1. The Digestive System Chapter 11 page 352 -373 MHR

2. Obj. 17 - Why do we have a digestive system?? To break large ingested (eaten) molecules into smaller, more simple compounds that can be easily absorbed into the circulatory system. What are the molecules that we need to break down?? Coming soon :)

4. Obj. 18 - Mechanical and Chemical Digestion Mechanical Digestion Physically breaking down food into smaller particles. Occurs in the mouth where the teeth chew and the tongue manipulates food. Chemical Digestion Separation of food into molecular components by chemical means. Begins in the mouth with saliva, continues in the stomach, and completes in the small intestine. Both work together to provide the nutrients that are absorbed into the body.

6. Major Organs and the Pathway of food through the Digestive System pg 359-362 (fig 11.3 pg 359) Mouth - food is chewed by the teeth, manipulated by the tongue, and mixed with saliva The top of the tongue is covered with Papillae which house the taste buds allow us to tell if food is sweet, sour, salty, or bitter. The uvula (“hangy ball”) hangs in the back of the throat and prevents food from entering the pharynx.

7. Salivary Glands - secretes saliva which lubricates food (pass easier through the digestive system) & is the beginning of chemical digestion Esophagus (fig 11.3, pg 359) - a tube-like structure that connects the mouth and stomach. Mucus produced by mucous lining lubricates food it is lined with muscles that push food down to the stomach.

8. Stomach (figs 11.5, pg 359; 11.6, pg 360) muscular J-shaped sac stomach wall has millions of gastric glands that secrete gastric juices which chemically breakdown food. stomach muscles help breakdown food into a thick liquid called chyme. At the junction of the stomach and the next part of the tract, a valve is present to control the amount of chyme leaving the stomach called the Pyloric Sphincter

9. Small Intestine (figs 11.5, pg 359; 11.7, pg 361) - After the stomach, food enters the small intestine tiny villi increase the surface area of the intestine to absorb as many nutrients as possible. has total absorptive surface area of a tennis court!! it has three sections: 1) duodenum, 2) jejunum, and 3) ileum 1) Duodenum (25-30 cm long) -The first part of the small intestine (shortest and widest of the three sections) the pancreatic and bile ducts open into this section it has many folds lined with villi - high surface area for absorption

11. 2) jejunum (2.5m long) - middle part; also has many folds (and villi) it breaks down remaining proteins and carbohydrates so their end products can be absorbed. 3) Ileum (3m long) - fewer folds, absorbs remaining nutrients, pushes undigested material to the large intestine.

12. Large Intestine (1.5m long) see fig 11.3 pg 359 much shorter than small intestine but has a larger diameter consists of the caecum, colon, rectum, and anal canal. 1) Caecum blind end of the large intestine; the appendix hangs from the caecum. 2) Colon - Undigested food travels up, across, and down the colon water and dissolved minerals are absorbed material that remains is now called feces.

13. 3) Rectum - last 20 cm of the large intestine stores feces until it is eliminated from the body 4) Anus - Feces passes out of the body through the anus anal sphincter allows the body to control the elimination of feces to some extent. Note: Food moves through the digestive system by wavelike muscular contractions known as peristalsis (Fig. 11.8 pg 362).

14. Related Organs (pg365-368) - Organs that are not directly in the digestive tract but which play an important role in digestion. The Liver (pg 365-368; fig 11.11 pg 368) produces bile salts which break up fat globules into tiny droplets that can be absorbed by the small intestine Other functions: breaks down/recycles some cells, stores some chemicals & detoxifies poisons

15. The Gall Bladder (pg 368; fig 11.3 pg 359) stores bile that the liver produces - a hormone causes it’s release into the duodenum The Pancreas (pg 368; fig 11.3 pg 359) Contains enzymes & produces a basic solution to neutralize chyme as it comes from the stomach into the small intestine

16. Essential Nutrients (page 354-358) A healthy diet must include the six essential nutrients. carbohydrates fats proteins minerals vitamins water A diet where these nutrients are present in the right proportions is called a Balanced Diet.

17. Carbohydrates made of atoms of carbon, hydrogen and oxygen a source of energy that can be accessed quickly can be simple (glucose) or complex (starch). Sources: pancakes, bread, pasta, cakes, and cookies.

18. Carbohydrates two or more simple sugars combine to form a polysaccharide. Glycogen performs the important function of energy storage in animals. stored in the liver. Chemical digestion mouth - salivary amylase breaks glycogen into maltose. small intestine - maltase breaks maltose down into two glucose molecules See structure of glycogen p. 44

19. Lipids fats used for energy and building materials for cell membranes and hormones layers of fat protect the body against cold and cushion against organ damage. Sources: nuts, meat, cheese, milk, butter, eggs, and cooking oils.

20. Lipids (fats) fats are broken down into fatty acids and glycerol in the small intestine by the enzyme lipase. here they are absorbed by microvilli some are transported to the liver and converted to glycogen others are passed to fat cells where they can be reconverted to fat.

21. Proteins Made up of peptides (made up of amino acids). we can’t make 8 out of the 20 amino acids we need these 8 are called essential amino acids they must come from food. A food source containing all eight is called a complete protein. Complete protein sources: meat, legumes, eggs, cheese, milk, and whole grain products. proteins in your body include enzymes & antibodies proteins build & repair muscles & cell membranes

22. Protein After digestion they are broken down into amino acids. absorbed into the bloodstream carried to the liver transported to cells to make new proteins the liver also breaks down amino acids for energy when fat and glycogen stores are low. Chemical Digestion Stomach: protein break down to peptides by pepsin Small intestine: peptides - break down to simpler peptides by trypsin.

23. Minerals inorganic compounds the body needs in small amounts enable certain chemical reactions help build bones and cartilage are essential components of hemoglobin, hormones, and enzymes

24. Vitamins required in relatively small amounts. function as coenzymes i.e. are needed to make enzymes function. involved in tissue growth help the body fight and resist disease. Of the four fat soluble vitamins (A,D,E and K) only A and K can be stored. The others must be consumed on a regular basis. See table 11.1 pg 358

25. Water You obtain water by drinking and eating. Water dissolves food materials so they can pass to the bloodstream. Most of the body’s chemical reactions occur in water solutions.

26. Digestive Enzymes pg 363-365 chemical digestion involves hydrolysis, or the breakdown of bonds by adding water occurs with carbohydrates, lipids and proteins breaks these down into smaller, absorbable molecules is made faster by enzymes 3 types: carbohydrases, lipases, and proteases they are formed in secretory cells and secreted into the digestive tract in several locations Fig 11.10 pg 364

27. Maltose + water → glucose + glucose

28. Dehydration Synthesis ●Dehydrate - ‘remove water’ ●Synthesis - ‘to make’ ●Join together simpler molecules to make more complex ones by removing water ●When used - storing glucose for ‘later’ maltose

29. Digestive Enzymes pg 363-365 carbs. + H 2 O → simple sugars proteins + H 2 O → amino acids lipids + H 2 O → glycerol + fatty acids Digestive enzymes = chemical digestion. Begins in the mouth and ends in the small intestine. No chemical digestion in the large intestine. Bacteria here are producers of vitamin B and K