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Biology for Secondary Schools

1. The presence of pinna which helps Externally, the eye is protected by eyelids,
to collect the sound waves from the eye lashes and eyebrows as shown in Figure
external environment and directs them 2.20. An eyelid is a thin fold of skin that
into the ear canal. covers and protects the eye externally

2. The presence of the tube-like canal against entry of foreign particles. There
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which directs the sound waves to the are two eyelids namely upper and lower
ear drum. eyelids. They are able to move and through

3. The existence of the ear ossicles which blinking they help keep the surface of the
increase the force of the vibration and eye moist. Blinking is the movement of
amplify the sound. eyelids is called blinking. The upper eyelid

4. Presence of fluid filled semicircular of the eye secretes a saline fluid which
contains enzymes that offer protection to
canals and utriculus which help the the eye by killing microorganisms that can
body to maintain its balance. attack the eye. Eye lashes are fine hairs that

5. The presence of the sensory hair grow at the edge of eyelid. They perform
cells that facilitate the detection of the function of protecting the eye from
the sound waves. entry of small foreign particles such as

The mammalian eye sand and dust. The eyebrow is an area of
thick, short hairs above the eye that follows
Task 2.12 the shape of the lower margin of the brow
Search from the library and internet riges. Their main function is to prevent
sources for animations about the vision sweat, water, and other debris from falling
mechanism of the human eye. Watch the down into the eye socket. They are also
videos and write short notes about your important in human communication and
observation. facial expression.
Eye brow
The eye is an organ for vision which Sclerotic layer
receives light from the environment and
converts it into electrical impulses. It is
roughly spherical in shape and located Eyelid
in a bony socket called orbit in the skull.
The orbit protects the eye against physical Pupil
damage. The eye has also a layer of fat
deposits around the eyeball which offers Iris
protection by acting as shock absorber
against mechanical injuries. The main Eye lashes
function of the eye is to control the amount Figure 2.20: Front view of mammalian
of light entering it and focus the image external eye
from the surroundings so that the objects
can be seen.

47 Student’s Book - Form Three

23/10/2025 11:52:37
BIOLOGY FORM 3 FINAL EDITED 16.09.2025.indd 47
BIOLOGY FORM 3 FINAL EDITED 16.09.2025.indd 47 KAMISHNA 23/10/2025 11:52:37 KAMISHNA