How animals move their blood: open and closed circulation, and the hearts of fish, frogs and mammals. The chambers, valves and nodal tissue of the human heart, and the two loops of the double circulation.
3 lessons, about 1 h 20 min4 simulations10 problems3 practice questionsPython in every lesson
Created by StemPy LabEvery animal moves its fluid round the body. In an open system, as in an insect, the blood leaves the vessels and bathes the organs in large spaces. In a closed system, as in an earthworm and in all vertebrates, the blood stays in vessels. Fish have a heart of two chambers, amphibians and most reptiles three, and birds, mammals and crocodiles four.
The human heart is a muscular organ of four chambers, lying in the chest between the two lungs. Valves keep the blood moving one way. A special tissue in the heart, the nodal tissue, makes the heart beat by itself. The SAN is the pacemaker. The signal goes to the AVN, then along the AV bundle and the Purkinje fibres to the ventricles.
In the human heart the blood makes two loops. The pulmonary circulation carries deoxygenated blood from the right ventricle to the lungs and brings oxygenated blood to the left atrium. The systemic circulation carries oxygenated blood from the left ventricle to the body and brings deoxygenated blood to the right atrium. The hepatic portal system and the coronary system are two special pathways.
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