The Digestive
System
Bleecker-Style 
Table of Contents
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Cells, Tissues, Organs, Organ Systems
Introduction to the Digestive System
What is Digestion?
2 Phases of Digestion
4 Components of Digestion
The Organs of Digestion
How the Body is Organized
1. Cellular Level
2. Tissue level
3. Organ Level
- Individual cells
are the basic
building blocks of
life
- Tissue is formed - An organ is a
when groups of
system of tissues
cells act together working together
4. System Level
- Many organs
acting together
form a system, such
as the DIGESTIVE
SYSTEM
Introduction to the Digestive
System
• The digestive
system is an organ
system that
ingests food,
breaks it down into
smaller chemical
units, and absorbs
the nutrient
molecules.
What is Digestion?
• Digestion is the mechanical and
chemical breakdown of food into
molecules small enough for the
body to absorb.
2 Phases of Digestion
1.
Mechanical Digestion – begins in the
mouth where the food is chewed.
- Saliva = watery fluid making it easier to
swallow. Also some enzymatic
digestion of starch
2.
Chemical Digestion – occurs in the mouth
and the stomach. HCl produced by the
stomach cells.
4 Components of
Digestion
1. Ingestion – the intake of nutrients
2. Digestion – the breakdown of
organic molecules
3. Absorption – the transport of
digested nutrients to body tissues
4. Egestion – the removal of materials
from food that the body cannot
digest
The Organs of
Digestion
Mouth
 Physical digestion begins
 Food is chewed into a bolus and
mixed with saliva
 Initial carbohydrate digestion
Parts of the Mouth
20 Baby Teeth
32 Adult Teeth
Wisdom Teeth …
Salivary Glands in the Mouth
Swallowing and the Epiglottis
Air enters via
pharynx
The epiglottis is a
flap of tissue that
has a very important
job
It covers the trachea
when swallowing to
prevent food to lungs
It covers the
esophagus when we
breath, so air goes
to lungs
Esophagus
• Peristaltic
contractions
move the food
from the mouth
to the stomach
through the
esophagus.
Stomach
 Food storage
 Initial protein
digestion
 Mechanical
digestion grinding
by muscles
 Chemical
breakdown of food
by HCl
Stomach Protection from
Acid
 What protects stomach
from digesting itself?
 HCl is nasty!
 Answer: cells also
secrete mucus that acts
as a barrier!
Stomach Ulcers
OUCH!
Small Intestine
 Site of the majority
of digestion and
absorption
 Digestion of proteins,
carbohydrates, and
lipids
 Folds of small
intestine increase the
SA for absorbing
nutrients
Small Intestine in Cross
Section
SA is increased by
fingerlike projections called
VILLI
These do the actual
absorbing of fats, proteins
and carbohydrates
Villi Close up
Small Intestine
– 3 Sections
Stomach
to
1. Duodenum
to
2. Jejenum
to
3. Ileum
Focus on the Duodemum
Enzyme Action in Duodemum
1. Bile from Liver is received from the
Gallbladder (green)
• The bile is used as an emulsifier to help
the body absorb fats
2. Lipase from the Pancreas breaks down fats
into fatty acids
3. Trypsin is activated by acid from the
stomach, and digests the protein further into
amino acids
4. Pancreatic Amylase – digests carbohydrates
Regulating Digestive Secretions
1. Gastrin
• Produced by stomach when churns
• Inhibited by duodenal response
2. Duodenum secretes GIP (gastro-inhibatory
peptides) to turn off gastrin production in
stomach (neg loop)
3. Duodenum also produces CCK (cholecystokinin) in
response to partly digested fat and protein as
well as secretin that increase the output of
bile from liver and pancreatic juice.
Classic Feeback
Loop
- CCK stimulates
liver and pancreas
Note that in Stomach, HCl
Activates an Enzyme
1. Acid activates Pepsin so
that protein is digested.
2. Hormone GASTRIN is
secreted and sent
through blood to brain to
suppress appetite!
Pancreas
•
Releases enzymes
such as
1. Amylase
2. Lipase
into the small
intestine to aid in
digestion
Liver
 Produces bile salts
which emulsify fats
 Storehouse for
glycogen(starch) and
vitamins
 Detoxifies many
substances in the
body (alcohol,
poisons, etc)
Gall Bladder
• Stores bile salts
Large Intestine
1. Stores food wastes long
enough to reabsorb
water
2. Forms the stool, aka
POOP
3. Houses bacteria which
use waste materials to
synthesize vitamins
3 Regions of Large Intestine you
must Know
AssiGnments
•
Ensure that The Breakdown Video
Wkst. is done and handed in before
you leave.
•
Complete Chp Review on pg. 148
#C1,C2,C4,C6,C7.
•
Readings: (relax, they’re like the
notes we just did)
Chapter notes for 7.3 & 7.4 (pg’s
140-148)
•
•
Color the rest of the digestive
system handout! Know it, because
you will be quizzed on it 