Post on 18-Dec-2015
transcript
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.