Digestive System

Which organ of the digestive system does

each picture represent?

Knife Food Processor Garbage Disposal

• The function of the digestive system is to break down food so that it can be used as energy in your body.

• The system consists of a series of complex organs and glands (which excrete enzymes) that break down food into small usable particles.

Mechanical Digestion:

-food is broken down mechanically, with movement

Ex: Teeth

Chemical Digestion:

-food is broken down with a chemical or enzyme

Ex: Saliva

• Peristalsis- series of involuntary smooth muscle contractions along the walls of the digestive tract.

• Moves food through the digestive system.

Organs Involved:1. Mouth2. Esophagus (A)3. Stomach (C)4. Small Intestine (E)5. Large Intestine (F)

• Appendix• Pancreas (D)• Liver (K)• Gall Bladder (J)

Digestion begins in the mouth.

As you chew your food, two processes are occurring:

1. TEETH- your teeth begin mechanical digestion by breaking down food into smaller pieces.

2. SALIVA- this enzyme helps break down starches chemically

1

The mouth completes both mechanical and chemical digestion!

As you swallow, the food must pass several structures:

• Pharynx- Back of the throat opens into esophagus

• Epiglottis- flap of tissue that keeps chewed food from going down the trachea to the lungs. As you swallow, the epiglottis flops closed.

• Larynx- Vocal cords

• The esophagus is a long tube that runs from the mouth to the stomach.

• After being chewed and swallowed, the food ball (bolus) enters the esophagus.

2

• The food is deposited in the Stomach.

• The stomach is a large, sac-like organ made of muscle.

3

• The stomach churns food AND bathes it in gastric juice (acidic).

• Food remains in the stomach for 2-4 hours, turning into a thin liquid soup called chyme.

3

The stomach completes both mechanical and

chemical digestion!

• The liquid chyme is the transported to the small intestine.

• SI is a narrow muscular tube about 6 meters long, lined with villi.

4

• Bile and other enzymes are injected into the Small Intestine to further break down the food.

4

Is this mechanical or chemical digestion?

Food remains in the SI for 3-5 hours

Don’t forget the Bacteria!

• Villi- finger-like extensions that absorb nutrients

• Villus expand surface area of SI.

4

• The function of the SI is to absorb all usable nutrients.

• The villi are covered with capillaries which pick up the nutrients for ALL cells in the body.

4

Blood vessels pick up nutrients

from SI

What system works with Digestive?

• Anything (liquid or solid) that is not absorbed by the SI is sent to the Large Intestine.

• The colon absorbs most excess liquids.

5

Don’t forget the Bacteria!

• After about 18-24 hours…

• The END process- solid waste (feces) is stored in the rectum until it is excreted through the anus.

5

• The digestive system is also part of the

Excretory system!

Your meal’s entire journey through the Digestive System has taken between 24 and 33 hours.

Many organs play a role in the digestion of foods but never come in contact with food, we call these accessory organs.

Three such organs are:

– Liver– Gall Bladder– Pancreas

• Liver- large organ located above and in front of the stomach.

• It filters toxins from the blood and makes bile (breaks down fats).

• Gall Bladder- small, sac-like organ located near the SI.

• It stores and releases bile into the small intestine.

• Pancreas- an enzyme producing organ located below the stomach and above the intestines.

• Enzymes from the pancreas aid in digestion of carbohydrates, fats and proteins in the small intestine.