chapt 5.1 nutrition

• The mouth is the first part of the digestive system
• the mouth and buccal cavity

  • Food enters from the mouth
  • Teeth break down large pieces of food into smaller pieces
  • Increases the surface area to volume ratio so enzymes can act on it more efficiently
  • Salivary glands secrete saliva containing salivary amylase
  • Tongue mixes food with saliva and moves food to the back of the mouth during swallowing
• Pharynx


  Connects the buccal cavity to the oesophagus and larynx, also leads to the windpipe
• The pharynx is the second part of the digestive system
• Oesophagus

  • Narrow muscular tube passing through the thorax, joining the mouth and stomach
  • Contains 2 layers of muscles: longitudinal and circular
  • Outer layer is longitudinal, inner layer is circular
  • Circular muscles contract to constrict the lumen
  • Longitudinal muscles contract to shorten and widen the lumen
  • Circular and longitudinal muscles are antagonistic
• The oesophagus connects the mouth and stomach
• The oesophagus contains two layers of muscles: longitudinal and circular
• The outer layer of the oesophagus is longitudinal, the inner layer is circular
• The circular muscles contract to constrict the lumen of the oesophagus
• The longitudinal muscles contract to shorten and widen the lumen of the oesophagus
• The circular and longitudinal muscles of the oesophagus are antagonistic
• When one set of muscles in the oesophagus contracts, the other set relaxes
• The oesophagus is a muscular tube
• The oesophagus passes through the thorax
• peristalsis

  1. rhythmic wave like contractions of the wall of the alimentary canal
  2. enables food to mix with digestive juices
  3. pushes food along the gut
• circular muscles contract,

  1. longitudinal muscles relax
  2. wall of gut contracts and becomes long and narrow
  3. food pushed forward
• longitudinal muscles contract,

  1. circulat muscles relax
  2. gut becomes wider and shorter
  3. food enters
• stomach

  inner surface lined with gastric glands secreting gastric juice
• stomach

  thick and developed walls
• small int

  consists of u-shaped duodenem and much coiled ileum. 1. most of digestion happens here. 2. lining of walls contain glands that secrete digestive enzymes
• large int

  1. consists of colon, rectum, anus
• large int

  colon : absorbs 90% or remaining water and mineral salts from undigested food.
• large int

  faeces temporarily stored in the rectum before it contracts, expelling it through the anus