The cardiovascular system consists of:
In a day, the average adult’s heart:
Blood is propelled mainly by contractions of the heart and arteries.
During each heartbeat, 60 to 90 ml (2 to 3 oz) of blood is pumped out of the heart.
If the heart stops pumping, death occurs within five minutes.
The main function of the system is:
The system is essentially a pump and a delivery process:
Among its vital functions, the circulatory system increases the flow of blood to meet increased energy demands during exercise and regulates body temperature.
In case of bleeding, the circulatory system sends clotting cells and proteins to the affected site, which quickly stop the bleeding and promote healing.
The heart, blood, and blood vessels are the three structural elements that make up the circulatory system.
The heart is the engine of the circulatory system.
It is divided into four chambers:
The right atrium: Collects deoxygenated blood.
The left atrium: Collects oxygenated blood.
The right ventricle: Ejects deoxygenated blood into the arteries.
The left ventricle: Ejects oxygenated blood into the arteries.
The pumping action of the heart occurs in two stages for each heart beat:
The heart is a hollow muscular organ (cardiac muscle) located between the lungs and above the diaphragm.
Blood Flow (Cardiac cycle):
Minimum blood pressure is essential to push blood through blood vessels to the body tissues for nutrient and waste exchange.
The heart ensures the unidirectional flow of blood through both the heart and the blood vessels.
Arteries- Vessels that carry blood away from the heart.
Arteries carry blood high in oxygen (except for the pulmonary arteries).
Arteries carry the nutrient-rich, oxygenated blood out to the rest of the body.
Arteries are thick layers of muscles.
The aorta is the largest artery in the body.
Capillaries are tiny links between arteries and veins where oxygen and nutrients diffuse to body tissues.
They provide a surface area over which:
Veins- Vessels that carry blood toward the heart.
Veins carry blood low in oxygen (except for the pulmonary veins).
Veins are thinner layers of muscles, compared to arteries which are tough, elastic tubes that carry blood away from the heart.
Veins contain valves, which keep the flow of blood in one direction.
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