Where is the sclera and what is its function?

The sclera is the tough white fibrous layer forming the outside of the eyeball, and it protects the eye, maintains its shape and provides attachment for the muscles that move it.

State two functions of the conjunctiva.

It secretes mucus and tears that keep the front of the eye moist and lubricated, and it helps protect the eye from infection and debris.

Give two features of the cornea that allow it to work as it does.

It is transparent because its collagen fibres are regularly arranged, and it is curved so that light is refracted towards the retina.

Describe the structure of the iris.

The iris is a pigmented disc of muscle in front of the lens, containing a ring of circular muscle and a set of radial muscles arranged like the spokes of a wheel.

OCR A-Level Biology B H422

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Monitoring Visual Function

The structure of the eye

3 things to know
Components 01, 02 and 03

Overview

Recall questions on the sclera, conjunctiva and cornea, the iris muscles and the pupil in bright light, the lens, ciliary body and suspensory ligaments in focusing on near and distant objects, the aqueous and vitreous humours, and the pigmented, blood-rich choroid.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is the conjunctiva?

Key term

Which part of the eye carries out most of the refraction of light entering it?

Key term

What is the pupil?

Questions from this subtopic

Each one with the model answer underneath.

1
Where is the sclera and what is its function?
Model answer
The sclera is the tough white fibrous layer forming the outside of the eyeball, and it protects the eye, maintains its shape and provides attachment for the muscles that move it.
2
What is the conjunctiva?
Model answer
The conjunctiva is a thin transparent membrane covering the front of the sclera and lining the inside of the eyelids.
3
State two functions of the conjunctiva.
Model answer
It secretes mucus and tears that keep the front of the eye moist and lubricated, and it helps protect the eye from infection and debris.
4
Which part of the eye carries out most of the refraction of light entering it?
Model answer
The cornea carries out about two thirds of the refraction of the light entering the eye.
5
Give two features of the cornea that allow it to work as it does.
Model answer
It is transparent because its collagen fibres are regularly arranged, and it is curved so that light is refracted towards the retina.
6
Describe the structure of the iris.
Model answer
The iris is a pigmented disc of muscle in front of the lens, containing a ring of circular muscle and a set of radial muscles arranged like the spokes of a wheel.

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The Developing Cell: Cell Division and Cell Differentiation

The Developing Individual: Meiosis, Growth and Development

The Development of Species: Evolution and Classification

Cells and Microscopy

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measles and .

tuberculosismalariacholera

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