Lecture 16 - Ear, Orbit, and Nasal Cavaties Flashcards
Outer Ear
Auricle: •Layer of skin over cartilage framework •Lobule = fibrous fatty tissue with no cartilage
Sensory innervation:
•Great auricular nerve
•Auriculotemporal nerve
•Lesser occipital nerve
External acoustic (auditory) meatus: •From auricle to tympanic membrane •2.5 cm in length •S-shaped •Lined by skin and ceruminous glands
Middle Ear
Tympanic Membrane Tympanic Cavity Auditory Ossicles Stapedius Muscle Tensor Tympani Muscle CN IX
Tympanic membrane:
•Dense fibrous membrane •Covered by skin externally •Covered by mucosa internally
Tympanic cavity:
•Air-filled cavity within petrous portion of temporal bone
- Round window:
- Enclosed by secondary tympanic membrane:
- Undergoes compensatory excursions with movement of stapes
•Oval window: •Closed by footplate of stapes
Auditory ossicles
- Malleus: •Attached to tympanic membrane
- Incus
- Stapes: •Attached to oval window (fenestra vestibuli)
Stapedius muscle
•Inserts onto neck of stapes •Contracts reflexively in response to loud sounds •Innervated by CN VII
Tensor tympani muscle:
- Inserts onto malleus.
- Contracts reflexively to loud sounds.
- Innervated by CN V-3.
CN IX
- Tympanic nerve: •GSA to mucosa of tympanic cavity, mastoid air cells, and auditory tube
- Lateral petrosal nerve: •Leaves tympanic cavity to floor of middle cranial fossa •Descends through foramen ovale to infratemporal fossa •Ends in otic ganglion
Inner Ear
Lies within petrous part of temporal bone.
Consists of:
•Bony labyrinth: •Lined with periosteum
•Membranous labyrinth
•Supplied by: •Labyrinthine artery (from basilar artery): •(Basilar artery is formed by fusion of two vertebral arteries)
Cochlea:
Vestibule: •Contains: •Utricle •Saccule
Vestibulocochlear (auditory) nerve (CN VIII)
Semicircular Canals
Utricle/Saccule
Semicircular canals
•Anterior, posterior, lateral •Arranged in three planes •Open into utricle •Dilated at one end to form ampulla: •With crista ampullaris •Senses rotational acceleration
Utricle and Saccule
•With macula •Senses linear acceleration and pull of gravity
Cochlea
•Resembles a snail shell •Three turns •Round window (fenestra cochlea)
Roof (Bones of Orbit)
- Orbital plate of frontal bone (A)
- Lesser wings of sphenoid (B)
- Related to: •Frontal cerebral lobes
- Special features: •Fossa for lacrimal gland
Floor (Bones of Orbit)
- Orbital plate of maxilla (A)
- Zygomatic (B)
- Orbital process of palatine
- Related to: •Maxillary sinus
- Special features: •Infraorbital groove and canal: •Infraorbital nerve: •Continuation of cranial nerve V2 •Infraorbital artery: •Branch of external carotid artery
Medial wall (Bones of Orbit)
- Lacrimal (A)
- Frontal (B)
- Ethmoid (C)
- Related to: •Ethmoid air cells •Sphenoid sinus •Nasal cavity
- Special features: •Fossa for lacrimal sac •Opening for nasolacrimal canal
Lateral Wall (bones of orbit)
- Zygomatic (A)
- Greater wing of sphenoid (B)
- Frontal
•Related to: •Temporal fossa containing temporalis muscle •Middle cranial fossa
External Features of the Eye
- Conjunctiva
* Eyelids: •Tarsal plates •Tarsal glands
Lacrimal apparatus
•Lacrimal papilla and puncta •Lacrimal canaliculi and sac •Nasolacrimal duct
Superior orbital fissure
- III
- IV
- V-1 (ophthalmic branch): •Frontal •Lacrimal •Nasociliary
- VI
- Superior ophthalmic vein
Optic canal
- Cranial nerve II
* Ophthalamic artery
Anterior and posterior ethmoidal foramina
Exit for anterior and posterior ethmoidal nerves
Inferior orbital fissure
Cranial nerves: •V2: •Infraorbital nerve •Zygomatic branch •Orbital branches
Six Extrinsic Muscles of the Eye
Inferior Oblique Superior Rectus Medial Rectus Inferior Rectus Superior Oblique Lateral Rectus ((Levator Palpebrae Superioris))
Sensory Innervation of Orbit
Optic nerve
Ophthalmic nerve (V1):
•Lacrimal nerve •Nasociliary nerve: •Infratrochlear •Anterior and posterior ethmoidal nerves •Frontal nerve: •Supratrochlear •Supraorbital
Hard Palate
- Anterior two-thirds of palate
- Palatine folds of maxillae
- Palatines
Soft Palate
- Posterior third of palate
* Fibromuscular fold
Teeth
- Maxillary
* Mandibular
Vestibule/Mucous Membranes
- Between lips/cheeks and gums/teeth
- Leads to: Oral cavity proper
- Receives: Parotid duct: Opposite upper second molar
Oral cavity/Mucous Membranes
- Bounded by: Teeth and gums, Hard/soft palates
- Leads to: Pharynx (oropharynx)
- Uvula
Sensory Innervation of Mucous Membranes
CN V2:
•Greater and lesser palatine nerves
•Nasopalatine nerves
CN V3: •Lingual nerve: •Floor of mouth •Buccal nerve: •Vestibule and cheek
Motor Innervation of Mucous Membranes
Sympathetics (see nasal cavity)
Sublingual and submandibular glands: •Parasympathetics from: •Superior salivatory nucleus via CN VII •To: •Submandibular/sublingual ganglia •To: •Submandibular and sublingual glands
Parotid glands:
•Parasympathetics from: •Inferior salivatory nucleus via CN IX
•To: •Otic ganglion
•To: •Parotid gland
Cranial Nerve VII
Facial Nerve
Tongue
Mass of skeletal muscles covered by mucosa.
•Location: •Anterior two-thirds in oral cavity proper •Posterior third in oropharynx
•Sulcus terminalis
•Foramen cecum
•Frenulum
•All intrinsic and extrinsic muscles of the tongue are innervated by CN XII
Maxillary teeth:
Superior alveolar branches of CN V-2
Mandibular teeth:
Inferior alveolar branches of CN V-3
Tongue: general sensory:
- Anterior two-thirds: •CN V3 via lingual nerve
* Posterior one-third: •CN IX
Tongue: taste:
- Anterior two-thirds: •CN VII via chorda tympani
* Posterior one-third: •CN IX
