Student name: ______________________________ Block: _____ Date: _________

The Digestive System The process of breaking down the food we eat into small molecules that the body can use is called ______________. Our bodies use these small molecules as ____________ and building blocks to form new cells and allow our bodies to function and to __________. Digestion is carried out in the Digestive System, and is helped along by special proteins called ____________. The Digestive System is essentially a single long ____________ that begins at your mouth and ends at your anus. The tube changes shape and size as it goes along, and different parts of the digestive process are carried out at different points along the tube. The digestive system is full of trillions of ____________ that aid the process of digestion, and use indigestible material to produce vitamins which our body uses. Digestion happens in 4 stages:

Student name: ______________________________ Block: _____ Date: _________

- Ingesting - Digesting - Absorbing - Eliminating

Stage 1: Ingesting Ingestion is the starting point of the digestive process. Ingestion occurs when food enters the body through the mouth.

Stage 2: Digesting Mouth: Digestion begins in the mouth with ______________ and chemical digestion. Mechanical digestion occurs when food is broken down into pieces small enough to ____________ by the teeth and tongue. Food also reacts with an ___________ called amylase in saliva which breaks down complex carbohydrates. The food is formed into a ball called a _________.The bolus is covered by saliva, aiding swallowing.

Esophagus: When swallowed, the bolus moves past the epiglottis which directs it into the ____________, a tube leading to ____________. The bolus is pushed down the esophagus to the stomach by the muscles in the esophagus in a process called __________. Stomach: In the stomach food is bathed in gastric juices; hydrochloric acid, mucus, and enzymes. Proteins in the food are broken down by the enzyme pepsin and by hydrochloric acid, while the stomach contracts to mix the food up to aid digestion. The stomach is lined with a __________ that protects it from the acidic gastric juices. The food, now a liquidy mix

Student name: ______________________________ Block: _____ Date: _________

called chyme, continues on to the next step.

Small intestine: Food enters the small intestine, a _______ long, 2.5cm wide tube, from the stomach. In the first meter of the small intestine, the digestion of food is completed by enzymes and bile, which break down carbohydrates, protein and fats. The enzymes are produced by an organ called the ___________, while bile comes from the liver, and is stored in the gallbladder. Trillions of bacteria in the small intestine also assist in the digestion of food and absorption of nutrients.

Stage 3: Absorption Small intestine: For the remaining 5 metres of the small intestine, nutrients are absorbed from the food by tiny finger-like structures called __________ lining the

Student name: ______________________________ Block: _____ Date: _________

inside of the intestine. The villi increase the surface area of of the small intestine by 500x, greatly speeding absorption.

Large intestine: The large intestine, a 1.5m long, 5cm wide tube, absorbs __________ and _________ from the food. By the time the food leaves the large intestine, 90 percent of the water has been reabsorbed.

Stage 4: Elimination Any remaining undigested material, called feces, is now mixed with waste from the body, such as dead red blood cells. Feces is stored in the rectum until it is expelled through the anus in a process called elimination. The full digestive process from ingestion to elimination takes about ____________ hours. Homework Problems (Answer in full sentences)

1. How many stages of digestion are there? 2. Describe the function of an enzyme and give an example. 3. What is a bolus? 4. Describe how a bolus is moved down the esophagus to the stomach. 5. What is the function of the mucus coating on the stomach wall? 6. Where are the enzymes in the small intestine produced, and what do they do? 7. How is the surface area of the small intestine increased? 8. What is the main function of the large intestine? 9. Describe the process of elimination in the digestive system. 10.Which organs and structures carry out digestion? Briefly mention the role of

each in digestion.