Everything about Systemic Circulation totally explained
Systemic circulation is the portion of the
cardiovascular system which carries
oxygenated
blood away from the heart, to the
body, and returns deoxygenated blood back to the heart. The term is contrasted with
pulmonary circulation.
Course
In the systemic circulation,
arteries bring oxygenated blood to the tissues. As blood circulates through the body, oxygen diffuses from the blood into cells surrounding the capillaries, and carbon dioxide diffuses into the blood from the capillary cells.
Veins bring deoxygenated blood back to the heart.
Arteries
Oxygenated blood enters the systemic circulation when leaving the
left ventricle, through the aortic
semi-lunar valve. The first part of the systemic circulation is the artery
aorta, a massive and thick-walled artery. The aorta arches and gives off major arteries to the upper body before piercing the diaphragm in order to supply the lower parts of the body with its various branches.
Capillaries
Blood passes from
arteries to
capillaries, which are the thinnest and most numerous of the blood vessels. These capillaries help to join tissue with arterioles for transportation of nutrition to the cells, which absorb oxygen and nutrients in the blood.
Peripheral tissues don't fully deoxygenate the blood, so venous blood does have oxygen, but in a lower concentration than in arterial blood. In addition, carbon dioxide and wastes are added.eiuf
Venules
The deoxygenated blood is then collected by
venules, from where it flows first into
veins, and then into the
inferior and
superior venae cavae, which return it to the
right heart, completing the systemic cycle. The blood is then re-oxygenated through the pulmonary circulation before returning again to the systemic circulation.
Veins
The relatively de-oxygenated blood collects in the venous system which coalesces into two major veins: the
superior vena cava (roughly speaking from areas above the heart) and the
inferior vena cava (roughly speaking from areas below the heart). These two great vessels exit the systemic circulation by emptying into the
right atrium of the
heart. The
coronary sinus empties the heart's veins themselves into the right atrium.
Advantage
Because the systemic circulation is powered by the left ventricle (which is very muscular), one advantage of this form of circulation - as opposed to
open circulation, or the gill system that fish use to breathe - is that there's simultaneous high-pressure oxygenated blood delivered to all parts of the body.
Further Information
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