Biomedical Engineering Reference
In-Depth Information
Fig. 2.2
The cardiovascu-
lar system. Gas exchange
takes place in the lungs that
oxygenate the blood by diffu-
sion of oxygen into the blood
stream through the alveoli.
The oxygenated blood is
then returned via the vena
cava back to the heart, and is
then transported around the
body to the organs. To move
the blood around the body
through the organs and lungs,
the heart acts as the central
pump for the entire cardio-
vascular system
2.1.2
Organization of the Cardiovascular System
The cardiovascular system can be sub-categorised further into the pulmonary, sys-
temic circulation, and coronary circulation (Fig.
2.2
) based on the routes that the
blood takes (i.e. circulates). The
pulmonary circulation
, as its name suggests, in-
volves blood transfer to and from the heart and lung. In this circulation, deoxygen-
ated blood is transported to the lungs and freshly oxygenated blood is taken back to
the left side of the heart. The
systemic circulation
, deals with the whole body and
the heart whereby oxygenated blood is circulated to the tissues and deoxygenated
blood returns to the right side of the heart. The
coronary circulation
involves the
blood that circulates in the heart itself.
2.1.2.1
Pulmonary Circulation
When blood is deprived of oxygen and contains waste materials, such as carbon
dioxide the de-oxygenated blood enters via two large veins called the
vena cavae
into the right atrium of the heart (lower chamber), which then contracts (systole)
and pushes the blood into the right ventricle (upper chamber) via the tricuspid valve
(right atrioventricular valve). The right ventricle then contracts forcing the fluid out
via the pulmonary semilunar valve into the pulmonary artery and into the lungs,
whereby gas exchange occurs (Fig.
2.3
).
The oxygenated blood is then returned into the left atrium via the pulmonary
vein, which is pumped into the left ventricle of the heart and expelled through the
aorta, the largest artery in the body (to withstand the high pressures), to the other
portions of the body. There are a series of valves within the heart and within the
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