Page 109 - Biology Form Two

Biology for Secondary Schools

Table 5.1: Adaptation of the heart to its functions
Adaptive feature Function
Muscular walls Contract to pump blood

Cardiac muscles Contract and relax continuously without getting fatigued to
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ensure continuous pumping of the blood
Valves Ensure blood flows in one direction
Septum Separates the left and right sides of the heart to prevent
mixing of oxygenated and deoxygenated blood

Sinoatrial node Sets time and rate of contraction of cardiac muscles
Coronary artery and The coronary artery nourishes the heart and supplies it with
coronary vein oxygen. The coronary vein removes waste that would harm
the heart if left to accumulate
Connection with Enables the heart to pump out deoxygenated blood to the
pulmonary artery and lungs and receives oxygenated blood from the lungs
pulmonary vein
Pericardial fluid Prevents friction as the heart beats

Connection with vena Enables the heart to receive deoxygenated blood and pumps
cava and aorta out oxygenated blood

Blood vessels Arteries
Arteries are thick-walled, muscular, and
Task 5.3 elastic vessels that transport blood from

Search the library and internet sources the heart to all parts of the body (Figure
for the structure of arteries, veins and 5.3). All arteries transport oxygenated
capillaries. Write short notes describing blood, except the pulmonary artery,
their structure. which transports deoxygenated blood
from the heart to the lungs.

Fibrous layer
Blood vessels are channels through
which blood is distributed to various Smooth muscles
parts of the body. They are distributed and elastic fibres

throughout the body. Mammals have Basement
membrane
three types of blood vessels, namely Endothelium
arteries, veins, and capillaries.
Lumen
Figure 5.3: Cross-section of an artery

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