blood pressure

• What is the purpose of the atria, describe why they are structured as such?


  The atria's function is to receive blood from the veins and push it into the ventricles. Their walls are thin because they do not need to create much pressure.
• What is the purpose of the right ventricle., and describe why it is structured as such?


  The walls of the right ventricle are thicker than the walls of the atria. this enables the right ventricle to pump blood out of the heart. the right ventricle pumps deoxygenated blood to the lungs. the lungs are in the chest cavity beside the heart, so that the blood doesn't need to travel too far, also the alveoli in the lungs are very delicate and can be damaged by high blood pressure.
• What is the purpose of the left vetircle, describe why it is structured as such?

  The walls of the left ventricle can be two or three times thicker than that of the right ventricle. the blood from the left ventricle is pumped out through the aorta and needs sufficient pressure to overcome the resistance of systemic circulation.
• cardiac muscle consists of fibres that branch producing cross bridges. these help spread the stimulus around the heart and ensure that the muscle can produce a squeezing action instead of a simple reduction in length. there are numerous mitochondria between the muscle fibrils to supply energy for contraction. the muscle cells are separated by intercalated discs which facilitate synchronized contractions. each muscle cell has a nucleus and is divided into contractile units called sarcomeres.