circulatory system

• Define "cardiovascular system"

  A system that consists of the heart (cardiac) and blood vessels.
• What is a double circulatory system?

  A circulatory system in which blood passes through the heart twice in one complete circuit of the body.

  1. Pulmonary circulatory system: blood is pumped from the right ventricle to the lungs and back to the heart via left ventricle
  2. Systemic circulatory system: blood from the left ventricle is pumped to the rest of the body
• Why do mammals have a double circulatory system?

  Mammals have higher metabolic rates compared to other animals, requiring a higher blood pressure to deliver oxygen and nutrients efficiently. The double circulatory system helps maintain this high blood pressure by reducing the distance that blood needs to travel between the heart and the body tissues, thus ensuring rapid delivery of oxygenated blood to all parts of the body.
• Explain the function of arteries

  Arteries carry blood away from the heart to the body's tissues. They have thick, muscular walls that help them withstand the high pressure generated by the heart when it pumps blood during systole (contraction).

  
  

  Structure:

  • thicker wall
  • smaller lumen
  • more elastic fibres than smooth muscle tissue to withstand high blood pressure
  • smooth muscle tissue
  • no valves (other than aorta/pulmonary artery)
  • high pressure transportation of oxygenated blood (except for pulmonary artery)
• Explain the function of Arterioles

  Arterioles are smaller branches of arteries. They help regulate blood flow into the capillaries by adjusting their diameter. When they constrict (get smaller), they increase blood pressure; when they dilate (get larger), they decrease blood pressure.

  
  

  Structure:

  • more smooth muscle tissue than elastic fibres
  • smooth muscles are under control of autonomic nervous system
  • contraction causes vasocontriction, reduces blood flow to capillaries
  • relaxation causes vasodilation, increased blood flow to capillaries
• Explainthe function of capillaries

  Capillaries are tiny blood vessels where the actual exchange of oxygen, nutrients, and waste products occurs between the blood and the body's cells. They have very thin walls, allowing for easy exchange of substances. The pressure in capillaries is much lower compared to arteries and arterioles, which facilitates the exchange process.
• Explain the function of veins

  1. Veins have thinner walls than arteries.
  2. They contain valves to prevent backflow, ensuring one-way blood flow.
  3. Veins mostly carry deoxygenated blood, except for the pulmonary vein.
  4. Larger vein diameter reduces blood flow resistance, ensuring blood returns to the heart efficiently.
  5. Veins have lower pressure than arteries due to pressure loss through capillaries.
  6. Muscular contractions around veins help squeeze blood back to the heart because heart contraction is not strong enough