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217 Cards in this Set
- Front
- Back
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C I
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Olfactory
Sensory for Smell Enters Olfactory Bulb at Base of Brain |
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C II
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Optic
Sensory for Vision From Retina, Covered with Dura Fibers cross at Optic Chiasm |
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C III
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Oculomotor
Superior division innervates: Levator palpebrae superioris Superior rectus muscles. Inferior division innervates : Medial rectus Inferior rectus Iinferior oblique muscles Parasympathetic to Sphincter Pupillae and Ciliary Muscle |
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C IV
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Trochlear
Motor to Superior Oblique |
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C V
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Trigeminal
Sensory to internal and external Head Motor to mastication muscles (V3) V1 : Ophthalmic V2 : Maxillary V3 : Mandibular Relays Parasympathetic Fibers |
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C VI
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Abducens
Motor to Lateral Rectus |
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C VII
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Facial
Motor to Muscles of Facial Expression Parasympathetic ? Taste - Anterior 2/3 of Tongue Branches Inside the internal acoustic meatus -Greater petrosal nerve - provides parasympathetic innervation to lacrimal gland, sphenoid sinus, frontal sinus, maxillary sinus, ethmoid sinus, nasal cavity, as well as special sensory taste fibers to the palate via the Vidian nerve. -Nerve to stapedius - provides motor innervation for stapedius muscle in middle ear -Chorda tympani - provides parasympathetic innervation to submandibular gland and sublingual gland and special sensory taste fibers for the anterior 2/3 of the tongue. branch to the tympanic plexus Outside skull (distal to stylomastoid foramen) -Posterior auricular nerve - controls movements of some of the scalp muscles around the ear -Branch to Posterior belly of Digastric and Stylohyoid muscle Five major facial branches (in parotid gland) - from top to bottom: Temporal (frontal) branch of the facial nerve Zygomatic branch of the facial nerve Buccal branch of the facial nerve Marginal mandibular branch of the facial nerve Cervical branch of the facial nerve |
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C VIII
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Vestibulocochlear
Sensory for equilibrium, positional sense and hearing Near Junction of Pons and Medulla |
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C IX
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Glossopharyngeal
Sensory from Pharyngeal plexus inc. posterior 1/3 of Tongue and Pharynx, external ear, external auditory meatus, tympanic cavity, epiglottis, tonsils, and auditory tubes Motor to Stylopharyngeus Parasympathetics to Parotid Gland via Auriculotemporal branch of V3 Taste to posterior 1/3 of Tongue Carotid N- sensory to baro/chemoreceptors of carotid body and carotid sinus |
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C X
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Vagus
Motor to pharynx, larynx and soft palate |
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C XI
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Spinal Accessory
Motor fibers accessory to Vagus Motor to Sternocleidomastoid and Trapezius No sensory components Origin between dorsal and ventral upper spinal cord |
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C XII
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Hypoglossal
Motor to intrinsic and extrinsic muscles of the Tongue (except palatoglossus) |
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Sympathetic Innervation of Head and Neck
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Synapse in Superior Cervical Ganglion
Target : Blood vessels, Salivary and Sweat glands, Hair Follicles, Dilator Pupillae, Tarsal Muscle |
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Parasympathetic Ganglia
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Ciliary (III)
Pterygopalatine (VII Nervus Intermedius) Submandibular (VII Nervus Intermedius) Otic (IX) |
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Spinal Innervation of Head and Neck
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?
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Carotid Sheath
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Carotid Artery
Jugular Vein Vagus Nerve Deep lymph nodes Sympathetic Fibers |
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Cervical Plexus - Sensory (Ventral Rami)
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C1 : None
C2/C3 : -Great Auricular Inferior to External Ear -Lesser Occipital Behind External Ear -Transverse Cervical Anterior Neck C3/C4 : Supraclavicular Nerves -Cutaneous for lower neck and shoulder |
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Cervical Plexus - Motor (Ventral Rami)
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C1/C2/C3 : Ansa Cervicalis
- Descendens Hypoglossi (C1) - Descendens Cervicalis (C2/C3) - Innervates Infrahyoid Muscles C2/C3/C4: - Phrenic Nerve - Longus Capitis - Levator Scapulae - Longus Colli |
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Dorsal Rami C1/C2/C3/C4
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Motor : Deep Muscles of Posterior Neck
Sensory : Dorsum of Head and Neck |
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Autonomic Innervation in the Cervical Plexus
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All nerves carry sympathetic fibers
None carry parasympathetic |
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Cranial Nerves with Parasympathetic Fibers
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3, 7, 9, 10
Relayed by 5 Targets: Mucus Secretion Salivation (Parotid Gland) Lacrimation Sphincter Pupillae Ciliary Muscle |
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Cranial Nerves with Special Sensory Functions
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1 - Smell
2 - Vision 8 - Hearing and Balance 7, 9, 10 - Taste |
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Cranial Nerves - Motor, Sensory or Mixed?
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Motor - 12 (Tongue), 3, 4, 6 (Eye)
Sensory - 1, 2, 8 Mixed - 5, 7, 9, 10, (11) |
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Anterior Cranial Fossa
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?
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Middle Cranial Fossa
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?
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Posterior Cranial Fossa
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?
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Innervation of Extrinsic Eye Muscles
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Lateral Rectus - Abducens/6
Superior Oblique - Trochlear/4 All Else - Oculomotor/3 |
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Foramen Magnum
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Junction of Spinal Cord and Brainstem
Vertebral Artery Anterior/Posterior Spinal Arteries Accessory Nerve 11 (spinal) Meningeal Branch of C1-3 |
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Hypoglossal Canal
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Hypoglossal Nerve
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Condylar Canal
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Emissary Vein and Meningeal branch of ascending Pharyngeal ARtery
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Jugular Foramen
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Sigmoid Sinus / Internal Jugular Vein
Glossopharyngeal Nerve Vagus Nerve Accessory Nerve Posterior Meningeal Artery Inferior Petrosal Sinus |
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Mastoid Foramen
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Auricular Branch of Vagus (Tympano-mastoid Fissure)
Emissary Vein |
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External opening of vestibular aqueduct
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Endolymphatic Duct
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Internal Acoustic Meatus
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Facial Nerve
Vestibulocochlear Nerve Labrynthine Artery |
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Hiatus for Lesser Petrosal Nerve
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Lesser Petrosal Nerve
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Hiatus for Greater Petrosal Nerve
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Greater Petrosal Nerve
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Foramen Lacerum
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Meningeal branch of ascending pharyngeal artery
Meningeal Lymph vessels Emissary veins from cavernous sinus to pterygoid venous plexus |
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Foramen Spinosum
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Middle Meningeal Artery and Vein
Meningeal Branch of Mandibular Nerve |
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Foramen Ovale
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Mandibular Nerve (V3)
Lesser Petrosal Nerve (9) Emissary Vein |
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Foramen Rotundum
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Maxillary Nerve (V2)
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Superior Orbital Fissure
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Oculomotor Nerve
Trochlear Nerve Abducent Nerve Superior ophthalmic vein Ophthalmic (V1) Branches : Lacrimal, Frontal and Nasociliary Sympathetics to Eye |
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Optic Canal
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Optic Nerve
Ophthalmic Artery |
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Posterior Ethmoidal Foramen
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Posterior Ethmoidal Artery, vein and nerve (V1)
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Foramina of Cribriform Plate
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Olfactory Nerve Bundles
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Nasal Slit / Anterior Ethmoidal Foramen
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Anterior Ethmoidal Artery, vein and Nerve
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Foramen Cecum
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Emissary vein to superior sagittal sinus
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Platysma Muscle
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Muscle of Facial Expression, Facilitates Jugular Blood Flow
Innervated by Facial Nerve Overlying skin innervated by cervical plexus Drained by anterior and external jugular veins Pierced by transverse cervical nerve? |
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Sternocleidomastoid Muscle
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?
