The Human Eye: Structure (Edexcel IGCSE Biology (Modular))

The Human Eye: Structure

• The eye is a highly specialised sense organ containing receptor cells that allow us to detect the stimulus of light

• The retina of the eye contains two types of receptor cells:

  • Receptor cells that are sensitive to light, known as rods, and receptor cells that can detect colour, known as cones

The eye is a sense organ that contains light receptor cells

The structures of the eye 

• Cornea - transparent lens that refracts light as it enters the eye

• Iris - controls how much light enters the pupil

• Lens - transparent disc that can change shape to focus light onto the retina

• Retina - contains light receptor cells – rods (detect light intensity) and cones (detect colour)

• Optic nerve - sensory neuron that carries impulses between the eye and the brain

• Pupil - hole that allows light to enter the eye

• Conjunctiva - a clear membrane that covers the white of the eye and the inside of the eyelids; it lubricates the eye and provides protection from external irritants

• Ciliary muscle - a ring of muscle that contracts and relaxes to change the shape of the lens

• Suspensory ligaments - ligaments that connect the ciliary muscle to the lens

• Sclera - the strong outer wall of the eyeball that helps to keep the eye in shape and provides a place of attachment for the muscles that move the eye

• Fovea - a region of the retina with the highest density of cones (colour detecting cells) where the eye sees particularly good detail

• Blind spot - the point at which the optic nerve leaves the eye, where there are no receptor cells