Digestion

• Four basic processes of the digestive system

  • Digestion
  • Absorption
  • Motility
  • Secretion
• Describe Digestion

  Physical and chemical breakdown of food
• Describe Absorption

  Transport of digestive end-products into bloodstream
• Describe Motility

  Peristaltic activity of muscle, propelling food along GI tract
• Describe Secretion

  Transport of digestive fluids into the GI tract
• What is the Nerve plexus

  Enteric nervous system
• What is Exocrine secretion

  Secretion of enzymes into a duct directed at target
• What is Endocrine secretion

  Secretion of hormones into the bloodstream
• Describe Saliva secretion

  • Controlled by the Autonomic nervous system
  • Secreted by salivary glands
• Two main Pancreatic cells

  
  

  • Acinar cells use exocrine secrete digestive enzymes and bicarbonate
  • Islets of Langerhans use endocrine secretion for hormones
• What are the types Islets of Langerhansand their functions.

  
  

  • Beta-cells make insulin
  • Alpha-cells make glucagon
  • Delta-cells make somatostatin for digestion and hormone regulation
• Describe Type 1 diabetes

  • Early-onset
  • Insulin dependant autoimmune disease
• Describe Type 2 diabetes

  Late-onset and non-insulin dependant disease.
• Define what is meant by microbiota

  Ecological communities of symbiotic and pathogenic microorganisms are found majority within the colon.
• Describe the role of Microbiota

  • Enhances digestion, absorption and production of nutrients
• What is the role of the crypts of Lieberkuhn

  Secrete copious amounts of bicarbonate-rich fluid to neutralise chyme from the stomach
• Describe the structure of the Colon

  • Appendix
  • Cecum
  • Ascending
  • Transverse
  • Descending
  • Sigmoid
• What enzymes are found within saliva

  • Alpha-amylase
  • Lingual lipase
• What are the role of oesophagal sphincters

  To prevent backflow, which can result in heartburn.
• What type of muscle is the upper oesophagus made of

  Skeletal
• What type of muscle is the lower oesophagus made of

  Smooth
• What are zymogens

  Inactive forms of enzymes.
• What is the zymogen for pepsin

  Pepsinogen
• What is the zymogen for chymotrypsin

  Chymotrypsinogen
• Where is chymotrypsinogen made

  Pancreas
• What is required to activate pepsinogen

  A low pH.
• Describe the activation of pepsinogen

  1. HCl in the stomach
  2. Cleavge of first 44 AA
• What is the pH range for activation of pepsinogen

  <5
• What type of peptidase is pepsin

  Endopeptidase
• What is an endopeptidase

  They break the internal peptide bonds.
• What is an exopeptidase

  They remove one Amino Acid at a time.
• How is chymotrypsinogen activated

  1. Proteolytic cleavage by Trypsin
  2. Loss of 2 dipeptides
• Describe the structure of chymotrypsin

  3 peptide chains held together by interchain disulphide bonds.
• Describe the pathology of Type 1 diabetes

  Loss of insulin secretion due to autoantibodies against the Beta-cells.
• Describe the pathology of Type 2 diabetes

  Development of insulin resistance due to lifestyle and eventually a reduction in insulin secretion.
• What is the effect of insulin secretion

  Decreased blood glucose.
• How do you treat type 1 diabetes

  Insulin
• Where is bile produced

  liver
• Where is bile stored

  gallbladder
• Where do the pancreas and gallbladder secrete into

  Duodenum