heart

• Blood enters the heart

  1. Through the atria

  2. Blood from two vena cavae enters the right atrium

  3. Blood from the pulmonary veins enters the left atrium

  4. The atria fill

  5. Followed by the ventricles

  6. Blood is prevented from flowing back into the atria by heart valves
• Blood leaves the heart

  1. In the body's main artery - the aorta - from the left side

  2. In the pulmonary artery, from the right
• Double circulation

  Humans have a double circulatory system. The heart pumps blood through two circuits: the pulmonary circulation and the systemic circulation
• Pulmonary circulation

  1. Transports blood to the lungs

  2. Oxygen diffuses into the blood from the alveoli - the blood becomes oxygenated

  3. Carbon dioxide diffuses from the blood into the lungs
• Systemic circulation

  1. Transports oxygen and nutrients to the body

  2. Transports carbon dioxide and other wastes away from cells
• Systemic circulation

  • Under high pressure - it has to deliver blood to the extremities of the body
• Pulmonary circulation

  • Under lower pressure, because blood is delivered to the lungs only, which are very close to the heart
  • In a healthy person, this lower pressure is optimum for the diffusion of gases
• Circulating blood

  1. Blood passes through the heart twice in one complete circulation of the body

  2. Deoxygenated blood from the body enters the right atrium

  3. Part of the blood is being delivered to the body, while the remainder of the blood is being transported to the lungs

  4. This means that oxygen can be picked up from the lungs, while at the same time, blood is also being delivered to the body
• Faulty heart valves

  • May not open as wide as they should, restricting blood flow through the heart
  • May not close properly and allow blood to leak back through into the atrium
• Restricted blood flow through the heart

  Less blood reaches the body, pressure builds up and the lungs can swell with fluid
• Specialised cells in the right atrium

  Generate electrical signals that make the heart contract independently of the nervous system
• Specialised cells in the right atrium

  Act as a natural pacemaker
• A patient will not always have symptoms
• Always carry blood away from the heartAlways carry blood to the heartCarry oxygenated blood, except for the pulmonary arteryAlways carry deoxygenated blood, except for the pulmonary veinCarry blood under high pressureCarry blood under low or negative pressureHave thick muscular and elastic walls to pump and accommodate bloodHave thin walls - have less muscular tissue than arteriesA type of supporting tissue called connective tissue provides strengthHave less connective tissue than arteriesThe channel in the blood vessel that carries blood - the lumen - is narrowHave a wide lumen
• Wave of contraction

  1. Spreads across the heart

  2. To the left atrium

  3. To the ventricles
• Heart's natural pacemaker process becomes disrupted

  Person's heart beats abnormally
• Scan of the heart

  Can diagnose the problem
• The walls of capillaries are just one cell thick. Capillaries therefore allow the exchange of molecules between the blood and the body's cells - molecules can diffuse across their walls. This exchange of molecules is not possible across the walls of other types of blood vessel
• Symptoms when present

  • Shortness of breath
  • Dizziness
  • Rapid heart rate
  • Chest pain
• • Oxygen diffuses through the capillary wall, into the tissue fluid, and the cells.
  • Carbon dioxide diffuses from the cells into the tissue fluid, then across the capillary walls into the blood plasma.
  • Glucose diffuses from the blood plasma, across the capillary walls to the tissue fluid, and then to the cells.
  • The waste product urea diffuses from the cells of the liver, to the tissue fluid, and then across the capillary walls into the blood plasma.
• Heart beats abnormally

  Can be abnormally slow or fast, or irregular
• Faulty heart valve condition

  Can lead to heart failure
• If a blockage builds up, the amount of oxygen reaching the heart muscle is reduced. A person will develop chest pain, and if left untreated, a heart attack is the result. This can cause damage to, or death of the heart muscle. Part of the heart muscle, or the whole heart, will die.
• Artificial pacemaker

  • Small, battery-operated electronic device implanted in a person's chest
  • Sends out regular, adjustable electrical impulses
  • Produces normal contractions of the heart
• If the condition is severe, the patient will require surgery
• Types of artificial pacemaker

  • Have electrical leads connected to different chambers of the heart
• Replacement options for faulty heart valves

  • Biological valve from a human donor
  • Biological valve made from animal tissue (pig or cow)
  • Mechanical valve made from strong, durable materials
• Fitting artificial pacemaker

  1. Wires are guided along a vein to the chamber of the heart that needs to be stimulated

  2. Lead extends to the pacemaker

  3. Pacemaker is fitted between the skin of the upper chest and the chest muscle
• Mechanical valves

  • Last longer
  • Blood can clot on them
• Statins

  Drugs that help to lower cholesterol in the blood by lowering its production in the liver
• The fitting of artificial pacemakers is one of the most common types of heart surgery performed in the UK
• Statins

  • Prescribed for people with heart disease or who have a high risk of developing it
  • Need to be taken long-term
  • Cholesterol levels will rise again if a person stops taking them
• Biological valves

  • More likely to wear out
• Some studies have raised concerns regarding the side effects of statin use

  Others believe they can bring additional positive benefits
• The operation to replace faulty heart valves is usually successful
• Statins

  • Not suitable for people with liver disease, or pregnant or breast feeding women
• A patient may need long-term medication that prevents blood clots developing
• Side-effects of statins

  • Headaches
  • Memory loss
  • Linked with type 2 diabetes
  • Liver damage
• Some argue that statins should be used more widely

  They may protect against other conditions such as Alzheimer's disease, but further research is needed
• Stents

  Coronary arteries that are blocked or have become narrow can be stretched open and a stent inserted to restore and maintain blood flow