PNS - Exam 4 (pt. 2 special sense organs)

The eye is derived from

ectoderm

What is the retina derived from

neuroectoderm of forebrain

What is the lens and cornea derived from

surface ectoderm

What is the sclera derived from

neural crest mesenchyme

The fibrous tunic (sclera and cornea) is the only tunic that is

complete

Sclera

thick, dense, opaque

The sclera is continuous with the cornea anteriorly via the

limbus

The sclera is continuous with what posteriorly

cranial N sheath

What is the primary refractory structure (1st structure light passes through, most important for focusing light on retina)

cornea

What is an irregularity of the cornea known as

astigmatism

Layers of the cornea

corneal epithelium

anterior limiting lamina

substantia propria

posterior limiting lamina

endothelium

What is the thickest layer of the cornea

substantia propria

Vascular tunic contains what three structures

choroid, ciliary body, iris

What part of the vascular tunic is loosely attached to the sclera

choroid

Choroid is thin but has a rich

blood supply (LOTS of SYMP)

Ciliary body is continuous with what two structures

choroid and iris

What are the two functions of the ciliary body

anchor lens

produce aqueous humor

Iris divides anterior segment into

anterior and posterior chambers

What two muscles control the iris

sphincter pupillae (circular fibers - PARA)

dilator pupillae (radial fibers - SYMP)

Nervous tunic (retina) is an outgrowth of the

diencephalon

The nervous tunic is in contact with what two structures

choroid

vitreous body

What layer in the retina contains the CB of rods and cones

outer nuclear layer

What layer in the retina is where synapses occur between rods/cones and bipolar cells

outer plexiform layer

What layer in the retina contains the CB of bipolar cells

inner nuclear layer

What layer in the retina is where synapses occur between bipolar cells and ganglion cells

inner plexiform layer

The sense of vision is a ____ neuron pathway

4/5

photoreceptors, bipolar, ganglion, lateral geniculate body, BA 17

Funduscopic exam is an examination of the

retina (fundus of eye)

Optic disc

blind spot (no receptors)

BV exit and enter here

Macula lutea

contains fovea centralis (clearest vision - cones)

Refractory components (4)

cornea**, aqueous humor, lens, vitreous body

Aqueous humor (anterior segment) leaves via what sinus

scleral venous sinus

A clinical aspect associated with aqueous humor is

glaucoma

Lens separates

anterior and posterior segments

A two clinical aspects are associated with the lens

presbyopia - decrease lens resilience

cataracts - decrease lens transparency

Vitreous body (posterior segment)

gelatinous and transparent

hyaloid canal (lens to optic disc)

Eye muscles innervation

LR6/SO4 all over 3

Lacrimal glands

secrete tears via excretory ducts

Lacrimal ducts

drain tears into lacrimal sac

Lacrimal sac

superior part of nasolacrimal duct

Nasolacrimal duct

drain tears into inferior nasal meatus

Tarsal glands are what type of glands

modified sebaceous glands

**secrete oily substance

Arterial supply to eye - how many long ciliary arteries

2

Arterial supply to eye - how many short ciliary arteries

6-12

**short ciliary nerves follow

Arterial supply to eye - how many anterior ciliary arteries

6-8

What is the one sole blood supply to the retina

central retinal artery

The ear is a thickening of ectoderm known as

placode

Auditory vesicle gives rise to

membranous inner ear

Ventral mandibular cartilage gives rise to

malleus

1st pharyngeal arch gives rise to

incus

2nd pharyngeal arch gives rise to

stapes

Interstitial mesoderm gives rise to

tympanic membrane

What is the auricle's function

funnel sound waves into EAM

EAM contain what type of glands

ceruminous glands

Ceruminous glands are what type of glands

modified sweat glands

**secrete ear wax

In order to view the EAM, how should you pull the lobule

out, down, anterior

Extrinsic auricular muscles (tell you their action in name)

Anterior/Superior/Posterior auricular muscles

Sensory nerve supply to external ear (3)

Auriculotemporal (V3)

Auricular (X)

Great auricular N (cervical plexus)

Motor nerve supply to external ear (2)

temporal and posterior auricular branches (VII)

Sympathetic nerve supply to external ear

branches from SCG

Middle ear two compartments

tympanic cavity

epitympanic recess

Middle ear bones

malleus, incus, stapes

Middle ear muscles

stapedius

tensor tympani

Roof of middle ear

petrous part of temporal bone

Membranous wall of middle ear

tympanic membrane

Mastoid wall of middle ear

aditus of mastoid antrum

What part of the middle ear exposes it to the outside world

Aditus of mastoid antrum (opening between middle ear and mastoid air cells)

What is clinically relevant with the pharyngotympanic tube

equalizes pressure

how pathogens enter = cause middle ear infections

What is the promontory

impression made by cochlea

The oval window contacts the foot of

stapes

The round window communicates with

scala tympani

Ossicles

malleus (largest + contacts tympanic membrane)

incus

stapes (foot against oval window)

Blood supply to middle ear

anterior tympanic branch

tympanic branch

Sensory innervation to middle ear

tympanic N (CN IX)

Motor innervation to middle ear

N to stapedius (CN VII)

Medial pterygoid N (V3)

Inner ear contains what two labyrinths

bony labyrinth

membranous labyrinth

Bony labyrinth structures

cochlea

vestibule

semicircular canals

Which labyrinth contains perilymph and which contains endolymph

perilymph - bony

endolymph - membranous

Membranous labyrinth structures

cochlear duct

utricle + saccule

semicircular ducts

Within the vestibular labyrinth (membranous), what connects saccule and cochlear duct

ductus reuniens

The cochlear labyrinth (bony) is a tube coiled around what

modiolus

What connects the cochlea to the modiolus

lamina

3 channels in cochlea

scala vestibuli (perilymph)

scala tympani (perilymph)

cochlear duct (endolymph)

Scala vestibuli

above cochlear duct

oval window at base

Scala tympani

below cochlear duct

round window at base

The scala vestibuli and scala tympani communicates at

helicotrema

The cochlear duct is anchored to the outer wall via

spiral ligament

The spiral organ in the cochlear duct is attached to the ______ and covered by the _____

basilar membrane; tectorial membrane

Spiral organ

hair like projection sensitive to frequency (pitch) and amplitude (volume)

Transmission of sound

EAM -> tympanic membrane vibrates -> ossicles ->

oval window -> perilymph in scala vestibuli + tympani ->

round window -> basilar membrane vibrates ->

receptors in spiral organ -> cochlear N

What forms the cochlear N

axons from spiral ganglion

Sense organs in the utricle and saccule are called

maculae (hair-like projections + otoliths)

Utricle maculae sense

centrifugal + linear accelerations in any direction

Saccular maculae sense

linear accelerations in vertical and AP planes

Sense organs in semicircular ducts are called

crista

Crista sense acceleration in

any direction (especially rotation)

Superior branch of vestibular N carry info from

Anterior and Lateral Semicircular ducts

Utricle

Voit's N (saccule)

Inferior branch of vestibular N carry info from

Posterior semicircular duct

Saccule

What forms the vestibular N

axons from vestibular ganglion

Blood supply to labyrinth

internal auditory artery

What is the internal auditory artery a branch from

basilar artery