

• It reforms as the lesser petrosal nerve, leaves cranial cavity through foramen ovale, & enters otic ganglion o Postgang PS fibers leave the ganglion & join the auriculotemporal nerve→jump off at the parotid gland

- Vagus Nerve (CN X):

o Leaves brain from medulla & exits cranial cavity through jugular foramen o Contains PS pre-ganglionic fibers to thoracic & abdominal viscera

o Descends in neck in the carotid sheath behind the internal & common carotid arteries & internal jugular vein

o Both R & L Va-Goose trunks pass through posterior mediastinum on the esophagus & enter abdominal cavity w/ the esophagus o In the lower thorax, the esophageal branches of the right vagus branches are found mainly on the posterior esophagus

 Just make the right hand turn on the wheel – the left vagus goes to the anterior

o Supplies viscera of neck, thorax, & abdomen to the left colic (splenic) flexure of large intestine

 Abdominal viscera below left colic flexure, & pelvis & genitalia supplied w/ pregang PS fibers from pelvic splanchinc nerves

o Vasomotor sympathetic fibers are thought to end on BVs

o Possesses Two Sensory Ganglia:

 Superior ganglion (lies on nerve w/in jugular foramen)

• Meningeal – supplies dura mater

• Auricular – supplies auricle, external auditory meatus

 Inferior ganglion (lies on nerve just below the jugular foramen)

• Pharyngeal

o Forms pharyngeal plexus o Supplies:

 Pharyngeal muscles, except stylopharyngeus (CN IX)

 Soft palate muscles, except tensor veli palati (V3)

• Superior laryngeal, divides into:

o 1) Internal laryngeal – travels w/ superior laryngeal artery & pierces thyrohyoid MB

 Supplies mucous MB of larynx above vocal folds

o 2) External laryngeal – travels w/ superior thyroid artery & supplies cricothyroid muscle o Sensory Portion of CN X:

 Somatic sensory fibers – to skin of the ear

• Cell bodies in the superior ganglion of CN X (somatic sensory nucleus)

• Axons enter spinal tract & nucleus of CN V

 Visceral sensory fibers – to pharynx, larynx, & thoracic & abdominal viscera to the left colic flexure (hunger pangs)

• Cell bodies in inferior ganglion of CN X (visceral sensory nucleus)

• Axons enter tractus & nucleus solitarius

 Visceral sensory fibers – to epiglottis (taste)

• Cell bodies in inferior ganglion

• Axons enter tractus & nucleus solitarius o Motor Portion of CN X:

 Branchiomeric motor fibers – to skeletal muscle derived from visceral arch muscle in larynx, upper esophagus & pharynx

• Cell bodies of these motor neurons are in nucleus ambgiuus

 Visceral motor fibers – to smooth muscles & glands of the organs of the neck, thorax, & abdomen

• These are the PS preganglionic fibers w/ cell bodies in

dorsal motor nucleus

of vagus

o One Q asked about the preG PS fibers of the duodenum – these are found in the dorsal motor nucleus of vagus

o Left vagus nerve:

 Enters thorax in front of the left subclavain artery & behind the left brachiocephalic vein

 Then crosses left side of the aortic arch & is itself crossed by the left phrenic nerve

 Then passes behind the left lung, forms the pulmonary plexus, & continues to form the esophageal plexus

 Enters abdomen in front of the esophagus through the esophageal hiatus of the diaphragm as the anterior vagal trunk o Right vagus nerve:

 Crosses anterior surface of the right subclavian artery & enters thorax posterolateral to the brachiocephalic trunk, lateral to the trachea, & medial (& just posterior) to the azygos vein

 Passes posterior to root of the lung, contributing to the pulmonary plexus

 Contributes to the esophageal plexus

 Enters abdomen behind the esophagus through the esophageal hiatus of the diaphragm as the posterior vagal trunk o R&L vagus nerves lose their identity in the esophageal plexus

 At lower end of the esophagus, branches of the plexus reunite to form the anterior vagal trunk (anterior gastric nerve)

• Anterior vagal trunk can be cut (vagotomy) to reduce gastric secretion o Right recurrent laryngeal nerve

 Arises from right vagus nerve in neck

 Hooks around subclavian artery & passes up/backwards behind artery & ascends in groove between trachea & esophagus (tracheoesophageal groove) (Plate 554 Clemente’s)

 Innervates:

• All muscles of the larynx (except cricothyroid – supplied by external laryngeal branch of superior laryngeal nerve) o The external laryngeal branch runs with superior thyroid artery to the cricothyroid

• Mucous MB of larynx below the vocal folds

• Mucous MB of upper part of the trachea

 Comes in contact w/ thyroid gland & comes into close relationship w/ inferior thyroid artery o Left recurrent laryngeal nerve

