1. Digestive System
HCT II

2. Objectives Label the pharynx, esophagus, stomach and small intestines
Explain the function of these digestive organs
Explain how food is absorbed into the body by the villi in the small intestine
Describe how gastric juices act on food in the stomach

3. Pharynx (throat) After food becomes bolus it enters the throat
This carries both air and food.
Carries air to the trachea
Carries food to the esophagus
When bolus is swallowed, muscle action causes the epiglottis to close over the larynx, prevents bolus from entering the respiratory tract and enter the esophagus.

4. Esophagus Muscular tube dorsal (behind) the trachea
Receives bolus from the pharynx and carries it to the stomach
Relies on Peristalsis (rhythmic involuntary wavelike movements) of its muscles to move food in a forward direction

5. Stomach Enlarged part of the alimentary canal
Receives food from the esophagus
Lined with a mucus membrane containing folds called rugae that disappear as the stomach expands

6. Cardiac Sphincter Circular muscle between the esophagus and stomach
Closes after food enters the stomach’
Prevents food from going back up into the esophagus
What is it called when food goes back up into the esophagus?
Reflux

7. Pyloric Sphincter
Circular muscle between the stomach and the small intestine
Keeps food in the stomach until it is ready to enter the small intestine
How many hours does food usually stay in the stomach?
1-4 hours

8. Gastric Juices Produced by glands in the stomach
Converts food into a semifluid material called chyme
Juices contain HCL
Kill bacteria
Facilitates the absorption of iron
Activates the enzyme pepsin
Juices also contain
Lipase- begins the chemical breakdown of fats
Pepsin- starts protein digestion
Enzyme rennin- in infants only (aids in the digestion of milk)

9. Small Intestine
Coiled section of the alimentary canal about 20 feet long and 1 inch in diameter
NOT SO SMALL!!!
Receives food in the form of chyme from the stomach.

10. Small intestine Three sections Duodenum Jejunum Ileum
First inches
Bile from the liver, gallbladder and pancreatic juices enter this section through ducts or tubes
Jejunum
About 8 feet long (the middle section)
Ileum
Final 12 feet
Connects with the large intestine at the cecum
Circular muscle called the ileocecal valve prevents food from returning to the ilium

11. Functions of the small intestine
Completes digestion
Absorbs the products of digestion into the blood stream for use by our cells

12. Produced by the small intestine
Intestinal Juices
Bile
Produced by the small intestine
Contain enzymes which break down sugars
Maltase
Sucrase
lactase
Also contains the enzyme peptidases, which completes digestion of proteins.
liquid from the liver and gallbladder
Emulsifies or breaks down fats
Why can fatty diets lead to gallbladder disease?

13. Pancreatic Juices
Liquid that enters the small intestine from the pancreas
Contains enzymes that complete the process of digestion
Amylase- acts on sugar
Trypsin and chymotrypsin- act on proteins
Lipase- acts on fats

14. Villi
Fingerlike projections lining the walls of the small intestine
Allow food to be absorbed and taken into the bloodstream
Blood capillaries
Absorb digested nutrients
Carry to the liver for storage
Release nutrients into the general circulation for use.
Lacteals-pick up digested fats and carry them to the thoracic duct
Where does the thoracic duct take them to?
*** when food has completely passed through the small intestine only wastes, water and indigestible materials remain.