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Biology 12 Human Biology – The Digestive System Chapter 21 Vocabulary absorption, anaerobic bacteria, anus, appendix, bile, capillary, cardiac sphincter, chemical digestion, digestive enzyme, digestive tract, duodenum, emulsification, epiglottis, esophagus, gall bladder, gastric juice, hydrochloric acid (HCl), insulin, intestinal juice, lacteals, large intestine (colon), lipase, liver, maltase, microvillus, nuclease, pancreas, pancreatic amylase, pancreatic juice, pepsin, pepsinogen, peptidase, peristalsis, pH, pharynx, physical digestion, protease, pyloric sphincter, rectum, salivary amylase, salivary gland, salivary juice/saliva, small intestine, sodium bicarbonate, stomach, swallowing, trypsin, villus It is expected that students will: C1 Analyse the functional inter-relationships of the structures of the digestive system C1.1 C1.2 C1.3 C1.4 C1.5 C1.6 identify and give a function for each of the following: – mouth – tongue – teeth – salivary glands – pharynx – epiglottis – esophagus – cardiac sphincter – stomach – pyloric sphincter – duodenum – liver – gall bladder – pancreas – small intestine – appendix – large intestine (colon) – rectum – anus describe swallowing and peristalsis identify the pancreas as the source gland for insulin, and describe the function of insulin in maintaining blood sugar levels list at least six major functions of the liver explain the role of bile in the emulsification of fats describe how the small intestine is specialized for chemical and physical digestion and absorption Biology 12: Digestive system Page 1 C1.7 C1.8 C1.9 C2 describe the structure of the villus, including microvilli, and explain the functions of the capillaries and lacteals within it describe the functions of anaerobic bacteria in the colon demonstrate the correct use of the dissection microscope to examine the various structures of the digestive system Describe the components, pH, and digestive actions of salivary, gastric, pancreatic, and intestinal juices C2.1 C2.2 C2.3 C2.4 C2.5 C2.6 relate the following digestive enzymes to their glandular sources and describe the digestive reactions they promote: – salivary amylase – pancreatic amylase – proteases (pepsinogen, pepsin, trypsin) – lipase – peptidase – maltase – nuclease describe the role of water as a component of digestive juices describe the role of sodium bicarbonate in pancreatic juice describe the role of hydrochloric acid (HCl) in gastric juice describe the role of mucus in gastric juice describe the importance of the pH level in various regions of the digestive tract Biology 12: Digestive system Page 2 This diagram illustrates the main stages of digestion: What is the difference between physical and chemical digestion? _________________________ ______________________________________________________________________________ ______________________________________________________________________________ What are the main sites of physical digestion in your body? Mouth is the first with teeth breaking food into small pieces. Stomach breaks lumps of food by the muscle contraction in three different directions _Bile separates fat particles from each other – called emulsification. What is the main site of chemical digestion in your body? First section of small intestine called duodenum. Where does most absorption occur? Last section of small intestine absorbs nutrients and the large intestine absorbs water and vitamins. Biology 12: Digestive system Page 3 During chemical digestion, polymers are hydrolyzed to monomers before they can be absorbed into the blood. Label the following diagram to show the hydrolysis of the four main groups of organic polymers: Biology 12: Digestive system Page 4 Label the parts of the human digestive system on the following diagram: mouth, salivary glands, pharynx, epiglottis, esophagus, cardiac sphincter, stomach, pyloric sphincter, duodenum, liver, gall bladder, pancreas, small intestine, appendix, large intestine (colon), rectum, anus. Biology 12: Digestive system Page 5 Here is a diagrammatic layout of the digestive system. Label the various parts. mouth, salivary glands, esophagus, cardiac sphincter, stomach, pyloric sphincter, duodenum, liver, gall bladder, pancreas, small intestine, appendix, large intestine (colon), rectum, anus. Biology 12: Digestive system Page 6 https://www.youtube.com/watch?v=b20VRR9C37Q overview of digestion Digestion in the mouth Mechanical digestion involves ______________________________________________________________________________ _____________________________________________________________________________ Chemical digestion in the mouth involves ___________________________ ________________. Saliva contains water together with two other important substances. What are they? __________________________________________________________________ What are the main functions of saliva? (3) __________________________________________________________________ __________________________________________________________________ http://www.factmonster.com/dk/encyclopedia/mouth Biology 12: Digestive system Page 7 The following diagram illustrates the stages in the swallowing reflex. Label the following structures: tongue, nasal cavity, pharynx, glottis, epiglottis, trachea, esophagus, esophageal sphincter, bolus of food Indicate where on the diagram peristalsis is taking place. http://www.d.umn.edu/~mmizuko/video/whole.mov What normally keeps the esophagus closed when you are not swallowing? ______________________________________________________________________________ What prevents food from entering the trachea when you swallow? ______________________________________________________________________________ Biology 12: Digestive system Page 8 This diagram illustrates the passage of food from your throat to your stomach and through the intestines. Describe this process: ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ Label the diagram: Biology 12: Digestive system Page 9 What do we call the lump of food that travels down the oesophagus and enters the stomach? ______________________________________________________ What is the function of the cardiac sphincter? __________________________________ _______________________________________________________________________ What is the function of the pyloric sphincter? __________________________________ _______________________________________________________________________ Approximately how long does food stay in the stomach? _____________ hours Name one digestive enzyme produced by the stomach wall, and the type of food substance it helps to break up? __________________________________________________________________ The stomach also produces acid. What is this acid for? __________________________________________________________________ __________________________________________________________________ How is the stomach wall protected from the acid? __________________________________________________________________ How does the muscle in the wall of the stomach help digestion? __________________________________________________________________ __________________________________________________________________ What do we call the material that leaves the stomach and enters the duodenum? ___________________________________ Biology 12: Digestive system Page 10 Biology 12: Digestive system Page 11 Label this diagram showing the organs associated with the first part of the small intestine: The digestive enzymes of the small intestine work best in alkaline conditions; how, therefore, is the acid from the stomach neutralised when it enters the duodenum? The pancreas secretes bicarbonate which neutralises the acidic gastric juices. Where is bile i) made? _____Liver_______ ii) stored? Gall bladder iii) mixed with food? _____duodenum _____ What does bile do? Breaks chunks of fat and oil into smaller droplets. Biology 12: Digestive system Page 12 The pancreas produces a juice pancreatic juice, which contains four important enzymes; name the enzyme which hydrolyzes: i) starch ____pancreatic amylase___to produce more disaccharides. _______ ii) protein ___trypsinogen is activated to form _trypsin __to produce dipeptides or short polypeptides ______ iii) fat (lipids) ______lipase__to produce fatty acids and glycerol__ iv) nucleic acids ________nuclease___to produce nucleotides______ This table summarizes the enzymes that hydrolyze polymers in the small intestine: Give two ways that the small intestine is adapted for digestion? 1. Large surface area from which enzymes are secreted. ________ 2. Smooth muscle layers contract to facilitate peristalsis to force food through the small intestine. As a result of digestion (hydrolysis) what are the following foods finally broken down into? i) starch __monosaccharides - glucose_, fructose and galactose________ ii) protein ___________amino acids iii) fat __________fatty acids and glycerol iv) nucleic acids _______nucleotides_and finally nitrogenous bases, pentose sugars and phosphates. Biology 12: Digestive system Page 13 Digestion in the small intestine takes place in the first section called the duodenum. Absorption of nutrients takes place in the rest of the small intestine: Why must food be digested before it can be absorbed? __________The food molecules must be small enough to move through the epithelial lining of the small intestine and into the bloodstream and then into the tissues of the body. Give six ways in which the wall of the small intestine is adapted to absorb digested food. 1. Villi and 2. micro villi increase surface area for absorption 3. 4. 5. 6. 7. The fold in the wall of small intestine increase the surface area The small intestine is very long. Well supplied by blood capillaries to collect the nutrient molecules. Lined with mucous to protect the epithelium from chemicals Smooth muscle facilitates peristalsis. Biology 12: Digestive system Page 14 8. What is the main function of the colon? Large Intestine 1. Absorption of water. 2. Absorption of vitamins and minerals (potassium, iron, magnesium, manganese, calcium, iodine, sodium, zinc) 3. Production of vitamins. For example vitamin K. _____________________________________ Why is roughage (or dietary fibre - cellulose) important in the human diet? 1. Provides bulk for elimination of digestive waste 2. Provides nutrient for vitamin producing bacteria. The large intestine (colon) contains a very large population of anaerobic bacteria. In fact 1/3 of your feces is bacteria. E. coli is a common bacterium in your colon. Your body actually has more bacterial cells in and on it than it has human cells! What are some benefits of these bacteria to your body? _________Produce vitamin K necessary for blood clotting. _______ _produce folic acid - necessary for a healthy nervous system Produce B vitamins Annotate this diagram: Biology 12: Digestive system Page 15 How does the liver act as the ‘gatekeeper of the blood’ with respect to: a) toxins such as alcohol picked up from the intestine? ___The liver filters the blood and detoxifies alcohols, drugs such as painkillers, amphetamines, chemicals such as preservatives, colorants. _Smooth Endoplasmic reticulum detoxifies the blood. ___ b) nutrients such as amino acids and glucose picked up from the intestine? __Excess Glucose is converted to glycogen by insulin and stored in liver or goes on to muscles via blood stream. Amino acids may be processed in the liver or continue in the blood stream. The hepatic portal vein carries blood from the small intestine to the liver. __ c) iron and fat-soluble vitamins (A, D, E, K, and B12)? ____The liver stores these. d) plasma proteins? _The liver produces plasma proteins, blood proteins, eg. Fibrinogen, globulins and albumins. Fibrinogen for blood clotting. Globulins for immunity and albumin to maintain osmotic pressure in the blood. Also