Circulatory system

• Blood is made from four parts:

  • Red blood cells - transport oxygen
  • White blood cells - (phagocytes) defend against disease
  • Platelets - clot blood, stop bleeding to help wound heal faster without infections
  • Plasma - yellow liquid that carries these cells and important nutrients to the body
• Red blood cells:

  • Biconcave disc shape - increase surface area, more membrane for oxygen to diffuse through - light can see through.
  • No nucleus - more space to carry oxygen
  • Cytoplasm containing haemoglobin for transport of oxygen
  • Another word = erythrocyte
• White blood cell (phagocyte):

  • Lobed nucleus
  • Phagocytes engulf other cells, particularly bacteria - then digest them (ingest) and then destroy them.
• DIFFERENCE in structure:

  Red blood cell

  • Circular - biconcave disc shape
  • No nucleus

  White blood cell

  • Irregular shape
  • Nucleus
• Plasma:

  Carries dissolved substances around the body.

  It carries…

  • CO2 - from body cells to lungs - exhaled
  • Soluble molecules - e.g. glucose from small intestine to all body cells
  • Urea - waste product made in liver to kidney - excreted
  • Hormones - from glands in body to where they are needed
  • Distributes heat
• Arteries:

  • Always carry blood away from the heart.
  • Carry oxygenated blood, except for the pulmonary artery.
  • Carry blood under high pressure.
  • Have thick muscular and elastic walls to pump blood and accommodate blood.
  • No valves
  • The channel in the blood vessel that carries blood - the lumen is narrow.
• Veins:

  • Always carry blood to the heart.
  • Carry deoxygenated blood, except for the pulmonary vein.
  • Carry blood under low or negative pressure.
  • Have thin walls - less muscular tissue than arteries.
  • Valves to prevent backflow.
  • Have a wide lumen - allows more blood to flow.
• Capillaries:

  • Allow the exchange of molecules between the blood and body cells - molecules can diffuse across their walls.
  • Carry nutrients to cells, and waste away from the cells.
  • They are one cell thick - very thin, allowing nutrients and waste to pass from cells easily and quickly - short diffusion distance.
  • Cells are close to a capillary as they need nutrients fast and remove waste quickly.
  • The walls are permeable - substances can pass through quickly.
• Heart is made of (cardiac) muscle, contracts to pump blood around the body.
• Coronary artery:

  Blood vessel which supplies the heart muscle with blood.

  On the surface of the heart.
• Left ventricle is the thickest muscular wall - pumps blood around the whole body - longer distance so higher pressure.
• Right ventricle is the thinnest wall - pumps blood to the lungs - shorter distance so less pressure.
• Two circulation:

  Pulmonary circulation - blood leaves the heart and travels to the lungs

  Systemic circulation - blood leaves the heart and travels to the body organs.
• DOUBLE CIRCULATION

  Blood goes through the heart twice in one circuit of the body.

  One circulation the lungs (pulmonary).

  One circulation to the rest of the body (systemic).
• Oxygenated blood (left) and deoxygenated blood (right) never mix - separated by septum.

  Hole in septum - blood mixes, lower concentration of Oxygen in blood, less energy released by respiration.
• Heart valves prevent backflow of blood when the chambers contract.
• Passage of blood:

  Vena cava -> Right atrium -> Tricuspid valve -> Right ventricle -> Semi-lunar valve -> Pulmonary artery -> Lungs -> Pulmonary vein -> Left atrium -> Bicuspid valve -> Left ventricle -> Semi-lunar valve -> Aorta -> Body
• Cardiovascular disease (CVD): A disease of the heart and circulatory system, like coronary heart disease, heart attacks, angina and strokes.
• Genetic factors, ethnic background and diabetes can make CVD more likely.

  Lifestyle factors can greatly increase risk:

  • Smoking
  • High fat diet - high blood cholesterol
  • High salt diet - high blood pressure
  • Obesity
  • No/lack of exercise
• Plaque: A fatty deposit that build up in the walls of the (coronary) arteries - resulting in CVD - medical term, atherosclerosis.
• Inflammation occurs (causes can be stress, high blood pressure, smoking), fatty streaks increase with high fat diets - increase of blood cholesterol levels.

  High cholesterol can cause the formation of plaques in the walls of the coronary arteries - damages vessels.

  Less blood can flow through narrowed arteries.

  If heart doesn’t receive enough oxygen, the heart cannot continue to contract, causing a heart attack - blockage could occur.
• If a heart attack doesn’t occur after this, people may have pains in the chest, angina.

  The slower flow of blood also makes it more likely that a clot will form, blocking blood vessels, causing a stroke.
• Treatment

  Lifestyle changes may reduce risk:

  • Exercise
  • Healthy diet
  • No smoking
  • Limit alcohol intake

  Lifestyle changes are less risky and cheaper than surgery, but problem is:

  • Hard to motivate to exercise

  Hard to lose body mass

  Smoking and alcohol are addictive
• Statins

  Drugs taken in tablet form

  They lower blood cholesterol levels, but don’t prevent or cure CVD, instead reduce.

  Placebo is a drug which has no effec.
• Angioplasty

  Surgery to widen narrowed arteries and can have long term success.

  Must ensure the correct lifestyle changes to prevent the problem reoccurring.

  1. Build up of cholesterol partially blocking blood flow through the artery.
  2. Stent with ballon is inserted into partially blocked artery.
  3. Balloon is inflated to expand stent.
  4. Balloon is removed from the expanded stent
• • Coronary vessels are found on the outside / surface of the heart muscle.
• • Coronary arteries supply the heart muscle with blood.
• • Coronary arteries supply the heart muscle with glucose and oxygen for aerobic respiration.
• • Coronary veins remove waste products like carbon dioxide.
• • All blood vessels have an endothelium lining in the linen, but the wall of a capillary is made of a single layer of endothelial cells.