The Eye

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Lacrimal apparatusLacrimal glands

Superior and lateral in each eyeProduces tearsSeveral small ducts liberate the

tear continuallyExcretory ducts

Accessory structures of the eye

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Lacrimal Apparatus

Lacrimal canalMedial in each eye

Lacrimal sacNasolacrimal ductTears

Salt solutionContains lysozyme and antibodiesCleanse, protect, moisten and lubricate

the eye ball

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Accessory structures of the eye

PalpebraeLateral canthusMedial canthusCaruncle – contains sweat and

sebaceous glands

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Accessory structures of the eye

EyelashesCiliary glands

Modified sweat glands between the eyelashes

Meibomian or tarsal glandsPosterior to the eyelashes. Secrete oil

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Accessory structures of the eye

StyAcute inflammation of the ciliary or

meibomian glandChalazio

Chronic inflammation of the meibomian gland

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Accessory structures of the eyeConjunctiva

PalpebralOcular or bulbarIt is a mucosa that secretes mucusConjunctivites

Inflamation of the conjunctivaExtrinsic muscles of the eye

Control eye movement

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Internal Anatomy of the eye

Outer fibrous tunicDense avascular connective tissueSclera Cornea

Transparent, anterior most portion

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Internal Anatomy of the eye

Middle vascular tunic (uvea)Iris

• Colored part of the eye• Smooth muscle acting as a diaphragm

Ciliary body• Ciliary muscles – control the shape of

the lens• Ciliary processes – secretes aqueous

humor• Suspensory ligaments 9

Internal Anatomy of the eye

ChoroidPosteriormost partContain melaninTapetum lucidum (only in animals)

Inner sensory tunic (Retina)Pigmented layer

Covers the choroid

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Internal Anatomy of the eye

Neural layerRods – photoreceptors cells for dim light.

Perceives gray tonesCones – photoreceptors cells for color.

They need high amount of lightOptic disc – blind spot. Emergency of the

optic nerveMacula lutea – high concentration of

cones. • Fovea 11

Internal Anatomy of the eye

LensHeld by the suspensory ligaments. Attaches

to the ciliary body.Catarats – lens become opaque and hard

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Internal Anatomy of the eye

Anterior segmentAqueous humor – clear fluid formed by the

ciliary process. It provides nutrients for the lens and cornea.

Scleral venus sinus (canal of Schlemm) – absorbs the aqueous humor

Glaucoma – increased intraocular pressurePosterior segment

Vitreous humor – helps to keep the retina in place 13

Figure 17.4a, b

The Sectional Anatomy of the Eye

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Microscopic anatomy of the retina

Pigmented epithelial layerLocated between the choroid and neural

layerNeural layer

Photoreceptors – rods and conesBipolar neuronsGanglion neurons

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Microscopic anatomy of the retina

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Visual Pathways to the brain

Optic nerveOptic chiasma

It is the crossing of the fibers of the optic nerve

Optic tractThalamusOptic radiationVisual cortex – located on the occipital lobe

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Visual Tests and Experiments

Blind SpotWhen the image fall on the optic disc

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Visual Tests and Experiments

Refraction of the light raysCorneaLens Vitreous humor

Accommodation of the lensNear-point accommodation

Presbiopia – difficult focus for close vision because of decreased lens elasticity

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Visual Tests and Experiments

Visual acuitySnellen chartEmmetropy MyopiaHyperopia

AstigmatismIrregularity in the curvatures of the lens

and/or cornea

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Visual Tests and Experiments

Color blindnessThree cone types- red, green and blue

Binocular visionThree dimensional visionAccuracy of locating objectsDepth perception

Panoramic vision

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Visual Tests and Experiments

Extrinsic muscles of the eyeConvergence

Medial eye movements for near visionKeep moving objects focused on the fovea

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Visual Tests and Experiments

Pupillary reflexPhotopupillary reflex

Constriction of the pupils when the retina is illuminated by a bright light

Intrinsic muscles of the eyeAccommodation pupillary reflex

Change of the pupil diameter for near focus

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Eye Dissection

WHOLE EYECorneaScleraOptic nerveExtrinsic muscles

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Eye DissectionFRONTAL CUT

Humors: aqueous, vitreousLensCiliary bodyIrisPupilChoroid Retina Posterior cavity

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