DIGESTION
By Erin and Courtney 
Evolution
• Two types of digestion
– Intracellular: Break down of
macromolecules takes place within the
cell.
– Extracellular: Break down of
macromolecules takes place outside of the
cell
•Advantages of extracellular digestion with evolution
•Allowed organisms to break down larger molecules, and gave
a wider variety of food choices.
So who does what?
Protists : Obtain their
food by filter feeding,
or absorbing there food
by engulfing it to form
a food vacuole. Food is
then taken within the
cell through
endocytosis.
Worms: Have a sac-like
gut, in which they take
in their food and digest
extracellular
Mollusks: Have a gut
into which is also used
to digest their food
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Arthropods: Complete gut
with regional
specialization. The
foregut, Midgut, and
Hindgut which use
extracellular digestion
in order to be completed
Echinoderms: They
exhibit a wide range of
feeding habits including;
suspension feeders,
deposit feeders,
carnivores, browsers and
parasites. They mostly
digest their food
externally.
DIGESTION IS COOL!
• The digestion system has one goal in
mind… it wants to convert food into
energy the body can use to grow and
maintain itself. It has evolved to be
more efficient by taking as many
nutrients out of the food as possible,
and leaving the rest to be excreted.
• It’s important because in order for the
cells to absorb all the important
nutrients, that slice of pizza, must be
converted into the smallest particle
possible so that it can be transferred
into the blood stream and carried
throughout the body to help build and
nourish cells, as well as provide
energy.
Mouth
Tongue
Liver
Gallbladder
Appendix
Rectum
Anal Canal
Pharynx
Salivary Glands
Esophagus
Stomach
Pancreas
Small Intestine
Large Intestine
How does it work?
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Digestion starts the moment
food gets into the mouth,
through mechanical digestion.
Saliva aids in digestion with
the help of enzymes, by
breaking down the chemicals
in food, to make it mushy
enough to swallow. The
tongue aids in this process by
pushing the food around to
various teeth, and then
eventually toward the back of
your throat into the opening of
the esophagus, the second
part of your digestive tract.
The esophagus is about 10
inches wide. As food travels
down, the epiglottis (a small
flap) covers the windpipe, or
trachea. This allows the food
to continue down the right
path, toward the stomach.
This process is done through
muscles that move the food in
a wave like motion to push it
down. It takes about 2-3
seconds.
STOMACH
• 3 main function
– Store food
– Break down the
food, liquefy
– Empty liquid
into small
intestine
This is all done through a somewhat simple process. Gastric juices that come from the
stomach walls and the wall muscles, help churn the food and break it down. The gastric juices
also aid in killing any harmful bacteria that may be in the food.
Chemical Digestion
• Chemical digestion of fats, proteins, and carbohydrates is
completed in the small intestine by intestinal enzymes and,
pancreatic enzymes. Alkaline pancreatic juice neutralizes acid
chyme and provides the proper environment for the operation of
enzymes. Both pancreatic Juice and bile are necessary for normal
fat breakdown and absorption. Bile acts as a fat emulsifier.
Secretin and cholecystokinin, hormones produced by the small
intestine, stimulate release of bile and pancreatic juice.
Segmental movements mix foods; peristaltic movements move
foodstuffs along the small intestine. Most nutrient absorption
occurs by active transport into the capillary blood of the villi. Fats
are absorbed by diffusion into both capillary blood and lacteals
in the villi.
Small intestine..well kinda
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Once in the small intestine, the absorption of
vitamins, minerals, proteins, carbohydrates, and
fats takes place.
With the help of the pancreas, liver, and
gallbladder.
With the help of the juices produced, the food is
able to be digested, and nutrients absorbed.
Function of Juices:
– Pancreas-> helps digest fats and proteins.
– Liver-> (called bile) help absorb fats into bloodstream.
– Gallbladder-> warehouse for bile, houses it until needed.
•
This process takes 4 hours, ends up as thin watery
mixture, and it’s nutrients are able to be absorbed
into the bloodstream. I don’t know about you, but
that time is worth it to me!
* The small intestine is actually 22 feet
long…that’s 22 notebooks lined up!
Last but not least
•The final steps to digestion.
•The nutrient rich blood enters the liver, where it goes
through a processing similar to email.
•Determines the junk mail, or wastes.
•Either will be excreted or turned into more bile.
•Determines what nutrients are to carried throughout the
body, or to be stored for later use as energy.
Where do the wastes go?
•To the large intestine!
•Once in the large intestine, it has one final place to
absorb any sort of nutrition by the colon.
•All other wastes are pushed through the large intestine
until it becomes a solid and reaches the rectum, and then
comes out of the anus.
Buddy System
•
Circulatory System
•
Skeletal System
•
The Digestive system works with the Circulatory system because the
Digestive system makes nutrients to give to the cells. The cells turn it into
energy. The body, needs energy, so the Circulatory system is like a delivery
system. The Circulatory system meets with the cells and the blood stream
dellivars the energy to the other parts of the body.
The Digestive system needs the food to be grind into tiny mushy piece called
pulp, so it is easier to swallow and digest. Also the ribs cover the digestive
system’s organs and protect them.
