suzanne d'anna1 anatomy of the eyeball. suzanne d'anna2 cavities of the eyeball separated...

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Suzanne D'Anna Anatomy of the Eyeball

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Page 1: Suzanne D'Anna1 Anatomy of the Eyeball. Suzanne D'Anna2 Cavities of the Eyeball separated by the lens n anterior n posterior

Suzanne D'Anna 1

Anatomy of the Eyeball

Page 2: Suzanne D'Anna1 Anatomy of the Eyeball. Suzanne D'Anna2 Cavities of the Eyeball separated by the lens n anterior n posterior

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Cavities of the Eyeball

separated by the lens anterior posterior

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Anterior Cavity between lens and cornea filled with aqueous humor (watery fluid) Divided into:

- anterior chamber (anterior to iris)

- posterior chamber (posterior to iris)

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Posterior Cavity between lens and retina filled with vitreous body (jelly-like

substance) also called vitreous chamber

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Lens elastic, transparent, biconcave structure separates anterior and posterior cavities

of eyeball suspended from ciliary body by

suspensory ligaments tension on suspensory ligaments

controls shape of lens

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Layers of Eyeball (tunics)

fibrous - outer

- sclera

- cornea vascular - middle

- choroid

- ciliary body

- iris retina - inner nervous

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Layers of Eyeball

pupil

cornea

ciliary body

sclera

choroid

iris

retina

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Sclera - outer fibrous

“white of the eye” outermost protects eye thick, tough connective tissue capsule that maintains shape of eye serves as point of attachment for extrinsic

muscles makes up 5/6 of sclera

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Cornea - outer fibrous

anterior 1/6 of fibrous tunic; continuous with sclera

bulges forward, forming convex surface

- refracts light rays as they enters eye transparent - allows light rays to pass lacks blood vessels receives nutrition from lymph has five layers

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Cornea - outer fibrous (cont.)

has touch and pain receptors injury causes scarring most exposed part of eye great ability to repair itself only tissue that can be transplanted

from person to person without rejection

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Scleral Venous Sinus also called canal of Schlemm junction of sclera and cornea drains aqueous humor from eyeball

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Choroid - middle vascular layer

vascular layer; blood rich contains dark pigment produced by

melanocytes

- absorbs pigment and prevents scatter of light after it passes through retina

anterior portion becomes ciliary body and iris

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Ciliary Body - middle vascular layer

thickest part of vascular tunic forms internal ring in anterior part of

eyeball within are projections or folds called ciliary

muscles

- secrete aqueous humor into anterior cavity

lens is attached via suspensory ligaments

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Iris - middle vascular layer

extends out from ciliary body anterior to lens thin diaphragm of connective tissue seen from outside as colored portion of

eye has rounded opening called pupil regulates amount of light entering

posterior cavity of eyeball through pupil

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Pupils bright light or close up - pupils constrict dim light or distance - pupils dilate

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suspensory ligaments

lens

anteriorchamber

posterior chamber

cornea

pupil

iris

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Retina - inner nervous layer

light sensitive is where light rays form an image image travels via optic nerve to cerebral

cortex if image is not focused correctly, corrective

glasses or lenses are required contains photoreceptors

- rods and cones

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Photoreceptors rods

- 20 million - recognize gray tones and dim light

cones

- 6 million - recognize primary colors together they interpret intermediary colors in moonlight only rods are functioning;

therefore we cannot see colors

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Fovea Centralis depressed area in center of macula lutea

- yellowish spot just lateral to optic axis of eyeball

has highest concentration of cones in retina

produces sharpest vision and best color perception

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Optic Disc also called blind spot medial to optic axis fibers from ganglion cells exit eyeball to

form optic nerve no photoreceptors; light striking this

area produces no image

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Color Blindness inability to distinguish colors caused by a lack or deficiency in one of

the three cone photopigments most common type is red-green color

blindness inherited condition affecting males more

often than females - sex-linked

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Intraocular Pressure caused when scleral venous sinus is

obstructed and reabsorption of aqueous humor cannot keep up with its secretion

pressure in chambers pushes lens back and puts pressure on vitreous body which in turn presses on retina which obstructs blood supply

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Intraocular Pressure (cont.)

retinal cells die and optic nerve may atrophy causing blindness (glaucoma)

symptoms usually go unnoticed until damage is irreversible

disease can be detected by use of tonometer used to measure intraocular pressure

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Glaucoma group of eye diseases characterized by an increase in

intraocular pressure pressure causes pathological changes

in optic disk and visual field defects

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Normal Flow of Intraocular Fluid

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Abnormal Flow of Intraocular Fluid

(most common type)

egress is partially blocked causing increased accumulation of fluid causing increase pressure and eventual blindness

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Acute Closed-Angle Abnormal Flow of Intraocular Fluid egress is totally

blocked causing permanent blindness suddenly

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Accessory Structures eyelids lacrimal apparatus extrinsic muscles cranial nerves

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Eyelid Composed of:

- skin covers outer surface

- conjunctiva covers inner surface of eyelid and anterior surface of eyeball (except cornea)

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Eyelid (cont.)

Composed of:

- tarsal glands

modified sebaceous gland (oil)

open at edge of each eyelid

also called Meibomian glands

- muscles

orbicularis oculi - surrounds eye

levator palpebrae - in upper eyelid

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Lacrimal Apparatus lacrimal gland superior and inferior canaliculi lacrimal sac nasolacrimal duct

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Lacrimal Gland located in upper portion of each orbit secretes constant flow of tears

- wash anterior surface of eyeball

- maintain moist and clean environment for cornea and conjunctiva

- contain antibacterial enzyme lysozyme that helps prevent eye infections

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Superior and Inferior Canaliculi collect tears after they have washed

over eyeball

Lacrimal Sac collects tears from canaliculi

Nasolacrimal Duct connects lacrimal sac to nasal cavity

where tears are swallowed

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Extrinsic Muscles arise from bones of the orbit inserted into broad tendons on sclera Six extrinsic eyeball muscles:

lateral rectus medial rectus

superior rectus inferior oblique

inferior rectus superior oblique

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superior oblique

trochlea

superior rectus

lateral rectus(cut)

inferioroblique

medial rectusinferiorrectus

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Primary Actions of the Eye Muscles abduction adduction elevation depression

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Abduction contraction of lateral rectus moves pupil

away from nose

Adduction contraction of medial rectus moves pupil

towards nose

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Elevation contraction of superior rectus or inferior

oblique muscles moves pupil upward

Depression contraction of inferior rectus or superior

oblique muscles moves the pupil downward

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Cranial Nerves of Eyeball Innervation

oculomotor (III)

- branches innervate superior rectus, medial rectus, inferior oblique, and inferior rectus

trochlear (IV)

- innervates superior oblique abducens (VI)

- innervates the lateral rectus