Purpose To reduce the size of large pieces of food to small molecules that can be absorbed into the blood stream and eventually into cells.

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2 Purpose To reduce the size of large pieces of food to small molecules that can be absorbed into the blood stream and eventually into cells. Cells are then able to maintain homeostasis

3 6 main components of the digestive system: Tongue Teeth Mouth/ Throat Esophagus Stomach Small Intestine Large Intestine Rectum/ Anus Salivary Glands

4 Different phases of digestion take place in each organ of the Alimentary Canal. Most foods that you eat cannot be used immediately by the body and must be broken down into nutrients; simpler substances that can be used by the body.

5 Nutrients are carried to all Nutrients include carbohydrates, cells of the body lipids, by the proteins, vitamins, minerals, and water. circulatory system (blood). In the cells, nutrients provide the energy and materials needed for cell growth and repair.

6 Step 1 Mechanical Digestion Reduces the size of large food pieces into smaller ones thereby increasing the surface area. Increased surface area allows for more surface contact between the food and the enzymes that will assist in breaking them down. Where this happens: Chewing, peristalsis, muscular contractions in the stomach, and emulsification of fat with bile.

7 Step 2 Chemical Digestion Large molecules are broken down into smaller ones through the action of enzymes and the addition of water (hydrolysis reactions). Digestive enzymes are the chemicals that break large insoluble food molecules into smaller soluble molecules.

8 Close your eyes and imagine your favourite food. Did your mouth water as you pictured something delicious? This occurs because the mouth contains salivary glands.

9 Salivary glands release saliva. Saliva contains enzymes to start the digestion of carbohydrates into simple sugars. Also coats food to make it slippery Teeth Chewing / mastication breaks up food into smaller pieces.

10 Tongue: moveable organ on the floor of the mouth. -Helps us taste, eat, and speak. -Contains taste buds that help us identify foods that are sweet, salty, sour and bitter. -Rolls food into a ball called a bolus. -Pushes the bolus to the back of the throat to be swallowed.

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12 Put a cracker into your mouth and chew it for a few minutes (don t swallow it!!) What do you notice about the taste of the cracker after chewing it? Tastes sweet bread is a carbohydrate and when the enzyme, amylase, in saliva comes into contact with the bread, it begins to digest/break it down into sugars.

13 After food is chewed, it is rolled into a bolus by the tongue and pushed to the back of the throat and down the esophagus. Small piece of tissue that covers the opening to the windpipe (trachea) to keep food and liquid out of the airway when you swallow.

14 Latin word for grape Blocks food from entering the nasal passage (nose). Aids in speech, and activates the gag reflex. Helps singers produce a vibrato, a wavy up-and-down sound.

15 Moves food from the back of the mouth to the esophagus. Both food and air move through the pharynx, therefore it is part of both the digestive and the respiratory systems.

16 To carry what is eaten Transports food to the stomach ( ~7 sec.) Lined with slippery mucus helps food travel through the digestive system easily.

17 Wave-like muscular contractions that propel food from the esophagus to the stomach. Muscles in front of the food relax, while those behind the food contract, pushing the food forward.

18 C-shaped pouch that receives the food bolus from the esophagus. Acts like a churn mixes food with acid and pepsin. Gastric/Hydrochloric acid; ph ~2 Pepsin enzyme that starts the digestion of proteins The acid breaks down the food into a milky substance called chyme Mucus lining of the stomach protects it from the acid. Fluid that passes from the stomach to the small intestine, consisting of gastric juices and partly digested food.

19 Stomach (peptic) ulcer is produced when acid comes into contact with the stomach wall. Extremely painful Causes: Infection with bacterium H. pylori Long term use of anti-inflammatory drugs (aspirin, ibuprofen, or naproxen)

20 Hunger is felt when an empty stomach is churning stomach growls. The stomach can hold litres 1 to 1.5 of food. Liquids pass through the stomach in 20 minutes or less. Solids have to be turned into chyme first. Stomach empties gradually into the small intestine 2-6 hours after a meal.

21 3 parts: duodenum, jejunum, ileum

22 Duodenum Food travels from the stomach and enters the duodenum where is it digested further. Liver releases bile into the small intestine Bile breaks down(emulsifies) fats Pancreas releases pancreatic juice into the small intestine Enzymes break down carbohydrates, proteins, and fats

23 Once nutrients are broken down, they are absorbed through the wall of the small intestine into the blood stream through villi. Small hair-like structures that have a large surface area for optimal absorption of nutrients.

24 Colon. Undigested food travels from the small intestine into the large intestine. Reabsorbs water from undigested food. Compacts the undigested food. *No digestion happens here.

25 Rectum: where feces are temporarily stored before being expelled from the body. Anus: ring of muscles where feces are expelled (egested)

26 Gateways between different parts of the digestive system. Controls the movement of substances between different organs. Example: Cardiac sphincter Separates esophagus from stomach Prevents stomach acid from entering the esophagus which could cause heartburn.