Download Digestive system 201.. - Junction Hill C

• Your digestive system is a
group of organs that work
together to digest food so
that it can be used by the
body
• The human digestive
tract may be more than 9
meters long
• Food is digested as it
passes through the
digestive tract
• The liver, gallbladder,
pancreas, and salivary
glands secrete
substances that are
used in digestion
Two Types of Digestion
• Mechanical
– The breaking, crushing, and mashing of
food is called mechanical digestion
• Chemical
– In chemical digestion, large molecules
are broken down into nutrients.
– Nutrients are substances in food that the
body needs for normal growth,
maintenance, and repair
Three major types of
nutrients
• Carbohydrates
• Proteins
• Fats
• Simple carbohydrates are sugars such as
glucose, fructose, lactose, and sucrose.
• Some simple sugars can be easily
identified, such as honey, corn syrup,
and maple syrup. But others are tougher
to find, especially in frozen dinners, white
breads, cereal, and yogurt.
• Excluding fruits and vegetables, most
simple carbohydrates do not have much
nutritional value
• Complex carbohydrates are long chains
of glucose molecules.
• They are usually comprised of starches,
which is the product of carbohydrate
storage in plants.
• The major source of complex
carbohydrates are whole grain products,
such as whole wheat bread, brown rice,
pasta, and beans.
• Proteins are a combination of many
chemicals called amino acids. Scientists
have found 20 different amino acids in
protein, and these 20 amino acids can
combine in lots of ways - in fact, they have
joined together to make thousands of
different proteins!
• Some types of amino acids are made by
your body. These are called nonessential
amino acids, and there are 11 of them. The
essential amino acids - all nine of them must come from food.
• Protein's biggest job is to build up, keep
up, and replace the tissues in your body.
Your muscles, your organs, even some of
your hormones are made up mostly of
protein.
• Protein helps your body in other ways, too.
It likes to make sure things get around by
making hemoglobin, the part of red blood
cells that carries oxygen to every part of
your body. It even makes antibodies, the
cells that fight off infection and disease.
• Proteins are in tasty foods like meat,
chicken, fish, eggs, and nuts. Dairy
products like cheese, milk, and yogurt are
good sources of protein
• In vegetable oil you see oils created from
different seeds and nuts. There is corn oil,
peanut oil, canola oil, olive oil... All seeds and
nuts contain some amount of oil, because oil is a
very good way to store energy.
• In different cuts of meat you see them outlined
by a layer of white, solid fat created by the animal
to store energy.
• In dairy you see butter and margarine -- fat made
from cream or vegetable oils, respectively
• Special substances called enzymes
break some nutrients into smaller
particles that the body can use.
• For example, proteins are too large to
be absorbed into the bloodstream,
but enzymes chop up the protein
chain into amino acids.
• These amino acids are small enough
to pass into the bloodstream
• Chewing creates
small, slippery pieces
of food that are easier
to swallow than big,
dry pieces
• Small pieces of food
are easier to digest.
Through the Teeth
• Teeth are very important
organs for mechanical
digestion
• With the help of strong
muscles and your jaw
bones, teeth are able to
break and grind food
• The outermost layer of a
tooth, the enamel, is the
hardest material in the
body.
• Enamel protects nerves
and softer material inside
the tooth
Different kinds of teeth
• The molars in the back
are well suited for
grinding food
• The premolars are
perfect for mashing
food
• The sharp teeth at the
front of your mouth,
the incisors and
canines, are for
shredding food
Over the gums
• As you chew, the food gets mixed
with a liquid called saliva.
• Saliva is made in salivary glands
located in and around the mouth
• Saliva contains an enzyme that
begins the chemical digestion of
carbohydrates.
• Saliva turns complex carbohydrates
into simple sugars.
Look out Stomach,
Here it Comes!
• Once the food has been
reduced to a soft mush, the
tongue pushes it into the
throat, which leads to a
long, straight tube called
the esophagus.
• The esophagus squeezed
the mass of food with
rhythmic muscle
contractions called
peristalsis
• Peristalsis forces the food
into the stomach.
• The stomach is a
muscular, baglike organ
attached to the lower
end of the esophagus.
• The stomach continues
the physical digestion of
your meal by squeezing
its contents with
muscular contractions.
