Human Sense Organs Quiz

Study Notes

Sense organs allow perception of external and internal environments.
Major sense organs are eyes, ears, tongue, nose, and skin, sensitive to light, sound, chemicals, touch respectively.
Additional senses include balance, body movement, hunger, thirst, and pain.
Receptors are specialized cells sensitive to specific stimuli.

Photoreceptors: rods and cones in the retina, responsible for vision.
Phonoreceptors: receptors in the inner ear, responsible for hearing and balance.
Chemoreceptors: receptors on the tongue and nose, responsible for taste and smell.
Thermoreceptors: temperature-sensing receptors in the skin, responsible for hot and cold sensations.
Mechanoreceptors: receptors in the skin, sensitive to touch, pressure, and vibrations.

Orbits: eye sockets, located on the front of the head.
Eyelids: upper and lower eyelids protect the front of the eyes and can shut out light.
Eyebrows: protect the eyes from rain and sweat.
Tear glands (lacrimal glands): located at the upper sideward portion of the orbit, secrete liquid that lubricates, cleanses, and disinfects the eye.
Tear ducts: drain tear fluid into a sac at the inner corner of the eye, leading to the nasal cavity.

Thin membrane covering the front of the eye, continuous with the inner lining of the eyelids.
Conjunctivitis is an infection that affects the conjunctiva.

Sclerotic layer (Sclera): tough, white fibrous tissue that forms the outer layer of the eyeball.
Cornea: transparent, bulged-out portion of the sclerotic layer in the front of the eye.
Choroid: middle layer of the eyeball, contains blood vessels.
Retina: inner layer of the eyeball, contains photoreceptor cells.

Myopia (Nearsightedness): difficulty seeing distant objects. Corrected with concave lenses.
Hyperopia (Farsightedness): difficulty seeing near objects. Corrected with convex lenses.
Presbyopia: age-related loss of focusing ability, corrected with bifocal lenses.
Astigmatism: uneven curvature of the cornea, causing distorted vision. Corrected with cylindrical lenses.
Cataract: clouding of the lens, causing blurred vision. Corrected with surgery.