•
Muscular System
•
Respiratory System
The Digestive system works with the Muscular system when you need to chew
your food. Muscles move your jaw bone to chew up the food. Also there are
muscles called the sphincter muscles, which lets food into one organ to
another. There are two intestinal muscles, that makes the ntestines move the
food from the small intestine to the large intestine. There is an other muscle
called the esophagus muscle which moves food down the esophagus to the
stomach.
The Digestive system works with the Respiratory system for example, when
you gulp too much air and it goes down the esophagus and into your stomach
the lungs give air and you burp, so too much air won’t hurt your stomach.
HOMEOSTASIS
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Maintaining Homeostasis: pH Balance
Although the digestive system may seem simple, it is complex. Maintenance
relies on a balance of pH and helpful bacteria to maintain homeostasis. Both
acidic and basic pHs are required at various points in digestion to maintain
balance during the process. Saliva in the mouth, the starting point of
digestion, is only mildly acidic for the purpose of initially breaking down the
food without damaging the teeth or delicate throat tissue. The stomach, on
the other hand, needs to be highly acidic to jump-start the breakdown
process as well as act as a defense for the body against any harmful
bacteria or other intruders. To balance things out on the basic side, it is
important that the small intestine has a high pH, because most of the
enzymes used in digestion can't function properly in an acidic environment.
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Maintaining Homeostasis: Helpful Bacteria
Helpful bacteria also are needed to maintain homeostasis in the digestive
system. These bacteria aid in digestion, help produce vitamins, help
formulate excrement and guard against harmful bacteria. When the bacteria
population in a digestive tract is off the host will notice a change in the pace
and quality of digestion.
Nutrition~
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Proteins - essential to growth and repair of muscle and other
body tissues
Fats - one source of energy and important in relation to fat
soluble vitamins
Carbohydrates - our main source of energy
Minerals - those inorganic elements occurring in the body
and which are critical to its normal functions
Vitamins - water and fat soluble vitamins play important
roles in many chemical processes in the body
Water - essential to normal body function - as a vehicle for
carrying other nutrients and because 60% of the human body
is water
Roughage - the fibrous indigestible portion of our diet
essential to health of the digestive system
57% Carbohydrates (sugar, sweets, bread, cakes)
30% Fats (dairy products, oil)
13% Protein (eggs, milk, meat, poultry, fish)
Problems?
Celiac disease: Celiac disease
is a digestive disease that
damages the small intestine
and interferes with
absorption of nutrients from
food. People who have celiac
disease cannot tolerate
gluten, a protein in wheat,
rye, and barley.
Gastroesophageal reflux disease (GERD)
is a more serious form of
gastroesophageal reflux (GER), which is
common. GER occurs when the lower
esophageal sphincter (LES) opens
spontaneously, for varying periods of
time, or does not close properly and
stomach contents rise up into the
esophagus. AKA: acid reflux or acid
regurgitation
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Lactose intolerance: is the inability or
insufficient ability to digest lactose, a
sugar found in milk and milk products.
Lactose intolerance is caused by a
deficiency of the enzyme lactase, which is
produced by the cells lining the small
intestine.
MOVIEEEEEEEE!!!!
• http://www.youtube.com/watch?v=Z7xKYNz9
AS0&feature=related
• http://youtu.be/Z7xKYNz9AS0
Cool…and your point?
• It is the largest and most evolved system in
our bodies
• With it the body is able to break down
important molecules, and well…dispose of the
useless ones.
• Without it you wouldn’t have the energy to be
here listening to this.
Works Cited
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Anatomy and Physiology Homepage. Web. 15 Apr. 2011.
<http://www.lrn.org/Content/Lessons/digestive.html>.
Carson, Nacie. "How Does the Digestive System Maintain Homeostasis? | EHow.com." EHow | How
to Videos, Articles & More - Trusted Advice for the Curious Life | EHow.com. Web. 15 Apr. 2011.
<http://www.ehow.com/how-does_4565570_digestive-system-maintain-homeostasis.html>.
"Celiac Disease." National Digestive Diseases Information Clearinghouse. Web. 15 Apr. 2011.
<http://digestive.niddk.nih.gov/ddiseases/pubs/celiac/index.htm>.
"Digestion System." Biology Questions. Web. 15 Apr. 2011. <http://www.biology-questions-andanswers.com/digestion-system.html>.
"Echinoderms." ReefED - Educate to Keep It Great. Web. 15 Apr. 2011.
<http://www.reefed.edu.au/home/explorer/animals/marine_invertebrates/echinoderms>.
"Protist." Wikipedia, the Free Encyclopedia. Web. 15 Apr. 2011.
<http://en.wikipedia.org/wiki/Protist>.
Taggart, Starr, comp. Biology The Unity and Diversity of Life. 11th ed. Belmont: Thomson
Brooks/Cole, 2006. Print.
Web.
"Work with Other Systems." Web. 15 Apr. 2011.
<http://homepage.mac.com/seisenelem/bodysystems/Digestive/othersystems.html>.
"Your Digestive System." KidsHealth - the Web's Most Visited Site about Children's Health. Web. 15
Apr. 2011. <http://kidshealth.org/kid/htbw/digestive_system.html>.