Circulation

principles of circulation
1. mass transport systems
  1. carry substances to every cell in the body, delivering oxygens and nutrients and removing waste products
  2. system of vessels that carry substances
  3. a way of making sure substances move in the right direction
  4. a means of moving materials substances fast enough to supply the needs of the organism
  5. a siutable transport medium
2. circulation systems
  1. open circulation - blood circulates in large open spaces (insects)
  2. closed circulation - blood contained within tubes (larger mammals)
  3. single circulation (fish)
    1. heart pumps deoxygenated blood to organs where gas exchange occurs, blood takes in oxgen and becomes oxygenated
      1. blood delivers oxygen to body cells before returning to the heart
  4. double cirulation
    1. required by animals who need more glucose and oxygen to function
    2. systematic circulation - carries oxygenated blood from the heart to where it is needed and deoxygenated blood back to the heart
    3. pulmonary circulation - carries deoxygenated blood from the heart to the lungs
    4. oxygenated and deoxygenated blood doesn't mix so tissue receive enough oxygen
    5. blood can be delivered at a high pressure
    6. maintains blood pressure around body
roles of the blood
1. plasma
  1. transports digested food products, nutrients, excretory products and chemical messages
  2. helps maintain a steady body temperature and acts as a buffer to pH changes
2. platelets
  1. found in bone marrow
  2. involved in blood clotting
3. erythrocytes
  1. contains haemoglobin
    1. carries oxygen and gives it the red pigment
  2. transports oxygen from the lungs to the rest of the body
  3. large SA:V - oxygen can diffuse rapidly
  4. no nucleus - more room for haemoglobin
4. leucocytes
  1. granulocytes - granules in cytoplasm, lobed nuclei
    1. neutrophils
      1. engulf and digest pathogens
    2. eosinophils
      1. respond to inflammation
  2. agranulocytes - no granules, unlobed nuclei
    1. monocytes
      1. engulf pathogens
    2. lymphocytes
      1. release antibodies
5. transport nutrients and waste, form tissue fluid, defend against foreign bodies
blood circulation
1. arteries
  1. carries mainly oxygenated blood away from the heart
    1. pulmonary artery - carries deoxygenated blood from heart to lungs
  2. narrow lumen to control blood flow
    1. muscle fibres trecth to withstand blood pressures
  3. lots of elastic fibres to stretch and accomodate high volumes of blood
  4. smooth lining to allow for easy bloodflow
2. capillaries
  1. short diffusion distances for rapid gas exchange
    1. thin walls - one cell thick
  2. very narrow lumen so bloodflow is slow and lots of time for diffusion to occur
3. veins
  1. carry deoxygenated blood back towards heart
    1. pulmonary vein - carries oxygenated blood from lungs back to the heart
  2. wide lumen, thin elastic and muscle fibres
  3. valves to prevent backflow as blood is at low pressure
    1. semi-lunar valves
human heart
1. right side of the heart receives blood from the body and pumps it to the lungs, the left side receives blood from the lungs and pumps it around the body
  1. the SEPTUM seperates the two sides so that oxygenated and deoxygenated blood does not mix
  2. the cardiac muscles are myogenic because it can contract regularly without resting or getting fatigued
    1. it has a good blood supply as the coronary artery brings blood to the muscle
    2. contains lots of myoglobin, which stores oxygen for the respiration needed to keep the heart contracting regularly
2. the flow of blood
  1. inferior vena cava collects deoxygenated blood from lower parts of body, superior vena cava collects it from top parts
    1. this blood is delivered to the right atrium
      1. once full, the pressure increases, causing the tricupsid valve to open and the blood flows into the right ventricle and the right atrium contracts
        tricupsid valve (atrioventricular valves) have tendinous cords make sure valves are not turned inside out
        the right ventricle then contracts and push the blood into the pulmonary arteries, which carries the blood to the lungs
        ventricles have thick muscular walls because they are under a high pressure
        oxygenated blood returns from the lungs to the pulmonary vein and flows into the left atrium, which pushes blood into the left ventricle
        backflow is prevented by the bicupsid valve
        the left ventricle pumps blood into the aorta
        the aorta pumps blood away from the heart at a very high pressure
        the left side of the heart has a veriy thick muscular layer because it needs to be able to pump the blood all around the body
      2. has thin muscular walls because it receives blood at a low pressure
      3. semi-lunar valves prevent the backflow of blood
3. cardiac cycle
  1. contraction of the heart = systole
    1. artrial systole - when atrium contract together forcing blood into the ventricles
    2. ventricular systole - ventricules contracting
      1. happens about 0.13s after atrial systole
  2. relaxation stage = diastole
4. controlling the heart
  1. SAN sends a wave of electrical excitation (depolarisation) that causes the artia to contract
    1. group of cells in the right atrium
    2. acts s a natural pacemaker
    3. the wave of excitation spreads through the atria as they contract and stimulate the artiaventricular node (AVN)
      1. the ANNULUS FIBROSUS is a region of non-conducting tissue that prevents the excitation spreading from the atria driectly to the venticles
      2. once the AVN is stimulated it produces a slight delay, before it passed the depolarisation into the bundle of His.
        the bundle of His is a conducting tissue found in the septum
        the delay ensures the atria have stopped contracting before the ventricles contract
        the bundle of His splits into two branches and carries the depolarisation into the PURKYNE TISSUE
        the purkyne tissue conists of conducting fibres that penetrate down through the septum and spreads through the ventricles
  2. ELECTROCARDIOGRAM
    1. investigates the rhythms of the heart by producing a record of the electical activity of the heart
    2. depolaristaion causes tiny electrical changes on the skin
    3. tachycardia = fast heart beat
      1. bradycardia = slow heart beat
Atherosclerosis
1. begins with damage to the endothelium lining of an artery
  1. white blood cells and cholestrol rush to the inflammation, hardening and forming a plaque
    1. artery becomes narrower and increasing the pressure within the artery causing more damage and the process repeats
    2. increased chances of a clot
2. risk factors: smoking, high LDL cholestrol diet, lack of exercise
tissue fluid and lymph
1. hydrostatic pressure = the residual pressure from the heartbeat that forces fluid out of the capillary walls
2. tissue fluid is the fluid that leaves the capillary
  1. capillary walls are permeable for all substances except erythrocyte and large plasma proteins
3. oncotic pressure = tendency of water to move into or out of a capillary by osmosis
4. when hydrostatic pressure is greater than the oncotic pressure, fluid leaves the capillary and tissue fluid is formed
5. 90% of tissue fluid is returned to capillaries, 10% is not and it drains into the lymph capillaries and becomes LYMPH
  1. lymph is returned to the blood in the neck
transporting oxygen and carbon dioxide
1. haemoglobin
  1. large globular protein
  2. four peptide chains, each with an iron containing prosthetic group
    1. can carry four molecules of oxygen
2. bohr effect
  1. the change in the oxygen dissociation curve that result as the change of the carbon dioxidde levels

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	Created by Amelie Mercer over 3 years ago