|
All
about digestion - Part I
Adrian
Whyte and Joanna Johnson, Contributor
 |
| A
group of students at the St. Jago
High School takes a break from
classes to share a laugh. - Ricardo
Makyn |
Digestion
occurs in two stages:
1)
Mechanical digestion
2)
Chemical digestion
MECHANICAL
DIGESTION
This
process occurs in the mouth where
the teeth physical break (cut and
chew) the food into smaller pieces
that have a larger surface area, to
facilitate chemical digestion.
QUESTION
What
are the four types of teeth you will
mainly find in mammals. State their
function.
ANSWER
| Types
of teeth |
Function
|
| Incisors |
Used
for cutting and biting off pieces
of food. |
|
Canines
|
Used
for biting and tearing off pieces
of food. |
|
Premolars
|
These
are the cheek teeth and are used
for the crushing and chewing of
food. |
|
Molars
|
These
are the cheek teeth and are used
for the crushing and chewing of
food. |
THE
STRUCTURE OF THE TOOTH
The
general structure of the tooth consists
of an exposed crown and a root, buried
in the gum and jaw. The crown is usually
at least partly covered by an outer
layer of an especially hard substance
related to bone called enamel. Beneath
the enamel is an intermediate layer
of material called dentine, which
is also similar to bone and is not
nearly as hard as enamel. It surrounds
an inner pulp cavity, which serves
as blood and nerve supply for the
tooth. Blood vessels and nerves reach
the pulp cavity through a channel,
the root canal that penetrates the
root.
CHEMICAL
DIGESTION
This
involves the use of enzymes. Enzymes
facilitate the break down of complex
molecules, which are too large to
pass through the walls of the alimentary
canal, into smaller molecules, which
will readily do so.
Recall
that enzymes are specific in nature,
and owing to this difference, enzymes
are needed for each type of food in
the diet.
| Where
the enzymes are made |
Name
of enzymes |
Where
they work |
Function
of enzymes |
|
| Salivary
gland |
amylase |
mouth |
starch
---- maltose |
|
|
Stomach
wall
|
pepsin |
stomach |
protein
---polypeptides |
|
|
Pancreas
|
amylase |
small
intestine |
starch
---- maltose |
|
| |
trypsin |
small
intestine |
protein
--- polypeptides
|
|
| |
lipase
|
small
intestine |
fats
fatty acid -- and glycerol |
|
|
Intestine
wall
|
maltase |
small
intestine |
maltose
---- glucose |
|
| |
|
small
intestine |
maltose
---- gluecose |
|
| |
peptidase
|
small
intestine |
polypeptides----
amino acids |
|
LAB
EXERCISE
Here
is an activity that you can try at
home.
1.
Get a small piece of water cracker.
2.
Chew the cracker for five minutes.
3.
Keep it in your mouth for as long
as possible.
4.
Make observations on the taste after
one, three and five minutes.
5.
Compare the texture of the cracker
before chewing and after five minutes
of chewing.
*
Adrian Whyte and Joanna Johnson
teach Biology at Ardenne High School.
|