Innervated by Accessory Nerve |
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Deep Cervical Fascia - External Investing Layer
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Encloses Sternocleidomastoid, Trapezius, Submandibular Gland (superiorly)
Pierced by external jugular Toughest layer of fascia Attaches to Scapula/Clavicle/Manubrium Forms roof over triangles of neck Clinical: An Infection in this layer will not spread beyond the Manubrium |
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Deep Cervical Fascia - Pretracheal Layer
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Two Components.
1. Invests Infrahyoid Muscles 2. 'Visceral' Fascia -Esophagus, larynx, trachea, thyroid gland -Inferior to buccopharyngeal fascia -Inferior blends with fibrous pericardium -Lateral blends with carotid sheath Infections between the 2 components, or between other layers of deep fascia, will spread from the neck into mediasteinum via fibrous pericardium Retropharyngeal / Retrovisceral Spaces ? Very Thin for easy neck movement |
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Infrahyoid Muscles (Strap)
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Sternohyoid
Sternothyroid Thyrohyoid Omohyoid |
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Deep Cervical Fascia - Prevertebral Layer
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Surrounds vertebral column and deep neck muscles
From base of skull to T3 Lateral as axillary sheath Penetrated by roots of Brachial Plexus Covers floor of posterior triangle Covers cervical plexus? Pus from an abscess posterior to the prevertebral layer may extend into the axilla through the axillary sheath |
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Deep Neck Muscles
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3 Scalenes
Splenius Capitis Splenius Cervicis Levator Scapulae Longus Colli Longus Capitis |
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Transverse Foramina of Cervical Vertebra
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Vertebral Artery and Vein
90% start at C6 5% start at C5 |
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Retropharyngeal Space
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Between prevertebral and pretracheal fascia
Important for spread of infections to mediasteinum. Can be entered via lacerations near pharynx Lymph nodes here drain nasal cavity, tonsils, auditory tube and pharynx. Infections of these organs can lead to retropharyngeal abscesses, or mediasteinal infections. Begins at pharynx and opens into the posterior mediastinum Route through which infections of the mouth and throat reach the mediastinum Retropharyngeal abscess Pus may penetrate the investing layer, enter the retropharyngeal space, cause abscess Lymph nodes in retropharyngeal space drain throat and nose, may become inflamed and cause abscesses Causes difficulty in swallowing (dysphagia) and speaking (dysartria) |
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Parapharyngeal space
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Carotid Sheath
Sympathetic Chain Accessory Nerve Hypoglossal Nerve |
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Vertebral Artery
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The two vertebral arteries join to form the Basilar Artery
Runs thru Transverse Foramina of C1-C6 |
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Anterior Triangle of the Neck
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Bordered by the lower mandible, anterior Sternocleidomastoid.
Roof - platsyma muscle Floor - Pretracheal Deep Fascia 4 Parts 1. Submandibular 2. Muscular 3. Carotid 4. Submental |
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Superficial Cervical Fascia
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Contains Platysma Muscle
Superficial Lymph Nodes Sensory nerves Blood vessels |
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Carotid Triangle
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Borders:
-Superior: Digastric -Medial: Omohyoid -Lateral: Sternocleidomastoid Contents: -Common Carotid (palpate) -External Carotid + Branches -Superior Thyroid Art. -Ascending Pharyngeal Art -Internal Jugular -Retromandibular Vein -Facial Vein -Inferior Thyroid Vein -Vagus -Accessory Nerve -Hypoglossal Nerve -Roots of Ansa Cervicalis Clinical: Close proximity of Vagus and Sympthetic trunk indicates good spot for combination nerve block via anesthetics for brain or upper limb |
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Submandibular Triangle
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Borders:
Superior: Mandible Lateral and Medial : Digastric Floor: Mylohyoid Contents: Submandibular Duct and Gland |
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External Carotid Artery
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Branches
Superior Thyroid A. Facial A. Superficial Temporal A. Maxillary A. Others: 1. Asc. Phar. A. 1. Occipital A. 2. Post. Auricular A. 2. Lingual A. |
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Internal Jugular Access
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Internal Jugular is most accessible where the two heads of the sternocleidomastoid divide
Easier on right side |
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Why not use the subclavian vein for catheters?
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Difficult to compress if bleeding occurs
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Posterior Triangle of the Neck
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Boundaries:
Anterior: Posterior border of SCM Inferior: Clavicle Posterior: Anterior border of Trapezius Roof: Deep investing fascia Floor: Deep prevertebral fascia Contents: Nerves -Cutaneous Cervical Plexus (transverse cervical, supraclavicular, greater auricular, lesser occipital) -Accessory N (deep to prevertebral fascia) -Phrenic -Brachial Plexus -Dorsal Scapular -Long Thoracic -Suprascapular -Subclavius N. Vessels -Subclavian Artery and Vein -External jugular (pierces the investing fascia -Transverse cervical artery Lymph Nodes |
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Root of the Neck / Thoracic Inlet
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Borders:
Manubrium 1st Rib T1 Verterbrae Contents: -Brachiocephalic Trunk (Right) Common Carotid/Subclavian (Left) -Internal Thoracic Artery -Internal Jugular Vein -Vagus Nerve: Superior Cardiac Nerve, Inferior Cardiac Nerve, Recurrent Laryngeal Nerves -Sympathetic Trunk -Strellate Ganglion -Ansa Subclavia |
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Antescalene Space
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-Intersection of Jugular and Subclavian
-Common Carotid Artery -Vagus -Phrenic Nerve -Thoracic/Right Lymphatic Ducts -Recurrent Laryngeal |
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Intescalene Space
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-Subclavian Artery
-Brachial Plexus (Roots, Trunks) -Costocervical Trunk Branch of sublclavian artery, branches into 1. Supreme Intercostal Art. and 2. Deep Cervical Art. |
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Scalenovertebral Space
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-Beginnings of Subclavians
-Vagus -Phrenic -Sympathetic Trunk -Ansa Subclavia -Right Recurrent Laryngeal -Common Carotid -Vertebral Artery -Cupula of Pleura |
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Thyrocervical Trunk
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Branch of Subclavian
1.Suprascapular 2.Transverse Cervical (Deep and Superficial) 3. Ascending Cervical 4. Inferior Thyroid |
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Lymph Nodes of the Head and Neck
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?
