1. Digestive System
Living Environment

2. What is it?
The digestive system is a group of organs working together to convert food into energy and basic nutrients to feed the entire body.
Everything you eat needs to be broken down into smaller molecules that your cells can use to make energy for your body.
Proteins  amino acids
Fruits, vegetables, grains, starches simple sugars
Fatty foods  fatty acids

4. Six Major Functions Ingestion of food
Secretion of fluids and digestive enzymes (ex. saliva, mucus, stomach acid, bile)
Mixing and movement of food and wastes through the body (ex. swallowing)
Digestion of food into smaller pieces
Absorption of nutrients (stomach & small intestines)
Excretion of wastes

5. Parts of the Digestive System
Mouth
Pharynx
Esophagus
Stomach
Small Intestine
Liver
Gallbladder
Pancreas
Large Intestine

7. Mouth
Food begins its journey through the digestive system in the mouth, also called the oral cavity
The tongue, teeth, and salivary glands all help in the digestion of food

8. Teeth
The teeth are 32 small, hard organs that cut and grind food into smaller pieces
They are made of dentin which is a bone-like substance
They are covered in a layer of enamel which is the hardest substance in the body
They are living organs and contain blood vessels and nerves

9. The Tongue
The tongue is a small organ made up of several pairs of muscles covered in a thin, bumpy, skin-like layer.
The outside of the tongue has many papillae for gripping food and moving it around the mouth.
Taste buds on the surface of the tongue detect taste molecules in food and connect to nerves to send taste information to the brain
The tongue pushes food to the back of the mouth

10. Salivary Glands
There are 3 sets of salivary glands that surround the mouth
They are accessory organs that produce saliva
Saliva moistens food and begins the digestion of carbohydrates.
Saliva also lubricates food so it passes easier through the mouth, pharynx, and esophagus

11. Pharynx Also known as the throat
It is connected to the back of the mouth
The pharynx’s job is to pass masses of chewed food from the mouth to the esophagus
It also is a pathway for air to the lungs
A flap of tissue known as the epiglottis acts as a switch to route food to the esophagus and air to the lungs

12. Esophagus
The esophagus is a muscular tube connecting the pharynx to the stomach that is part of the upper gastrointestinal tract
It carries swallowed masses of chewed food into the stomach
A muscular ring, called the sphincter, is located at the bottom of the esophagus and makes sure that food stays in to stomach once it passes through

13. Stomach
The stomach is a muscular sac located on the left side of your abdomen, right under the diaphragm
The stomach is about the size of two fists placed next to each other
It acts as a storage tank for food so that the body has time to digest large meals properly
It contains hydrochloric acid and digest enzymes that continue the digestion of food that started in the mouth

14. Small Intestine
The small intestine is a long, thin tube about 1 inch in diameter and about 10 feet long.
It is located right under the stomach and takes up most of the space in the abdomen.
It is coiled up like a hose and its inside surface is full of ridges and folds
The folds maximize the digest of food and absorption of nutrients
By the time food leaves the small intestine, about 90% of all nutrients have been taken out of the food

15. Liver
The liver is roughly triangular accessory organ of the digestive system located to the right of the stomach, under the diaphragm, and above the small intestine
It weighs about 3 pounds and it is the 2nd largest organ in the body
Its main function in digestion and the production of bile and its secretion into the small intestine

16. What’s Bile?
Bile is a fluid that is made and released by the liver and stored in the gallbladder
Bile helps with digestion
It helps the enzymes in your body to break down fats into fatty acids which can then be taken into the body

17. What are enzymes?
Enzymes are usually proteins that help to start chemical reactions within the body
They initiate change
In the digestive system they help to break down food into smaller macromolecules that can be used by the body for energy

18. Gallbladder
The gallbladder is a small, pear-shaped organ located right behind the liver
It is used to store and recycle excess bile from the small intestine so that it can be reused for the digestion of future meals

19. Pancreas
The pancreas is a large gland located just below and behind the stomach
It’s about 6 inches long and shaped like a short, lumpy snake
It secretes digestive enzymes into the small intestine to complete the chemical digestion of foods

20. Large Intestine
The large intestine is a long, thick tube about 2 ½ inches in diameter and about 5 feet long
It’s located right under the stomach and wraps around the small intestine
Its function is to absorb water and contains many symbiotic bacteria that aid in the breaking down of wastes to get any remaining nutrients that weren’t absorbed in the small intestine
Feces in the large intestine exit the body through the anal canal