Transcript Digestive System Power point Powerpoint

What is Digestion?
A. The process of
breaking down large
food molecules into
smaller molecules
that the body can use
B. There are 2 types of
digestion:
– Mechanical
– Chemical
Mechanical Digestion
Chemical Digestion
C. The Path of Food Through the Digestive
System:
• Organs include: mouth,
pharynx, esophagus,
stomach, small and large
intestines and anus
B. The Mouth
• Food enters the mouth and
both mechanical and
chemical digestion begins.
• This is the primary source
of carbohydrate digestion
C. The Pharynx
• After food is swallowed, it enters the
pharynx (throat) and passes into the
esophagus
The Pharynx
D. The Esophagus
• A short tube (~ 25
cm long) between
the mouth and the
stomach
• Lined with mucus
which helps food
move easily
through tube
*How does Food get to the
stomach?
•
•
•
Gravity – helps food
move down
Peristalsis – muscle
contractions help
move food down the
esophagus
Peristalsis can push
against gravity, so
that you can
swallow even when
you are standing on
your head!
*What happens if air & food enter
the body at the same time?
• Air goes into the
windpipe (trachea)
• Food enters the
esophagus
• The Epiglottis is a flap of
tissue covering the
opening of the trachea to
help prevent food/water
from entering the lungs
E. The Stomach
• The stomach works by
both mechanical and
chemical digestion
• We call this “Churn and
Burn”
• The “churn” part refers
to Mechanical digestion–
• Remember: churn and burn. The “burn” part
refers to Chemical digestion
• The stomach secretes a liquid known as gastric juice
which is composed of water, HCl and enzymes
• An enzyme called pepsin also transforms proteins into
amino acids.
• Lipids are metabolized with the help of an enzyme
called lipase. But most of the lipid digestion occurs in
the small intestine.
F. Small Intestine (S.I.)
• A narrow muscular tube
about 20 feet long and 2.5
cm wide
• Food moves through by
peristalsis
• Chemical digestion of
starches, proteins, and
fats is completed in the
S.I by digestive juices
secreted from the liver,
pancreas, and the SI itself
Increased absorption of food: *Villi
• Absorption of the broken
down food takes place in
the wall of the SI
• The inner lining is folded
and has millions of tiny
fingerlike projections
called VILLI
• These villi help food pass
into the bloodstream
SI
The Large Intestine is
made up of 3 parts:
1.The Cecum
2.The Colon
3.The Rectum
The Cecum
• The cecum is a small sac at the
beginning of the large intestine.
The Colon: The Holder
• The function of
the colon is to
absorb water to
maintain the
consistency of the
feces.
The Rectum: The kicker
• The waste or feces that
are expelled from the
large intestine have no
nutritional value.
• The body has already
taken everything out of
the food that it can use.
Pancreas
• The pancreas does
not digest food but it
makes most of the
enzymes for your
body.
• The pancreas sends
the enzymes to the
small intestine.
Liver
• The liver is the largest
organ in the body. It weighs
~3 pounds.
Functions:
• It is responsible for cleaning
up dead blood cells.
• It detoxifies substances
such as alcohol or some
drugs.
• The liver also serves a very
important role in the
digestion of fats.
Bile
• The liver produces a
liquid known as bile
which is stored in the gall
bladder.
• Bile helps to break the
fats into smaller pieces.
• It is secreted in response
to food in the stomach
a. Indigestion
• Indigestion is commonly referred
to as “heartburn” even though it
has nothing to do with the heart!
• The burning feeling is caused by
acid and other juices that digest
food leaking up (refluxing) from
the stomach into the esophagus
• The acid manages to escape when
the valve (lower esophageal
sphincter) at the top of the
stomach stops working properly.
• The valve is meant to let food and
fluid down, and nothing back up.
b. Ulcer
• When stomach acids
eat away at the lining
of the stomach and
create a hole or sore
c. Appendicitis
• Inflammation of the
appendix
• The appendix is located
where the SI and the LI
join
• It occurs when food gets
trapped in the appendix
and becomes infected
with bacteria
d. Diarrhea
• Occurs when water is
not reabsorbed in the
large intestine
because peristalsis is
moving the waste
through too quickly
• Can be brought on
by stress, bacteria, or
viruses
e. Constipation
• When peristalsis
actions in the large
intestine are too slow
or too weak
• Waste moves slowly
and water in the wastes
are totally absorbed
• The waste becomes
more solid than normal
and is difficult to
eliminate