1. The Digestive System

2. The digestive system is a group of organs that work together to digest food so that it can be used by the body
The digestive tract is a series of tubelike organs that include your mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum and anus
The liver, gall bladder, pancreas and salivary glands are part of the digestive system, but food does not pass through these organs

3. Breaking Down Food

4. Digestion is the process of breaking down food into a form that can pass from the digestive tract to the bloodstream
Two types of digestion – mechanical and chemical
Mechanical digestion – the breaking, crushing and mashing of food
Chemical digestion – large molecules are broken down into nutrients
Enzymes – substances that break down larger molecules into smaller units

5. Nutrients

6. Three major nutrients – carbohydrates, proteins and fats – make up most of the food you eat
Enzymes break some nutrients into smaller particles that the body can use
For example – proteins are too big to be absorbed into the bloodstream – enzymes break them up into amino acids which can be absorbed

7. Digestion Begins in the mouth

8. Teeth – very important for mechanical digestion – break and grind food – makes smaller pieces of food easier to digest
Saliva – made in the salivary glands located in the mouth - contain enzymes that begins the chemical digestion of carbohydrates
Esophagus – a long straight tube that squeezes the mass of food with rhythmic muscle contractions called peristalsis – peristalsis forces food into the stomach

9. The Harsh Environment of the Stomach

10. The stomach is a muscular, saclike digestive organ attached to the lower end of the esophagus
Continues mechanical digestion by squeezing food with muscle contractions
Tiny glands in the stomach produce enzymes and acid – work together to break down food
Stomach acid kills bacteria that might be in food
Food reduced to soupy mixture called chyme

11. The Pancreas

12. Most chemical digestion takes place after the food leaves the stomach
When the chyme leaves the stomach, it is very acidic
The pancreas makes fluids that protect the small intestine from the acid
Pancreas – oval organ located between the stomach and the small intestine
Pancreatic fluid flows into the small intestine – contains enzymes to break down chyme and bicarbonate to neutralize acid
Pancreas is part of the endocrine system by making hormones that regulate blood sugar

13. Small intestine

14. Small intestine is a muscular tube that is about 2.5 cm in diameter
Stretched out, it is usually about 6 m long
Inside wall of the small intestine is covered with fingerlike projections called villi
Villi are covered with tiny nutrient – absorbing cells
Once nutrients are absorbed, they enter the bloodstream

15. The Liver

16. The liver is a large, reddish brown organ that helps with digestion
Located toward your right side, slightly higher than your stomach
Liver helps make bile to break up fat
Liver stores nutrients
Liver breaks down toxins
Bile that is made by the liver is temporarily stored by the gall bladder
Gall bladder squeezes bile into the small intestine to break down fat droplets

17. The End of the Line

18. The large intestine is the organ of the digestive system that stores, compacts and then eliminates indigestible material from the body
Has a larger diameter than the small intestine (7.5 cm)
Undigested material enters the large intestine as a soupy material from the body
Most of water is absorbed from the mixture by the large intestine

19. Changes the mixture to a semi – solid called feces
Whole grains, fruits and vegetables contain cellulose, or fiber, that cannot be digested
The rectum is the last part of the large intestine – it stores feces until it can be expelled through the anus
It takes your sandwich about 24 hours to make the journey through your digestive system