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Suboccipital Triangle
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Borders:
Rectus capitis posterior major - above and medially Obliquus capitis superior - above and laterally Obliquus capitis inferior - below and laterally Terminal Branches of Vertebral Artery Dorsal Rami of C1 |
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Cervical Viscera Locations
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Larynx - anterior neck, C5/C6
Trachea - C7 to T1/2 Vertebrae Pharynx - Base of Skull to inf C6. Posteriorly borders retropharyngeal space. Laterally borders the parapharyngeal space. Cervical Esophagus - C5 to T1/2. Several millimeters lateral to (L) common carotid . |
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Internal Carotid Artery
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Supplies structures inside the skull - hypophysis cerebri (pituitary gland), the orbit, and most of the supratentorial part of the brain
Branches: Anterior Cerebral Artery Middle Cerebral Artery Ophthalmic Arises from the common carotid at the level of the superior border of the thyroid cartilage Enters the carotid canal in the petrous part of the temporal bone Enters the middle cranial fossa beside the dorsum sellae of the sphenoid bone |
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Basilar Artery
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Formed by the union of the two vertebral arteries.
Branches: Two posterior cerebral arteries |
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External Carotid Artery
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Branches:
Superior Thyroid A Lingual A Facial A Ascending Pharyngeal A Occipital A Posterior Auricular A Maxillary A Superficial Temporal A |
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Details of the Branches of the External Carotid
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?
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Internal Jugular Vein
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?
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Circle of Willis
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Anastomosis between the four arteries that supply the brain.
-Posterior cerebral -Posterior communicating -Middle Cerebral -Anterior cerebral -Anterior communicating arteries |
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Anterior Cerebral Arteries
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Branch from Internal Carotid A
Supplies most of the medial and superior surfaces of the frontal pole |
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Middle Cerebral Artery
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Supplies the lateral surface and temporal pole
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Posterior Cerebral Arteries
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Supplies the lateral surface and temporal pole
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Middle Meningeal Artery
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Branch of Maxillary Artery
Enters the skull through the foramen spinosum Runs within the Dura Matter Supplies the dura and the calvaria Clinical: Runs beneath the pterion. It is vulnerable to injury at this point, where the skull is thin. Rupture of the artery may give rise to an epidural hematoma. |
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Falx Cerebri
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A folding over of dura between the cerebral hemispheres and above the Corpus Callosum.
It is attached anteriorly to the Crista Galli and posteriorly helps to form Tentorium Cerebelli and Falx Cerebelli. |
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Tentorium Cerebelli
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A horizontal fold of dura that separates the cerebral and cerebellar hemispheres from one another of both sides.
Laterally it attaches to the crest of the Petrous Temporal Bone |
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Falx Cerebelli
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Separates left and right cerebellar hemispheres.
Attached to Internal Occipital Protuberance and Tentorium Cerebelli. |
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Diaphragm Sellae
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Dura which forms roof over the hypophyseal fossa.
It is penetrated by the stalk of the Pituitary gland. |
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Superior Sagittal Sinus
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Runs in the upper end of the Falx Cerebri as a separation between regular dura and Periosteal layer.
Runs from Crista Galli to Confluence of Sinuses at Internal Occipital Protuberance. Receives the major portion of CSF returning to venous system. |
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Inferior sagittal Sinus
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Runs in lower edge of Falx Cerebri.
Ends at anterior end of Tentorium Cerebelli where it is joined by the Great Cerebral Vein (of Galen). These two go to join the Straight Sinus |
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Straight Sinus
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Formed by Inferior Sagittal Sinus and Great Cerebral vein.
It runs in the union of the Falx Cerebri with the Tentorium Cerebelli. It empties into the Confluence of Sinuses. |
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Transverse Sinuses
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Paired sinuses that run from Confluence of Sinuses laterally to the lateral part of the Crest of the Petrous portion of Temporal bone.
At this point it is joined by the paired Superior Petrosal Sinuses. |
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Sigmoid Sinuses
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Continuation of the Transverse Sinuses.
Makes an S-shaped curve down to the Jugular Foramen and helps to form the Internal Jugular vein. |
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Cavernous Sinuses
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Paired. Found on sides of the body of the Sphenoid bone.
These are connected to each other via the anterior and posterior intercavernous Sinuses. This sinus receives the Super Ophthalmic veins, Sphenoparietal Sinus, and Pterygoid Plexus of veins. |
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Superior Petrosal Sinus
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Runs from Cavernous Sinus along the crest of Petrous Temporal bone in lateral edges of Tentorium Cerebelli.
Drains into junction of Transverse and Sigmoid Sinuses. |
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Inferior Petrosal Sinuses
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Runs from Cavernous Sinuses straight down the Dorsum Sellae and Clivus to the Jugular Foramen where they also contribute to the formation of the Internal Jugular vein.
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Incisive Foramen
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Nasopalatine Nerve
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Greater Palatine Foramen
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Greater Palatine Artery, Vein, and Nerve
(Branches of Maxillary A/N) |
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Lesser Palatine Foramen
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Middle and Posterior Palatine Nerve and Artery
(Branches of Maxillary A/N) |
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Tympanic canaliculus
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Tympanic Branch of Glossopharyngeal (9)
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Stylomastoid foramen
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Facial Nerve
Stylomastoid Artery |
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Condyloid foramen
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Occipital emissary vein
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CSF Circulation
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FORMATION: Choroid Plexus -mostly in the lateral ventricles
FLOW: Latreral Ventricles foramina of Monro Third Ventricle Aqueduct (of Sylvius) Fourth Ventricle Exits Fourth Ventricle via paired lateral openings (Foramen of Luschka) and a median opening (Foramen of Magendie) basal cisterns over surfaces of cerebellum and brain stem, through tentorial notch, over surfaces of cerebral hemispheres, towards superior sagittal sinus. ABSORPTION: into superior sagittal sinus via arachnoid granulations |
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Venous Drainage of Head and Neck
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Superior/Inferior Sagittal Sinuses -> Transverse Sinus -> Sigmoid Sinus -> Internal Jugular V
Opthalmic V -> Cavernous Sinus -> Pterygoid Plexus of Veins -> Superior Petrosal Sinus -> Transverse Sinus... Maxillary & Superficial Temporal Vs -> Retromandibular V -> External/Internal Jugular V Ext/Int Jugulars -> Subclavian V |
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Brain Anastomoses
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?
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Lymphatic Drainage of Head and Neck
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?
