Chapter 15: Anatomy Of The Eye Flashcards
What are the 5 special senses?
- Vision
- Taste
- Smell
- Hearing
- Equilibrium
How is the eye protected?
By fat cushion and bony orbit
What are the 5 accessory structures of the eye?
- Eyebrows
- Eyelids
- Conjunctiva
- Lacrimal apparatus
- Extrinsic eye muscles
Describe the Eyebrows
Location: over lie supraorbital margins
Functions: shade, prevents perspiration
Describe the Eyelids
Location: separate at palpebral (slit), meet in the corners at medial and lateral commissures
Function: blinks reflexively every 3-7 seconds, offers protection from foreign objects and spreads secretion
Eyelashes
Tarsal (Meibomian) glands
Tarsal (Meibomian) glands
Modified sebaceous glands produce oily secretion that lubricates lid and eye
Describe the Conjuctivia
Transparent mucous membrane that produces a lubricating mucous secretion
Conjunctivitis
Inflammation of the conjunctiva resulting in reddened, irritated eyes
Pink Eye
Conjunctival infection caused by bacteria or viruses
Lacrimal Apparatus
Consists of lacrimal gland and ducts (that drain into nasal cavity)
Process:
1) lacrimal gland secretes lacrimal secretion (tears)
2) tears drain into lacrimal sac and nasolacrimal duct
3) empties into nasal cavity
What causes watery eyes when you have a cold (or nasal inflammation) ?
Lacrimal mucosa are swelled which constricts the ducts and prevents tears from draining–> watery eyes
Describe Extrinsic Eye Muscles
6 strap like extrinsic eye muscles
- Origin: bony orbit and insert on eyeball
- Function: enables eye to follow moving objects, maintain shape of eyeball, and hold it in orbit
What are the 3 layers of the wall of the eye?
1) Fibrous layer
2) Vascular layer
3) Inner layer
- internal cavity filled w/ liquid (humors)
Describe the Fibrous Layer
Has 2 regions
- Sclera: protects and shapes eyeball
- Cornea: lets light enter and bends light
• Numerous pain receptors (blinking and tearing reflexes)
Describe the Vascular Layer
Also called uvea
Has 3 regions:
- Choroid
- Ciliary Body
- Iris
Choroid region
Posterior portion of uvea
- supplies blood to all layers of eye
Ciliary Body
Anteriorly, choroid becomes ciliary body
- Consists of smooth muscle bundles, ciliary muscles–> controls shape of lens
- Capillaries of ciliary processes secrete fluid
- Ciliary zonule (from ciliary processes to lens): holds lens in place
Iris
Contains the pupil (controls amount of light entering the eye)
Describe the Inner Layer (Retina)
Contains:
• Photoreceptor cells (transduce light energy)
• Neurons
• Glial cells
Has 2-layered membrane
- Outer pigmented
- Inner neural layer
Outer pigmented layer
Covers ciliary body and iris
- Function:
1) absorbs light and prevents it from scattering
2) Phagocytizes photoreceptor cell fragments
3) Stores vitamin A
Inner Neural Layer
3 types of neurons:
1) Photoreceptors
2) Bipolar cells
3) Ganglion cells
Journey of Light:
Signal–> Photoreceptors –> Bipolar cells –> Ganglion cells —(exits eye)—> Optic nerve–> brain
Optic disc (blind spot): optic nerve leaves eye
2 types of photoreceptors:
1) Rods
2) Cones
Rods
Dim light, peripheral vision
- more numerous and more sensitive to light
- no color vision
Cones
Bright light
- color vision
• Macula lutea
• Fovea centralis
Macula lutea
Area at posterior pole lateral to blind spot
- contains mostly cones
Fovea centralis
Tiny pit in center of macula lutea that contains all cones, so is region with best visual acuity
- eye movement allows to focus on object so fovea can pick it up
Internal chambers and fluids
The lens and ciliary zonule separate eye into 2 segments:
1) Posterior segment
2) Anterior segment
Posterior segment
Vitreous humor: transmits lights and contributes to intraocular pressure
- forms in embryo and lasts whole lifetime
Anterior segment
Aqueous humor: plasma-like fluid continuously formed by capillaries of ciliary processes
- drained by scleral venous sinus
- Function: supplies nutrients and oxygen mainly to lens and cornea and retina, and remove wastes
