Circulatory System

• what is the circulatory system?

  The circulatory system is the network of blood vessels, the heart, and blood that transports oxygen, nutrients, hormones throughout the body and removes waste products
• what is the function of blood?

  transportation of substances to cells in the body and removed waste.
• what are the components of blood?

  red blood cells

  white blood cells

  platelets

  plasma
• red blood cells

  transport oxygen

  absorb oxygen from lungs and transport it through blood vessels, oxygen is released to cells and used for aerobic respiration.

  • contain haemoglobin (red protein which absorbs oxygen)

  • have no nucleus

  • biconcave shape to increase surface area for oxygen absorption
• white blood cells

  • defend the body against disease

  • phagocytes - ingest and destroy pathogens (microorganisms causing disease) like bacteria

  • phagocyte engulfs the pathogen

  • pathogen is broken down by enzymes inside the phagocyte

  This process is called phagocytosis.
• platelets

  • blood contains tiny fragments of cells called platelets, these clot blood and form scabs

  • when skin is wounded the platelets are able to release chemicals that cause soluble proteins to form a mesh of insoluble fibres across the wound and stick together to form clumps that get stuck in the mesh, red blood cells also get stuck which forms a clot
• plasma

  straw coloured liquid that makes up over half the volume of blood

  • transports CO2 from respiring cells to the lungs

  • transports digested food from the small intestine to respiring cells

  • transports urea from the liver to the kidneys for excretion

  • distributes heat around the body

  • transports hormones from the glands to the target organs
• What are the four chambers of the heart?

  Right atrium, left atrium, right ventricle, and left ventricle.
• the heart

  The heart is a muscular organ. It’s function is to pump blood. The cardiac muscle of the heart contracts to pump the blood from the atria into the ventricles and from the ventricles into the arteries. The cardiac muscle of the heart requires energy from respiration to continue to contract, and is supplied with the glucose and oxygen required by coronary arteries.
• What are the two circuits of the heart?

  • Pulmonary circuit - right side pumps blood to the lungs

  • systemic circuit - left side pumps blood around the body
• what are ventricles?

  lower chamber of the heart that receives blood from the atrium and pumps it into arteries
• what are atria? (plural - atrium)

  the upper chambers which collect blood returning from the body (right atrium) or the lungs (left atrium)
• Deoxygenated blood

  Blood on the right side of the heart that has been around the body and supplied the cells with oxygen carried by the red blood cells, now depleted of oxygen
• Blood flow through the heart

  1. Enters right atrium through vena cava

  2. Right atrium contracts and pushes blood into right ventricle

  3. Right ventricle contracts and pushes blood out through pulmonary artery to lungs

  4. Blood returns to left atrium through pulmonary vein

  5. Left atrium contracts to push blood into left ventricle

  6. Left ventricle pumps oxygenated blood out through aorta
• Heart

  • Contains valves to prevent blood flowing backwards
  • Right side has tricuspid valve
  • Left side has bicuspid valve
  • Both sides have semilunar valves at entrances to pulmonary artery and aorta
• The left ventricle has a thick muscular wall to provide sufficient pressure to pump the oxygenated blood to the furthest areas of the body
• Arteries

  -Carry blood away from the heart (always oxygenated apart from the

  pulmonary artery which goes from the heart to the lungs).

  -Have thick elastic and muscular walls.

  -Have small passageways for blood (lumen).

  -Contain blood under high pressure.
• Veins

  • Carry blood to the heart (always deoxygenated apart from the pulmonary vein which goes from the lungs to the heart).
  • Have thin, less muscular walls.
  • Have larger passageways for blood (internal lumen).
  • Contain blood under low pressure.
  • Have valves to prevent blood flowing backwards.
• Capillaries

  • Found near every living cell of the body.
  • Microscopic – walls are one cell thick, this allows for the diffusion of substances into the cells from the capillaries and out of the cells into the capillaries.
  • Very low blood pressure.
• Artery Structure

  Type of blood - oxygenated

  Direction - away from heart

  Pressure - high

  Size of lumen - small

  Wall thickness - Thick

  Valves - No
• Vein Structure

  Type of blood - deoxygenated

  Direction - towards heart

  Pressure - low

  Size of Lumen - Large

  Wall Thickness - Thin

  Valves - Yes
• Capillaries

  Type of blood - both

  Direction - from arteries to veins

  Pressure - low

  Size of Lumen - very small

  Wall Thickness - 1 cell thick

  Valves - no
• What is coronary heart disease?

  The coronary arteries supply blood to the heart muscle. These may become blocked by a build-up of fatty plaques containing cholesterol, resulting in coronary heart disease.
• What happens if an artery becomes blocked?

  If a coronary artery is blocked, the blood supply to part of the heart muscle is cut off. That part of the heart cannot continue to contract, causing a heart attack.
• Main causes of coronary heart disease:

  • poor diet – eating more saturated fat tends to increase cholesterol levels
  • stress and smoking – increases blood pressure
  • salt – eating too much causes high blood pressure
  • lack of exercise
  • genetic factors
• What treatments can help manage CHD?

  • statins
  • Angioplasty
  • lifestyle changes
• What are statins? What are the advantages and disadvantages?

  Statins are daily medications used to control blood cholesterol levels.

  Advantage - drugs reduce blood cholesterol levels

  Disadvantage - can cause side effects
• What is an angioplasty? advantages and disadvantages?

  Angioplasty is a surgery to insert a small balloon into a blood vessel which is then inflated to remove a blockage

  Advantages - Minimally invasive, can improve blood flow in coronary vessels.

  Disadvantages - Risk of complications, arteries may re-narrow (temporary measure)
• What are lifestyle changes? advantages & disadvantages?

  Diet and exercise, stopping smoking etc

  advantage - reduces risk of CHD and reduces blood pressure

  disadvantage - high level of willpower and self discipline needed to make lifestyle changes