Download - Digestive System
Digestive SystemHCT II
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
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
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
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
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
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
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)
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.
Small intestine Three sections Duodenum
First 9- 10 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
Functions of the small intestine Completes digestion
Absorbs the products of digestion into the blood stream for use by our cells
Intestinal Juices Produced by the small intestine
Contain enzymes which break down sugars Maltase Sucrase lactase
Also contains the enzyme peptidases, which completes digestion of proteins.
Bile liquid from the liver and
gallbladder
Emulsifies or breaks down fats
Why can fatty diets lead to gallbladder disease?
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
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.