SPECIAL SENSES

Eyes

Receptors of light waves

Anterior 1/6 of the eye

composed of cornea, 2 chambers, iris, and lens

Posterior 5/6 of the eye

vitreous chamber

Outer fibrous layer

contains cornea and sclera

Vascular layer

contains the choroid, ciliary body, and iris

Inner retinal layer

contains receptor cells

Visual cortex

Located in the occipital lobe; interprets the visual input from the eye

Cornea

In the course of light waves, this is where the first bend of light waves occur.

Has the highest refractive power, and is a transparent avascular structure.

In order to refract light properly, this has to be a perfect sphere.

Corneal epithelium

Outermost part where errors of refraction can occur when damaged.

Bowman’s layer

Anterior limiting lamina; separating the epithelium from the Stroma.

Stroma

Thickest layer of the cornea.

Descemet’s membrane

Posterior limiting lamina; separated the stroma from the corneal endothelium.

Corneal endothelium

Lines the inner surface of the cornea.

Anterior chamber

Posterior to the cornea and anterior to the iris.

Posterior chamber

Posterior to the iris, anterior to the lens.

Aqueous humor

Regulates intraocular

This humor is replaceable

Produces aqueous flow from Posterior Chamber to Anterior Chamber, draining into the Canal of Schlemm in a singular direction, connecting to the Venous System

Glaucoma

A type of blindness that occurs when the Canal of Schlemm is clogged, causing an accumulation of fluid leading to an increase in the intraocular pressure and the tearing of the retina.

Sclera

Opaque white part of eyeball

Bulbar conjunctiva

Attached to the edge of the sclera

Choroid

Part of the sclera that provides nutrients and is the most vascular part.

Ciliary body

At the edges of the iris, composed of two parts: muscles and processes.

Ciliary process

Produces aqueous humor.

Ciliary muscles

Adjusts the shape of the lens

Iris

Constricts and dilates the pupil

Colored ring encircling the central opening or pupil

Constricts when surroundings are light, dilates when surroundings are dark

Dilator pupillae

Dilator muscle of the iris

Sphincter pupillae

Constrictor muscle of the iris

Retina

Innermost lining that is reddish orange in color

Optical part of Retina

Receives light through cone and rod receptors

Rods

Perceives the brightness of light

Unable to perceive colors

Black and white only

Cones

Allow light for color perception

Color blindness

Common in males to lack the genes to perceive red and green

Lens

Behind the posterior chamber

Transparent biconcave and flexible structure that refracts light

Cataract

Lens opacifies due to aging

Zonular fibers

Hold the lenses in place and allows it to become round to refract and create a focal point

When pulled, lens becomes thin. When relaxed, lens thickens.

Vitreous chamber

Located after the lens

Vitreous humor

a steady, irreplaceable gel-like substance that provides the shape of the eyeball

Macula lutea

A depression in the retina that produces the clearest image

Fovea centralis

The central yellowish part of the macula lutea that produces clear sharp images with the most number of cones and rods.

Optic disc

Collection of nerves from the retina

Blind spot of the eye

No rods and cones

Optic nerves

Extension of the optic disc that connects the eye to the brain

Passes through the optic chiasma to read to visual cortex in the occipital lobe

Diplopia

Double vision

Amblyopia

Lazy eye, brain shuts off one eye

Convergence

eye moves medially

Divergence

eye moves laterally

Suspensory ligament

Hammock-like structure beneath the eyeballs, suspending them.

Check ligaments

Medial and lateral

Restricts and holds the eyeball in place

Abducens nerve

Innervates the Lateral rectus muscle

Levator palpebrae superioris

Elevates the upper eyelids

Motor innervation by oculomotor nerve, sensory by ophthalmic nerve

Trochlear nerve

Innervates superior oblique muscle

Limbus

Inseparable junction of cornea and sclera.

Ears

Receive and collects soundwaves

External ear

Extends from the auricle to the tympanic membrane

Lateral extension of the head that is composed of mainly cartilage, except at the lobule.

Helix

Outermost curved edge of the pinna

Antihelix

Inner curved ridge

Tragus

small bump of cartilage at the anterior of the ear canal

Antitragus

Small triangular cartilage opposite the tragus

Concha

Shell-shaped hollow cavity that has a role in capturing sound

Intertragic notch

Soace separating the tragus from the antitragus

Scaphoid fossa

Between helix and antihelix

Lobule

Fleshy lower part that does not contain cartilage

Triangular fossa

Shallow depression between the two crura of the antihelix

External Acoustic Meatus

Canal divided into two parts: Lateral 1/3 (cartilage) and Medial 2/3 (bone)

Wider laterally than medially

Has a length of 2.5 cm

Has bends

Lined with skin that has sebaceous secretions

Cerumen

Ear wax or sebaceous secretion of the ears

Tympanic membrane

Creates sound production or sound waves

Separated the External and the Middle ear

A thin membrane

Cone of light

A reflection of light on the tympanic membrane when an otoscope is used.

Umbo

Central point of attachment of the handle of malleus

Concave due to the pull of the malleus.

Pars tensa

Tense surface called by pulling

Pars flaccida

Loose part of the membrane

Middle ear

“hub”

A box with 6 walls where branches of the facial nerve pass through

Malleus

Transfers the vibrations from the tympanic membrane to the incus

Incus

Articulates with the malleus and stapes that acts as the central link of the ossicular chain

Stapes

Transmits the vibrations to the oval window leading to the cochlea.

Medial / Labyrinthine wall

Separates the middle and inner ear

Promontory

Bulging part that is the first turn of cochlea

Prominences

• Promontory

• Prominence of Facial nerve

• Prominence of Lateral Semicircular Canal

Oval window

Where footplate of stapes attaches to

Located superior to the promontory

Round window

Located inferior to promontory

Posterior wall

Where the mastoid antrum enters and exits; contains the nerve to stapedius and chorda tympani.

Mastoid antrum

Space between the mastoid bone and behind inner ear with an opening (aditus)

Nerve to stapedius

Enters via pyramidal eminence and innervates the stapedius muscle

Stapedius muscle

Lessens vibrations located in the posterior wall innervated by the facial nerve

Chorda tympani nerve

Enters via facial canal to traverse the middle ear from the posterior to anterior wall

Anterior wall

Contains the tensor tympani and the pharyngotympanic tube and where chorda tympani exits

Tensor tympani

Dampens loud sounds or noises located in the anterior wall

Innervated by the mandibular trigeminal nerve

Roof of the middle ear

Floor of the middle cranial fossa where temporal bone sits on and has the tegmen tympani

Tegmen tympani

Separates the middle cranial fossa from the middle ear

Floor

located beneath the internal jugular vein

Laterall wall

composed of the tympanic membrane

Inner Ear

composed of the bony and membranous labyrinths

Bony labyrinth

Outer covering of the membranous kabyrinth

• Semicircular canals

• Vestibule

• Cochlea

Membranous labyrinth

inside the bony labyrinth

• Semicircular duct for balance

• Utricle and saccule for balance

• Cochlear duct for hearing

Perilymph

Fluid in the bony labyrinth

Endolymph

Fluid in the membranous labyrinth

Cochlea

Spiral or snail-like structure looping around the the central cone

Modiolus

bony structure of cochlea

Helicotrema

tip of structure

Scala vestibuli

Upper part of the cochlea

Scala tympani

Lower part of cochlea

Scala media / Cochlear duct

Middle part of the cochlea within basement membrane

Organ of corti

connects sound waves to electrical impulses located within the basement membrane