Body Systems

The Digestive System

The Basics

• We all need energy to live • We get it from different sources

– Carbohydrates (sugars/starches)– Lipids (fats/oils)– Proteins (meat/lentils/beans)

• The Digestive system takes these sources and makes them useable to the body

Types of Digestion• Two Types…• Mechanical: physical breakdown of food

– Chewing/mixing– Teeth/jaw & tongue

• Chemical: breaking down large particles into smaller particles using enzymes

Teeth – Cool Photo

• Food enters our body through our mouth• We chew and grind it down • It also mixes with saliva which comes from

3 different saliva glands • They release the

enzyme amylase• Starch molecules

into sugarmolecules

Step 1: Mouth & Esophagus

Why is saliva important?

Aside - Carbohydrates• Why are they important? What do they do?

– They are the main fuel source for our body– The energy that gets used first – Recommended that 45-60% is

carbohydrates

• Where do they come from?– Vegetables, grains, low-fat dairy, fruits

Step 1: Mouth & Esophagus• When ready to swallow food tongue pushes

the food back • Flap of skin called epiglottis moves across

your windpipe • Into the esophagus it goes• It is pushed down your throat by the

muscles that line the esophagus … this is peristalsis – Chewed food is known as bolus – Swallowing is known as delutition

Esophagus

Swallowing Video

Step 2: The Stomach• A little history …

• Alexis St. Martin & Dr. William Beaumont• Alexis had big wound in his left side• Could not be repaired entirely • What did they do?• Dr. Beaumont put food on a string and

dangled it into the stomach to see what happened – lol science history!

As if you are

letting me do

this! Lol!

Step 2: The Stomach - Cont

Step 2: The Stomach• Food enters the stomach through a

sphincter (esophageal) • Muscular wall of the stomach mixes it around

with the gastric juices• What is that?

– Water– Mucus– Hydrochloric Acid– Digestive Enzymes

Step 2: The Stomach• The acid, enzymes and water liquefy the

food and break it down chemically • It passes into the small intestine through

another sphincter (pyloric)• Why do we need mucus in the stomach?

– So acid does not burn a hole thru the stomach!– The acid in the stomach is hydrochloric acid

Acid Video

Step 2: The Stomach

Step 3: Gastrointestinal Tract• The pancreas, a large gland in the back of the

stomach, helps break down food, sends digestive enzymes into the small intestine

• Enzymes complete the breakdown of starches and proteins into small particles which are more easily absorbed by the body

Step 3: Gastrointestinal Tract

Step 3: Gastrointestinal Tract• The liver produces a substance called bile

(which is stored in the gall bladder)• The gall bladder sends bile into the small

intestine, where it breaks up large amounts of lipids into small drops

Step 3: Gastrointestinal Tract• When food is broken down into smaller particles,

the small intestine absorbs these particles. • The inner surface of the small intestine contains

villi (small, finger like objects)– Villi increases the

surface area of the intestine to help absorb nutrients.

– Villi is covered with epithelial tissue & food molecules get absorbed by this tissue.

Bacteria … Can Be Good?

Step 4 – The End of the Road• Food then passes from the small

intestine to the large intestine • Key part here is that water is absorbed in

the large intestine • When it hits the end of the road …

washroom break!

Summary Video

Digestive System