blood

• why is the circulatory system known as a double circulatory system?

  the blood flows through the heart twice in one journey around the body and is made up of two circuits:

  • pulmonary circuit: blood vessels taking blood to the lungs and back.
  • systemic circuit: blood vessels taking the blood to the rest of the body and back
• what are the chambers of the heart?

  -upper left atrium

  -upper right atrium

  -lower left ventricle

  -lower right ventricle
• describe the passage of blood through the heart

  the blood flows into the upper atria of the heart.

  • the right atrium receives blood from the vena cava of the body and the head
  • the left atrium receives blood from the pulmonary vein coming from the lungs.

  the blood then flows downwards from both atria into the respective ventricles. the ventricles then pump out the blood from the heart.

  • the right ventricle pumps blood into the pulmonary artery, which takes it to the lungs.
  • the left ventricle pumps blood into the main artery, the aorta, which takes the blood around the body.

  
• functions of the atria and the ventricles.

  -atria: receive blood from the lungs and the body, and supply it to the ventricles.

  -ventricles: pump blood out of the heart and all around the body.

  
  

  • right ventricle: pumps blood to the lungs which are close to the heart.
  • left ventricle: pumps blood all around the body.
• describe the arteries

  
  

  • carry blood away from the heart
  • divide to form capillaries
  • blood pressure is high
  • thick elastic walls to withstand the pressure
  • no valves due to the high force
  • narrow lumen
  • rapid and irregular blood flow
• describe the veins.

  • carry blood towards the heart
  • blood pressure is low
  • thin walls and have valves to direct the blood flow
  • wide lumen
  • slow and regular blood flow
• describe the capillaries.

  • carry blood from arteries to veins
  • very low blood pressure
  • walls are one cell thick
  • very narrow lumen
  • blood flow is slow
• demonstrate how the structures of the blood vessels differ from one another.

  -arteries: more elastic fibres, more muscle fibres, thicker wall, no valves, small lumen

  -veins: less elastic fibres, less muscle fibres, thinner wall, valves, large lumen

  -capillaries: wall is one cell thick

  
• describe the function of coronary arteries

  supply blood to the cardiac muscles.
• describe the different valves in the heart

  -atrioventricular valves: valves between the atria and ventricles in a heart

  • bicuspid: on the left side and made up of 2 parts
  • tricuspid: on the right side and made up of 3 parts

  -semilunar valves: valves in the pulmonary artery and the aorta
• describe the cardiac cycle.

  the heart contracts and relaxes. (systole and diastole)

  • Atrial Systole

  -the atrial muscles contract squeezing blood down to the ventricles.

  -the atrioventricular valves are open but the semilunar valves are closed.

  • Ventricular Systole

  -the heart becomes smaller and the ventricles squeeze blood out to the arteries.

  -semilunar valves are open but the atrioventricular valves are closed.

  
  

  • Diastole

  -the heart becomes larger

  -the atria and ventricles fill up with blood

  -the atrioventricular valves are open but the semilunar valves are closed
• describe red blood cells.

  -transport oxygen and blood around the body.

  -biconcave structure -> to increase surface area for absorbing more oxygen

  -elastic cell membrane

  -contain haemoglobin

  
• describe white blood cells.

  2 main types of white blood cells.

  • phagocytes: collect at the site of infection to engulf and digest the bacteria by phagocytosis.
  • lymphocytes: produce antibodies -> protein molecules with a shape which is specific to that of the pathogens.
• describe the functions of blood

  -regulation of body temperature

  -transport of oxygen, carbon dioxide, waste products

  -defence against disease
• describe the lymphatic system.

  -site where exchange of gases and nutrients takes place is when the capillaries are in close proximity to the tissue cells.

  
• describe the functions of the lymphatic system.

  1. It removes waste products of the cells
  2. It contains lymphocytes which fight infection
  3. It transfers body fluids into the blood circulatory system
• list different defence mechanisms.

  -clotting

  -body defences: i.e. cilia which trap dust, outer layer of dead cells on skin, tears, etc.

  -blood groups and transfusions

  -white blood cells
• distinguish between passive and active immunity.

  active - when antibodies are made by the body.

  • active induced: being vaccinated against a disease
  • active natural: lymphocytes learning how to make antibodies against a disease

  passive - they have been given antibodies that were made by another individual. doesn't last for a long time.