The+Eye+and+Ear

The Eye and Ear __ **Parts and functions of the eye:** __ __** Aqueous Humor: **__ Clear watery fluid in the anterior of the eye, maintains pressure and nourishes the cornea and lens. **__ Vitreous Humor: __** Clear, jelly-like fluid found in the back portion of the eye. it maitains shape of he eye and attaches to the retina. **__ Blind Spot: __** Small area of the rtina where the optic nerve leaves the eye. Any image falling here will not be seen. **__ Ciliary muscles: __** Involuntary muscles that change the lens shape to allow focussing images of objects at different distances. **__ Cornea: __** Transparent tissue covering the front of the eye. Does not have blood vessels, but it does have nerves. **__ Cones: __** Photoreceptors responsive to colour and in bright conditions, used for fine detail. **__ Fovea: __** Central part of the macula that provides sharpest vision, contains only cones. **__ Iris: __** Circular band of muscles that controls the size of the pupil. The pigmentation of the iris gives colour to the eye. **__ Lens: __** Transparent tissue that bends light passing through the eye to focus light, the lens can change shape. **__ Macular: __** Small central area of the retina that provides vision for fine work and reading. **__ Optic Nerve: __** Bundle of over one million axons from ganglion cells that carry visual signals from the eye to the brain. **__ Pupil: __** Hole in the center of the eye where light passes through. **__ Choroid: __** Thin tissue layer containing blood vessels, sandwiched between the sclera and retina, also because of the high melanocytes content, the choroid acts as a light-absorbing layer. **__ Retina: __** Layer of tissue on the back portion of the eye that contains cells responsive to light. **__ Sclera: __** Tough, white outer covering of the eye, extraocular muscles attach here to move the eye. __ **Parts and functions of the ear:** __ **__ Pinna: __** Collects sounds and funnels them into the aditory canal. **__ Auditory Canal: __** Connects the outer ear with the eardrum. **__ Ear Drum: __** The beginning of the middle ear and is made of a thin sheet of muscle and skin that vibrates in respons to sounds. Vibrations are passed to the ossicles. **__ Ossicles- anvil, hammer, stirrup: __** By the time the sound has reached the stirrup, it has been amplified about thirty times. The Stirrup vibrates against a section called the oval window. **__ Cochlea: __** The fluid inside the cochlea passes vibrations to tiny hairs connected to auditory nerves. **__ Auditory Nerve: __** These send messages to the brain, which are then interprited as sounds. **__ Round window: __** A membrane covered openning in the inner wall of the middle ear that compensates for changes in cochlea pressure. __ **Eustachian Tube:** __ Tube that connects the middle ear with the pharynx and equalizes the pressure between the two sides of the ear drum. **__ Ear Canal: __** Than narrow passage through which sound enters the ear.