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| 1. |
Describe the structure and function of human heart |
| Answer» StructureThe heart consists of four chambers, right and left atria above right and left ventricles. The functions of each part are as follows.• The right atrium links to the right ventricle by the tricuspid valve. This valve prevents backflow of the blood into the atrium above, when the ventricle contracts.• The left atrium links to the left ventricle by the bicuspid valve (mitral valve). This also prevents backflow of the blood into the atrium above. • The chordae tendonae attach each ventricle to its atrioventricular valve. Contractions of the ventricles have a tendency to force these valves up into the atria. Backflow of blood would be dangerous, so the chordae tendonae hold each valve firmly to prevent this from occurring.• Semi-lunar (pocket) valves are found in the blood vessels leaving the heart (pulmonary artery and aorta). They only allow exit of blood from the heart through these vessels following ventricular contractions. Elastic recoil of these arteries and relaxation of the ventricles closes each semi-lunar valve.• Ventricles have thicker muscular walls than atria. When each atrium contracts it only needs to propel the blood a short distance into each ventricle.• The left ventricle has even thicker muscular walls than the right ventricle. The left ventricle needs a more powerful contraction to propel blood to the systemic circulation (all of the body apart from the lungs). The right ventricle propels blood to the nearby lungs. The contraction does not need to be so powerful. If blood moved in the wrong direction, then transport of important substances would be impeded. | |