Human eye Flashcards
How does the iris carry out its function?
The iris controls the amount of light entering the eye. In bright light, the circular muscles contract and the radial muscles relax. In dim light, the circular muscles relax while the radial muscles contract.
What is the function of the conjunctiva?
It secretes mucus to keep the front of the eyeball moist.
What is the function of the sclera?
It protects the eyeball from mechanical damage.
What is the function of the eyelashes?
It shields the eye from dust particles.
What is the function of the tear gland?
It secretes tears which wash away dust particles, keep the cornea moist for atmospheric oxygen to dissolve, and lubricate the conjunctiva.
What is the function of the eyelids?
It protects the cornea from mechanical damage, and contributes to the control of the amount of light entering the eye.
How do the ciliary muscles carry out its function?
It relaxes when focusing on a distant object, pulling on the suspensory ligaments, and contracts when focusing on a near object, relaxing their pull on suspensory ligaments.
What is the function of the cornea?
It refracts or bends light rays into the eye.
What is the function of the aqueous and vitreous chamber?
It keeps the eyeball firm and helps refract light into the pupil.
How does the lens carry out its function?
It becomes thinner and less convex when focusing on a distant object and becomes thicker and more convex when focusing on a near object.
What is the function of the choroid?
It prevents internal reflection of light and contains blood vessels for exchange of nutrients.
How does the fovea carry out its function?
It contains the greatest concentration of cones and no rods, enabling a person to have detailed colour vision in bright light.
What is the function of the retina?
It contains photoreceptors to form images.
How does the eye see?
Light rays are refracted through the cornea and the aqueous humour onto the lens. The lens cause further refraction and the rays are brought to a focus on the retina. The image on the retina stimulates either the rods or the cones depending on light intensity. Nerve impulses are then produced and sent to the brain via the optic nerve.
