organising animals and plants B4

the blood
1. blood is a tissue
  1. the plasma contains: red blood cells, white blood cells and platelets
    1. red blood cells: biconcave discs, contain haemoglobin, carry oxygen to organs
    2. white blood cells: have a nuclear, defend the body against pathogens, some produce antibodies
    3. platelets: are fragments of cells, no nucleus, help blood clot
      1. blood clotting
        fibrinogen changes to fibrin
        forms a network of fibres that trap blood cells
        form a scab
the blood vessels
1. blood vessels: arteries, veins and capillaries
  1. arteries: carry blood away from the heart, have thick walls and small lumen
  2. veins: carry blood towards the heart, have thinner walls and bigger lumen, have valves to prevent blackflow
    1. capillaries: are narrow thin walled vessels, carry blood through organs, allow exchange of substances
the heart
1. the right pump forces deoxygenated blood to the lungs
  1. after returning to the heart the right pump forces it round the body
    1. the right atrium receives blood through the vena cava
      1. the left atrium receives blood through the pulmonary vein
2. coronary heart disease
  1. arteries become blocked with fatty material
  2. stents open up the arteries
  3. bypass surgery can also replace coronary arterys
    1. statins lower cholesterol to reduce fatty material
helping the heart
1. leaky valves cause blood to flow in the wrong direction
  1. artificial or animal valves can reverse damaged valves
    1. if someones heart is faulty or damaged they may require a transplant. donor hearts are not always available so artificial one are being developed
2. irregular heart beat
  1. artificial pacemaker is electric and can be fitted in the chest
breathing and gas exchange
1. when you breathe in
  1. muscles contract moving the ribcage up and out
    1. diaphragm contracts and flattens
      1. volume of lungs increase
      2. pressure in lungs decrease and airs draw in
2. when you breathe out
  1. muscles and diaphragm relax
    1. ribcage moves down and the diaphragm domes
      1. volume of lungs decrease
        pressure increases and air is forced out
3. adaptations of the alveoli
  1. large surface area to absorbs lots of oxygen
    1. lungs are ventilated to maintain a steep concentration gradient
      1. oxygen diffuses into the capillaries and co2 diffuses out
tissues and organs in plants
1. plant tissues
  1. epidermal: covers the plant
    1. palisade mesophyll: many chloroplasts
      1. spongy mesophyll: large surface area for diffusions of gases
        xylem: transports water and dissolved minerals
        phloem: transports dissolved food from leaves to the rest of the plant
  2. organs
    1. tissues are arranged to form organs
      1. stems, roots and leaves are plant organs
        they form organ systems to transport materials
transport systems in plants
1. phloem and xylem
2. all the cells need sugar for respiration
  1. sugar and mineral are needed for growth
    1. water is needed for photosynthesis
      1. water is needed to support the cells
factors effecting transpiration
1. temperature: as it increases molecules move faster so more water evaporates
  1. humidity: faster in dry air than humid air
    1. air flow: windy conditions increase the rate of evaporation.
      1. light intensity: more light means increases photosynthesis
evaporation and transpiration
1. water loss from the leaves
  1. gas diffuses in and out through stomata
    1. the size of stomata is controlled by guard cells
      1. water vapour diffuses out of the stomata, this is transpiration
        guard cells can close stomata to reduce water loss

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organising animals and plants B4

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