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Infection b/w investing layer and pretrachial can spread into thorax anterior to pericardium
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word
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Thyrocervical Trunk
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From Subclavian
Branches: Suprascapular Transverse Cervical Ascending Cervical Inferior Thyroid |
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Inferior Thyroid Artery
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From Thyrocervical Trunk
Middle Cervical Ganglion lies on it Supplies posterior/inferior Thyroid Gland Anastamoses with Superior Thyroid Artery (External Carotid) Runs close to the Recurrent Laryngeal Nerve (vulnerable during surgery) |
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Recurrent Laryngeal Nerve
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Branch of Vagus
motor to everything except cricothyroid Sensory below vocal cords |
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Superior Laryngeal Nerve
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Branch of Vagus
Branches: 1. External Laryngeal N : (motor to cricothyroid) 2.Internal Laryngeal N : (sensory to larynx above vocal cords) Clinical: Superior laryngeal nerve often anesthetized for endotracheal intubation |
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Intrinsic Muscles of the Larynx
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1. Cricothyroid
external laryngeal n. Tenses 2. Posterior cricoarytenoid Recurrent laryngeal n. Abducts (only 1!) 3. Lateral cricoarytenoid, Recurrent laryngeal n. Adducts 4. Transverse arytenoid Recurrent laryngeal n. Adducts 5. Oblique arytenoids Recurrent laryngeal n. Adducts 6. Thyroartenoid Recurrent Laryngeal N Relaxes / Shortens / Decreases Tension 7. Vocalis Recurrent Laryngeal N Relaxes / Shortens / Decreases Tension |
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Submental Triangle (Anterior)
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Submental lymph nodes,
Part of mylohyoid |
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Muscular Triangle (Anterior)
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Infrahyoid muscles
Thyroid gland |
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Maxillary Artery
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From External Carotid
Branches: Middle meningeal artery Inferior alveolar Buccal Deep temporal Sphenopalatine Infraorbital |
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Sympathetic Innervation of the Head
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1. Eye
From: T1/T2 Synapse: SCG Plexus: Internal Carotid Plexus Ganglion: Ciliary Nerve: Nasociliary Function: Dilate Pupil (dilator muscle of the pupil), Raise Eyelid (superior tarsal muscle) 2. Lacrimal Gland From: T1/T2 Synapse: SCG Plexus: Internal Carotid/ Deep Petrosal Ganglion: Pterygopalatine Nerve: Lacrimal Function: Decrease Secretion 3. Sublingual/Submandibular From: T1/T2/T3/T4 Synapse: SCG/MCG/ICG Plexus: External Carotid Ganglion: Submandibular Nerve: Direct Function: Decrease Secretion 4. Parotid Gland From: T1/T2 Synapse: SCG Plexus: External Carotid / Maxillary / Middle Meningeal Ganglion: Otic Nerve: Parotid Function: Decrease Secretion |
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Infections in the neck between...
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Superficial and Investing - contained
Investing and Pretracheal 1 - contained Pretracheal 1 and Pretracheal Visceral - to pericardium Pretracheal Visceral and Prevertebral - to mediasteinum |
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Steps in eating and swallowing
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1. Tongue pushes bolus against hard palate
2. -Bolus pushed further back -Soft palate raised by: levator veli platini (X) tensor veli palatini (V) (and sup. pharnygeal constrictor) 3. -Bolus pushed further back -Pharynx and larynx raised by suprahyoid muscles: Stylopharyngeus* (IX) Palatopharyngeus (X) Stylohyoid (VII) Mylohyoid (V) 4. Epiglottis closed by posterior tongue 5. Bolus enters esophagus |
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If bolus is inhaled
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Richly innervated false vocal cords trigger cough reflex
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Lateral Cricothyroid muscles
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Function: Lengthen / Increase Tension (tense vocal cords)
Nerve: Superior Laryngeal (External) |
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Costocervical Trunk
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From Subclavian Art.
Branches: 1. Supreme Intercostal 2. Deep Cervical |
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Parasympathetic Innervation of the Head
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1. Eye
Cranial Nerve: III From: Midbrain Preganglionic Fibers: Ciliary Nerve of 3 Ganglion: Ciliary Postganglionic Fibers: Short Ciliary Nerve Function: Pupil Constriction (Sphincter Pupillae) and Cililary Muscle 2. Lacrimal Gland / Nasal and Palatine Mucus Gland Cranial Nerve: 7 From: Medulla Preganglionic Fibers: Nervus Intermedius (Genticulate Ganglion, Greater Petrosal N, Nerve to Pterygoid Canal) Ganglion: Pterygopalatine Postganglionic Fibers: Lacrimal N, Greater/Lesser Palatine, Sphenopalatine Function: Increase Secretion **Hay Fever Ganglion 3. Submandibular/Sublingual Glands Cranial Nerve: 7 From: Medulla Preganglionic Fibers: Nervus Intermedius (Chorda Tympani, V3 Lingual) Ganglion: Submandibular Postganglionic Fibers: Direct Function: Increase Secretion 4. Parotid Gland Cranial Nerve: 9 From: Medulla Preganglionic Fibers: Tympanic Branches of 9, Lesser Petrosal N Ganglion: Otic Postganglionic Fibers: Auricotemporal (V3), Direct Parotid Function: Increase Secretion |
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Pterygopalatine Fossa
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Major relay station for the distribution of the parasympathetic fibres from VII to the lacrimal gland, nasal cavity, and upper half of the oral cavity
Openings: Foramen Rotundum (Maxillary Nerve) Pterygoid Canal (Greater Petrosal Nerve - Parasympathetic 7) (Deep Petrosal Nerve - Sympathetics from Internal Carotid) (Deep + Greater Petrosal Nerve = Nerve of Pterygoid Canal) Exits: SPHENOPALATINE foramen to achieve the nasal cavity INFERIOR ORBITAL FISSURE to reach the orbit and maxillary sinus GREATER and LESSER PALATINE CANALS to reach roof of mouth, hard and soft palate PALATOVAGINAL CANAL to reach the posterior nasopharynx |
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Autonomic Lesions in the Head
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A. Parasympathetic Lesion: Dilated pupil caused by denervation of constrictor muscle of iris (Sphincter pupillae).
B. Sympathetic Lesion: Horner's Syndrome = ptosis, miosis, anhidrosis. Ptosis (drooping eyelid) denervation of superior tarsal muscle, smooth muscle in the upper eyelid. Miosis (constricted pupil) denervation of dilator muscle of iris (Dilator pupillae). Anhidrosis (lack of sweating) denervation of sweat glands. (Note: Ptosis can also occur because of CNIII lesion, leading to denervation of levator palpebrae superioris muscle). |
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Olfactory Nerve
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Origin: Olfactory bulb of forebrain.
Route: Bundles of 15-20 nerve axons pass through separate foramina of the cribriform plate of ethmoid bone. Distribution: Sensory to olfactory epithelium of upper posterior nasal cavity. |
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Optic Nerve
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OriginDefined at optic chiasm.
RouteOptic canal orbital cavity. DistributionTo retinal neural epithelium; "nerve" defined at back of eyeball. |
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Oculomotor Nerve
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OriginMidbrain.
RouteMiddle cranial fossa lateral wall of cavernous sinus superior orbital fissure orbit. Distribution. A. To 4 extraocular muscles (superior, medial and inferior recti, and inferior oblique) and the levator palpebrae superioris muscle. B. Parasympathetic fibers to ciliary ganglion intraocular (pupillary sphincter and ciliary) muscles. |
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Trochlear Nerve
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OriginDorsal aspect of midbrain.
RoutePosterior and middle cranial fossae lateral wall of cavernous sinus superior orbital fissure orbit. DistributionMotor to superior oblique (extraocular) muscle. |
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Trigeminal Nerve
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OriginMidbrain at ventrolateral surface of pons.
RouteMiddle cranial fossa to the sensory trigeminal (semilunar) ganglion in trigeminal cave (Meckel's). It divides into 3 major divisions: ophthalmic (V1), maxillary (V2) and mandibular (V3). |
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Abducens Nerve
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OriginPontomedullary junction.
RouteMiddle cranial fossa cavernous sinus near internal carotid artery superior orbital fissure orbit. DistributionMotor to lateral rectus (extraocular) muscle. |
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Facial Nerve / Nervus Intermedius
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OriginLower border of pons.