• While squeezing is going on in the stomach, tiny glands
produce enzymes and acid.
• Acids and enzymes work together to break food into
nutrients
• Stomach acid also kills most bacteria that you might
swallow with your food
• After a few hours of combined physical and chemical
action, your food is reduced to a soupy mixture called
chyme.
• Chyme is slowly released into the small
intestine through a small ring of muscle that
works like a valve.
• This valve keeps food in the stomach until it
has been thoroughly mixed with digestive
fluids
• Then the valve opens and closes, letting a
small amount of chyme squirt into the small
intestine each time.
• Releasing chyme slowly from the stomach give
the intestine more time to mix the chyme with
fluids from the liver and pancreas.
• A thick substance called
mucus covers the stomach’s
lining and offers some
protection from its harsh
environment.
• However, the acids still
damage the lining, and the
entire lining must be
replaced every few days.
• The small intestine is a muscular
tube that is about 2.5 cm (about 1
inch) in diameter.
If you stretched
out your small
intestine, it
would be about 6
meters (20 feet)
•
If you flattened out the
surface of the small
intestine, it would be
larger than a tennis
court.
• The inside wall of the small intestine is
covered with fingerlike projections
called villi
• The villi are covered with tiny nutrientabsorbing cells
• These cells allow the nutrients to enter
• Most chemical digestion
takes place in the small
intestine
• Chyme from the
stomach moves very
slowly through the small
intestine by peristalsis.
• Proteins, carbohydrates,
and fats In the chyme
are digested with the
help of enzymes
produced in the small
intestine and the
pancreas.
• The pancreas is a fish-shaped
organ located between the
stomach and small intestine.
• It makes pancreatic juice that
flows into the small intestine.
• This juice contains digestive
enzymes and bicarbonate that
neutralizes the acid in chyme
• The liver is a large
reddish brown organ that
helps with digestion.
• A human liver can be as
large as a football.
• Your liver is located
toward your right side,
slightly higher than your
stomach
Functions of the Liver
1. Your liver makes a green liquid
called bile that is used in fat
digestion
2. Your liver stores nutrients
3. Your liver breaks down toxic
substances in the blood
4. Your liver makes cholesterol for
cell membranes
• Although bile is made by the liver, it
is temporarily stored in a small
baglike organ called the gallbladder.
• Bile is squeezed from the
gallbladder into the small intestine,
where it breaks up large fat droplets
into very small droplets
• After nutrients are broken down,
they are absorbed into the
bloodstream and carried through
the body
• Nutrients that are not needed right
away are stored in the liver.
• The liver then releases the stored
nutrients into the bloodstream as
needed.
• The liver also captures and
detoxifies many substances in the
body.
• The large intestine is the organ of
the digestive system that stores,
compacts, and then eliminates
indigestible material from the
body
• The large intestine has a diameter
of about 7.5cm (3 inches) and is
about 1.5 meters (2 feet) long.
• It takes food
approximately 24 hours
to complete the digestive
journey
Problems in the Digestive
System
• Disorders of the digestive system are
frequently related to eating behaviors.
• However, digestive problems can also be
caused by diseases.
• Some common digestive disorders are
– Heartburn
– Constipation and Diarrhea
– Colon Cancer
– Gastric Ulcer
• Backflow of chyme from the
stomach to the esophagus
causes a burning pain in
the chest called heartburn.
• Eating too much, eating
right before going to bed,
and eating very acidic
foods sometimes cause
heartburn.
• When the body does not get
enough fiber, water, or exercise, the
contents of the large intestine can
become dry.
• Bowel movements become difficult
and less frequent
• This condition is called
constipation.
• When bowel movements are frequency
and watery, the condition is called
diarrhea.
• Diarrhea occurs when too little water is
removed from digested food in the large
intestine
• Diarrhea may cause dehydration and is
especially dangerous for infants and
small children
• Colon cancer is a serious disease of the
digestive tract that can lead to death
• The colon is the long tubular portion of the
large intestine.
• When certain colon cells divide
uncontrollably, a tumor forms
• Tumors interfere with the normal functioning
of organs.
• An open sore in the stomach lining is
called a gastric ulcer
• Gastric ulcers are often caused by
bacteria and can be treated
successfully with antibiotics