Structure of the Mammalian Heart

Esmeralda Harcourt
The human circulatory system is described as closed, because the blood is contained either within the hearts or the vessels. It is also described as double, because the blood passes through the heart twice per circuit. The right pump sends deoxygenated blood to the lungs where it becomes oxygenated and returns back to the heart. The left pump sends the newly oxygenated blood around the body
The heart sends blood away to the lungs, this is known as the pulmonary circuit. The pulmonary circuit replenishes the blood with oxygen, as well as dropping off CO2 which has been taken from the body's tissues
1. After the blood has gone around the pulmonary circuit, it is then sent around the systemic circuit, which takes it around the rest of the body to all of the tissues
2. Because there are 2 circuits, 2 pumps are needed - one to send blood around the systemic circuit, and one to send blood around the pulmonary circuit.
  1. Every time the blood goes through both circuits, it goes through the heart twice (double)
The right side of the heart pumps blood around the pulmonary circuit to re-oxygenate after returning from body tissues
1. Blood returns from the body into the vena cava (vein). The blood is low in oxygen and high in CO2
  1. The right side pumps the blood into the pulmonary artery and then into the pulmonary circuit
The left side of the heart pumps blood round the systemic circuit to deliver oxygen to respiring tissues of the body
1. The blood from the lungs comes back through the pulmonary vein and drains into the left side of the heart. The blood is oxygenated and needs to be sent around the body
  1. The left side pumps the blood into the aorta (the biggest artery in the body) where it is then distributed around various parts of the body
    1. The heart needs its own supply of oxygen and nutrients, and the coronary arteries deliver these to the heart tissue. Cardiac veins remove the cellular wastes.
2. Internal structure
  1. 4 chambers - atria and ventricles, both left and right
  2. The atria are thin-walled elastic chambers which recieve blood from the veins. They can expand and withstand rising pressure
    1. Deoxygenated blood enters the vena cava into the right atrium. Oxygenated blood enters the pulmonary vein into the left atrium
      1. The ventricles are thick-walled chambers that pump blood out through the arteries. They need thicker walls to pump blood to organs, not just other chambers like the atria
        The right ventricle recieves deoxygenated blood from the right atrium. The right ventricle contracts and sends the deoxygenated blood out to the lungs via the pulmonary artery.
        The left ventricle recieves oxygenated blood from the left atrium. The ventricle contracts and sends the blood to the rest of the body. Therefore, the left ventricle requires much more muscle in order to efficiently pump the blood
        The atria and ventricles are separated by atrio-ventricular valves that prevent blood flowing in the wrong direction
        The arteries leading from the heart are separated from the ventricles by semilunar valves
        Cardiac muscle is a specialed type of muscle found in the walls of the heart; it can contract automatically without a signal from the brain
        Cardiac muscle contains branched fibres and myofibrils separated by intercalated discs. The branches help to form a sheet, and each muscle cell is connected by the intercalated discs which allow the communication of the muscle contraction to run through the whole sheet.
        The structure of cardiac muscle ensure that contraction of the heart has a pumping effect, i.e. from atria to ventricles and out again
4 main vessels related to the heart: the vena cava which brings deoxygenated blood from the body into the right side
1. The right side sends blood out to the lungs in the pulmonary artery
  1. This blood comes back to the left side through the pulmonary vein
    1. The left side sends blood out to the body via the aorta

Nächster

Structure of the Mammalian Heart

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	Erstellt von Esme Harcourt vor etwa 3 Jahre