Ch11_Medical_Terminology_PART2_Eyes_Function_&_Structures

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havenwood
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148489
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Ch11_Medical_Terminology_PART2_Eyes_Function_&_Structures
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2012-04-19 22:57:41
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11 Medical Terminology Health Professionals 6e JCCC AAC 130
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Ch11 Medical Terminology - PART 2 - Eyes - Function & Structures
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  1. Function of the eyes
    • Eyes are the receptor organs of sight. They:
    • 1. Receive images
    • 2. Transmit them to the brain
  2. Abbreviations to identify eyes
    • OD = Oculus Dexter = Right eye
    • OS = Oculus Sinister = Left eye
    • OU = Oculus Uterque = Each eye or Both eyes
  3. Structures of the eye:
    • 1. Eyeball
    • 2. Adnexa (structures outside the eyeball):
    • .....a. Orbit
    • .....b. Eye muscles
    • .....c. Eyelids
    • .....d. Eyelashes
    • .....e. Conjunctiva
    • .....f. Lacrimal apparatus
  4. Adnexa of the Eyes (adnexa oculi)
    • 1. Means appendages or accessory structures of an organ
    • 2. Structures outside the eyeball:
    • .....a. Orbit
    • .....b. Eye muscles
    • .....c. Eyelids
    • .....d. Eyelashes
    • .....e. Conjunctiva
    • .....f. Lacrimal apparatus
  5. The Orbit (eye socket)
    1. Bony cavity of skull

    • 2. Contains & protects the eyeball and its associated:
    • .....a. Muscles
    • .....b. Blood vessels
    • .....c. Nerves
  6. Muscles of the Eye
    • 1. There are 6 major eye muscles, arranged in three pairs
    • .....a. Superior & Inferior Obliques
    • .....b. Superior & Inferior Rectus
    • .....c. Lateral & Medial Rectus

    2. These muscles enable a wide range of very precise eye movements.

    • 3. Muscles of both eyes work together in coordinated movements
    • 4. Coordinated movement enables normal binocular vision.
  7. Binocular
    1. Refers to use of both eyes working together

    2. This helps make depth perception possible
  8. Eyelids
    • 1. Upper & lower eyelids help protect eyeball from:
    • .....a. Foreign matter
    • .....b. Excessive light
    • .....c. Injuries due to other causes

    • 2. Includes:
    • .....a. Cathus
    • .....b. Inner canthus
    • .....c. Epicanthus
    • .....d. Outer canthus
    • .....e. Tarsus
    • 3. Edges of eyelids contain oil-producing sebaceous glands.
  9. Cathus
    Angle where upper & lower eyelids meet
  10. Inner canthus
    Where eyelids meet nearest to nose
  11. Epicanthus
    Vertical fold of skin on either side of nose
  12. Outer canthus
    Where eyelids meet farthest from nose
  13. Tarsus (tarsal plate)
    • 1. Framework within upper & lower eyelids
    • 2. Provides the necessary stiffness & shape
  14. Eyebrows & Eyelashes
    1. Prevent foreign matter from reaching the eyes.

    • 2. Eyelashes: Consist of small hairs known as cilia
    • Note: Cilia also found in the nose.
  15. Conjunctiva (plural: conjunctivae)
    • 1. Transparent mucous membrane that:
    • .....a. Lines the underside/inside of each eyelid
    • .....b. Continues to form a protective covering over the exposed surface of the eyeball
  16. Lacrimal Apparatus (tear apparatus)
    • 1. Consists of structures that:
    • .....a. Produce
    • .....b. Store
    • .....c. Remove tears
    • 2. Structures include:
    • .....a. Lacrimal glands
    • .....b. Lacrimal fluid
    • .....c. Lacrimal canal
    • .....d. Lacrimal sac
    • .....e. Lacrimal duct
  17. Lacrimal glands
    • 1. Secrete lacimal fluid (tears)
    • 2. Located:
    • .....a. On underside of the upper eyelid
    • .....b. Just above outer corner of each eye
  18. Lacrimation
    Secretion of tears
  19. Lacrimal fluid (tears)
    1. Function is to maintain moisture on the anterior surface of the eyeball.

    2. Blinking distributes lacrimal fluid across the eye.
  20. Lacrimal canal
    1. Consists of a duct in the inner corner of each eye.

    • 2. Ducts:
    • .....a. Collect tears
    • .....b. Empty tears into the lacrical sacs

    3. Crying is overflowing tears from lacrimal canals
  21. Lacrimal sac (tear sac)
    An enlargement of the upper portion of the lacrimal duct
  22. Lacrimal duct (nasolacrimal duct)
    Passageway that drains excess tears into the nose.
  23. Eyeball (globe)
    1. 1-inch sphere with only about one-sixth of its surface visible
  24. Optic
    Means pertaining to the eye or sight
  25. Ocular
    Means pertaining to the eye
  26. Extraocular
    Means outside the eyeball
  27. Intraocular
    Means within the eyeball
  28. Walls of the eyeball
    • 1. The walls of the eyelid are made up of 3 layers:
    • .....a. Sclera - white of the eye
    • .....b. Choroid - opaque midle layer
    • .....c. Retina - sensitive innermost layer
  29. Sclera (white of the eye)
    1. Maintains the shape of the eye

