week 2: eyes and ears

What are the three subdivisions of the ear?

External ear

Middle ear

Inner ear

What structures are involved in balance and hearing?

Structures of the ear are involved in balance and hearing

What are the structures of the external ear?

Auricle

External acoustic meatus

Tympanic membrane

Ceruminous glands

What are the structures of the middle ear?

Tympanic cavity

Auditory ossicles (Malleus, incus, and stapes)

Auditory tube (Pharyngotympanic tube)

What are the auditory ossicles?

Malleus incus stapes

What is another name for the auditory tube?

Pharyngotympanic tube

What does the Eustachian tube do?

Equalizes pressure in middle ear

What is another function of the Eustachian tube?

Allows fluid to drain from the middle ear

Why are children more prone to middle ear infections?

Eustachian tube is positioned horizontally in children resulting in stasis of fluid

What are the structures of the inner ear?

Vestibule semicircular canals cochlea utricle saccule

What is the function of the vestibular complex?

Provides equilibrium sensations by detecting rotation gravity and acceleration

What structure is located at the beginning of each semicircular duct?

Ampulla

What structure is found within each ampulla?

Cristae with hair cells

What structures are present on each hair cell?

Kinocilium and stereocilia

What gelatinous material covers the hair cells in the ampulla?

Cupula

What moves the cupula and hair cells?

Movement of fluid in the canal

What are clusters of hair cells in the utricle and saccule called?

Maculae

What are statoconia?

Calcium carbonate crystals

What is an otolith?

Gelatinous material and statoconia collectively

What structure detects rotational movement?

Crista ampullaris

Which semicircular duct is associated with “yes” movement?

Anterior semicircular duct

Which semicircular duct is associated with “no” movement?

Lateral semicircular duct

Which semicircular duct is associated with tilting the head?

Posterior semicircular duct

What is the cochlea shaped like?

Snail-shaped spirals

What central structure do the cochlear spirals coil around?

Modiolus

What cranial nerve is associated with sensory neurons in the cochlea?

CN VIII

What is another name for the organ of Corti?

Spiral organ

What are the three layers of the cochlea?

Scala vestibuli scala tympani scala media

What fluid is found in the scala vestibuli?

Perilymph

What fluid is found in the scala tympani?

Perilymph

What fluid is found in the scala media?

Endolymph

What membrane supports the organ of Corti?

Basilar membrane

What membrane contacts the hair cells of the organ of Corti?

Tectorial membrane

What stimulates the organ of Corti?

Distortion of the tectorial membrane

What is the pathway of sound through the ear?

Sound waves enter the external acoustic meatus tympanic membrane vibrates ossicles vibrate stapes vibrates against the oval window perilymph begins to move

What cranial nerve is responsible for hearing and equilibrium?

Vestibulocochlear nerve CN VIII

What are the accessory structures of the eye?

Palpebrae medial and lateral canthus palpebral fissure eyelashes conjunctiva glands

What is the palpebral fissure?

Area between the eyelids

What triggers the blinking reflex?

Root hair plexus in the eyelashes

What are the glands associated with the eye?

Glands of Zeis tarsal glands lacrimal gland lacrimal caruncle

What are the six extrinsic muscles of the eye?

Superior rectus inferior rectus medial rectus lateral rectus superior oblique inferior oblique

What is the innervation of the superior rectus?

CN III

What is the innervation of the inferior rectus?

CN III

What is the innervation of the medial rectus?

CN III

What is the innervation of the lateral rectus?

CN VI

What is the innervation of the superior oblique?

CN IV

What is the innervation of the inferior oblique?

CN III

What mnemonic is used for extraocular muscle innervation?

LR6 SO4 3

What is the conjunctiva?

Epithelial lining of the eyelids

What does the conjunctiva prevent?

Prevents these layers from becoming dry

What is the palpebral conjunctiva?

Inner lining of the eyelids

What is the ocular conjunctiva?

Outer lining of the eye

What are the glands of Zeis?

Sebaceous glands associated with eyelashes

What do tarsal glands secrete?

Lipid-rich product

What is the function of tarsal glands?

Keeps the eyelids from sticking together

Where are lacrimal glands located?

Superior lateral portion of the eye

What do lacrimal glands produce?

Tears

What do lacrimal caruncle glands produce?

Thick secretions

What structures make up the lacrimal apparatus?

Lacrimal glands lacrimal canaliculi lacrimal sac nasolacrimal duct

Where do tears flow after crossing the ocular surface?

Into the nasolacrimal canal

Why does crying cause a runny nose?

Tears flow through the nasolacrimal canal into the nasal cavity

What are the major structures of the eye?

Sclera cornea pupil iris lens anterior cavity posterior cavity retina

What are the three tunics of the eye?

Fibrous tunic vascular tunic neural tunic

What structures make up the fibrous tunic?

Sclera and cornea

What is the function of the fibrous tunic?

Provides protection and attachment sites for extraocular muscles

What is the cornea?

Modified sclera

What structures are included in the vascular tunic?

Iris ciliary body choroid

What are the functions of the vascular tunic?

Regulates amount of light entering the eye secretes and reabsorbs aqueous humor controls shape of lens

What gives the eye its color?

Pigment in the iris

What changes the diameter of the pupil?

Smooth muscles of the iris

What structures connect the ciliary body to the lens?

Suspensory ligaments

What is the choroid?

Highly vascularized layer

What are the two layers of the retina?

Pigmented layer and neural layer

What are rods responsible for?

Night vision

What are cones responsible for?

Color vision

What fills the anterior chamber and posterior chamber?

Aqueous humor

What fills the vitreous chamber?

Vitreous humor

Where is aqueous humor produced?

Cells at the ciliary body area

What is the flow of aqueous humor?

Posterior chamber through pupil anterior chamber canal of Schlemm venous circulation

What is glaucoma?

Pressure builds up when aqueous humor cannot drain through the canal of Schlemm

What is the function of vitreous humor?

Supports shape of eye position of lens and position of retina

What can happen if vitreous humor loses proper consistency?

Detached retina

What part of the retina contains 100% cones?

Fovea centralis

What type of vision occurs at the fovea centralis?

Best color vision

What area of the retina has 0% rods and cones?

Optic disc

What is another name for the optic disc?

Blind spot

Why do we see color in daylight?

Cones require light to be stimulated

Why can we see at night but not determine color?

Cones deactivate and rods become activated