2.2 Absorption + Egestion

• Absorption

  • Once polymers have been converted to monomers, they must be absorbed by our body
  • Monomers are absorbed by our

  >stomach

  >Small intestine

  >Large Intestine

  • Monomers are absorbed by both our

  >circulatory system

  >Lymphatic system

  • Monomers are transported via diffusion ( high concentration to low) so no NRG needed
  • Majority of absorption takes place in the small intestine
• Stomach Absorption

  • the stomach absorbs some water and glucose
  • also certain vitamins and alcohol
• Small Intestine Absorption

  • The small intestine absorbs the majority of digested monomers

  >monosacchrides

  >amino acids Are absorbed by capillaries (blood vessels)

  >nucleotides

  >Vitamins and Water

  • glycerol and fatty acids are absorbed by LACTEAL (part of the lymphatic system )
• Villi

  • greatly help the small intestine in absorption
  • The walls of the small intestine are lined with finger-like projections called villi
  • They exponentially increase the surface area of the small intestine
  • The greater the surface area > the more can be absorbed
  • Villi are covered with even more projection called microvilli
• Large Intestine absorption

  • no digestion happens in the large intestine
  • but the large intestine absorbs

  >water

  >MINERALS into the blood

  >VITAMINS

  • Now absorption is DONE
• Large intestine continued

  • Even though it is shorter than the small intestine, it is called LARGE, because it is larger in DIAMETER
  • Material that is not absorbed by the small intestine enters the Large intestine through the ILIOCAECAL sphincter
• Appendix

  • The beginning of the large intestine is called the caecum
  • At the beginning of the large intestine is an organ called the appendix
  • Appendix is an organ that no longer has a function
  • It remained from a time our evolutionary ancestors used to digest cellulose
• Importance of cellulose ( AKA FIBRE )

  • Humans are unable to digest cellulose to acquire energy

  so why is it an important part of our diet ?

  • FIBRE helps draw water back into the large intestine

  > leads to a softer stool

  • our bodies are also adapted to best process when in the presence of fibre
  • Reason why WHOLE WHEAT GRAINS are healthier is cuz they contain fibre
• RECTUM + ANUS

  • at the end of the large intestine, remaining material is stored in the rectum
  • the anus is just a sphincter that opens up allows feces to be released
  • Sometimes the veins at the end of the rectum becomes inflamed > called a haemorrhoid