Digestion

The Stomach and Digestion Site of food storage and protein digestion J-Shape organ that can store up to 1.5 L of food Movement of food in and out of stomach is regulated by sphincters Cardiac sphincter: regulates food from esophagus Pyloric sphincter: regulates food from stomach to small intestine A good way to describe what a sphincter to your students is like a drawstring Grade 11 focuses more on the chemical digestion but you can see in the picture at the bottom 3 layers of smooth muscle running in different directions - Because of this it allows the stomach to churn the food from contractions and relaxations

The Stomach and Digestion cont. There are millions of cells that line the wall of the stomach that secrete many fluids which called collectively called gastric juice Gastric juice : Hydrochloric acid (HCl) mucus, pepsinogens and other materials Pepsinogens: enzymes that when exposed to a low pH such as conditions in the stomach, turns into its active form pepsin which is a enzyme the digests proteins What do we know about HCl? Good way to get your students thinking… HCl, we know is acidic, low pH, could burn through a carpet or even your hand if touched Acidic, low pH (1-3) Kills many harmful substances that are ingested by food Pepsinogens: enzymes that when exposed to a low pH such as conditions in the stomach, turns into its active form pepsin which is a enzyme the digests proteins Both break down food into a thick liquid form called chyme and moved to the intestines

Mucus A protein produced by a layer of epithelial cells that provide a protective coating It is alkaline in nature which is basic and protects lining of the stomach from both acid from HCl and pepsin from breaking down proteins of stomach lining However when mucus is destroyed or not being produced…

Disorder: Stomach Ulcer Ulcer: a lesion along the surface of an organ -when the mucus membrane is destroyed a peptic ulcer can be formed resulting in tissue being burned and an allergic reaction can become stronger resulting in blood vessels breaking down

Heliobacter pylori - Useful tool to students would be showing them a picture of this bacteria Heliobacter pylori - introduce that along with stress, diet and other factors this bacteria is thought to be the main cause of peptic ulcers

Stomach Disorders: Ulcers cont. Case Study Have students in pairs or small groups uncover this bacteria Heliobacter pylori and other information about ulcers Prevalence, demographics, how to detect this bacteria, bacterial weight/amount, effects on every day living/side effects, treatment etc. are all topics the students could discover Could be in the form of a report, or a presentation, or even a jigsaw activity Will post on website

Small Intestine Introduction Activities http://www.youtube.com/watch?v=4waSJqOEJts Easy way to get the students thinking about the small intestine is having 7m of yard, tubing etc. and having it passed around the classroom After this have them put it in a small box Small intestine is not named small because of its length rather its diameter!

Small Intestine Cont. 3 parts of the small intestine are the: Duodenum: - most digestion occurs here Jejnum: has many folds that continue breakdown and absorption of remaining proteins and carbohydrates Ileum: less absorption occurs here, unabsorbed particles are pushed through and continued

Digestion in the Small Intestine How is the small intestine protected if HCl and pepsin- soaked food is sent to it from the stomach?

Small Intestine and Pancreas Interaction Process: HCl enters the duodenum from the stomach - HCl stimulates the coversion of prosecretin into secretin When acids enter the small intestine an inactive chemical called prosecretin is converted to secretin - it is then absorbed into the bloodstream and carried to the pancreas, which released biocarbonate ions Discussion What do we know about bicarbonate ions?– basic, they can neutralize acids -so basic that it raises the pH from about 2.5 to 9 which alternatively inactivates PEPSIN = therefore no digestion of proteins of the small intestine lining

Small Intestine and Pancreas Interaction Bicarbonate ions are not the only molecules secreted by the pancreas The pancreas continues to secrete several enzymes to aid in digestion within the small intestine First is trypsinogen which is inactive until it is converted from enterokinase (an enzyme within the small intestine) which activates it to trypsin which acts on partially digested proteins. - breaks these long chain polypeptides into shorter chains in which EREPSIN another enzyme foundin both pancreas and small intestine complete breaking down these polypeptides into amino acids Also above is a chart of other various enzymes secreted by the pancreas and small intestine which aid in digestion

Liver and Gall Bladder: Role in Digestion COAL- UH -SIS –TO- KINE- IN CEAR ROSES Produces a fluid called bile which contains bile salts They speed up fat digestion; which stomach is empty it is stored and concentrated in the gall bladder Cholecystokinin (CCK) is released when fat is in the small intestine CCK is carried to the gall bladder and it triggers the release of bile salts which break down fat into droplets Gall-stones, jaundice and cirrhosis are a few disorders associated with these organs This breakdown into droplets is physical digestion. It aids in chemical digestion as the breakdown of lipids into fat droplets results in an increase of surface area = increase of digestion from lipases - STUDENTS CAN DO CASE STUDIES ON THOSE DISORDERS AND WHY IT MAY AFFECT DIGESTION