Strong fibrous opaque membrane covered by the conjunctiva; it surrounds the eyeball and protects the inner structures.
superior rectus muscle
Muscle allowing the eyeball to move upward.
fovea
Central depression of the yellow spot composed entirely of cones; the place where visual acuity is at its maximum.
lens
Transparent elastic area of the eye; focuses images on the retina to obtain clear vision.
choroid
Richly veined membrane located between the sclera and the retina, to which it carries nutrients and oxygen.
retina
Inner membrane at the back of the eye covered in light-sensitive nerve cells (photoreceptors); these transform light into an electrical impulse that is carried to the optic nerve.
Area of the retina where the cones are concentrated; it plays an essential role in day vision and the perception of colors.
optic nerve
Nerve formed by the juncture of the nerve fibers of the retina; it carries visual information to the brain, where it is interpreted.
papilla
Protuberance formed by the anterior terminal part of the optic nerve in the retina; it has no light-sensitive cells and thus no vision. It is also called the blind spot.
vitreous body
Transparent gelatinous mass (almost 90% of the eye); it maintains constant intraocular pressure so the eye keeps its shape.
inferior rectus muscle
Muscle allowing the eyeball to move downward.
ciliary body
Muscle tissue secreting the aqueous humor; its muscles enable the lens to change shape to adapt vision for near or far.
suspensory ligament
Fibrous tissue connecting the ciliary body to the lens, holding it in place inside the eyeball.
iris
Colored central portion of the eyeball composed of muscles whose dilation or contraction controls the opening of the pupil.
Fine transparent mucous covering the sclera and inner surface of the eyelid; it facilitates sliding thus giving the eyeball its wide range of movement.
aqueous humor
Transparent liquid contained in the anterior and posterior chambers; it nourishes the iris and maintains the pressure and shape of the eye.
pupil
Central orifice of the eye whose opening varies to regulate the amount of light entering the eye; light causes the pupil to contract.
