Heart

• Heart


  A four-chambered muscular pump which pumps blood round the circulatory system
• Blood circulation


  1. Deoxygenated blood enters right atrium

  2. Pumped through valve to right ventricle

  3. Pumped through pulmonary valve to pulmonary artery

  4. Oxygenated blood enters left atrium

  5. Pumped through valve to left ventricle

  6. Pumped through aortic valve to aorta
• Arteries


  • Thick walled muscular tubes that carry blood away from the heart at high pressure
• Capillaries


  • Very narrow tubes with thin walls to allow glucose and oxygen to diffuse through
• Veins


  • Thin walled tubes that carry low pressure blood back to the heart, with valves to prevent backflow
• Blood vessels called the coronary arteries supply blood to the heart muscles
• Heart attack


  1. Fatty deposits build up in coronary arteries

  2. Blood clot forms on fatty deposit

  3. Blood clot blocks coronary artery

  4. Heart muscle cells don't get oxygen and nutrients

  5. These cells start to die
• In the UK about 300,000 people have a heart attack every year
• Factors that increase risk of heart disease

  • Smoking
  • High blood pressure
  • High levels of salt in diet
  • High levels of saturated fat in diet
• High levels of salt in diet

  Lead to increased blood pressure
• High levels of saturated fats in diet

  Lead to build up of cholesterol in arteries, causing plaque and narrowing
• Blood pressure


  Blood is under pressure in the arteries so that it reaches all parts of the body
• Arteries


  • Carry blood away from the heart
  • Blood in the arteries is under pressure because of the contractions of the heart muscles
  • This allows the blood to reach all parts of the body
• Measuring blood pressure


  • Measured in millimetres of mercury (mmHg)
  • Systolic pressure - the higher measurement when the heart beats, pushing blood through the arteries
  • Diastolic pressure - the lower measurement when the heart rests between beats
• A young, fit person should have a blood pressure of about 120 over 70, which means their systolic pressure is 120 mmHg and their diastolic pressure 70 mmHg
• Factors that can increase blood pressure


  • Smoking
  • Being overweight
  • Drinking a lot of alcohol
  • Stress
• How smoking affects blood pressure


  1. Smoking increases blood pressure by raising the heart rate

  2. Nicotine itself increases the heart rate

  3. Carbon monoxide reduces the oxygen-carrying capacity of the blood

  4. This causes an increase in heart rate to compensate for the reduced amount of oxygen carried in the blood
• A balanced diet and regular exercise can reduce high blood pressure
• Problems caused by extremes of blood pressure


  • High blood pressure can cause:
  • Kidney damage
  • Burst blood vessels
  • Damage to the brain, including strokes
  • Low blood pressure can cause:
  • Dizziness
  • Fainting
  • Poor blood circulation
• The heart has four chambers: two atria and two ventricles
• Blood flows from the right atrium into the right ventricle through the tricuspid valve