2.7 absorption of materials

• oxygen and nutrients from food must be


  absorbed into bloodstream to be delivered to cells for respiration
• capillary networks


  allows exchange of materials at a cellular level in tissues
• efficient features, surfaces in the body have, if involved with lots of exchange


  good blood supply to maintain a steep diffusion gradient, large surface areas to maximise rate of diffusion, thin walls to minimise diffusion distance
• gas exchange occurs in


  alveoli in lungs
• gases are exchanged from


  blood capillaries surrounding alveoli
• lungs


  exchange organs (O2 + CO2 are exchanged here)
• alveoli


  tiny air sacs which provide large surface area
• small intestine


  location of absorption of nutrients
• villi


  millions of thin walled, large surface area, good blood supply, finger-like projections in the inner walls of small intestine that absorb nutrients from food
• water soluble food products

  glucose + amino acids
• water soluble food products absorbed into


  blood capillary
• fat soluble food products

  fatty acids + glycerol
• fat soluble food products absorbed into


  central lacteal
• digestion


  breakdown of large food molecules to small soluble molecules with enzymes, absorbed across lining of small intestine into blood
• starch ->


  maltose
• protein ->


  amino acids
• fat ->


  fatty acids + glycerol