The Heart

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• The Heart
  • Heart Valves
    • Cuspid
      • Lie between the atria and the ventricles
      • When blood is flowing from atrium to ventricle the valve is pushed open
        • It lies flat against the heart wall
      • As the ventricles contract blood is forces into the cusps which closes the valve
        • Cusps are small membrane-like flaps
      • The valve tendons keep the cusps firmly in position
        • Papillae are the points where the valve tendons are attached to
    • Semi-lunar
      • Aorta and pulmonary artery
      • Blood forces the valves open
      • When open it lies flat against the artery
      • Blood can’t flow back because the valve pockets fill with blood
  • Types of circulatory systems
    • Closed circulatory
      • Most animals have closed systems
      • Blood remains inside tunes until it returns to the heart
      • Movement of blood is easily controlled
    • Double circulation
      • We have two circulatory systems in our bodies
        • Pulmonary
          • From the heart to the lungs and back to the heart
        • Systemic
          • From the heart to the body and back to the heart
  • The external structure of the heart
    • Position
      • Middle of the thorax
      • Between the lungs
      • Slightly to the left
        • Left lung is smaller than right
      • Bottom of the heart is pointy
        • Apex
    • A double membrane known as the pericardium surrounds the heart
      • Fluid between membranes
        • Reduces friction
          • When the heart contracts and relaxes
    • Made up of cardiac muscle
    • Coronary blood vessels supply blood to the heart
      • A blockage here can result in a heart attack
  • Blood Vessels
    • Arteries
      • Carry blood away from the heart
        • Almost all blood in arteries in oxygenated
          • The exception being the pulmonary artery
      • Structure
        • 1. Lumen
        • 2. Endothelium
        • 3. Muscle and elastic fibre layer
        • 4. Fibrous outer layer
      • The bulging of the artery is what we feel as a pulse
      • High pressure
      • Arteriole
        • Branch of an artery
    • Capillaries
      • The thinnest vessel
        • Red blood cells travel in single file
      • Single layer of endothelium
        • Easy diffusion
      • Slow down the rate of flow of blood
    • Veins
      • Carry blood to the heart
        • All blood is deoxygenated except for the pulmonary vein
      • Low pressure
        • Structure
          • 1. Lumen
          • 2. Muscle and elastic fibre layer
            • Thinner than in arteries
          • 3. Fibrous outer layer
      • Venule
        • A branch of a vein
  • Blood
    • Composition
      • Liquid plasma
        • 55%
          • 95% Water
          • Clear/yellowish
          • Carries
            • Vitamins
            • Blood cells
            • Proteins
            • Blood-clotting factors
            • Minerals
            • Hormones
            • Enzymes
            • Antibodies
      • Red blood cells (erythrocytes)
        • 40-50%
          • Biconcave
          • Disc shaped
          • Contains a pigment called haemoglobin
            • Carries oxygen and carbon dioxide
      • White blood cells (leucocytes)
        • 1%
          • Large cells with nuclei that have unusual shapes
          • Kills foreign cells
          • Get rid of dead or drying blood
      • Platelets
        • >1%
          • Cell fragments that lack a nucleus
            • Clot blood
              • Forming scabs
            • Fight infection
    • Functions
      • Blood carries substances
      • Blood plays an important role in fighting disease and infection
      • Blood helps to control and regulate body temperature
    • Substances carried
      • Water
        • Carried from intestines to the rest of the body
      • Food
        • Specifically
          • Sugars
          • Amino acids
          • Fats
        • Carried from the small intestine to the liver then the rest of the body
      • Waste products
        • Called urea
        • From all parts of the body to the kidneys
      • Oxygen
        • From the lungs to the rest of the body
      • Carbon dioxide
        • From the rest of the body to the lungs
      • Hormones
        • From hormone-secreting glands to the various target organs
  • The internal structure of the heart
    • Upper chambers
      • Atria
    • Lower chambers
      • Ventricles
    • Double pump
      • Separated by a muscular wall
        • Known as the septum
    • = right
      • Deoxygenated
    • = left
      • Oxygenated
    • Valves
      • Between atria and ventricle
        • Atrioventricular (AV)
          • Tricuspid
            • Left
          • Bicuspid
            • Right
      • Semi-lunar
        • Base of the two major arteries
          • Carry blood away
    • Major blood vessels
      • Venae cavae
        • Superior and inferior
      • Pulmonary veins
      • Pulmonary artery
      • Aorta
  • Cardiac Cycle
    • Enters right atrium via the vena cava
      • Flows into the right atrium via the tricuspid AV valve
        • Flows into the lungs via the pulmonary artery which is accessed by the pulmonary valve
          • From the lungs blood flows back to heart in the pulmonary veins and enters the left atrium
            • Blood flows down into the left ventricle via the bicuspid AV valve
              • Blood is pushed out the left ventricle into the aorta via the aortic valve
                • Cycle repeats
    • The cycle
      • Atrial systole (0.1sec)
        • Atria contract
        • AV valved are open
      • Ventricular systole (0.3sec)
        • Ventricles contract
        • AV valves closed
        • Semi-lunar valves open
      • General diastole (0.4sec)
        • Heart relaxes
        • AV valves open
          • So that blood trickles into the ventricles
        • Semi-lunar valves closed
    • Control
      • Natural pacemaker
        • Sinoatrial node
          • Connected to the brain by the
            • Sympathetic nerve
              • Tells the heart to slow down
            • Parasympathetic nerve
              • Tells your heart to beat faster
              • Stimulated by adrenaline (epinephrine)