Week 2 Anatomy of the Face and orbit, eyelids, CN III, IV, VI Flashcards
List the muscles of facial expression and their functions
- Frontalis muscle: “surprise” wrinkle forehead and raises eyebrows
- Orbicularis oculi: around orbital margin and eyelids. Close eyelids “blink/wink”
- Orbicularis oris: encircles and inserts into lips. pursing lips, protruding them, and compressing them against teeth. speech production. “whistling/kissing”
- Buccinator: inserts at angle of mouth and into orbicularis oris. keeps cheeks taut and keeps food away from cheek pouches and from entering vestibule of mouth
- Zygomaticus major: elevate labial commissure and used in “smiling”
- Platysma: depress mandible and tense skin of lower face and neck against resistance “grimace”
Describe the peripheral distribution of CN VII, the facial nerve
Exits from stylomastoid foramen
- divides into temporal, zygomatic, buccal, mandibular, cervical branches, (nerve to stylohyoid muscle, nerve to posterior belly of digastric), posterior auricular nerve
- Tiny zebra bite my clit please
Describe the clinical features of Bell’s palsy
site of lesion: below the stylomastoid foramen, where CNVII exits the skull
symptoms: ipsilateral
- drooping of mouth, drooling (orbicularis iris)
- drooping of eyelid and eversion (dry eye and tearing) (orbicularis oculi)
- accumulation of food between cheek and teeth when chewing (buccinator and orbicularis iris)
- inability to close eye or wrinkle forehead (frontalis and orbicularis oculi)
Describe the anatomical relationships of the parotid gland and the parotid duct
- parotid gland: antero-inferior to external auditory meatus
- parotid duct: passes horizontally over masseter muscle and pierces buccinator muscle. Enters oral cavity near 2nd maxillary molar
Describe the innervation of the parotid gland
Inferior salivatory nucleus (para/pre cell bodies)–>travel with CN IX (lesser petrosal nerve)–>exits through foramen oval, synapse in otic ganglion–>travel with CN V3 (auriculotemporal nerve).
Describe the peripheral distribution of the three division of CN V, trigeminal nerve
CN V1 (ophthalmic): supraorbital nerve exits supraorbital notch on forehead CN V2 (maxillary): infraorbital nerve goes through infraorbital foramen- cheek, skin and conjunctiva of lower eyelid, skin and mucus membrane of upper lip, upper teeth and gums, nasal mucosa CN V3 (mandibular): mental nerve-exits mental formaen
Describe the clinical features of trigeminal neuralgia
- can affect single or multiple divisions of CN V (V2 or V3 usually)
- episodes of intense pain lasting a few seconds to a few minutes
- cause unknown, related to compression of trigeminal nerve by adjacent vessel
Trace the course of the facial artery and facial vein
- Facial artery: branch of external carotid artery-winds way to inferior border of mandible, crosses superficially. crosses over buccinator and maxilla and takes diagonal course toward medial angle of eye. Tortorous
- Facial vein: begins near medial angle of eye, runs inferoposteriorly through face, posterior to facial artery. Joined by retromandibular vein and drains into Internal jugular
list the neighboring anatomical regions and structures related to each wall of the orbit
- superior: frontal sinus and frontal lobes of brain in anterior cranial fossa
- posterior: temporal lobes of brain in middle cranial fossa
- apex: cavernous venous sinus and sphenoid sinus
- medial: ethmoid air cells
- inferior: maxillary sinus
List the fascial structures of the orbit and their function.
- periorbital: periosteum that lines orbit walls
- orbital septum: closes off orbital opening anteriorly where it extends from orbital margin to tarsal plates
- tarsal plates (superior and inferior): dense connective tissue within upper and lower eyelid. connected to orbital septum. joined medial and laterally by palpebral ligaments
- optic sheath: continuation of meningeal layer of dura around optic nerve
- sclera: touch whitish outer layer of eyeball that extra ocular muscles are attached to.
- bulbar sheath: thin membranous fascia that separates eyeball and extra ocular muscles
What are the five structural layers of the eyelids?
