A Tour Through the Digestive System

Magic School Bus – “What’s For Lunch?” As you watch this

episode, complete your graphic organizer so that you can map the pathway food takes as it is digested.

Magic School Bus: What’s For Lunch?_28min

Mouth Mechanical digestion begins in the mouth.

In mechanical digestion, food is physically broken down into smaller pieces.

Your teeth carry out mechanical digestion. THINK! – What are the four types of teeth?

Incisors, Canines, Premolars, & Molars

In addition to teeth, a fluid called saliva moistens your food.

This begins chemical digestion, whereby chemicals break down food into smaller substances.

Esophagus As you swallow your food and it enters

your esophagus.

The esophagus is a long muscular tube that attaches your mouth to your stomach.

In order to help the food reach the stomach, smooth muscles contract involuntarily pushing the food downward.

These muscle contractions are known as peristalsis. View peristalisis in Action!

THINK! – How is food prevented from entering your windpipe when you swallow? When you swallow, a flap of skin

called the epiglottis seals off your windpipe

In your stomach, mechanical and chemical digestion are occuring.

First, your stomach muscles contract creating a churning motion to break down your food. THINK! – Mechanical or Chemical

Digestion?

Then, your stomach secretes an enzyme called pepsin as well as hydrochloric acid to break down food. THINK! – Mechanical or Chemical

Digestion?

Both mechanical and chemical digestion turn your food into an acidic liquid called chyme.

Stomach

From the stomach, chyme enters a long tube called the small intestine.

Here, digestion is completed and absorption of nutrients takes place.

As food travels through the small intestine it mixes with digestive juices from other organs. The liver produces bile. Bile is then stored and released from

the gallbladder. Bile helps to break down fat into

smaller droplets. The pancreas also secretes digestive

juices into the small intestine.

Small Intestine, Liver, and Pancreas

Check out the Villi of the Small Intestine! The inner surface lining of

the small intestine is covered with finger shaped projections called villi.

Villi have tiny blood vessels running through them.

Nutrients pass into these blood vessels.

The blood stream carries the nutrients to the rest of the body.

The Large Intestine, Rectum, & Anus By the time material reaches the large

intestine (a.k.a. the colon) most of the nutrients have been absorbed.

The material entering the large intestine contains water and undigested food such as fiber.

As material moves through the large intestine, water is absorbed into the bloodstream and the remaining solid waste material is readied for elimination.

The large intestine ends in a short tube called the rectum. Here waste material is compressed into solid form called feces and exits through a muscular opening called the anus.

How LongDoes DigestionTake? Esophagus?

Small Intestine?

Stomach?

Large Intestine?

4-8sec

2-4hr

3-5hr

hr-days

Activity: Color Code the Digestive System

mouth

Salivary Glands

Esophagus

Stomach

Pancreas

Rectum

Small Intestine

Large Intestine

LiverGallbladder

Teeth