    2. Protects the delicate inner layers of tissue.

    3. Tough, fibrous tissue

    4. Forms outer layer of eye, except for part covered by cornea
  30. Choroid (choroid coat)
    1. Opaque middle layer of eyeball

    2. Contains many blood vessels & provides blood supply for entire eye.
  31. Opaque
    Means that light cannot pass through this substance
  32. Retina
    1. Sensitive innermost layer

    2. Lines posterior segment of the eye

    3. Receives nerve impulses & transmits them to brain via optic nerve (second cranial nerve)
  33. Segments of the eyeball
    • The eyeball is divided into 2 segments:
    • ..1. Anterior segment
    • .....a. Front 1/3 of eyeball.
    • .....b. Divided into 2 chambers filled with aqueous humor:
    • ..........(1.) Anterior chamber - in front of iris
    • ..........(2.) Posterior chamber - behind iris
    • ..2. Posterior segment
    • .....a. Lined with retina
    • .....b. Filled with vitreous humor
  34. Anterior segment
    • 1. One of two major segments of the interior of the eyeball.
    • 2. Makes up the front 1/3 of the eyeball
    • 3. Divided into two chambers:
    • .....a. Anterior chamber
    • .....b. Posterior chamber
  35. Anterior Chamber
    • 1. One of two chambers of the anterior segment of the eyeball
    • 2. Located:
    • .....a. Behind the cornea
    • .....b. In front of the iris
    • 3. Filled with aqueous humor (aqueous fluid)
  36. Posterior Chamber
    • 1. One of two chambers of the anterior segment of the eyeball
    • 2. Located:
    • .....a. Behind the iris
    • .....b. In front of the ligaments holding the lens in place
    • 3. Filled with aqueous humor (aqueous fluid)

    Note: DO NOT CONFUSE with posterior segment!
  37. Aqueous
    Means watery or containing water
  38. Humor (as used in reference to the eye)
    Any clear liquid or semifluid substance
  39. Aqueous humor (aqueous fluid)
    • 1. Helps eye maintain its shape
    • 2. Nourishes the intraocular surface.
    • 3. Fluid is constantly litered & drained through:
    • .....a. Trabecular meshwork
    • .....b. Canal of Schlemm.
    • 4. Produced by the ciliary body located within choroid.
  40. Intraocular pressure (IOP)
    • 1.Measurement of the fluid pressure inside the eye.
    • 2. Pressure regulated by rate at which aqueous fluid enters & leaves the eye
  41. Posterior segment
    • 1. Makes up the remaining 2/3s of the eyeball
    • 2. Lined with retina
    • 3. Filled with vitreous gel (vitreous humor)
  42. Vitreous humor (Viterous gel)
    • 1. Soft, jelly-like mass that contains millions of fine fibers.
    • 2. These fibers (which are attached to the surface of the retina), & help the eye maintain its shape.
  43. Structures of the retina
    • Structure include:
    • .....1. Rod & cones
    • .....2. Macula
    • .....3. Fovea centralis
    • .....4. Optic disk
    • .....5. Optic nerve
  44. Rods & Cones
    1. Receive images that have passed through the lens of the eye.

    2. These images are converted into nerve impulses & transmitted to brain via the optic nerve

    3. Rods = black & white receptors

    4. Cones = color receptors
  45. Macula (macula lutea)
    Responsible for central vision.
  46. Fovea centralis
    1. Is the area of sharpest central vision.

    2. Is a pit in the middle of the macula.

    • 3. Color vision best in this area becuase it contains:
    • .....a. A high concentration of cones
    • .....b. No rods.
  47. Optic disk (blind spot)
    1. Small region in the eye where the nerve endings of the reina enter the optic nerve.

    2. Called the 'blind spot' because it does not contain any rods or cones to convert images into nerve impulses.
  48. Uveal Tract
    • 1. Pigmented layer of the eye
    • 2. Has a rich blood supply & consists of:
    • .....a. Choroid
    • .....b. Ciliary body
    • .....c. Iris
  49. Ciliary body
    • 1. Located within the chorid
    • 2. Set of muscles & suspensory ligaments that:
    • .....a. Adjust the thickness of the lens
    • .....b. Refine the focus of light rays on the retina.
    • 3. Produces the aqueous fluid that fills the anterior segment of the eye.
    • 4. To focus vision:
    • .....a. Nearby objects - adjust muscles to make lens thicker
    • .....b. Distant objects - adjust muscles to stretch the lens, making it thinner.
  50. Iris
    • 1. Colorful, muscular layer of the eye that surrounds the pupil.
    • 2. Muscles within the iris control amount of light allowed to enter eye thru the pupil:
    • .....a. Decrease light - circular muscles contract making pupil smaller
    • .....b. Increase light - circular muscles dilate (relax) making pupil smaller
  51. Cornea
    • 1. Transparent outer surface of the eye.
    • 2. Covers the iris and pupil.
    • 3. Primary structure focusing light rays entering the eye.
  52. Pupil
    • 1. Black circular opening in the center of the iris
    • 2. Permits light to enter the eye.
  53. Lens (crystalline lens)
    • 1. Clear, flexible curved surface
    • 2. Focuses images on the retina.
    • 3. Lens is contained within a clear capsule
    • 4. Located behind the iris & pupil.

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