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- Characteristics Of Life:
C. = Cells
H. = Homeostasis – Maintain Balance
A. = Adapt to environment
R. = Reproduce
G. = Grow and develop
E. = Run energy transformations
R. = Respond
- For organisms to grow, repair
themselves, fuel their cells, reproduce,
and undergo cell division; they must
acquire building blocks and energy-rich
molecules from their environment.

12-2
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
INGESTION
– Act of
taking in food
and drink
into body
DIGESTION
BREAKDOWN –
Chemical and
Physical
ABSORPTION
– Nutrient
molecules
absorbed from
gut into
bloodstream
ELIMINATION
– Ridding the
body of
undigested food
waste

During Mechanical digestion food is broken down to
create more surface. Food is mushed up and broken
apart. Example. Chewing with teeth or churning food
in stomach. No new molecules are produced!

During Chemical digestion food
molecules are broken down by
enzymes to produce brand new
smaller molecules. This requires
digestive enzymes and water as a
substrate to run these hydrolysis
reactions.

In many parts of the digestive tract both types of
digestion are happening simultaneously. For example:
in the stomach.

Fig. 12.1
Our goal today is to get more
familiar with the anatomy (parts)
and physiology (function) of the
digestive tract.

Fig. 12.2a
The mouth is a good
starting point: different
teeth have different
functions

Fig. 12.2b
Two
main
regions
of a
tooth

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• Tonsils at the back sides of the mouth protect against
infections.
• Tonsillitis results when the tonsils become inflamed;
the infection can spread to the middle ears.
• Three pairs of salivary glands (parotid, sublingual,
submandibular) send saliva (containing salivary
amylase for digestion of starch to maltose) into the
mouth.

Fig. 12.3
During
swallowing, we
need to prevent
food from going
up into the
nasopharynx or
into the trachea.

Fig. 12.4
Why do you think that it is important that the digestive tract
is lubricated on both the inside (mucosa puts out mucus) as
well as on the outside (serosa puts out lubricant)?

12-12
• The esophagus is a muscular
tube that conducts food through
the thoracic cavity and
diaphragm into the stomach.
• Peristalsis begins in the
esophagus; this collapsed tube
moves the bolus of food
downward after swallowing
occurs.
• Heartburn is a burning pain
when acidic stomach contents
enter the esophagus.

Fig. 12.5

1. Storage of a meal – most expanded structure along the
alimentary canal

2. Mechanical Digestion of food – Stomach is very muscular
and it squeezes to churn and mix food to physically break it
down

3. Chemical Digestion of food – Adds PEPSIN enzyme to
start chemically breaking proteins into small peptide
chains

4. Protection against Germs – HCl (acid) helps activate
enzymes but it also helps kill many of the bacteria that we
ingest.

Fig. 12.6

The Duodenum is only
about 45 cm (18 inches
long) but it plays a couple
of very important roles:
1. Receives incoming
Stomach Chyme,
Pancreatic Juices and
Bile from Liver and Gall
bladder.
2. Secretes digestive juces/enzymes from
duodenal glands

1. Receives undigested waste and helps absorb fluid
from those wastes back into the bloodstream, to help
keep us from dehydrating
2. Helps compact and form
feces.
3. Harbours helpful bacteria which
can further break down wastes to
free up minerals and some bacteria
will help produce and free up some
vitamins, such as Vitamin K