Download The Small and Large Intestines

The Digestive System
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The digestive system provides
nutrients and energy for your body
through the digestion of food.
mastication
peristalsis
gastric juices
bile
peptic ulcer
appendicitis
What Happens During Digestion
In digestion, foods are broken down and
absorbed as nourishment or eliminated as
waste.
The foods you eat must be broken down into
nutrients to be absorbed into the blood and
carried to the body’s cells.
What Happens During Digestion
Three Main Processes of the Digestive System
Digestion
The mechanical and chemical breakdown of
foods within the stomach and intestines for
use by the body’s cells.
Absorption
The passage of digested food from the
digestive tract into the cardiovascular
system.
Elimination
The body’s expulsion of undigested food or
body wastes.
How Digestion Works
The digestive system consists of the mouth,
esophagus, stomach, and intestines.
Carbohydrates begin digesting in the mouth,
protein begins digesting in the stomach, and
fats begin digesting in the small intestines.
How Digestion Works
Digestion includes two processes.
Mechanical
Processes
Chewing, mashing, and breaking food
down.
Chemical
Processes
Secretions produced by digestive organs.
How Digestion Works
The teeth break the food you eat into smaller
pieces. Mastication prepares food to be
swallowed.
Mastication
The process of chewing
How Digestion Works
Salivary glands produce saliva, which contains an
enzyme that begins to break down the starches
and sugars in food into smaller particles.
The tongue prepares chewed food for swallowing
by shaping it.
The Esophagus
When food is swallowed, it moves through the
esophagus, stomach, and intestine through
peristalsis.
Peristalsis
A series of involuntary muscle
contractions that moves food
through the digestive tract
The Stomach
The stomach has three tasks:
Mixing foods
with gastric
juices
Storing
partially
digested food
and liquid
Moving food
into the small
intestine
The Stomach
The hydrochloric acid in gastric juices kills
bacteria taken in with food and creates an acidic
environment for pepsin to do its work.
Gastric juices
Secretions from the stomach lining that
contain hydrochloric acid and pepsin,
an enzyme that digests protein
The Stomach
The stomach holds the food for further digestion
before it is moved into the small intestine.
As food is digested in the stomach, it is converted
to chyme, a creamy, fluid mixture of food and
gastric juices, which is moved into the small
intestine.
The Stomach
The three layers of stomach muscles each move
in different directions to aid both mechanical and
chemical digestion.
The Stomach
The Pancreas, Liver, and Gallbladder
The liver produces bile and the pancreas produces
other enzymes that break down the carbohydrates,
fats, and proteins in food in the small intestine.
Bile
A yellow-green, bitter fluid
important in the breakdown and
absorption of fats
The Small and Large Intestines
The small intestine is 20 to 23 feet in length and 1
inch in diameter.
It consists of three parts: the duodenum, the
jejunum, and the ileum.
The Small and Large Intestines
About 90 percent of all nutrients are absorbed
through the small intestine.
Unabsorbed material leaves the small intestine in
the form of liquid and fiber and moves by
peristalsis into the large intestine.
The Small and Large Intestines
The inner wall of the
small intestine
contains millions of
fingerlike projections
called villi that are
lined with capillaries
that absorb the
nutrients.
The Small and Large Intestines
The undigested parts of the food—fiber, or
roughage—pass into the colon, or large intestine.
Its function is to absorb water, vitamins, and
salts, and to eliminate waste.
Digestive System Problems
Digestive problems range from indigestion to
acute conditions that require immediate
medical attention.
Taking care of your digestive system begins
with the foods you eat and how you eat them.
Digestive System Problems
Tips for Maintaining Digestive Health
Eat a variety of low-fat, high-fiber foods.
Wash your hands before preparing or eating meals.
Eat slowly and chew your food thoroughly.
Drink at least eight 8-ounce glasses of water a day.
Avoid using food as a way of dealing with your emotions.
Functional Problems
Indigestion
Discomfort in the abdomen, sometimes with
gas and nausea.
Constipation
Feces become dry and hard, making bowel
movements difficult.
Heartburn
A burning sensation in the chest that may
rise up to the throat.
Gas
Cramps or an uncomfortable feeling of
fullness in the abdomen.
Nausea
A feeling of discomfort that sometimes
precedes vomiting.
Diarrhea
The frequent passage of watery feces.
Structural Problems
Tooth decay
Makes it difficult to chew foods thoroughly.
Gastritis
Inflammation of the mucous membrane that
lines the stomach
Gallstones
Blockage of the bile duct between the
gallbladder and the small intestine.
Lactose
Intolerance
An inability to digest lactose, a type of sugar
found in milk and other dairy products.
Colitis
Inflammation of the large intestine, or colon.
Structural Problems
Colon cancer
Cancer that usually develops in the lowest
part of the colon, near the rectum.
Hemorrhoids
Veins in the rectum and anus that may
become swollen and inflamed.
Crohn’s Disease
Inflammation of the lining of the digestive
tract.
Cirrhosis
Scarring of the liver tissue caused by
prolonged heavy alcohol use.
Structural Problems
Appendicitis can cause the appendix to burst,
spreading infection throughout the abdomen,
which can lead to death.
Appendicitis
Inflammation of the appendix
Structural Problems
Peptic ulcers can be caused by a bacterial
infection or the overuse of aspirin. They can cause
stomach bleeding.
Peptic ulcer
A sore in the lining of the
digestive tract
Structural Problems
Cirrhosis is caused by
prolonged heavy
alcohol use. It can lead
to liver failure and may
cause death.
After You Read
Reviewing Facts and Vocabulary
1. What functions of the digestive system
take place in the small intestine?
Digestion and absorption
After You Read
Reviewing Facts and Vocabulary
2. Describe the actions that cause food to
move through the digestive tract.
A series of involuntary muscle contractions,
called peristalsis
After You Read
Reviewing Facts and Vocabulary
3. What are three behaviors that help
prevent indigestion?
Sample answer: Eat less food, eat meals
slowly, and chew food thoroughly.