H2+Digestion

H Further human physiology - H1 Hormonal control - H2 Digestion - H3 Absorption of digested foods - H4 Functions of the liver - H5 The transport system - H6 Gas exchange


 * Assessment statements** (IBO notes added to some point to clearly indicate what needs to be understood and what does not)
 * H.2.1 || State that digestive juices are secreted into the alimentary canal by glands, including salivary glands, gastric glands in the stomach wall, the pancreas and the wall of the small intestine. ||
 * H.2.2 || Explain the structural features of exocrine gland cells. Include the secretory cells grouped into acini and ducts, and the ultrastructure of secretory cells as seen in the electron micrographs. ||
 * H.2.3 || Compare the composition of saliva, gastric juice and pancreatic juice. ||
 * H.2.4 || Outline the control of digestive juice secretion by nerves and hormones, using the example of secretion of gastric juice. Limit this to the initial release of gastric juice under nerve stimulation after sight or smell of food, and sustained release under the influence of gastrin secreted when food is in the stomach. ||
 * H.2.5 || Outline the role of membrane-bound enzymes (e.g. maltase) on the surface of epithelial cells in the small intestine in digestion. ||
 * H.2.6 || Outline the reasons for cellulose not being digested in the alimentary canal. ||
 * H.2.7 || Explain why pepsin and trypsin are initially synthesized as inactive precursors and how they are subsequently activated. ||
 * H.2.8 || Discuss the roles of gastric acid and Helicobacter pylori in the development of stomach ulcers and stomach cancers. ||
 * H.2.9 || Explain the problem of lipid digestion in a hydrophilic medium and the role of bile in overcoming this. ||

An alternative set of notes from [|i-Biology] is available via [|this link].
 * Workbooks and Worksheets **

Good place to start is with an introduction. Develop/Review your overall understanding of digestion before moving on to the specific specified by your assessment statements:
 * Presentations and tutorials **
 * [|Overview of Digestion from Mcgraw and Hill]
 * The [|digestion timeline on WHFoods] and proceeding sections detail the role of the different organs involved in digestion
 * [|Digestion simplified] by Mr T Brown is good simple visual representation of how the digestive system works

Steven Taylor ( [|i-Biology] ) has a great presentation to view and take notes from before starting your notebook media type="custom" key="24444902"

This McGraw and Hill animation contains more detail than needed (for H.2.5), but does give a good account of how gastric juice secretion is controlled media type="custom" key="20497968"

Biology in motion uses a cartoon animation to explain the action of bile in lipid digestion

Understanding the hormonal control of bile is not necessary, but none-the-less this animation and explanation of lipid emulsification is a good starting point: media type="custom" key="20505218"

An alternate Stomach Ulcers, Cancers and Helicobacter pylori: > media type="custom" key="20506240"
 * [|What is an ulcer?] Notes and animations from McGraw and Hill
 * [|What is helicobacter pylori?] from John Hopkins Medicine
 * [|Sumanas Inc] shows how helicobacter pylori can cause ulcers and also talks a little about Marshall and Warren who discovered the link between the two
 * [|Gastric Ulcer] shows real video footage of ulcers using an endoscope
 * Marshall and Warren gained the Nobel Prize for Physiology or Medicine in 2005 for their work on H. pylori. The [|press release] is a good summary and includes a very helpful diagram (see below).
 * The [|Nobel prize website] also contains 'illustrated information', i.e. a presentation which goes into more depth and is very good for developing your notes.

Use [|click4biology] to review and complete your notes

Use the Bioknowledgy notes to develop and reinforce your understanding. media type="custom" key="24445046"
 * Approach**

__Extension: TOK (independent research and discussion)__ H.2.8 is an example of a paradigm shift, where existing ideas about the tolerance of bacteria to stomach acid were incorrect but persisted for a time despite the evidence. Research and take notes on:
 * how Robin Warren and Barry Marshall made the discovery
 * outline their discovery (refer back to the assessment statement)
 * why they struggled to convince the scientific and medical community


 * Useful Links **