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The Human Eye - Biology

The document provides an overview of the human eye, detailing its main parts and their functions, including the cornea, iris, pupil, lens, and retina. It explains the processes of accommodation for focusing on objects at different distances and the pupil reflex in response to varying light conditions. Additionally, it describes the two types of light-sensitive cells, rods and cones, which enable vision in different lighting situations.

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80 views2 pages

The Human Eye - Biology

The document provides an overview of the human eye, detailing its main parts and their functions, including the cornea, iris, pupil, lens, and retina. It explains the processes of accommodation for focusing on objects at different distances and the pupil reflex in response to varying light conditions. Additionally, it describes the two types of light-sensitive cells, rods and cones, which enable vision in different lighting situations.

Uploaded by

leylaolanrewaju1
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as DOCX, PDF, TXT or read online on Scribd
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The Human Eye (IGCSE Biology)

The eye is a sense organ that detects light and allows us to see.

🔹 Main Parts of the Eye & Their Functions

Part Function

Clear front part that bends (refracts) light into the


Cornea
eye

Iris Coloured part; controls the size of the pupil

Hole in the centre of the iris; controls how much


Pupil
light enters

Transparent; changes shape to focus light on the


Lens
retina

Change the shape of the lens for focusing


Ciliary muscles
(accommodation)

Suspensory
Connect the ciliary muscles to the lens
ligaments

Contains light-sensitive cells (rods and cones) that


Retina
detect light

Optic nerve Carries impulses from the retina to the brain

Sclera White outer part; protects the eye

Choroid Contains blood vessels; prevents internal reflection

Aqueous humor Clear liquid at the front of the eye

Vitreous humor Jelly-like substance inside the eye to keep its shape

🔸 Accommodation (Focusing on Near and Distant Objects)

Objec Ciliary Suspensory Lens


t muscles ligaments shape

Near Contract Slack Fat and


Objec Ciliary Suspensory Lens
t muscles ligaments shape

round

Thin and
Far Relax Tight
flat

🔸 Pupil Reflex (Response to Light)

Bright Light Dim Light

Pupil gets smaller Pupil gets larger


(constricts) (dilates)

To protect the retina To allow more light in

Circular muscles Radial muscles


contract contract

🔸 Light-Sensitive Cells

 Rods – see in dim light (black & white)

 Cones – detect colour (need bright light)

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