GI tract
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What are the organs that makeup the GI tract ?
• mouth • pharynx • salivary glands • oesophagus • stomach • pancreas • liver • gallbladder • small intestine • large intestine
What is meant by exocrine secretions ?
secretions out of the body
What is the exocrine secretions and functions of the mouth, pharynx and salivary glands ?
• salt and water • mucus • amylase • chewing • swallowing reflex • moistens, lubricates and digests polysaccharides
What is the exocrine secretions and functions of the oesophagus ?
• mucus • lubricates contents • peristaltic waves
What is the exocrine secretions and functions of the stomach ?
• HCl • pepsin • mucus • food solubilisation • kills microbes • digests proteins • lubrication
What is the exocrine secretions and functions of the pancreas ?
• enzymes • bicarbonate • digests carbohydrates, fats and proteins • neutralises HCl
What is the exocrine secretions and functions of the liver ?
• bile salts • bicarbonate • organic waste products • solubilises water insoluble fats • neutralises HCl • elimination of waste
What is the exocrine secretions and functions of the gallbladder ?
• no exocrine secretions • storage and concentration of bile
What is the exocrine secretions and functions of the small intestine ?
• enzymes • salt and water • mucus • food digestion • maintain fluidity • lubrication
What is the exocrine secretions and functions of the large intestine ?
• mucus • lubrication
How much water is ingested and lost overall per day from the body ?
ingested = 2 litres per day lost = 100 ml per day lost in faeces
How much water is secreted through saliva and what is the pH ?
• 1.5 litres per day • pH 6.8 - 7
How much water is secreted through gastric secretions and what is the pH ?
• 2.3 litres per day • pH 1.5 - 3
How much water is secreted through bile and what is the pH ?
• 500 ml per day • pH 7.8 - 8
How much water is secreted through pancreatic juices and what is the pH ?
• 1 litre per day • pH 8 - 8.4
How much water is secreted through intestinal secretions and what is the pH ?
• 1.5 litres per day • pH 7 - 7.4
How much water is reabsorbed into the body and where does this take place ?
small intestine = 8 - 8.5 litres per day colon = 0.4 - 1 litre per day
How long does the food remain in the mouth ?
30 seconds - 1 minute
How long does the food remain in the oesophagus ?
8 - 12 seconds
How long does the food remain in the stomach ?
1 - 3 hours
How long does the food remain in the small intestine ?
4 - 6 hours
How long does the food remain in the colon ?
10 - 20 hours
How long does the food remain in the rectum ?
20 - 100 hours
Describe the nervous system in relation to the gut
• the gut has its own nervous system known as the enteric nervous system • the Myenteric plexus or Auerbach’s plexus is located in the muscularis externa and it is largely motor in function • the submucosal plexus or Meissner’s plexus is located in the submucosa and is mainly sensory in function • parasympathetic innervation to the gut increases motility • sympathetic innervation to the gut decreases motility