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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