Digestive system

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  • Digestive system
    • Alimentary canal
      • Oesophagus
        • Tube through thorax, no digestion, glands secreet mucus
        • Wave of circular muscle contractions open and close the tube and push food through
      • Stomach
        • Food is stored and churned by muscle into a liquid - chrome and slowly release into S.I.
        • Gastric pits lead to gastric glands which secreete gastric juiceto kill bacteria and mucus to lubricate food and protect lining of the stomach
      • Small intestine
        • First 30cm - duodenum. Most digestion due to Pancriatic juice (amalyse, protiase & lipase) and bile secreeted by liver, stored in gall bladder, aids lipid digestion and nutrialises acid and sodium hydrogen carbonate
        • Ileum - final digestion and absorption. Glands produce enzymes, mucus and Sodium hydrogen carbonate
          • Large SA - folds, villi and microvilli
          • Short distance -one layer of endothelium, and capillary
          • High concentration difference - movement of fluids on both sides.
      • Large intestine
        • Contains vili and mucus glands
    • Carbohydrates
      • Starch + amalayse = maltose + maltase = glucose
      • Salivary amalasye
        • digestion of starch - mouth, denatures in stomach but kills bacteria
      • Pancreatic amalayse
        • Digests remaining starch - duodenum. Forms disaccharide maltose. Also digests glycogen
      • Disaccharide
        • Borken down into monosaccharides by epithelial cells in ileum
        • Maltose + maltase = glucose
        • Lactose + lactase = glucose + galactose
        • Sucrose + sucrase = glucose + fructose
    • Glucose
      • Absorbed by co-transport. Sodium-potasium ATPase
      • Sodium & potassium ions are pumped back out to maintain gradient
      • Sodium is the facilitated diffusion protein, glucose is the co-transporter protein
      • High concentration of glucose in epithelials, blood diffuses into blood through tissue fluid through a carrier protein and into the blood for use


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