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
Examiner Tip
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.