RoutePosterior cranial fossa the internal auditory meatus. Here the sensory and motor branches diverge. Distribution: 1. Branches to the muscles of facial expression, plus the buccinator, stylohyoid and posterior belly of digastric (2ndbranchial arch derivatives) The stem of the facial nerve emerges through the stylomastoid foramen and branches radially in the parotid gland. These motor nerves divide into 5 branches: temporal, zygomatic, buccal, mandibular, cervical. 2. Greater petrosal nerveSeparates at the geniculate ganglion (sensory ganglion in the petrous bone) and enters the middle cranial fossa via the hiatus of the facial canal. Is joined by sympathetic fibers, called deep petrosal nerves, to become the nerve of the pterygoid canal. This enters the pterygopalatine ganglion. Secretomotor (parasympathetic) fibers are distributed to mucous glands of nose and palate. Taste fibers are directed to the soft palate. 3. Stapedius nerveLeaves facial nerve in facial canal, enters tympanic cavity (= middle ear) to supply the stapedius muscle (also 2nd branchial arch). 4. Chorda tympani nerveLeaves facial nerve in facial canal, travels through the tympanic cavity and exits the petrotympanic fissure. Then joins lingual nerve of V3 in the infratemporal fossa. Receives taste from anterior 2/3 of tongue and sends parasympathetic branches to the submandibular ganglion which are secretomotor to the sublingual and submandibular salivary glands. 5. Sensory branches from external ear, tympanic membrane, nasopharynx, Eustachian tube. |
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Ophthalmic Nerve V1
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RouteLateral wall of cavernous sinus superior orbital fissure orbit.
Distribution. 1. Frontal nerve (sensory)Branches leave orbit through supraorbital and supratrochlear foramen (nerve branches of same name) to be distributed to skin of forehead and upper eyelids. 2. Nasociliary nerve (sensory)Ciliary branch passes through ciliary ganglion short ciliary nerves for sensation in eyeball; long ciliary branch bypasses ciliary ganglion to reach eyeball; and infratrochlear branch exits orbital cavity below trochlea to bridge of nose. Ethmoidal branches enter ethmoidal air cells and anterior ethmoidal nerve terminates as external nasal on dorsum of apex of nose. 3. Lacrimal nerve (sensory)To lacrimal gland, conjunctiva and eyelid. |
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Maxillary Nerve V2
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RouteIn the middle cranial fossa travels in the lateral wall of cavernous sinus foramen rotundum pterygopalatine fossa.
Distribution. 1. Zygomatic nerve, branches to Zygomaticofacial, Zygomaticotemporal nn. 2. Infraorbital nerve (sensory)Enters orbit through infraorbital groove. Most fibers exit onto the face via the infraorbital foramen. Proximal branches travel in the maxillary bone to join the upper dental sensory plexus (via anterior and middle superior alveolar nerves). 2. Posterior superior alveolar nerve (sensory)Travels in the maxillary bone to upper dental plexus directly after the pterygopalatine fossa. 3. Greater and lesser palatine nerves (sensory)Pass through pteryopalatine ganglion to the greater and lesser palatine foramina mucosa of hard and soft palate. |
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Mandibular Nerve V3
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RouteMiddle cranial fossa foramen ovaleinfratemporal fossa
Distribution. 1. Meningeal nerveTo dura of middle cranial fossa. 2. Motor branches to muscles of mastication, (temporal, masseter, external and internal pterygoid) tensor tympani and tensor palati, the mylohyoid and anterior belly of digastric (First branchial arch derivatives). 3. Buccal n.To buccal cavity. 4. Lingual n.Sensory to anterior 2/3 tongue, mouth, and gingiva. Is joined by chorda tympani from VII whose parasympathetic branches go through the submandibular ganglion (which is suspended off the lingual nerve) and are distributed to submandibular and sublingual salivary glands. 5. Inferior alveolar n.Sensory to teeth, gingiva, chin and lower lip. 6. Auriculotemporal n.Sensory to skin of temporal region, and external ear. Relays parasympathetics from IX to parotid glandthese fibers originate in the lesser petrosal nerve. |
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Vestibulocochlear Nerve
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OriginCerebellopontine junction.
RouteInternal auditory meatus petrous part of temporal bone internal ear. DistributionCochlear nerve for hearing and vestibular nerve for sense of position and balance. |
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Glossopharyngeal Nerve
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OriginMedulla oblongata.
RoutePosterior cranial fossa jugular foramen outside of the skull. Distribution. 1. Tympanic nerveRe-enters tympanic cavity by traveling through the tiny tympanic canaliculus. It is sensory to tympanic cavity. 2. Lesser petrosal nerveSeparates from tympanic nerve in tympanic cavity. Runs across the middle cranial fossa and exits the foramen ovale to end up in the infratemporal fossa. Here it synapses in the otic ganglion which is suspended off V3, and hooks up with the auriculotemporal branch of V3 to deliver parasympathetic secretomotor fibers to the parotid gland. 3. Motor nerve to stylopharyngeus muscle, a derivative of 3rd branchial arch. 4. Sensory and taste fibers from posterior 1/3 of tongue. 5. Pharyngeal nervesSensory to pharynx, tongue (posterior 1/3) as the afferent part of "pharyngeal plexus." This includes sensory fibers to external ear, external auditory meatus, tympanic cavity, epiglottis, tonsils and auditory (Eustachian) tube. 6. Carotid nerveSensory to the baroreceptors and chemoreceptors of the carotid body and carotid sinus. |
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Vagus Nerve
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OriginMedulla oblongata.
RoutePosterior cranial fossa jugular foramen ->outside of the skull Distribution. 1. Meningeal branchRe-enters jugular foramen to supply sensory fibers to dura in posterior cranial fossa. 2. Auricular nerveSensory to auricle, auditory meatus, and tympanic membrane. 3. Pharyngeal nervesMainly motor to pharyngeal muscles as the efferent part of "pharyngeal plexus." 4. Superior laryngeal n.Separates in the neck into the internal laryngeal nerve which supplies sensory innervation to pharynx and larynx above the vocal cords, and the external laryngeal nerve which is motor to cricothyroid muscle. 5. Recurrent laryngeal n.On the right side it separates from the vagus to hook under the subclavian artery; on the left side it hooks around the aortic arch posterior to the ligamentum arteriosum. It passes under the inferior constrictor muscle and enters the larynx and supplies motor innovation to all intrinsic muscles of larynx except the cricothyroid. It is sensory to the larynx below the vocal cords. 6. Sensory fibers to thoracic and abdominal viscera. 7. Parasympathetic (visceral motor) fibers to cardiac, pulmonary, celiac and intestinal plexus to supply thoracic and abdominal viscera. 8. Taste fibers to epiglottic region. 9. Special sensory fibers to chemoreceptors of carotid sinus and body. |
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Accessory Nerve
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OriginRootlets arise in line from medulla oblongata and spinal cord, and ascend through the vertebral canal and foramen magnum into the posterior cranial fossa.
Distribution. 1. Cranial partExits the posterior cranial fossa and jugular foramen and joins the vagus to be distributed to muscles of larynx and pharynx. 2. Spinal partExits the posterior cranial fossa and jugular foramen, and travels to innervate trapezius and sternocleidomastoid. |
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Hypoglossal Nerve
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OriginMedulla oblongata.
