Duodenum

• What is the pH in the duodenum?

  7.0-8.5
• What is the duodenum?

  -first section of small intestine

  -main site of digestion

  -receives secretion from 3 places
• What are the 3 places that the duodenum receives secretion from?

  The liver, pancreas and Brunner's glands
• What does the liver secrete into the duodenum and what is its function?

  -bile salts

  • these emulsify lipids to increase surface area for lipase
  • neutralises stomach acid to provide the optimum pH for digestion and the duodenum
• What does the pancreas secrete into the duodenum?

  Pancreatic juice, this travels down the pancreatic duct into the duodenum
• What are the components of pancreatic juice?

  -pancreatic amylase

  -pancreatic lipase

  -trypsinogen

  -sodium hydrogencarbonate (NaHCO3)
• What is trypsinogen?

  An inactive precursor of tripsin (an endopeptidase) that is found in pancreatic juice
• What is trypsinogen activated by?

  Enterokinase (secreted by the duodenum)
• Where are the Brunner's glands and what do they secrete?

  -found in the sub-mucosa of the duodenum wall

  -secretes intestinal juice (alkaline mucus)
• Describe and explain features that are important in the functioning of villus.?

  -microvilli increases surface area

  -capillaries provide a good blood supply which maintains a concentration gradient

  -lacteal absorbs lipids

  -thin epithelium creates a short diffusion pathway
• What is the role of the smooth muscle layer in the small intestine wall?

  Action of circular and longitudinal muscles forces food along for more efficient digestion and absorption (peristalsis)
• What happens to excess amino acids after they have been absorbed by the villi?

  -some are transported to the liver

  -the rest go through deamination: converted into urea