- Skin
- subcutaneous layer: eyelashes and sebaceous glands
- muscular layer: made of lavatory palpebrae superiors inserting into superior tarsal plate and interdigitating with orbicular is oculi
- tarsofascial layer: orbital septum inserting into tarsal plates. tarsal glands in plates.
- palpebral conjunctiva: thin moist transparent epithelium covering inside of lid
What is the superior tarsal muscle (mueller’s muscle)?
-smooth muscle arising from legator palpebrae superiors and inserting into tarsal plate. maintains elevated position of upper eyelid against gravity. innervated by symp/post from cervical sympathetic trunk ganglion
List the innervation and anatomical function of each extraocular muscle.
- superior rectus muscle: oculomotor nerve, elevates and adducts (medial)
- inferior rectus muscle: oculomotor nerve, depresses and adducts
- medial rectus muscle: oculomotor nerve, adducts
- lateral rectus muscle: abducent nerve, abducts
- superior oblique muscle: trochlear nerve, depresses and abducts
- inferior oblique muscle: oculomotor nerve, elevates and abducts
MULTIFUNCTIONAL MUSCLES: pass medial to vertical axis
-inferior and superior rectus: pull posteriorly
-inferior and superior oblique: pull anteriorly
Trace the pathway of parasympathetic innervation to the eye.
edinger-westphal nucleus (para/pre cell bodies)–>via CN III–>ciliary ganglion (para/post cell bodies)–>ciliary nerves–>sclera on the back of the eyeball–>through walls around circumference of eyeball–>ciliary body (accommodation or focusing)+sphincter pupillae muscle (constriction)
What do the motor components of the oculomoter nerve (CNIII) supply?
levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, inferior oblique muscles
Trace the pathway of the oculomotor nerve.
middle cranial fossa–>wall of cavernous sinus–>superior orbital fissure–>orbit–>upper and lower divisions that supply muscles above and below level of optic nerve
What nerve and nerve component is responsible for innervating the smooth muscles related to the constriction of the pupil and accommodation and focus?
parasympathetic component of oculomotor (CNIII). Via ciliary nerves.
Trace the pathway of the trochlear nerve. What nerve components are there?
trochler nucleus–>middle cranial fossa–>wall of the cavernous sinus–>superior orbital fissure–>orbit–>superior oblique muscle
-motor only
Trace the pathway of the abducent nerve. What nerve components are there?
abducent nucleus–>posterior cranial fossa–>cavernous sinus–>superior orbital fissure–> orbit–>lateral rectus muscle only (motor only)
What is innervated by the ophthalmic nerve (CNV1) with respect to the eyes, orbit, eyelids?
- upper eyelid: conjuctiva and outside skin (branches include nasociliary)
- bulbar conjunctiva covering eyeball
- cornea reflex: afferent is SS via opththalmic nerve and efferent is SM via facial nerve contracting obicularis oculi
What is innervated by the maxillary nerve (CN V2) with respect to the eye, orbit, eyelids?
-lower eyelid: inside and outside
What component of the facial nerve innervates the lacrimal gland. Trace the pathway of the facial nerve to the lacrimal gland.
-Parasympathetic pathway
superior salvatory nucleus–>facial nerve–>geniculate ganglion–>greater petrosal nerve–>nerve of pterygoid canal–>pterygopalatine ganglion (para/post)–>branches of maxillary and ophthalmic nerves–>orbit–>lacrimal gland
What do the sympathetic innervations of the eyeball innervate?
- superior tarsal muscle=smooth muscle between legator palpebrae superiors and superior tarsal plate that maintains position of upper eyelid against gravity
- Dilatory pupillae muscle=smooth muscle in iris responsible for enlarging pupil
Trace the pathway of the sympathetic nerves to the eyeball.
lateral gray horn of T1-4/5–>ventral roots–>spinal nerve–>white rami–>sympathetic trunk–>superior cervical sympathetic ganglion–>jump onto internal carotid artery as carotid plexus–>hitchhike onto CN 3,4,5,6 to eye muscles
