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.