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The Human Digestive System
Unit 2
The Basic Functions of the Digestive System
 Ingestion-taking nutrients into the body, i.e.,
eating

Digestion-the mechanical and chemical
breakdown of food into a usable form

Absorption-the movement of molecules
through the mucosal lining of the stomach
and small intestine, and into the blood

Excretion-the removal of solid waste from the
body

Sphincters-circular muscles that contract and
move food through the GI tract.
Quick Write/Pair Share

What is the difference between Ingestions,
Digestion, and Absorption?

Share this with a neighbor, are your answers
the same?
The Digestive Organs
Mouth
Pharynx
Larynx
Esophagus
Stomach
Small Intestines – 3
duodenum, jejunum, ileum
 Large Intestines – 4
ascending, transverse, descending, sigmoid
 Rectum
 Anus






Quick Write/Pair Share

From this list of organs, which ones sound like
they should belong to another body system?
Which ones and which systems would you pair
them with?

Share this with a neighbor, are your answers
the same?
Mouth
Digestion starts here!!!

Mechanical Digestion- The breaking down
physically of food by chewing (mastication).
First stage of digestion.

Chemical Digestion-Breaking down and
converting of food chemically by enzymes
into a suitable substance for absorption. In
the mouth, Chemical Digestion of
Carbohydrates begin.
Pharynx
 Also
called the throat
Nasopharynx
Oropharynx
Laryngopharynx
A
passageway for food, liquids, and air
Esophagus
 Muscular
trachea
tube located behind the
(About 10 inches long)
 Transports
stomach
 Has
food from the pharynx to the
both Upper and Lower esophageal
sphincters
Stomach
 J-shaped
pouch located below the
diaphragm
 Chemical
digestion of protein occurs in
the stomach due to gastric juice
secretion
 Mechanical
digestion occurs in the
stomach due to maceration (churning).
Three layers of muscles in the stomach
create the movement of maceration.
Quick Write/Pair Share
 What
is the difference between
mastication and maceration? Where
does each occur?
 Share
this with a neighbor, are your
answers the same?
Small Intestines
Chemical digestion of nutrients and
absorption of nutrients is completed in
the small intestines
Three divisions of the small intestines:


◦
◦
◦
Duodenum – first portion of the small
intestine where the majority of chemical
digestion occurs.
Jejunum – middle portion of the small
intestine where the majority of absorption
of nutrients occurs.
Ileum – final portion of the small intestine
where absorption occurs.
Large Intestines
 The
large intestines are the last part of
the digestive system.
 Absorption
of water, vitamins,
electrolytes, production of vitamin K, and
formation of feces occurs in the large
intestines.
 Consists
of the Ascending, Transverse,
Descending, and Sigmoid colons.
Rectum
 The
last portion of the large intestine
which functions as a temporary storage
of solid wastes before excretion.
Anus

The final portion of the rectum where
solid waste is excreted from the body.