Anatomy II: Eye

Cornea

• Transparent, tough layer on the front of the eye

• Allows for light to pass through

• AVASCULAR (No blood vessels)

Sclera

Tough, white, semi transparent layer on the outercornea

Lens

• BICONVEX shape

• Changes shape to focus light onto the retina

Iris

• Colored part of eye

• Controls pupil (opening, closing, dilation)

Aqeous Humor

• Watery part in the first chamber

• Helps nourish cornia, maintains pressure, brings nutrients

Vitrious Humor

Holds lens and retina in place

The pupil ______ when in a dark room

Dilates (bigger)

Pupil

• Iris opening

• Regulates amount of light entering

The pupil ______ when in a bright room

Constricts (gets smaller)

Choroid Layer

• Vascularized middle layer

• Pigment in layer prevents light from scattering

Retina

• Location of photoreceptors

  • Inner Layer

Macula Lutea

• Rich in cones (mostly cones)

Fovea Centralis

All cones

• Clearest vision

Optic Nerve

Message carrier

Optic Disc

• Blind spot

• No photoreceptors

Emmetropia

Normal Vision (20/20)

Hyperopia

• Farsighteed (Can’t see close)

Shape: Shorter than normal

Treatment: Biconvex lens

Focal Point: Behind the retina

Myopia

• Nearsighter (Can’t see far)

Focal Point: Front of the retina

Shape: Longer

Treatment: Concave Lens

• COMMON IN OLD AGE

Amblyopia

Lazy eye, when 1 or both eyes don’t develop vision

Color Blindness

• Inherited trait (sex - linked)

• More common in males

• Lacking one or more cones

Glaucoma

• Occurs when the fluid from aquous humor builds up due to clogging

• Increases pressure on optic nerve

Cataracts

• Lens gets cloudy

Ciliary Body

• Structure sarrounding the lens that connects chorid and iris

  • Controls shape of lens and produces aqeous humor

When does Accomodation Occur

As an object moves closer to the eye

Accessory Structures

• Eyebrows

• Eyelashes

• Eyelids

Eyebrow

• Protection from sweat, things in hair

Eyelids

• Protection from friction in the eyes

  • Drying out

Eyelid Structures

• Protection from Small Particles

Tarsal Plate: Gives structure

Tarsal Glands: Modified sebaceous oil glands in the tarsal plates

Conjunctiva: Transparent mucus membran over the iris and the pupil

• Creates a tight seal and lubricates so it is easy to open and close the eyes

• Pink eye

Lacrimal Apparatus

• Responsible for Tears

Tears: Have antibodies, lysosomes, mucus

Lacrimal Gland

Tears Journey

Pass Puncta - Canaliculi - sac - nasaolacrimal duct - nasal cavity (sniffles)

Fibrous Layer

• Sclera

• Cornea - only human tissue that can be transplanted without fear of rejectin

Accomodated

Close Objects

• Ciliary Bodies Contract

• Ligaments Relax

• Lens Thickens

Far Objects

• Ciliary Bodies loosen

• Ligaments contract

• Lens is stretched

Phototransduction

1. Rhodopsin - light sensitive protein that initiates vision

2. Consists of opsin and cis-retinal which changes shape upon light absoprtion

3. This shape change triggers a series of events that leads to an electrical signal in a photoreceptor cell

4. Rhodopsin is regenrated after each ligth activation - allowing coninuous light detection