Valves in the heart keep blood fl owing in only one direction through the heart.
Because the left ventricle pumps blood against a much higher pressure than the right ventricle, its wall is three times thicker. The left atrium empties the blood into the left ventricle, which then pumps the blood through the aortic valve into the aorta and throughout the body with each contraction. Share the wealthįrom the lungs, blood travels to the left atrium through the pulmonary veins. The blood then travels to the lungs to be oxygenated. Inferior vena cava - returning blood from the lower bodyĬoronary sinus - returning blood from the heart muscle Get some fresh airīlood in the right atrium empties into the right ventricle and is then ejected through the pulmonary valve into the pulmonary artery when the ventricle contracts. Superior vena cava - returning blood from the upper body Deoxygenated venous blood returns to the right atrium through three vessels: They also boost the amount of blood moving into the lower ventricles, which fill primarily by gravity.īlood moves to and from the heart through specific pathways. The upper atria have thin walls and serve as reservoirs for blood.
The heart has four chambers - two atria and two ventricles - separated by a cardiac septum. The space between the two layers contains 10 to 30 ml of serous fluid, which prevents friction between the layers as the heart pumps. It has an inner, or visceral, layer that forms the epicardium and an outer, or parietal, layer. Leading into and out of the heart are the great vessels:Ī thin sac called the pericardium protects the heart. The exact position of the heart may vary slightly with each patient. The left border lines up with the left midclavicular line.
The right border of the heart lines up with the right border of the sternum. The heart spans the area from the second to the fifth intercostal space.
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