called serum proteins. Biology 12: Digestive system Page 16 Why is this system called ‘hepatic portal’ and what is its value to the successful functioning of the organism? Biology 12: Digestive system Page 17 Annotate this diagram that shows the relationship between the liver and the small/large intestines with the associated blood vessels: Biology 12: Digestive system Page 18 The liver can convert amino acids into glucose if glucose levels are low. What toxic nitrogenous waste molecule is produced from the deamination of the amino acids? __Ammonia_ The liver then converts the ammonia into another nitrogenous waste called urea. Which is more toxic, ammonia or urea? __________________________ by how much? _________________ How does the body rid itself of the urea produced by the liver and other body cells? _Blood carries the urea to the kidneys where it is excreted as part of the urine. ______________________________________________________________________________ _________________________________________________________________________ The liver also produces bile, which it sends to the gall bladder for storage prior to secreting it into the duodenum. What are the two major components of the bile, and what is the main function of each? 1. Bile salts are produced from cholesterol and they emulsify fats into smaller droplets to increase surface area for enzyme breakdown 2. Bile pigments are produced from the haemoglobin of old red blood cells. (bilirubin) Bilirubin count is measured in newborns to monitor the activity of their liver. Biology 12: Digestive system Page 19 Complete the following table of digestive glands and their secretions: Name of enzyme Salivary Amylase Name of Secretion Saliva Name of Related Gland Salivary Glands Pepsin (a protease) Trypsin (a protease) Location of Gland 3 separate pairs of glands; beneath tongue, beneath lower jaw, side of face in angle of jaw Substrate Starch Product Maltose Notes -functions best at neutral pH -saliva also contains water and mucus for lubrication Polypeptides dipeptides pancreas secretes bicarbonate to neutralise acidic chime so that trypsinogen converts to trypsin Lipase Pancreatic Amylase Biology 12: Digestive system Page 20 Nuclease Name of enzyme Name of Secretion Name of Related Gland Peptidases Location of Gland Substrate Product Notes dipeptides Maltase From the two lists below, match each structure with its correct function. __c___ Salivary glands a. produces enzymes which pass into the duodenum __e___ esophagus b. controls the passing of feces ___j__ stomach c. produce saliva __h___ pyloric sphincter __g___ duodenum __k___ small intestine d. is where most water is absorbed e. carries food from the mouth to the stomach f. stores bile __l___ bile duct g. receives juices from the gall bladder and pancreas ___a__ pancreas h. controls the amount of food leaving the stomach __f___ gall bladder i. stores waste feces for several hours __d___ colon Biology 12: Digestive system j. produces hydrochloric acid Page 21 __i___ rectum k. is where most digested food is absorbed __b___ anus l. takes bile from the gall bladder to the duodenum Biology 12: Digestive system Page 22 Glucose Homeostasis What do we mean when we say that the pancreas is an exocrine gland? It secretes digestive enzymes which reach the duodenum via the pancreatic duct. Exocrine glands have ducts. This allows enzymes and bicarbonate to be secreted into the duodenum. What do we mean when we say that the pancreas is an endocrine gland? Endocrine glands are ductless and the pancreas secretes insulin as well as glucagon directly into the blood stream via capillaries that flow through it. What is the source gland for insulin? (ie. Which endocrine gland produces insulin?) ___The pancreas and the cells in it that secrete insulin are called the Islets of Langerhans made up of specialised cells called beta cells. ___ Biology 12: Digestive system Page 23 The set point for blood glucose is about 100 mg/100 mL of blood. This is the concentration that the body tries to maintain. It does this by a process of NEGATIVE FEEDBACK. Study the following negative feedback diagram to see how insulin affects glucose homeostasis: What is the STIMULUS for the release of the insulin? __increase in blood glucose level_____ Where are the RECEPTOR cells? ___Beta cells in the pancreas____________ What is the CONTROL CENTRE? The liver because it takes up the glucose and converts it to glycogen. The overall control of all hormone secretion occurs in the hypothalamus in the brain. What are the EFFECTORS and what do they do? The liver and body cells (mainly muscle) which take up the glycogen for storage. ________________________________________________________________________ _____ Biology 12: Digestive system Page 24 What is the RESPONSE? _____Insulin secretion increases to convert glucose to glycogen. __ Why do we refer to this process as NEGATIVE FEEDBACK? __As soon as the insulin increases the glucose level will drop and if it drops too low then glucagon will be secreted by the alpha cells to convert glycogen back to glucose. If the blood glucose level drops too low (for example, after you have not eaten for a while), how does your body bring the level back up to the SET POINT again? __By converting glycogen back to glucose until the optimum level for glucose in the blood is 100mg/ 100ml If the pancreas does not secrete enough insulin, the person has _Diabetes 1or type I__. This condition is treated with __insulin injections. _____________. If the body secretes enough insulin, but the body cells do not respond to the insulin, the person has ____Diabetes II or Type II____. This condition is treated with ______controlled diet. In both types of diabetes, the person’s urine contains large quantities of ____glucose____. Draw a graph to combined effects glucagon on the in your blood over Biology 12: Digestive system show the of insulin and level of glucose time: Page 25