Eye parts



Here are functions to go with the structures:

Aqueous humour: helps maintain the shape of the anterior chamber of the eyeball.

Blind spot: the location where the bundle of optic nerve fibers exit the retina. Because this area lacks photoreceptor cells (due to a developmental fluke*), it is thus 'blind' to the visual scene.

Choroid: a pigmented layer that makes the retina appear black and prevents light reflection within the eyeball. Has a network of blood vessels to supply nutrients and remove wastes.

Ciliary body: contains ciliary muscles that enable the lens to change shape during accommodation (focusing on near and distant objects), with suspensory ligaments that hold the lens in place. Also secretes the aqueous humour.

Conjunctiva: the thin protective covering of epithelial cells. It protects the cornea against damage by friction (tears from the tear glands help this process by lubricating the surface of the conjunctiva

Cornea: the transparent, curved front of the eye which helps to converge the light rays which enter the eye

Fovea (yellow spot): the area of the retina with the highest concentration of cone cells, responsible for best high resolution visual perception

Iris: the pigmented muscular structure consisting of an inner ring of circular muscle and an outer layer of radial     muscle. Its function is to help control the amount of light entering the eye so that 1) too much light does not enter the eye which would damage the retina and 2) enough light enters to allow a person to see

Lens: the transparent, flexible, curved structure (unlabeled, but in blue in the picture above) which focuses incoming light rays onto the retina thanks to its refractive properties

Pupil:  the hole in the middle of the iris where light is allowed to continue its passage (unlabeled in the picture above). In bright light it is constricted and in dim light it is dilated.

Retina: the layer of sensory neurons, in particular the photoreceptors (rods and cones) that respond to light and relay and sensory neurons that transduce impulses along the optic nerve to the visual cortex of the brain.

Sclera: an opaque, fibrous, protective outer structure. It is soft connective tissue, and the spherical shape of the eye is maintained by the pressure of the liquid inside. It also provides attachment surfaces for the eye muscles.

Vitreous humour: the transparent, jelly-like mass located behind the lens. It acts as a ‘suspension’ for the lens so that the delicate lens is not damaged. It helps to maintain the shape of the posterior chamber of the eyeball.


 * in contrast to situation in the octopus eye, with photoreceptor cells 'inverted,' so they can detect light even in this area of the retina...

Thanks to BiologyMad.com for their eye structure info!