Eyes System Flashcards
External Anatomy
Eyelids Palpebral Fissure Limbus Canthus -Caruncle Tarsal Plate Meibomian Glands Conjunctiva -palpebral Conjunctiva -Bulbar Conjunctiva Lacrimal Apparatus Puncta
Eyelids- protect the eye from injury, strong light, & dust
Palpebral fissure- the open space between the eyelids
Limbus- border between cornea & sclera
Canthus- corner of the eye
-Caruncle- the inner canthus (contains sebaceous glands)
Tarsal plates- strips of connective tissue that give upper lid its shape
Meibomian glands- modified sebaceous glands that secrete lubricant onto lids
Stops the tears from overflowing + forms airtight seal
Conjunctiva- transparent covering on eyeball
- Palpebral conjunctiva- lines the eyelid
- Bulbar conjunctiva- overlies the eyeball
Lacrimal Apparatus- produces tears
Puncta- where tears drain into
Flow of tears
Lacrimal Gland to Puncta to Nasolacrimal Duct
What is a extra ocular muscle
What are the 6 muscles (4 for straight and 2 for slanting)
And what kind of movement do they achieve
Extraocular muscles- secure the eyeball in the orbit (socket) and move it in almost any direction
6 Extraocular Muscles: 4 rectus muscles (straight): -Superior rectus -Inferior rectus -Lateral rectus -Medial rectus
2 oblique muscles (slanting):
- Superior oblique
- Inferior oblique
Conjugate movement- eyes move as a pair
What Cranial nerves move the specific extraocular muscles
3
Movement of extraocular muscles is stimulated by cranial nerves
CN III Ocular
- Superior rectus
- Inferior rectus
- Medial rectus
- Inferior oblique
CN IV- Trochlear
-Superior oblique- downward and inward movement
CN VI- abduscence
-Lateral rectus- lateral movement
Internal Anatomy
What are the 3 coats the eye is composed of?
1) Outer fibrous sclera
2) Middle vascular choroid
3) Inner nervous retina
Outer fibrous sclera
Sclera
Cornea
Sclera
o Tough and protective white covering
o Continuous with cornea
Cornea
o Bends incoming light rays so they focus on the retina
o Sensitive to touch
o Corneal reflex- CN V (Trigemal) (Cotton wisp)
Middle vascular choroid
choroid
Ciliary Body
Lens
-function
Choroid
o Darkly pigmented layer (prevents light from reflecting internally)
o Heavily vascularized (delivers blood to retina)
Ciliary body
o Muscles of the ciliary body control the lens thickness
Lens o Refracts (bends) light o Function: to keep a viewed object in continual focus on the retina o Bulges- to focus on near objects o Flattens- to focus on far objects
Lens Refraction and Accommodation
What happens when you look at something far and close
Nearly parallel rays from distant objects flattening the lens
Divergent Rays from close object bulging the lens
In both instances the image is flipped and put back to normal in our occipital lobe
What is a myopic eye and how is it corrected
what is a hyperopic eye and how is it corrected
(nearsightedness) = Image is focused in front of retina, seeing close objects clearly but not distant, eye is longer or has a thicker lens
- Solved nearsighted issues with a concave lens
(Farsighted) = Can see distant objects clearly and not close, eye ball length is too short, or thinner then normal
-Use convex lens
Middle vascular choroid
Iris, function and what does is consist of
Pupil, should look like what, and the size depends on what?
Iris
o Coloured portion of the eyeball with pupil at center
o Function: control the amount of light entering the eye
o Consists of circular and radial smooth muscle fibers that contract and dilate
Pupil
o The hole in the center of the iris
o Should be round and regular
o Size depends on:
Constricts = Parasympathetic stimulation, bright light, near vision
Dilates = Sympathetic stimulation, dim light, far vision
• Can signal drugs in system, brain injury
Middle vascular choroid
Anterior Chamber
Posterior Chamber
-functions
Vitreous Chamber
Anterior Chamber
Between the cornea and the iris
Posterior Chamber
Behind the iris and to the sides of the lens
Functions:
- Contain watery aqueous humor (produced by the ciliary body)
- Aqueous humor delivers nutrients to surrounding tissues and drains metabolic wastes
- Controls intraocular pressure
Vitreous Chamber
-Between the lens and retina. Contains the vitreous body that holds the retina in place.
Inner nervous retina
What is the retina and what are the 3 important structures
Retina- Layer where light waves are turned into nerve impulses (nervous tissue)
Important structures:
1) Optic disc
2) Retinal vessels
3) Macula
What is the optic disc and what are the characteristics 4
What is are the retinal vessels
what is a macula
-Fovea centralis
1) Optic disc
Where fibres from the retina converge to form the optic nerve
Characteristics:
Colour- from creamy yellow-orange to pink
Shape- round or oval
Margins- distinct and sharp
Physiological cup- where blood vessels exit & enter
2) Retinal vessels
Paired artery and vein extending to each quadrant
3) Macula
Darker pigmented region. Surrounds fovea centralis
Fovea centralis- Area of sharpest vision
What is the Visual pathway 4
- Objects reflect light
- Light rays are refracted (bent) through transparent layers to strike the retina
- Transparent layers include: cornea, aqueous humor, lens - The retina transforms the light stimulus into nerve impulses
- The nerve impulses are conducted through the optic nerve and follow this path:
- optic nerve (CN II) → optic tract → visual cortex of the occipital lobe
- Image on retina is upside down and reversed
Visual Pathway & Visual Fields
What is Image orientation, why are the light strikes significant and how does the brain correct this
What is the optic chiasm 2
Image orientation- Image on the retina is upside down & reversed
- Light from the right side of an object strikes the left side of the retina
- To correct this, the brain “learns” early in life to coordinate visual images with the orientation of an object
Optic chiasm- where the optic nerves cross over
- Left optic tract- has fibres only from the left half of each retina
- Right optic tract- has fibres only from the right half of each retina
