Lecture 6: Skull, face, ear and eye Flashcards
How many bones compose the skull?
22
How many bones are in the neurocranium?
8
How many bones are in the viscerocranium?
Facial bones
14
Bones of the neurocranium
Parietal (paired)
Temporal (paired)
Frontal
Occipital
Sphenoid
Ethmoid
See figure
Paired bones of viscerocranium
- Nasal
- Zygomatic
- Lacrimal
- Maxilla
- Inferior conchae
- Palatine
See figure
Singluar bones of viscerocranium
Vomer
Mandibula
See figure
What are muscles of facial expression innervated by? Where does it exit?
Cranial nerve VII
Stylomastoid formaen, protected by mastoid process
Major muscles of facial expression
Note: 17 muscles total
Orbicularis oris
Orbicularis oculi
Buccinator
Frontalis
See figure
Function of orbicularis oris
Sphincter of mouth
Works with buccinator and tongue to keep food between the teeth during mastication
Protrudes lips (kissing)
Function of buccinator
Works with orbicularis oris and tongue to keep food between the teeth during mastication
Presses teeth against molar teeth: active during sucking, blowing, whistling
Active in smiling
Function of orbicularis oculi
Closes the eyelids
Assists the flow of lacrimal fluid (tears)
Winking
Muscles of mastication
Temporalis
Masseter
Medial pterygoid
Lateral pterygoid
See figure
Innervation of mastication muscles
Mandibular nerve
Third branch of trigeminal nerve (CN V3)
Which muscles close the mouth?
masseter
temporal
medial pterygoid
Which muscles open the mouth?
lateral pterygoid
supra‐/infrahyoid muscles
Which muscles cause protrusion of mouth?
lateral pterygoid
masseter
medial pterygoid
Which muscles cause retrusion?
temporal
masseter
Major branches of the external carotid artery
- Superior thyroid
- Lingual
- Facial
- Occipital
- Ascending pharyngeal
- Maxillary
- Posterior auricular
- Superficial temporal
See figure
What are anastomoses between the internal and external carotid arteries?
They are connections between the ICA and ECA
Important clinically because if you have an external injury, the germs could have an access route to the brain
See figure
Major veins of the face
- Facial
- Occipital
- Maxillary
- Retromandibular
- Superficial temporal
- Pterygoid plexus
- Superior thyroid
- External jugular
See figure
What do the major veins of the face drain into?
The internal jugular vein
Anatomy of the human eye
Sclera
Choroid
Retina
Fovea
Optic nerve
Ciliary body
Iris
Lens
Pupil
Cornea
See figure
What is the role of the eyelid?
Controls influx of light, protects retina from overstimulation
Bones making up the orbit
- Frontal
- Zygomatic
- Maxillary
- Nasal
- Lacrimal
- Ethmoidal
- Sphenoid
- Palatine
See figure
What extra ocular muscles does the oculomotor nerve (CN III) innervate?
Levator palpebrae superioris
medial rectus
Inferior rectus
Inferior oblique
Which nerves innervate the extra ocular muscles?
Oculomotor nerve (CN III)
Trochlear nerve (CN IV)
Abducens nerve (CN VI)
What extra ocular muscles does the trochlear nerve (CNIV) innervate?
Superior oblique
What extra ocular muscles does the abducens nerve (CNVI) innervate?
Lateral rectus
What movements are produced by extra ocular nerves?
Levator palpebrae superioris (lifts eye upper lid)
medial rectus (moves pupil medial)
inferior rectus (moves pupil down)
inferior oblique (moves pupil lateral and up)
Superior oblique (moves pupil lateral and down)
Lateral rectus (moves pupil lateral)
See figure
Posterior compartment of the eye
Retina
See figure
What is the blind spot?
Optic nerve
Two main sources of blood to the retina
Choroidal arterial vessels: supply >70% of blood, located at outside of retina, essential for survival of receptors
Central retinal artery: supplies 20-30% of blood, located on inside of retina, nourishes inner retinal cell layers
Choroidal and central retinal arteries are branches of the ophthalmic artery which is a branch of the internal carotid artery
See figure
Three parts of the ear
Outer ear
Middle ear
Inner ear
See figure
Content of outer ear
Auricle
Outer ear canal
Content of middle ear
Ossicles
Tympanic cavity
Auditory tube (eustachian)
Content of inner ear
Cochlear and vestibular system
What is the importance of the eustachian tube?
Connects to pharynx and plays important role in equilibrating pressure differences between outside and middle ear
What is the audible range of frequencies?
20 Hz - 20 kHz
What is the most sensitive hearing range?
1.2 kHz - 4 kHz
What are the three ossicles?
Malleus
Incus
Stapes
See figure
Where is the inner ear located?
Within the temporal bone
What does the cochlea contain that is important for hearing?
Sensory hair cells
Hearing
1) Sound waves entering external ear stroke the tympanic membrane, causing it to vibrate
2) Vibrations initiated at the tympanic membrane are transmitted through the ossicles of the middle ear and their articulations
3) The base of the stapes vibrates with increased strength and decreased amplitude in the oval window
4) Vibrations of the base of the stapes create pressure waves in the perilymph of the scala vestibuli
5) Pressure waves in the scala vestibuli cause displacement of the basilar membrane of the cochlear duct. Shorter waves (high pitch) cause displacement near the oval window. Longer waves (low pitch) cause more distant displacement. Movement of the basilar membrane bends the hair cells of the spiral organ. Neurotransmitter is released, stimulating action potentials conveyed by the cochlear nerve to the brain
6) Vibrations are transferred across the cochlear duct to the perilymph of the scala tympani
7) Pressure waves in the perilymph are dissipated (dampened) by the secondary tympanic membrane at the round window into the air of the tympanic cavity
See figure
What is the role of the vestibular system
Balance system
Controls posture, co-ordinates body, head, and eye movements, maintains balance, and spatial orientation
2 main parts of vestibular system
Kinetic labyrinth (red)
Static labyrinth (orange)
See figure
Components of kinetic labyrinth
Crista (sensory epithelium) within ampulla in each semicircular duct
Function of kinetic labyrinth
Detects rotational movements of head
Components of static labyrinth
Saccule & Utricle are the OTOLITH ORGANS which contain sensory epithelium (macula)
Function of static labyrinth
detect linear acceleration/ deceleration (forward/backward, up/down lift movements)
Function of frontal muscle
Raises eyebrows, wrinkles forehead
