Special Senses 1+2

Why don’t we hear __ourselves__ chewing

Tensor tympani dampens excess vibrations

What supplies the retina and where does this run?

central artery of retina which runs in the centre of the optic nerve

How does the ophthalmic artery enter the orbit

Through optic canal

Muscles involved in elevation of eye

* superior rectus
* inferior oblique

Which bone is the infraorbital notch found in?

maxillary bone

which bone is the supraorbital foramen/notch found in?

frontal bone

which nerve comes out of the supraorbital foramen/notch?

branches of ophthalmic division of trigeminal

which nerve comes out of the infraorbital notch?

Branches of maxillary division of trigeminal

Which walls of the orbit are parallel, and which are not parallel?

medial walls - parallel

lateral walls - not parallel

Type of fat in the orbital

periorbital fat

Name the muscles found in the eye

extra ocular muscles

what type of muscles are extraocular muscles?

skeletal muscles

innervation of extraocular muscles?

general somatic nerves

What are the 3 types of extraocular muscles and how many are present in the orbit?

* 4 x rectus muscles
* 2 x oblique muscles
* Levator Palpeprae Superioris

What are the names of the types of rectus muscles

Superior, medial, inferior, lateral rectus

What are the names of the types of oblique muscles

Superior, inferior oblique

Where do the oblique muscles insert into the eye?

insert into back of eyelid

direction of rectus muscles vs oblique muscles

rectus - straight

oblique - diagonal

function of levator palpeprae superioris

* attached to upper eyelid
* elevates upper eyelid

Where do all the extraocular muscles come from (except which one)

All muscles except for inferior oblique come from common tendinous ring around optic canal

Muscles involve in depression of eye

* Superior oblique
* Inferior recuts

Muscles involved in adduction of eye

* Medial rectus

Muscles involved in abduction of eye

* Lateral rectus

Muscles involved in intorsion of eye

superior oblique

Muscles involved in extorsion of eye

inferior oblique

what is extorsion and intorsion of eye?

unconscious movement - whilst head moves, eye counteracts

Where do the nerves of the orbit pass through?

All pass through superior orbital fissure

function of oculomotor in orbit

supply majority of muscles in the eye

parasympathetic to some intrinsic muscles of the eye

function of trochlear in orbit

supplies superior oblique eye muscle

function of abducens in the orbit

Only supplies lateral rectus (muscle of abducting)

Function of ophthalmic division of trigeminal and branches

sensory innervation

branches of facial nerve hitchhike to supply lacrimal gland

Name of the ganglion in the orbit and function

ciliary ganglion

contains motor and parasympathetic fibres for controlling intrinsic muscles of the eye - pupil size

function of optic nerve in orbit

special sensory - vision

What vasculature supplies the orbit

mostly from ophthalmic artery and it’s branches

what supplies the ophthalmic artery?

internal carotid artery

branches of the ophthalmic artery

anterior and posterior ethmoidal arteries

Veins for the orbit

Superior and inferior ophthalmic veins

Where do the ophthalmic veins drain?

Drain **posteriorly** into **cavernous sinus**

Drain **anteriorly** into **facial vein**

What gland produces lacrimal fluid?

Lacrimal gland

What doesn’t the conjunctiva cover?

Coloured part of the eye

Name the 3 layers of the eye

* fibrous layer
* vascular layer
* inner layer of eyeball

Name the parts of the fibrous layer

* sclera
* cornea

describe the sclera

white, opaque part of the eye where extra ocular muscles insert, holds the shape of the globe

describe the cornea

transparent layer over the cornea which lets light into the eyeball

name the parts of the vascular layer of the eye

* choroid
* ciliary bodies
* iris

Describe the choroid in the eye

Black, vascular, pigmented layer which prevents light escaping to allow light to focus

Function of ciliary bodies in the eye

Contain muscles which change the shape of the lens to focus

How do ciliary bodies work?

