Chapter 13 <ul><li>Special Senses: The Eye and Ear </li></ul>
The Eye <ul><li>Contains the sensory receptor cell for vision </li></ul><ul><li>The eyeball is the organ of sight that tra...
Eye Figure The internal structures of the eye.
The Eyeball <ul><li>The eyeball is composed of 3 layers: </li></ul><ul><ul><li>sclera: Outer “white” layer; tough protecti...
The Eyeball  (cont.) <ul><ul><li>Retina:The 3rd and innermost layer of the eyeball. </li></ul></ul><ul><ul><ul><li>Contain...
Eye Muscles <ul><li>6 muscles connect the eyeball to the skull </li></ul><ul><ul><li>4 rectus-- pull the eye up, down, lef...
The Eyelids <ul><li>A pair of eyelids over each eyeball provides protection from foreign particles, injury from intense li...
Conjunctiva <ul><li>The mucous membrane lining that forms a continuous covering on the underside of each eyelid and across...
Lacrimal Apparatus <ul><li>The lacrimal gland is located under the outer upper corner of each eyelid.  </li></ul><ul><li>G...
The Path of Vision <ul><li>When light rays strike the eye, the pass: </li></ul><ul><ul><li>cornea--> pupil-->aqueous humor...
The Ear <ul><li>Contains the sensory receptors for hearing and equilibrium (balance) </li></ul><ul><li>Hearing and equilib...
Ear Figure The internal structures of the ear.
External Ear <ul><li>Consist of 3 parts: </li></ul><ul><ul><li>auricle: also known as the pinna; referred to as “the ear” ...
Middle Ear <ul><li>Located in a small cavity in the temporal bone of the skull </li></ul><ul><li>Air-filled cavity that co...
Inner Ear <ul><li>Located in a cavity within the temporal bone </li></ul><ul><li>Fluid-filled cavity is referred to as the...
The Path of Sound <ul><li>Sound waves travel down the external auditory canal strike the eardrum, causing it to vibrate.  ...
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Med Term Presentation #3

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Special Senses: The Eyes and Ears