 Crosses arch of the aorta, hooks around ligamentum arteriosum, & ascends in groove between trachea & esophagus

 Arises from left vagus

 Innervates:

• Same muscles as right recurrent, but on left side o A few cardiac branches arise from CN X & enter cardiac plexus

 When BP goes up, then these branches increase firing

 These are pre-gang PS nerves

 Innervate heart mucle & conducting system (SA node, etc.) - Accessory Nerve (CN XI):

o Innervation to the SCM and Trapezius - Hypoglossal Nerve (CN XII):

o Motor nerve supplying all intrinsic & extrinsic muscles of the tongue (except palatoglossus – CN X and Genioglossus C1 via XII) o Leaves skull through hypoglossal canal medial to carotid canal & jugular foramen

o Passes above hyoid bone on the lateral surface of hyoglossus muscle deep to the mylohyoid muscle (Between Hyoglossus and mylohyoid) – pp 565 ECA 2^nd ed.

o Landmark  Loops around occipital artery(Clemente 444)& passes between the external carotid artery & internal jugular vein

o Soon after it leaves the skull through the hypoglossal canal. it is joined by C1 fibers from cervical plexus

 TO then supply Genioglossus, Geniohyoid, Thyrohyoid

o Unilateral lesions – result in deviation of protruded tongue toward the affected side – due to lack of function on diseased side o LMN Injury of CN XII eventually produces paralysis & atrophy of tongue on affected side w/ tongue deviated to the affected side

 Dysarthria (inability to articulate) may also be found

o NOTE: if genioglossus muscle is paralyzed, tongue has tendency to fall back & obstruct oropharyngeal airway – suffocation risk - Cranial Nerve lesions:

o CN V (motor) – jaw deviates TOWARD side of lesion o CN X – uvula deviates AWAY from side of lesion o CN XI – head turns TOWARD side of lesion o CN XII – tongue deviates TOWARD side of lesion

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- Sympathetic ganglia:

o Sympathetic trunks – two long chains of symp ganglia on either side of vertebral column that extend from base of skull to coccyx

• Damage to the sympathetic trunk causes Horner’s Syndrome

 Lie close to vertebral column & end below by joining to form a single ganglion – the ganglion impar (unpaired)

 Sympathetic ganglia are located at intervals on each sympathetic trunk alongside vertebral column

• Generally there are 3 cervical, 12 thoracic, 4 lumbar, & 4 sacral

 Gray rami connect sympathetic trunk to every spinal nerve

 White rami are limited to the spinal cord segments between T1 & L2

 Cell bodies of visceral efferent fibers (in visceral branches of the sympathetic trunk) – located in lateral horn of spinal cord (Intermediolateral cell column).

 Cell bodies of visceral afferent fibers – located in dorsal root ganglia

o Sympathetic nerves (Splanchics) arise from thoracic sympathetic ganglia (T5-T12) – they all pass through diaphragm o PreG Symp fibers may pass through ganglia on thoracic part of sympathetic trunk w/out synapsing

 These myelinated fibers form the splanchnic nerves:

• Greater – symp fibers from T5-T9 pierce diaphragm & synapse w/ excitor cells in the ganglia of celiac plexus o Nerves consist primarily of preganglionic visceral efferent fibers

o The thoracic splanchnic nerves to the celiac ganglion consist predominantly of preG visceral efferents o PostG fibers arise from excitor cells in celiac plexus & are distributed to smooth muscle & glands of viscera o Travels just posterior to the azygos vein

• Lesser – symp fibers from T10-T11 pierce diaphragm & synapse w/ excitor cells in aorticorenal ganglion

• Least – symp fibers from T12 pierce diaphragm & synapse w/ excitor cells in ganglia of the aorticorenal plexus

 The fibers from the thoracic splanchnics (T5-12) and the lumbar splanchnics synapse largely in 3 ganglia:

• 1) Celiac ganglion

• 2) Superior Mesenteric ganglion

• 3) Inferior Mesenteric ganglion

o Some nerve fibers go even more inferior to the superior hypogastric plexus to provide sympathetic innervation to the pelvic viscera

o NOTE: PS innervation of the upper 2/3 of the abdominal viscera comes via the vagus nerve which goes through the celiac plexus w/o synapsing like the sympathetics do

 The remaining inferior portions come by way of the parasympathetics from S2, S3, S4 via pelvic splanchnics o Cervical Ganglia:

 Sympathetic innervation to head & neck structures is distributed via the blood vessels (NOT CN III, VII, IX, X)

 Sympathetic innervation to head & neck structures is distributed via the blood vessels (NOT CN III, VII, IX, X)

In document The role of low-mass star clusters in the formation of massive stars (página 152-159)