● Most are found toward the edges of the retina ● Allow vision in dim light and peripheral vision ● All perception is in gray tones

- Organ of sight - Protected by the orbital socket of the skull, the eyebrows, eyelids and eye lashes. - The location of the eye in front of the head allows for superimposition of images from each eye. — This enables us to see stereoscopically in three dimensions: LENGTHS, WIDTH, AND DEPTH

Age-related ear problems - type of sensorineural deafness that may result from otosclerosis

is a snail shaped structure where sound vibrations are converted into nerve impulse

Electrical signals pass from photoreceptors via a two-neuron chain

- consist of smooth muscles that hold the biconvex. - Transparent and flexible lens in place.

Muscles responsible for moving the eye within the orbital socket are attached to the outside of the sclera — known as ______ (superior, inferior, lateral, medial, rectus and the superior, inferior oblique)

EXTERNAL EAR • Is line with hairs and modified sebaceous glands called ceruminous glands — produce earwax or cerumen. • The hair and ear wax protect the eardrum from foreign objects.

Internal Structures: The eyeball INSIDE LAYER

contain the organ of corti-pick up the nerve impulses and transmit them through the vestibulocochlear of the brain

- Gel-like substance posterior to the lens - Prevents the eye from collapsing - Helps maintain intraocular pressure

eye focuses images correctly on the retina

• guides the intake of meat and cheese to meet our protein needs, sweet guides the intake of sugar to meet the needs for carbohydrates, salty guide the needs for necessary minerals and sour guides the intake of certain fruits to meet the need for vitamin C • Bitter taste protects us by helping us detect spoiled food and poisons.

• Images are blurry • Results from light focusing as lines, not points, on the retina because of unequal curvatures of the cornea or lens

Age-related eye issues old vision results from decreasing lens elasticity that accompanies aging — Causes difficulty to focus for close vision

• Near objects are blurry, whereas distant objects are clear • Distant objects are focused behind the retina • Results from an eyeball that is too short or from a "lazy lens”

____ is the central egg-shaped cavity of the labyrinth.

Age-related ear problems - ear ossicles fuseear ossicles fuse

is a blood-rich nutritive layer that contains a pigment (prevents light from scattering) — It is modified anteriorly into two smooth muscle structures

EXTERNAL EAR ● Silvery gray in color ● very delicate ● sounds waves cause it to vibrate. ● Separates the outer and the middle ear

• Contains the sensory receptors for hearing and balance.

EXTERNAL EAR ● Links middle ear cavity with the throat ● Equalizes pressure in the middle ear cavity so the eardrum can vibrate

● also lie within the middle ear ● contain a liquid and delicate hair like cells that bend when the liquid is set in motion by head and body movements ● These impulses are sent to the cerebellum, helping maintain body

EXTERNAL EAR ● Flexible, visible part which composed mainly of elastic cartilage. ● Allows sound waves to enter the ear canal, which then directs those waves to the delicate eardrum or membrane.

• is the air-filled cavity that contains the three auditory ossicles or ear bones: • Malleus or hammer • incus or anvil • Stapes or stirrup. • These bones transmit the sound vibration from the eardrum to the oval window

- Watery fluid found between lens and cornea - Similar to blood plasma - Helps maintain intraocular pressure - Provides nutrients for the lens and cornea - Reabsorbed into venous blood through the scleral venous sinus, or canal of Schlemm

- lateral to blind spot - Area of the retina with only cones - Visual acuity (sharpest vision) is here

● can detect about 10,000 different smells. ● In the nasal cavity is a patch of tissue about the size of a postage stamp called the olfactory epithelium, which has a plentiful supply of nerve cell with specialized receptors. ● These receptors send signals to the adjoining olfactory bulbs, an extension of the brain. ● This stimulus is transmitted by the olfactory nerve to the limbic system thalamus, and the frontal cortex. ● This explains why odors are tied to feelings

1. Outer pigmented layer absorbs light and prevents it from scattering 2. Inner neural layer contains receptor cells (photoreceptors)

- Sometimes referred to as window of the eye. - Transparent to permit the passage of light rays - Consist of five layers of flat cells - Possessing pain and touch receptors, it is sensitive to any foreign particles that come in contact with its surface. - Any injury to the ___ may cause scarring and impaired vision

• located under the base of the stapes • the membrane that separates from the middle ear from the inner ear. • Vibration reach the inner ear through this structure.

Internal Structures: The eyeball OUTSIDE LAYER

- Outermost layer - It is a tough, unyielding, fibrous capsule that maintains the shape of the eye and protects the delicate structure within.

Structure of the inner ear is called the _____.

- (blind spot) is where the optic nerve leaves the eyeball - Cannot see images focused on the ___

• Distant objects appear blurry • Light from those objects fails to reach the retina and are focused in front of it • Results from an eyeball that is too long

- Crystalline structure located behind the iris and pupil - Focuses images on the retina - Held in place by a suspensory ligament attached to the ciliary body - Situated between the anterior chamber and the posterior chamber

protect the eye from foreign object

rounded opening in the iris

found in tears, combat eye infection

Are those organs and receptors that are associated with touch (sensory receptors) vision, hearing, smell and taste.

● a mass of muscle tissue with a structure called papillae. ● Located on the papillae are the taste buds for sweet, sour, salty, bitter and umami ● Taste buds are stimulated by the taste of food • All taste buds can detect all five sensations

lubricates the surface of the eye by spreading tears that are produced by the lacrimal glands

regulates amount of light entering eye — Pigmented layer that gives eye color

● Allow for detailed color vision ● Densest in the center of the retina

helps shade the eye and keep perspiration from getting into the eye and causing irritation to the eye.

Internal Structures: The eyeball MIDDLE LAYER