Download The Human Digestive System

THE HUMAN DIGESTIVE SYSTEM

When you eat foods such as bread, meat,
and vegetables - they
are not in a form that
the body can use as
nourishment.

Food and drink
consumed must be
broken down into
smaller molecules so
that they can be
absorbed into the body


The Digestive Tract is a series
of hollow organs joined in a
long, twisted tube from the
mouth to the anus.
Oral
Cavity
(mouth)
Organs involved:






Mouth
Esophagus
Stomach
Liver
Pancreas
Small Intestine
Large Intestine
Rectum
Small
Intestine
Esophagus
E
DIGESTIVE ENZYMES

Digestive enzymes help to break the food into
smaller pieces so that it is easier to digest
Enzymes Video
The entire length of the
digestive tract is lined with
epithelial tissue.
Contains lots of goblet
cells which secrete mucus.
The mucus does two things
1. Protects tract from
digestive enzymes
2. Moves materials along
the tube
Digestion Video
Bill Nye
Digestion begins in the oral cavity (mouth) where 2
types of digestion take place:
&
Mechanical Digestion:
Chewing breaks up large
pieces of food into smaller
ones
FOOD
Chemical Digestion: The Human Body
releases 1 – 1.5L of saliva per day from
glands in your cheeks (salivary glands)
Saliva converts Carbohydrates into simple
sugars like Glucose.
Glucose
Saliva also contains mucus and water
which makes food easier to swallow.
Chewing Crackers Part 2 – Copy down a
new chart and record your observations
Place a cracker in your mouth and let it sit for 1.5 min. before
chewing
What it feels like initially
in your mouth
- Is it sweet/bland?
What is feels like after 1
min. in your mouth
- Is it sweet/bland?
What it feels like after 1.5
min. in your mouth
What it feels like when
you chew it

What was the main texture (feeling)
difference in your mouth between chewing
right away and waiting before?

When the cracker is in your mouth your
saliva is starting to break it down  Get’s
softer
Food enters the
esophagus which is a
narrow, muscular tube
about 25 cm long.
Food is swallowed by
voluntary action (you
control) of the tongue.
Ruler
The Trachea (Wind Pipe)
and Esophagus are
connected: – Why does food
not go into lungs?
There is a small flap
consisting of connective
tissue
which prevents food from
entering the trachea when
swallowing (Epiglottis).
Trachea
The wall of the esophagus is
made up of two layers of
smooth muscles which push
the food down into the
stomach
If a person were to swallow
while being upside down you
could see the muscles in
action.
1)Place your hand over your
throat then swallow
- What do you feel?
2)Turn to someone next to you.
• Have your partner tilt their
head up
• Watch their neck as they
swallow – reverse roles
The stomach acts as a
storage place for food as well
as a place of digestion.
It is also described as an
elastic “bag” made
of muscle which expands.
- It can hold up to 4L
Chemical Digestion
:
-Stomach cells produce acid
(HCl) which helps break down
proteins
-The stomach cells also
secrete mucus to protect its
lining from the acid.
- Sometimes this acid exits
the stomach and enter the
esophagus
Can lead to heart burn
Mechanical Digestion: The
muscles of the stomach wall
contract and expand to churn
food and move it towards the
small intestine
The growling sound you
sometimes here is your
stomach moving.
This is smooth muscle
The small intestine further splits food into smaller
pieces. Most of the nutrients we take in are
absorbed in the small intestine.
Blood
Small Intestine Video
Recieves many digestive enzymes from pancreas
and liver
• Move food through
using smooth muscle
cell contraction
• The lining of the
intestine secretes
protective mucus
Sometimes called the Colon
Its function is to absorb water and some vitamins
from the remaining food
, as well as store the useless nutrients and wastes
before they are flushed from the body.
It has a much larger
diameter, that’s why it is
called the large intestine
The rectum acts as a temporary storage
facility for feces
before it is excreted from the body.
ACCESSORY ORGANS

The Liver, Pancreas, and Gall Bladder all help with
the digestion by supplying digestive enzymes

The Liver also produces bile which helps digest
fats

These substances are delivered into the small
intestine
- It produces bile which is stored in the gall
bladder. Bile is then sent to the small intestine
to break down fats.
Gall Bladder
• The pancreas is involved in
supplying enzymes required for
digestion directly into the small
intestine.
• It also secretes a hormone called
insulin directly into the blood
stream.
 Insulin causes most of the
body's cells to take up circulating
glucose (cell food) from the blood.
Insulin Video