 Create a cluster diagram of everything you know about the digestive system.  DO NOT USE YOUR BOOK!!!!!!  You must include at 5 facts but you can include more. Digestive System Fact

30.3

 Converts food into small molecules that can be used by the cells of the body  Four phases:  Ingestion  Digestion  Absorption  Elimination

 The process of putting food into your mouth – the opening of your digestive tract

 Food is broken down in two ways  Mechanical digestion – the physical breakdown of large pieces of food into smaller pieces  Those pieces can then be swallowed and accessed by digestive enzymes  Chemical digestion – enzymes break down food into the small molecules the body can use

 Once broken down, food can be absorbed by cells in the small intestine  From there they enter the circulatory system

 Not all ingested food is digested and absorbed  That travels through the large intestine and is eliminated from the body as feces

 Digestive system is built around an alimentary canal  One-way tube that passes through the body  Flow of food during digestion MouthesophagusStomach Small intestines

 Chewing begins the process of digestion with mechanical breakdown of the food  Saliva starts the chemical breakdown by breaking down complex carbohydrates into smaller molecules.

 Anchored by the bones of the jaw  Surface is covered by a coating of mineralized enamel  The incisors, cuspids and bicuspids cut into and tear the food  Molars grind and crush food into a fine paste  The tongue moves food around so that it comes in contact with your teeth

 Write and answer the following questions  How do your teeth help you ingest and digest food?  Can you think of tools that perform similar mechanical functions as human teeth?

 Secreted by the salivary glands  Helps to moisten the food and make it easier to chew  Under the control of the nervous system  Triggered by the scent of food

 Eases the passage of food and begins chemical digestion  Contains the enzyme amylase that breaks down the chemical bonds in starches, forming sugars  Contains the enzyme lysozyme that fights infection by digesting the cell walls of many bacteria

 Once food is chewed, the tongue and throat muscles push the bolus, clump of food, down the pharynx  The epiglottis is covering the trachea to prevent choking

 The tube that leads to the stomach  Contraction of the peristalsis, smooth muscles, provide the force that moves the food to the stomach  The cardiac sphincter closes the esophagus after food enters the stomach to provide backflow.  Overeating or drinking excess caffeine causes heartburn which is a result of stomach acid back flowing into the esophagus.

 Stomach is a large muscular sac that continues the chemical and mechanical digestion of food  Glands release hydrochloric acid and the enzyme pepsin into the stomach  Pepsin breaks proteins into smaller polypeptide fragments.  Mucus is also released into the stomach to lubricate and protect the stomach walls  Peptic ulcers form when the mucus layer fails and acid erodes the stomach lining  Usually a result of a bacteria infection

 Page 881 Question 2

 Alternating contractions of the stomach’s three smooth muscle layers thoroughly churn and mix the swallowed food  Chyme is produced  After an hour or two, the pyloric valve leading to the small intestine opens and chyme begins to spurt into the small intestine

 Chyme enters the duodenum which is the first part of the small intestine  Almost all of the digestive enzymes enter the intestines here  Most of the chemical digestion and absorption of food occur in the small intestine  Enzymes and digestive fluids from the pancreas, the liver and lining of the duodenum enter in the duodenum

 Located just behind the stomach  Produce hormones that regulate blood sugar  Produces enzymes that break down carbohydrates, proteins, lipids and nucleic acids  Produces sodium bicarbonate that neutralizes stomach acid

 The liver produces bile  A fluid loaded with lipids and salts  Bile is stored in the gallbladder  When fat is present in the duodenum, the gallbladder releases bile through a duct to the small intestines  Bile breaks up the fat globs into smaller droplets to make it possible for enzymes to break them down

 Where do the substances that digest food in the small intestine come from?  What does each structure provide and what does it break down?

 After digestion, nutrients must be absorbed from the alimentary canal  Most is absorbed through the walls of the small intestines  The large intestines  absorbs water and several vitamins  Prepares waste for elimination

 When chemical digestion is complete, the chyme is now a rich mixture of small- and medium-sized nutrient molecules that are ready to be absorbed.  Small intestines are made for absorption  Folded surface and fingerlike projections (villi) provide an enormous surface area  Villi are covered in microvilli that absorb nutrient as the chyme is moved along the surface by slow, wavelike contractions

 Most products of carbohydrate and protein digestion are absorbed into the capillaries in the villi.  Most fats and fatty acids are absorbed by the lymph vessels.  When chyme leaves the small intestines it is basically nutrient-free.  Water, cellulose and other undigestible substances remain  Enters the large intestine after pass by the appendix  Appendicitis is when the appendix becomes clogged and inflamed. It must be removed before rupture

 Also called the colon  Much shorter than the small intestine, gets it name because its diameter is larger  Main function is to remove water from the undigested food  Contains rich colonies of bacteria that produce compounds that the body is able to absorb and use including vitamin K  Large doses of antibiotics can kill these bacteria leading to vitamin K deficiency

 Feces – concentrated waste material – remains after most of the water is removed  Passes into the rectum and is eliminated through the anus  If not enough water is absorbed, diarrhea occurs.  If too much water is absorbed, constipation occurs