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Flashcards in senses Deck (9):

what are the senses?

- vision
- auditory
- olfactory
- gustatory
- equillibrium


the eye

- delicate organ
- eyebrows function in preventing perspiration from entering the eye


how is the eye protected

- most of the eye is hidden and protected by a cushion of fat and the bony orbit
- eyelids protect the eye anteriorly, eyelashes contain nerve endings of follicles to initiate reflex blinking
- lacrimal gland produces tears
- 6 extrinsic eye muscles originate from the bony orbit and both enable the eye to follow moving objects and maintain shape of eyeball



- separates eyeball into anterior and posterior segments
- biconvex, transparent, flexible, elastic and avascular structure which allows focusing of light on retina
- becomes less elastic and more dense with age and cataracts



- whites of the eye which protects and shaped the eyeball, and anchors extrinsic eye muscles
- transparent anterior portion that bends light is the cornea which contributes to tar reflexes and blinking



- middle vascular pigmented layer
- choroid - brown pigmented most posterior portion that supplies blood to all layers of the eyeball
- cillary body - a ring of smooth muscle and ligaments surrounding the lens that control lens shape and position
- iris - coloured part and the pupil is the opening that regulates the amount of light entering



- inner sensory layer, a delicate, richly vascularised two layered membrane
- outer pigmented area stores vitamin A and absorbs light
- inner neural layer consists of multiple cells that transmit and process impulses
- optic disc (blind spot) lacks photoreceptors and is the site where the optic nerve leaves the eye



- rods and cones are highly specialised sensory receptor cells which respond to electromagnetic radiation (light)
- rods are numerous at the periphery of the retina, operate in dim light/nigh vision, and provide indistinct, fuzzy, non colour peripheral vision (black and white)
- cones are found in the macula lutea, operate in bright light and provide high-acuity colour vision and fine focus


pathway of light entering the eye

cornea - aqueous humor - lens - vitreous humor - neural layer of retina - photoreceptors
- light is refracted at the cornea as is enters the lens and as it exits the lens