Nutrition

• Emulsification


  Large fat droplets are broken into smaller droplets which increases the surface area for lipase action
• Co-transport


  Transporting two different molecules together, e.g. glucose and sodium ions, and is the mechanism by which glucose is absorbed in the small intestine of mammals
• Regional specialisation of the mammalian gut

  1. Mouth (buccal cavity): Digestion begins, teeth mechanically digest food, tongue contains amylase and mucus

  2. Oesophagus: Muscles contract to move food towards stomach via peristalsis

  3. Stomach: Food digested for 4 hours by muscular action and gastric juice (hydrochloric acid and pepsin), mucus produced

  4. Duodenum: Receives secretions from liver and pancreas, bile neutralises acidic food and emulsifies fats, pancreatic juice contains enzymes, Brunner's glands produce alkaline secretions, villi with enzymes complete digestion
• Pepsin is an endopeptidase that is secreted in an inactive form pepsinogen, and activated by H+ ions
• The acidic pH of around 2 in the stomach also kills bacteria
• Trypsinogen is inactive, and converted to the active form trypsin by enterokinase
• Maltase, lactase and sucrase enzymes are bound to the epithelial cells and complete the digestion of carbohydrates
• The mucosa of the small intestine is heavily folded to form villi
• Endocrine glands include the pituitary gland, thyroid gland, parathyroid glands, adrenal glands (including cortex and medulla), pancreas, ovaries/testes, and pineal gland.