Smooth muscle – parasympathetic supply from oculomotor nerve

Zonular fibres attach ciliary muscles to lens to change shape of lens

Describe the accomodation reflex

Controls the shape of the lens for focusing of an image

* Relaxed – long and flat lens for distance looking
* Contracted – spherical lens for close looking

Function of the iris

Pigmented part of the eye, contain muscles to control shape of lens + size of pupil, attaches to lens

Type of muscle in the eye and how do they work?

smooth muscle - circular and radial which act in opposition

* Circular – make pupil smaller (bright light), parasympathetic control from oculomotor nerve
* Radial – pull pupil larger (dim light), sympathetic control from sympathetic chain

Why do both pupils always remain the same size?

Due to pupillary light reflex

What are cataracts?

Protein deposits in cornea which stop light from entering

What is found in the nervous layer of the retina?

Rods and cones present for vision

Function of rods vs cones

* Rods – low light vision, black + white
* Cones – Detailed, coloured vision

What is the optic disc?

Where the arteries of the retina run from and where the optic nerve lies

What is found in the macula

high concentration of cones which provide high visual acuity

What is found in the fovea and where is the fovea found and what is it’s function?

many cones present

found in the centre of the macula

many cones present for high visual acuity

Name the chambers of the eye

* anterior chamber
* posterior chamber
* vitreous chamber

name the fluid found in the following chambers

* anterior chamber
* posterior chamber
* vitreous chamber

anterior → aqueous humor

posterior → aqueous humor

vitreous → vitreous humor

texture of vitreous humor

raw egg white texture

Which bone is the ear found in?

temporal bone

Why is there a link between tooth pain and ear infection symptoms?

External acoustic meatus close to TMJ

Which nerves pass through internal acoustic meatus?

vestibulocochlear nerve

facial nerve

Where is the external ear found?

Up to tympanic membrane

Function of external ear

Collects sound and channels it down the auditory canal to vibrate ear drum

What is the pinna?

Folds on the actual ear

Function of sebaceous glands

produce oil

Function of ceruminous glands

produce ear wax

Where are sebaceous and ceruminous glands found?

Within skin lining external ear

Which nerves supply external ear?

Auricoulotemporal nerve of V3

Spinal nerves (lesser occipital, greater auricular)

Vagus

Blood supply to external ear

Branches of external carotid artery

* Occipital artery
* Posterior auricular
* Superficial temporal

What causes cauliflower ear?

Problems with blood supply to cartilage

Function of tympanic membrane

passes vibrations onto middle ear

What is tympanic membrane attached to

ossicles

Where is middle ear?

Tympanic membrane → round window

What happens in the middle ear

Vibrations picked up by ossicles and transferred to inner ear

Names of the ossicles and the types of joints between them

Malleus

Incus

Stapes

Connected by synovial joints

Supply to the following muscles in the inner ear

* Tensor tympani
* Stapedius muscle

Tensor tympani - mandibular division of trigeminal

Stapedius muscle - facial nerve

Function of stapedius muscle

reduces sound of our own voice

Function of tensor tympani

dampens excess vibrations (chewing)

What is the tympanic reflex?

Contracts tensor tympani and stapedius so when anticipating to hear something loud (eg firework) ear is protected

Why does tympanic reflex only work for expected noises

slow

where does the chorda tympani exit the middle ear?

petrotympanic fissure

what nerve does glossopharyngeal branch into in the middle ear?

lesser petrosal nerve

Why may a middle ear tumour cause loss of taste?

chorda tympani present in the middle ear

Where is the inner ear found?

round window onwards

What is found in the inner ear?

Organs of hearing and balance

Bony and membraneous labyrinth

Supply to inner ear

* Vestibular nerve
* Cochlear nerve
* Facial nerve

What does vestibular nerve supply?

organs of balance - semi-circular canal

What does cochlear nerve supply?

organs of hearing - coachlear

What does the cochlear look like

spiral looking structure

Function of semicircular canals

contains crystals which tell the brain head orientation