RoutePosterior cranial fossa to exit via hypoglossal canal. DistributionMotor nerve branches to all intrinsic and most extrinsic muscles of tongue (except palatoglossus muscle). |
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Hiatus of Facial Canal
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Greater Petrosal Nerve (7)
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Inferior Orbital Fissure
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V2 (Zygomatic)
Infraorbital Artery and Vein Orbital Branch from Pterygopalatine ganglion Ophthalmic Vein |
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Infraorbital Foramen
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Infraorbital Nerve, Artery, Vein
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Mandibular Canal
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Inferior Alveolar Artery, Nerve, Vein
Mental Nerve |
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Mental Foramen
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Mental Nerve, Artery and Vein
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Nasal Slits of Crista Gallli
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Anterior Ethmoidal Nerve and Artery to nasal cavity
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Palatovaginal (Pharyngeal) Canal
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Pharyngeal branch of V2
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Petrotympanic Fissure
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Chorda Tympani (7)
Tympanic N (9) Anterior Tympanic Artery Tympanic branch of Maxillary Art. |
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Pterygoid Canal
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Artery and Vein to Pterygoid Canal
Deep and Greater Petrosal Nerve |
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Pterygomaxillary Fissure
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Connects infratemporal fossa and pterygopalatine fossa, carries Maxillary Artery and Vein
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Hiatus of Facial Canal
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Greater Petrosal Nerve (7)
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Inferior Orbital Fissure
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V2
Infraorbital Artery and Vein Zygomatic Nerve Orbital Branch from pterygopalatine ganglion Ophthalmic Vein |
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Infraorbital Foramen
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Infraorbital Nerve, Artery, Vein
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Mandibular Canal
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Inferior Alveolar Artery, Nerve (V3), Vein
Mental Nerve (V3) |
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Mental Foramen
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Mental Nerve, Artery and Vein
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Nasal Slits of Crista Gallli
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Anterior Ethmoidal Nerve and Artery to nasal cavity
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Palatovaginal Canal
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Pharyngeal branch of V2
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Petrotympanic Fissure
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Chorda Tympani (7)
Anterior Tympanic Artery Tympanic branch of Maxillary Art. |
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Pterygoid Canal
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Artery and Vein to Pterygoid Canal
Deep and Greater Petrosal Nerve |
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Pterygomaxillary Fissure
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Maxillary Artery and Vein
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Supraorbital Foramen
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Supraorbital nerve, artery and vein
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Zygomaticofacial Foramen
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Zygomaticofacial Nerve Artery and Vein (V2)
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Zygomaticotemporal Foramen
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Zygomaticotemporal Nerve (V2)
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Bell's Palsy
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paralysis of the facial nerve resulting in an inability to move the facial muscles on the infected side of the face
my papa had it, so one side of his face is more wrinkly than the other... |
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Subdural Hemorrhage
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Cerebral Veins / Bridging Veins
Crescent Shaped Radiology Long Period of Lucidity Shearing Forces? Blood Accumulates between Dura and Arachnoid Layers |
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Epidural Hemorrhage
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Middle Meningeal artery
Radiology: Football shaped |
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Subarachnoid Hemorrhage
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Cerebral artery / Artery feeding the CNS
-Aneurysm (Barry) or AV malformation Diffuse blood (bright white) Very bad headache Complications :Hydrocephalus, Cerebral Vasospasm and Hyponatremia |
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Thyroid
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It starts in the tongue and moves down the thyroglossal duct which usually obliterates after descent.
The remenant of the part of the tongue where is starts is foramen cecum. If it doesn’t move properly, you can get a lingual thyroid. |
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Muscles of Mastication
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Innervated by Lingual V3
Elevation/Depression Elevators: Masseter Temporalis Medial Pterygoid Depressors: Digastrics Mylohyoid Geniohyoid Platysma **Lateral Pterygoid Protrusion/Retraction Lateral Pterygoid (bilateral) Temporalis Side to Side (grinding) Movements Medial and Lateral Pterygoid (unilateral, opposite side), Temporalis (unilateral, same side) |
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Drainage of Venous Sinuses in the Head
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• Superior sagittal sinus -> confluence -> Transverse sinus -> Sigmoid Sinus -> Internal Jugular Vein
• Inferior sagittal sinus + great cerebral vein (of Galen) -> straight sinus -> confluence -> Transverse Sinus -> Internal Jugular Vein • Sphenoccipital Sinus + Superior Ophthalmic Vein -> Cavernous Sinus • Cavernous Sinus -> Superior Petrosal Sinus -> Sigmoid Sinus -> IJV • Cavernous Sinus -> Inferior Petrosal Sinus -> IJV |
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Nasal Cavity
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Innervation:
Lateral wall -greater palatine nerve (V2) Nasal septum -nasopalatine nerve (V2) Parasympathetics to mucosa from pterygopalatine ganglia (VII) Blood Flow anterior/posterior ethmoidal superior labial (facial) sphenopalatine Kiesselbach’s area -90% of epistaxis |
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Cavernous Sinus
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Nerves:
OCULOMOTOR (CN III) TROCHLEAR (CN IV) ABDUCENT (CN VI) OPHTHALMIC (CN V1) MAXILLARY (CN V2) Artery: INTERNAL CAROTID |
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Anastomoses of External & Internal carotids
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ECA --> facial --> angular --> dorsal nasal --> ophthalmic --> ICA
ECA --> superficial temporal --> supraorbital --> ophthalmic --> ICA ECA --> transverse facial --> inferior lateral palpebral --> lacrimal --> ophthalmic --> ICA |
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Temporomandibular Joint
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2 planes of movement:
1. Hinge – between the articular disc and the head of the mandible (elevation and depression) 2. Gliding – between the articular disc and the mandibular fossa (protrusion and retraction; lateral movements) *Lateral Pterygoid m. fibers extend onto articular disc |
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Hydrocephalus
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Accumulation of CSF in ventricles
Communicating: normal CSF drainage pathways are intact Noncommunicating: blockage in normal CSF pathway |
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Paranasal Sinuses
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Frontal Sinus: drains inferiorly into semilunar hiatus of middle meatus via frontonasal duct
Maxillary Sinus: drains into semilunar hiatus of middle meatus Sphenoid Sinus: drains anteriorly into sphenoethmoidal recess Ethmoid Sinuses: -Anterior cells drain into middle meatus -Middle cells drain into ethmoid bulla -Posterior cells drain into superior meatus Maxillary sinus most affected in sinus infection cases! |
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Pharyngeal Tonsil
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The pharyngeal tonsils (ADENOIDS) can become inflammed (adenoiditis) and can obstruct the passage of air from the nasal cavities in the nasopharynx as well as blocking the eustachian tubes.
