Module 13: Eye and Ear

Special Senses: The Eye and Ear

Cassandra Braun

OPTHALMOLOGY: The study of the eye FUNCTION: The eye provides vision through

sensory receptor cells

The Eye

Anatomy and Physiology of the Eye

Eyeball: composed of three layers Sclera Choroid Retina

External Structures: Eye muscles Eyelids Conjunctiva Lacrimal apparatus

The Sclera (white of the eye) is the outer most layer of the eyeFunction: tough protective coating for inner structuresCornea: anterior area of the sclera that allows light to enter the interior of the eyeball.

- the cornea refracts light rays

The Eyeball: Sclera

The Choroid is the middle layer of the eyeball

Function: opaque layer providing blood supply to the eye

Contains:Iris: colored portion of the eye containing smooth musclePupil: opening in the center of the iris that allows light rays to enterCillary Body: connected to the lens, changes the shape of the lens to focus incoming light on the retina

The Eyeball: Choroid

The retina is the innermost layer of the eyeball

Function: responds to light rays through cones and rodsContains:Rods: active in dim light; help us to see grey tonesCones: active only in bright light; responsible for color visionMacula lutea: when looking at an object, image falls on this areaFovea centralis: central area of macula luteaOptic Disk: point where retinal blood vessels enter and exit the eyeball and where the optic nerve leaves the eyeballAqueous tumor: liquid that fills the space between the cornea and lensVitreous humor: semisolid gel in the large, open area between the lens and the retina

The Eyeball: Retina

Function: Six muscles connect the eyeball to the skull – allow for change in direction of each eye and support

Four rectus muscles are straight, pulling the eye up, down, left, right or straight.

Two oblique muscles are on an angle, producing diagonal eye movement

Muscles of the Eye

Function: provides protection from foreign particles

Eyelashes (cilia): protect the eye from foreign particles

Sebaceous glands: located in the eyelids secrete lubricating oil onto the eyeball

The Eyelids

The conjunctiva is a mucous membrane lining

Function: serves as a protection for the eye by sealing off the eyeball in the socket

Conjunctiva

Lacrimal gland is located under the outer upper corner of each eyelid; produces tears

Lacrimal ducts inner corner of the eye socket collects tears and drain them into the nasolacrimal duct, which ultimate drains into the nasal cavity.

Lacrimal Apparatus

Vision: How We See

OTOLOGY: the study of the ear FUNCTION: the ear provides hearing and

equilibrium from sensory receptors

The Ear

The ear contains three main components: External Ear Middle Ear Inner Ear

Anatomy and Physiology of the Ear

External Ear contains three sections: auricle, auditory canal, and tympanic membrane

Auricle (pinna): only visible portion, acts like a funnel to capture sound waves and channel them to the external auditory meatus

Auditory canal: sound moves across and causes the tympanic membrane

External Ear

Middle Ear contains the auditory tube, Eustachian tube, incus, malleus, ossicles, oval window, stapes

Ossicles are the air-filled cavity that contain the three ear bones: malleus, incus, and stapes- these bones amplify the vibrations in the middle ear and transmit them to the inner ear

Oval window is the very thin membrane that covers the opening to the inner ear

Eustachian tube connects the nasopharynx with the middle ear and opens each time you swallow- the connection allows pressure to equalize

Middle Ear

Inner Ear contains the cochlea, labyrinth, organs of Corti, saccule, semicircular canals, and the utricle

Labyrinth is the fluid filled cavity which contains hearing organs (cochlea) and equilibrium organs (semicircular canals, utricle, saccule)

Organs of Corti: the hair cells in the cochlea

Inner Ear

How We Hear