Digestive system

• how long is the GI tract?

  4.5 m (living), 9m (autopsy)
• what is digestion?


  physical and chemical breakdown of food
• what is absorption?


  transport of digestive end-products in to bloodstream
• what it is motility?


  Peristaltic activity of muscle, propelling food along GI tract
• what is secretion?


  transport of digestive fluids into the GI tract
• why is GI tract longer after death?

  as very muscular organ so relaxes at death
• what are some accessory glands?

  salivary glands, pancreas, liver gall bladder
• what does the liver do?

  all absorbed nutrient passes into liver for further digestion
• what does secretion?


  accessory glands
• how many sphincter are there?

  5
• what does a sphincter do?

  controls rate of flow through GI tract
• what is a ileocecal sphincter known as?

  apendix
• what makes up the mucosa layer?


  epithelium, lamina propria and muscular mucosa
• what makes up the submucosa?

  connective tissue, blood and lympathic vessels
• what makes up muscularis?


  circular layer, longitudinal layer
• what does the serosa do?

  contains intentestine from surronding made up of connective tissue
• what nerve plexus do?

  enteric nervous system
• what are the types of epithelial cells of mucosa?

  absorptive cells, exocrine cell, goblet and endocrine cell
• what does a exocrine cell do?


  secretion of enzymes into a duct directed at target
• how quickly is mucus membrane replaced?


  every 5 days
• how much saliva is secreted per day?

  0.75-1.5 litres (near 0 at night)
• which nervous system stimulates saliva?

  autonomic
• what does salivary alpha-amylase do?

  digests glycogen and starch
• what enzymes are inside saliva?


  salivary alpha-amylase and lingual lipase
• what are the saliva glands?

  parotid glands, sublingual gland, submandibular gland
• how long is oesophagus?

  25cm long
• what does oesophagus connect?

  pharynx to stomach
• what does upper and lower esophageal sphincter do?

  prevent backflow, if not controlled can lead to heartburn
• which section of the oesophagus contains skeletal muscle?

  upper
• what size can the stomach grow to?

  50ml to 1-2 l
• what does the gastric gland (mucosa) contain?

  parietal cells and chief cells
• what does a parietal cell secrete?

  HCl
• what does chief cells secrete?

  pepsinogen
• what triggers the release of pepsinogen and HCl?

  hormone gastrin and vagus nerve
• what nervous system does the vagus nerve belong to?

  parasympathetic
• how is H+ made for HCL?

  H+ ion, made from Co2 and water by carbonic anhydrase
• where are h+ transported into?

  actively transported into the lumen in exchange for K+
• what activates pesinogen?


  HCl
• how is pepsin generated?

  first 44 amino acids are removed from pepsinogen
• what is maximal activity of pepsin?


  pH 2 and inactive at pH greater than 6.5