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Muscles of the Eye
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Medial Rectus
Oculomotor (CN III) Adduction of eyeball Lateral Rectus Abducent (CN VI) Abduction of the eyeball Superior Rectus Oculomotor (CN III) Elevation, adduction, intorsion Inferior Rectus Oculomotor (CN III) Depression, adduction, extorsion Superior Oblique Trochlear (CN IV) Depression, abduction, intorsion Inferior Oblique Oculomotor (CN III) Elevation, abduction, extorsion |
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Blood Supply to the Retina
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1. Ophthalmic Artery.
a. Main blood supply to eye and orbit. b. Branch of the internal carotid artery. c. Gives off central retinal artery (see below). d. Branches that supply the orbit include: long and short posterior ciliary, anterior ciliary, and lacrimal arteries. e. Branches that supply the face, nasal cavity and sinuses include: supraorbital, supratrochlear, dorsal nasal and anterior/posterior ethmoid arteries. 2. Central Retinal Artery. a. Runs deep to the dura mater and pierces the optic nerve near the eyeball. b. No significant collateral anastomoses. c. Supplies all retinal neurons (except rods and cones, which are supplied by the choroid capillary plexus from the ciliary arteries). d. Branches can be viewed using an ophthalmoscope. 3. Venous Drainage. a. Superior and inferior ophthalmic veins—empty into cavernous sinus. b. Central retinal vein—drains into cavernous sinus. c. Vorticose veins from vascular layer of eye—empty into inferior ophthalmic vein. d. Scleral venous sinus—recirculation of aqueous humor (blockage = glaucoma). |
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Muscles of the Tongue
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Extrinsic: Primarily MOVE the tongue. ex: Genioglossus, hyoglossus, styloglossus, palatoglossus. All innervated by CN XII except the latter, which is innervated by CN X.
Intrinsic: Primarily CHANGE SHAPE of the tongue. ex: Superior longitudinal, inferior longitudinal, transverse, vertical. All innervated by CN XII. Palatoglossus and Palatopharyngeus depress the soft palate |
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Lingual Frenulum
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Small fold of mucous membrane extending from the floor of the mouth to the midline of the underside of the tongue.
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Innervation of Tongue
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Anterior 2/3:
Lingual/V3 (Sensory) Chorda Tympani / 7 (Taste) Posterior 1/3: Glossopharyngeal Epiglottus: Vagus |
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Types of Taste
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Sweet
Salty Sour Bitter Umami |
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Innervation of Teeth
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Lower Jaw:
Inferior Alveolar from Mandibular/V3 (Anasthetised by dentist; also gets mental (branch of V3) and lingual |
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Lateral Pterygoid
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Moves head of mandible forward from articular fossa to articular tubercle
1. Depression 2. Protrusion 3. Grinding |
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Nasal Conchae
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On the lateral wall of the Nasal Cavity
Humidifies and warms up air breathed in through nose Superior, Middle and Inferior 1. Sphenoethmoidal Recess: (above the superior concha) Opening of the sphenoid sinus. 2. Superior Meatus:Opening of the posterior ethmoid cells. 3. Middle Meatus: Opening of the frontal sinus (enters semilunar hiatus through the frontonasal ducts), opening of the maxillary sinus and the anterior and middle ethmoid cells. 4. Inferior Meatus: Opening of the nasolacrimal duct. |
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Epistaxis
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Nosebleeds
90% from Kiesselbach's Plexus Other's from posterior / due to atherosclerosis of Sphenopalatine Artery |
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Kiesselbach's Plexus
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Anteroinferior Nasal Cavity
Anastamoses of * anterior ethmoid artery * great palatine artery * sphenopalatine artery * superior labial artery |
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Arterial Supply of Nasal Cavity
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Sphenopalatine (Maxillary)
Anterior/Posterior Ethmoid (Ophthalmic) Facial (External Carotid) |
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Maxillary Sinus
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**Likely to get infected because it has to drain upwards into the semilunar hiatus of middle meatus
1. Maxillary Sinus: Tetrahedral shape; largest of the sinuses. a. Aperture. Middle meatus; will not drain if the head is erect (most commonly infected). b. Relations. (1) Superior¾Infraorbital nerve and orbit. (2) Medial¾Nasal cavity. (3) Ant and Lateral¾Cheek. (4) Posterior¾infratemporal fossa, pterygopalatine fossa and ganglion, maxillary artery. (5) Inferior¾Roots of premolar and molar maxillary teeth. c. Nerve Supply. Anterior, Middle, and Posterior Superior Alveolar nerves. d. Blood Supply. Maxillary a. (superior alveolar and greater palatine branches). e. Clinical. Pain from maxillary sinusitis in cheek or teeth. |
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Frontal Sinus
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Infections here can spread to frontal lobe of brain
Drains inferiorly into semilunar hiatus a. Aperture. Drains at an inferiomedial angle via hiatus semilunaris into the middle meatus. b. Relations. (1) Superior¾Anterior cranial fossa and contents. (2) Anterior¾Forehead, supraorbital and supratrochlear nerves. (3) Medial¾Other frontal sinus. (4) Inferior¾Orbit, anterior ethmoid sinuses. (5) Posterior¾Anterior cranial fossa. c. Nerve Supply. Supraorbital and Supratrochlear nerves. d. Blood Supply. Ophthalmic artery. e. Clinical. Pain from frontal sinusitis is around eyes and forehead. |
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Ethmoid Sinus
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Drains into 3 different places
a. Aperture. Anterior group into middle meatus via hiatus semilunaris, middle group on bulla and posterior group into superior meatus. b. Relations. (1) Medial¾Nasal cavity. (2) Lateral¾Medial wall of orbit. (3) Superior¾Anterior cranial fossa. c. Nerve Supply. Ophthalmic division via anterior and posterior ethmoids and from maxillary division via nasal branch. d. Blood Supply. Anterior and posterior ethmoid arteries, sphenopalatine a. via lateral nasal branch. e. Clinical. Pain from ethmoid sinusitis located in the retro-orbital area between the eyes. |
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Sphenoid Sinus
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**A potential complication of sphenoid sinusitis is cavernous sinus thrombosis.
Drains anteriorly into sphenoethmoidal recess a. Aperture. Drains anteroinferiorly into sphenoethmoidal recess. b. Relations. (1) Medial¾Sinus of other side. (2) Superior¾Hypophyseal fossa, pituitary gland and optic chiasm. (3) Lateral¾Cavernous sinus, internal carotid artery, CN III, IV, V, and VI. (4) Anterior¾Nasal cavity. (5) Inferior¾Nasopharynx, pterygoid canal. c. Nerve Supply. Ophthalmic division via posterior ethmoidal nerve and maxillary division via sphenopalatine branch. d. Blood Supply. Posterior ethmoid arteries and sphenopalatine artery. e. Clinical. Pain at the vertex, occipital as well as the retro-orbital region. |
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Taste Papillae
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Circumvillate, Foliate and Fungiform (not filiform)
taste receptors are NOT neurons, they're specialized Ectoderm/Epidermis Synapse with neurons Onion like |
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Olfaction
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Upper 1/3 of nasal cavity
(And some via oropharynx behind the soft palate) Odor molecules have to dissolve in mucus to reach olfactory receptors Trigeminal nerve also involved |
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Middle Ear
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Bones: Ossicles (Malleus, Incus, Stapes)
Opens to the nasopharynx via Eustachian tube Air filled (from nasopharynx, to mastoid air cells) *Infections can spread to mastoid air cells |
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Ossicle Action
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When tympanic membrane is moved, malleus (attached) moves, incus moves, stapes moves (attached to oval window), fluid waves generated in inner ear
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Eustachian Tube
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Middle air to Nasopharynx
Opened by contraction of Levator Veli Palatini and Tensor Veli Palatini During Swallowing, tube is closed Prone to infection in kids -> Retards speech development ->Can spread to mastoid air cells |
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Muscles of Inner Ear
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Tensor Tympani (V3)
Stapedius (7) Function: Reduce oscillation of ossicles; protect from loud sounds (and while talking) |
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Caudal pharyngeal complex
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Pharyngeal Arches 4-6
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Components of each pharyngeal arch
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Cartilaginous bar
Muscle component Nerve Aortic Arch Artery |
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Pharyngeal Arch Divisions
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Exterior - ectoderm
Grooves Interior - endoderm Pouches Between grooves and pouches - closing membrane |
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Closing Membrane
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Between pharyngeal grooves and pouches
1st closing membrane becomes the tympanic membrane |
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Branchial Cist / Fistula
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2nd branchial arch grows over the 3rd and 4th to meet the future neck region of the embryo
Forms cervical sinus. This normally obliterates but fails to do so in a small number of individuals. Can be open to inside, outside, or both (fistula) Can spread infections Branchial cysts, sinuses and fistulae. Remnants of branchial primordia which either open into the pharynx (internal sinus) or onto the exterior of neck (external sinus). Fistulae are patent tracts that connect the interior of the pharynx with the surface of the neck, and are most common for the second pouch and cleft due to failure of closure of the cervical sinus. Mucus may drip from this opening, which connects the tonsillar fossa (remnant of pouch 2 location) with the skin over the anterior margin of the sternomastoid. |
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Nerves of the Pharyngeal Arches
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* 1st arch: The trigeminal nerve (V). The first arch consists of two processes, the maxillary and the mandibular. The maxillary branch of the trigeminal (V2) innervates the maxillary process, and the mandibular branch (V3) innervates the mandibular process. The ophthalmic branch of the trigeminal (V1) innervates the structures deriving from the fronto-nasal process, which is sometimes called arch zero.