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Med Term Presentation #3

  1. 1. Chapter 13 <ul><li>Special Senses: The Eye and Ear </li></ul>
  2. 2. The Eye <ul><li>Contains the sensory receptor cell for vision </li></ul><ul><li>The eyeball is the organ of sight that transmits an external image by the way of the nervous system- optic nerve-to the brain. </li></ul><ul><li>Other structures that play a role in vision: </li></ul><ul><ul><li>eye muscles </li></ul></ul><ul><ul><li>eyelids </li></ul></ul><ul><ul><li>conjunctiva </li></ul></ul><ul><ul><li>lacrimal apparatus </li></ul></ul><ul><li>The study of the eye is known as ophthalmology. </li></ul>
  3. 3. Eye Figure The internal structures of the eye.
  4. 4. The Eyeball <ul><li>The eyeball is composed of 3 layers: </li></ul><ul><ul><li>sclera: Outer “white” layer; tough protective coating for the inner structures of the eye. </li></ul></ul><ul><ul><ul><li>cornea: anterior, transparent portion of sclera which allows light to enter; bends/refracts light rays </li></ul></ul></ul><ul><ul><li>choroid: Middle, opaque layer that provides the blood supply for the eye </li></ul></ul><ul><ul><ul><li>iris: colored portion which contains smooth muscle; muscles change the size of pupil, thereby controlling how much light enters </li></ul></ul></ul><ul><ul><ul><li>pupil:opening in the center of the iris that allows light rays to enter the interior of the eyeball </li></ul></ul></ul><ul><ul><ul><li>ciliary body: intraocular eye muscles that change the shape of the lens </li></ul></ul></ul>
  5. 5. The Eyeball (cont.) <ul><ul><li>Retina:The 3rd and innermost layer of the eyeball. </li></ul></ul><ul><ul><ul><li>Contains rods and cones </li></ul></ul></ul><ul><ul><ul><li>macula lutea (yellow spot) </li></ul></ul></ul><ul><ul><ul><ul><li>fovea centralis: depression within macula lutea which is the point of clearest vision </li></ul></ul></ul></ul><ul><ul><ul><li>optic disk: lacks sensory receptors and causes a blind spot in each eye’s field of vision </li></ul></ul></ul><ul><ul><ul><li>aqueous humor: watery-fluid space between cornea and lens </li></ul></ul></ul><ul><ul><ul><li>vitreous humor: semisolid gel large open area between the lens and the retina </li></ul></ul></ul>
  6. 6. Eye Muscles <ul><li>6 muscles connect the eyeball to the skull </li></ul><ul><ul><li>4 rectus-- pull the eye up, down, left and right; </li></ul></ul><ul><ul><li>2 oblique muscles--produce diagonal eye movement </li></ul></ul>
  7. 7. The Eyelids <ul><li>A pair of eyelids over each eyeball provides protection from foreign particles, injury from intense light, and trauma. </li></ul><ul><li>Both upper and lower edges of the eyelids have eyelashes or cilia that protect the eye from foreign particles. </li></ul><ul><li>Sebaceous glands secrete lubricating oil onto the eyeball </li></ul>
  8. 8. Conjunctiva <ul><li>The mucous membrane lining that forms a continuous covering on the underside of each eyelid and across the anterior surface of each eyeball. </li></ul><ul><li>Serves as protection for the eye by sealing of the eyeball in the socket. </li></ul>
  9. 9. Lacrimal Apparatus <ul><li>The lacrimal gland is located under the outer upper corner of each eyelid. </li></ul><ul><li>Glands produce tears. Tears function of washing and lubricating the anterior surface of the eyeball. </li></ul><ul><li>Lacrimal ducts are located in the inner eye socket and collect tears and drain them into the nasolacrimal duct, which ultimately drains tears into the nasal cavity. </li></ul>
  10. 10. The Path of Vision <ul><li>When light rays strike the eye, the pass: </li></ul><ul><ul><li>cornea--> pupil-->aqueous humor--> lens-->vitreous humor-->retina (rods and cones) </li></ul></ul><ul><ul><li>When light rays hit the retina, and upside-down image is sent nerve impulses to the optic nerve, which are sent to the brain, where the upside-down image is translated into the right-side up image we see. </li></ul></ul><ul><li>Vision requires: </li></ul><ul><ul><li>coordination of external eye muscles so that both eyes move together </li></ul></ul><ul><ul><li>correct amount of light admitted by the pupil </li></ul></ul><ul><ul><li>correct focus of light on the retina by the lens </li></ul></ul><ul><ul><li>optic nerve transmitting sensory images to the brain </li></ul></ul>
  11. 11. The Ear <ul><li>Contains the sensory receptors for hearing and equilibrium (balance) </li></ul><ul><li>Hearing and equilibrium sensory information is carried to the brain by the vestibulocochlear (cranial) nerve. </li></ul><ul><li>The ear is subdivided into 3 areas: </li></ul><ul><ul><li>external ear </li></ul></ul><ul><ul><li>middle ear </li></ul></ul><ul><ul><li>inner ear </li></ul></ul><ul><li>The study of the ear is referred to as otology, and the study of hearing disorders is called audiology. </li></ul>
  12. 12. Ear Figure The internal structures of the ear.
  13. 13. External Ear <ul><li>Consist of 3 parts: </li></ul><ul><ul><li>auricle: also known as the pinna; referred to as “the ear” because this is the only visible portion; earlobe functions like a funnel to capture sound waves as they pass the outer ear and channel through the external auditory meatus </li></ul></ul><ul><ul><li>auditory canal: canal that leads from exterior opening of the ear to the eardrum </li></ul></ul><ul><ul><ul><li>ear wax or cerumen is produced within the auditory canal to help protect and lubricate the ear </li></ul></ul></ul><ul><ul><li>tympanic membrane: eardrum; as sound moves along auditory canal, it strike the membrane causing it to vibrate; this conducts the sound into the middle ear </li></ul></ul>
  14. 14. Middle Ear <ul><li>Located in a small cavity in the temporal bone of the skull </li></ul><ul><li>Air-filled cavity that contains 3 tiny bones called ossicles that are vital for the hearing process: </li></ul><ul><ul><li>malleus:also known as the hammer </li></ul></ul><ul><ul><li>incus:also known as the anvil </li></ul></ul><ul><ul><li>stapes:also known as the stirrup; last of the ossicles that is attached to a very thin membrane that covers the opening to the inner ear called the oval window </li></ul></ul><ul><li>The eustachian tube or auditory tube connects the nasopharynx with the middle ear. Each time one swallows the tube opens; this connection allows pressure to equalize between the middle ear cavity and atmospheric pressure. </li></ul>
  15. 15. Inner Ear <ul><li>Located in a cavity within the temporal bone </li></ul><ul><li>Fluid-filled cavity is referred to as the labyrinth </li></ul><ul><li>Contains the hearing and equilibrium sensory organs that contain hair cells (sensory receptors): </li></ul><ul><ul><li>cochlea (hearing): hair cells referred to as organs of Corti </li></ul></ul><ul><ul><li>semicircular canals (equilibrium) </li></ul></ul><ul><ul><li>utricle (equilibrium) </li></ul></ul><ul><ul><li>saccule (equilibrium) </li></ul></ul>
  16. 16. The Path of Sound <ul><li>Sound waves travel down the external auditory canal strike the eardrum, causing it to vibrate. </li></ul><ul><li>The ossicles conduct these vibrations across the middle ear from the eardrum to the oval window. </li></ul><ul><li>Oval window movements initiate vibrations in the fluid that fills the cochlea. </li></ul><ul><li>As fluid vibrations strike a hair cell, they bend the small hairs and stimulate the nerve ending, which then sends an electrical impulse to the brain on the cochlear portion of the vestibulocochlear nerve. </li></ul>

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