Human Body Systems

Lesson 2 Terms and Definitions

Major Organs of the Digestive System

1. Mouth

2. Esophagus

3. Stomach

4. Small intestine

5. Large intestine

6. Rectum

7. Anus

http://www.pediatricfeeding.org/images/gi_anatomy/A_digestive_system.png

Accessory Organs of the Digestive System

1. Tongue

2. Teeth

3. Salivary glands

4. Liver

5. Gallbladder

6. Pancreas

Accessory Organs are important for

mechanical and chemical digestion

produce or store enzymes

What is the purpose of Digestion?

Digestion

Purpose – break foods down into a form that can be absorbed into the bloodstream and transported to the cells of the body.

Digestion is NOT a single activity BUT a series of processes. (Mechanical and

Chemical)

Mechanical Digestion

Mechanical Digestion – The physical breaking down, tearing, and mashing of

food from large to small pieces.

Example: Teeth tearing, tongue mashing, churning of food by muscles that line the

digestive tract.

Chemical Digestion

Chemical Digestion – Breakdown of the chemical bonds in nutrients so that they can be absorbed into the bloodstream.

Example: Enzymes breaking down carbohydrates, fats, and proteins.

Fun Facts…

Digestive Tract – Single convoluted tube

8-10 meters long

Muscle Activity in the digestive tract

Peristalsis –wave like motions, caused by the muscles in the digestive tract, that move food slowly through the digestive

tract.

Crazy! – Peristalsis contractions are so strong that food would continue to

move through your digestive system if you stood on your head!

http://z.about.com/d/gymnastics/1/0/B/4/-/-/Step7.jpg

Muscle Activity in the digestive tract

• Sphincters – rings of thickened muscle that control the passage of food from one organ to another– Keeps food moving in the same direction

(Down! Not back up!)

Example – lips and anus, but also between organs.

Mucus

• Mucus – slippery secretion that coats the inner walls of the digestive tract and helps facilitate the movement of food.

Also coats the lining of the stomach and small intestine to prevent acidic gastric juices from eating away at the stomach lining.

http://www.thethinkingblue.com/pics/Stomachabc.jpg

Small Intestine…

• Small Intestine (SI)– Where most nutrient absorption occurs in

duodenum (first 25 cm of SI)– Entire SI – 6-8 meters long

http://cache3.asset-cache.net/xc/85824240.jpg?v=1&c=IWSAsset&k=2&d=C82013BE001AABCB31C0B7E4AA7CE1E8

Large Intestine

• Food – all that’s left is waste or Feces!

What is a FART?

A fart is…

• Flatus – intestinal gases produced bacteria feeding on undigested wastes.

Digestive Timeline!

6 seconds

2 hrs

4 ½ hours

4-12 hours

18 hours

12-24 hours