* 2nd arch: The facial nerve (VII). * 3rd arch: The glossopharyngeal nerve (IX). * 4th-6th arch: The vagus (X) and accessory (XI) nerves. |
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Arteries of the Pharyngeal Arches
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* 1st arch: Regresses considerably to form maxillary artery.
* 2nd arch: Regresses almost totally to form stapedial artery in middle ear. * 3rd arch: Proximal parts form the common carotids; distal portions give rise to part of internal carotids. * 4th arch: On left, gives rise to part of the aortic arch; on right, to the subclavian artery. * 6th arch: Becomes pulmonary trunk, with ductus arteriosus connecting the left pulmonary artery and aorta. The right distal portion of the pulmonary trunk regresses; this is why the left recurrent laryngeal branch of the 6th arch nerve (vagus) loops around the 6th arch-derived ligamentum arteriosum while the right recurrent laryngeal branch, after the right 6th arch artery regresses, loops around the next most cranial structure, the subclavian artery. |
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Muscles of the Pharyngeal Arches
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o 1st arch: Muscles of mastication (masseter, temporalis, pterygoids) as well as the anterior belly of the digastric, the mylohyoid, the tensor tympani and tensor veli palatini. These are innervated by the nerve of the 1st arch, the trigeminal, specifically the mandibular division (the only branch of V with a motor component).
o 2nd arch: All muscles of facial expression; posterior belly of the digastric, the stylohyoid. (Facial nerve innervation.) o 3rd arch: The stylopharyngeus. (Glossopharyngeal innervation.) o 4th-6th arches: The intrinsic muscles of the larynx; trapezius and sternocleidomastoid. The latter two are innervated by the accessory (XI). |
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Cartilage of the Pharyngeal Arches
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* 1st arch: Meckel's cartilage ossifies intramembranously to form the mandible. 1st arch cartilage also gives rise to two bones of the middle ear, the malleus and the incus and its perichondrium gives rise to the sphenomandibular ligament.
* 2nd arch: Reichert's cartilage gives rise to the stapes bone of the middle ear and perhaps contributes part of the malleus and incus. 2nd arch cartilage also gives rise to the styloid process, the lesser cornu and upper body of the hyoid bone and its perichondrium gives origin to the stylomandibular ligament. * 3rd arch: Greater cornu and most of the body of the hyoid bone. * 4th-6th arches: The cartilages of the larynx: thyroid, arytenoid, cricoid, corniculate and cuneiform. |
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External Ear
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Arises from 1st and 2nd arch
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Pharyngeal Pouch Derivatives
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1: Tubotympanic Recess
2: Tonsillar fossa and epithelium of palatine tonsils 3: Inferior parathyroid glands and most of thymus 4: Superior parathyroid glands and small portion of thymus * 1st pouch: Gives rise to the tubotympanic recess (this part of the middle ear encloses the ear ossicles and communicates with the nasal cavity) through the eustachian tube. * 2nd pouch: Gives rise to the tonsillar fossa and epithelium of the palatine tonsils. * 3rd and 4th pouches: Give rise to the thymus and the parathyroid glands. Pouch 3 gives rise to the "inferior" parathyroids and the major part of the thymus. Pouch 4 gives rise to "superior" parathyroids and a small part of the thymus. |
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Parathyroid Development
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The inferior parathyroids hitch a ride with the thymus down to their ultimate position on the thyroid gland. As a result, they end up below the parathyroids from pouch 4.
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Ectopic Parathyroid / Thymus / Thyroid
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All Descend and can stop anywhere along the way
Parathyroids might not move from thymus to thyroid Undescended thyroid - lingual thyroid Thyroid descends through thyroglossal duct (obliterates) and Foramen Cecum? 3. Ectopic thymus: Thymus may fail to reach mediastinum and ectopic tissue/accessory tissue may be found anywhere along its expected track. 4. Ectopic/undescended thyroid: Lingual thyroid. At puberty, growth of thyroid may lead to pharyngeal obstruction. Also remnants of thyroglossal duct may remain. Treatment of lingual thyroid involves excision and thyroid replacement therapy. |
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DiGeorge syndrome
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3rd and 4th Pouch defect
CATCH22 : Cardiac Defects Abnormal facies Thymic hypoplasia Cleft Palate Hypocalcemia Due to abnormal migration of neural crest cells to pharyngeal pouches Congenital thymic aplasia and absence of parathyroid glands. Infants were born with a variety of facial defects and succumbed early in life to many types of infection. Autopsy showed absence of thymic and parathyroid tissue. Defects are related to teratogens acting in 4th-6th week of development, yielding a broad range of pharyngeal region abnormalities. |
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Treacher-Collins syndrome / mandibulofacial dysostosis
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First Arch defect
Defect of neural crest migration. Lack of zygomatic bone Mandibular hypoplasia Eyelid defects Micrognathia (small jaw) Defects of the external ear. |
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Pierre - Robin Syndrome
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First arch defect
Small mandible does not allow tongue to descend Non descended tongue blocks palatine shells from fusing U shaped palatal cleft Tongue can occlue oropharynx Initiating defect is small mandible which doesn't allow descent of tongue. Palatine shelves which are vertically oriented, have to swing to a horizontal position to normally fuse and form the hard palate. Since the palatine processes never fuse, there is a U-shaped palate cleft. |
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Embryology: Facial Processes
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Frontonasal: Forehead, primary palate (premaxilla), most of nose (from medial and lateral nasal swellings)
Maxillary: Lateral parts of upper lip, secondary palate Mandibular: Lower jaw and lower lip |
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Tongue Development
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1st Arch: Lateral Lingual Swellings, Anterior 2/3
3rd Arch: Posterior 1/3 4th Arch: Epiglottis Motor innervation: Hypoglossal (Except palatoglossus - Vagus) |
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Facial Development
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Cleft Lip / Palate
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