CIRCULATORY SYSTEM
There are 3 types of circulations:
A. Systemic circulation: It begins in the left ventricle where the oxygenated blood passes
through the aorta and its branches to reach all the tissues of the body, where exchange
of gases and materials occur. The deoxygenated blood is collected by small veins, then
by large veins and finally by superior vena cava and inferior vena cava into the right
atrium. The blood passes from the right atrium to the right ventricle where this circulation
ends and a new cycle starts.
B. Pulmonary circulation: It starts from the right ventricle where the venous blood passes
through the pulmonary artery and its 2 branches to reach both lungs, where exchange of
gases occurs. The oxygenated blood returns to the left atrium via the 4 pulmonary veins,
then to the left ventricle, where a new cycle occurs.
C. Portal circulation: The venous blood from stomach, spleen, pancreas and intestine, is
collected into the portal vein which enters the liver (through the porta hepatis) and divides
into many branches which end in liver sinusoids. The blood leaves the liver sinusoids by
the hepatic veins which end in inferior vena cava, then to right atrium.
Circulations of blood