CIRCULATORY SYSTEM

what is the circulatory system

the circulatory system includes all blood vessels, capillaries, and the heart. it is also called the cardiovascular system. (think “pumps, pipes, and fluid”)

what is the heart

• a muscular organ with two pumps, one on the left side and another on the right

what are the functions of its right and left pumps?

• right pump: receives deoxygenated blood from the body and sends it to the lungs to drop off carbon dioxide and pick up oxygen on its way to the left heart

• left pump: receives oxygenated blood from the lungs and sends it throughout the body. it is the stronger of the two pumps, with a greater workload than the right pump

what divides the heart into left and right sides?

a septal wall

what are the three layers of the heart wall, from inner to outer

• endocardium

• myocardium

• epicardium

and what is the pericardium?

a fibrous sac that surrounds the heart

what is the endocardium

the smooth, thin lining on the inside of the heart

what is the myocardium

the thick middle, muscular layer of the heart

what is the epicardium

the outermost layer of the heart and innermost layer of the pericardium

what are the chambers and valves of the heart

• atria

• ventricles

• heart valves

what are the atria, and what is their function?

the two upper chambers of the heart. blood returning to the heart on both sides enters the atria (atrium). the atria pumps the blood into the ventricles just before the ventricles contract. this is called the “atrial kick” and helps increase cardiac output

what are the ventricles, and what is their function?

they are the lower and larger chambers of the heart. the ventricles receive blood from the atria and send it out of the heart during ventricular contraction. under normal circumstances, this generates a palpable pulse. the left ventricle sends oxygen-rich blood throughout the body under high pressure. the right ventricle sends oxygen-depleted blood to the lungs under low pressure