Page 126 - Biology Form Two

Biology for Secondary Schools

is mainly caused by the following:
excessive alcohol intake; smoking;
stress; too much fat in the diet; lack of
Lumen physical exercise; and old age.
Effects of arteriosclerosis: Arteriosclerosis
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causes swelling of part of a blood vessel
(a) Normal artery and rupturing of the artery walls. It also
causes total blockage of an artery, thus
depriving some tissues of oxygen. This
can cause severe damage or death of the
Lumen
affected tissue.
Fat deposit
Prevention of arteriosclerosis: People
can reduce chances of developing
(b) Artery with narrow lumen arteriosclerosis by avoiding excessive

alcohol intake and smoking, reducing
Figure 5.18: Effect of arteriosclerosis
stress, minimising intake of fatty
As a result, the heart has to pump harder foods, and engaging in regular physical
in order to supply the tissues with exercise.
enough blood. This may result to an
increased risk of heart diseases, stroke Sickle-cell anaemia
This is a genetic disorder resulting
and high blood pressure (hypertension). from the production of abnormal
High blood pressure usually has no haemoglobin and malformed red blood
specific symptoms. However, it can cells. Its effect is the reduction of the
cause headache, dizziness, and ringing blood’s capacity to transport oxygen.
in the ears. The disease gets its name from the
Causes of arteriosclerosis: Arteriosclerosis crescent or sickle shape of the red
blood cells, as shown in Figure 5.19.

(a) Normal red blood cell (b) Sickle-shaped red blood cell

Figure 5.19: Normal and sickle shaped red blood cells

120 Student’s Book - Form Two

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