Digestion

• 1. Digestion occurs in the alimentary canal, which is a tube of muscular walls running from the mouth to the anus
• The alimentary canal consists of 5 parts, which are:

  1. mouth
  2. oesophagus
  3. stomach
  4. small intestines [deuodenum, jejenum, ileum]
  5. large intestines [appendic, caecum, colon, rectum, anus]
• Other parts of the digestive system which are NOT in the alimentary canal are the liver, gallbladder and pancreas
• The Mouth is the site of ingestion and mechanical digestion by teeth, it is also the site of starch digestion by the enzyme salivary amylase [converts starch to maltose]
• Gullet/Oesophagus - where peristalsis motion occurs to move food to the stomach
• The Stomach is where protein digestion takes place by enzymes pepsin and renin [only in small children]. The Hydrochloric acid present kills microrganisms and provides acidic PH for enzymes . Mechanical digestion also occurs by churning, this creates chyme.
• The Small Intestine - Duodenun, Jejenum, Ileum. This is where digestion and food absorption in the ileum occurs.

  Duodenum - Digestion continues

  Jejenum - Digestion continues

  Ileum - last site of digestion, site of food absorption [via villi]
• Large Intestine - Appendix, Caecum, Colon, Rectum, Anus.

  Appendix - no function in man but can rupture and kill you. Often removed when infected

  Caecum - no function in man

  Colon - water absorption

  Rectum - faeces stored

  Anus - site of egestion, removal of faeces
• Liver - largest organ in the body, produces bile and bile salts, aids in mechanical fat digestion, breaks up fat into small droplets
• Gall Bladder - Stores bile, releases bile when food empties into duodenum, also releases food into duodenum
• Pancreas - produces a wide range of enzymes, releases enzymes via a duct into the duodenum
• Saliva - not an enzyme, moistens food and contains and has a PH of 7.2 [sligtly alkaline] for salivary amylase to work.
• Pepsin - meat + legume digestion

  Renin - milk digestion
• Bile Salts - break down fat into fat droplets
• If lacking water in diet - constipation/hard stool

  If enough water in diet - stool is soft
• When little/no water is absorbed by the colon, diarrhea is caused and watery stool is released often
• Pancreas - produces enzymes to break down all types of food

  Carbohydrase - to break down carbs into glucose [a monosaccharide]

  Lipase - to break down fats/liquids into fatty acid + glycerol

  Protease - to break down protein into amino acids