Human Bio

• Functions of the Digestive System

  • Ingestion
  • Mastication
  • Propulsion
  • Mixing
  • Secretion
  • Digestion
  • Absorption
  • Elimination

  
• Mesentery

  Connective tissues that hold small intestine in place and support the blood vessels and nerves supplying these organs

  
• Oral Cavity

  • Tongue
  • Hard palate
  • Soft palate
  • Epiglottis
  • Uvula
  • Tonsils
• Teeth

  • Adults normally have 32 teeth
• Salivary glands

  Many (3 major pairs), secrete salivary amylase
• Swallowing

  Voluntary and involuntary phases
• The Stomach

  • Oesophageal sphincter
  • Rugae
  • Pyloric sphincter
  • Oesophagus
  • Duodenum
• Purpose of the rugae

  Mixes the food with stomach secretions to form chyme
• Histology of the Stomach

  • Gastric pit
  • Gastric gland: Mucous cells (mucus), Parietal cells (HCl), Chief cells (pepsinogen)
• Secretions of the stomach

  • Pepsinogen (to breakdown proteins)
  • Hydrochloric Acid (HCl) (to kill pathogens and activate pepsinogen)
  • Mucus (to lubricate and protect epithelial lining)

  
• Small Intestine

  • Duodenum (25cm)
  • Jejunum (2.5m)
  • Ileum (3.5m)

  
• Purpose of the circular folds and villi

  Absorption of nutrients in small intestine

  
• Large Intestine

  • 1.5-2m long
  • 18-24h for material to pass through
  • Bacteria produce vitamin K and B-complex vitamins which is absorbed
  • Main site for water absorption

  
• Peritoneum and Mesenteries

  • Peritoneum are the serous membranes that line abdominal cavity
  • Mesenteries are connective tissues that hold small intestine in place and support the blood vessels and nerves supplying these organs

  
• Digestive Enzymes and Secretions

  • Salivary amylase (produced by salivary glands, function: breakdown carbohydrates)
  • Pepsinogen (produced by stomach, function: breakdown proteins)
  • HCl (produced by stomach, function: kill pathogens)
  • Bile (produced by liver, function: neutralise pH, emulsify lipids)
  • Pancreatic Amylase (produced by pancreas, function: breakdown carbohydrates)
  • Pancreatic Lipase (produced by pancreas, function: breakdown lipids)
  • Pancreatic Nuclease (produced by pancreas, function: breakdown nucleic acids)
  • Trypsin (Pancreatic protease) (produced by pancreas, function: breakdown proteins)

  
• Pepsinogen


  An inactive form of the enzyme pepsin, responsible for breaking down proteins into smaller peptides during digestion. Converted to its active form, pepsin, in the presence of hydrochloric acid in the stomach.
• Hydrochloric Acid (HCl)


  Creates a low pH environment in the stomach, necessary for the activation of pepsinogen and the digestion of proteins. Also helps to kill any pathogens that may have been ingested with food, providing an important defense mechanism for the body.
• Mucus


  Coats the lining of the stomach and protects it from the harsh, acidic environment created by HCl. Helps to lubricate the food as it passes through the stomach, making it easier to move through the digestive tract.
• Function of Pepsinogen


  Responsible for breaking down proteins into smaller peptides during digestion. Lipases are the enzymes responsible for breaking down fats into smaller fatty acids and glycerol.