The Human Eye: Structure (Edexcel IGCSE Science)

Spec point — 2.91 · describe the structure and function of the eye as a receptor

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 receptor cells sensitive to light

The eye is a sense organ that contains light receptor cells

The structures of 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
• Cornea - transparent, curved layer at the front of the eye that refracts light as it enters the eye
• 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
• Pupil - circular opening in the centre of the iris that allows light to enter the eye
• Iris - controls how much light enters the pupil
• Lens - transparent disc that can change shape to focus light onto the retina
• 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
• Retina - contains receptor cells sensitive to light
• Fovea - region of the retina that contains densely packed cones (allows eyes to see in good detail and colour)
• Optic nerve - carries impulses between the eye and the brain
• Blind spot - the point at which the optic nerve leaves the eye, where there are no light receptor cells

Exam Hint Make sure you can identify the structures of the eye on a diagram because diagrams with labels are a very common form of exam question for this topic.