Stephanie Malouf
What is it?
 Digestion is the process through which food
and drink are broken down so that their
nutrients can be transported throughout the
body by the way of the circulatory system.
How does it work?
 The digestive process uses both mechanical
and chemical processes to breakdown food
and drink to acquire nutrients.
 Breaking down particles involves:
 Movement: peristalsis
Peristalsis is the process of moving food
and drink along the digestive tract.
 Secretion: release of the digestive fluids
 Digestion: breakdown food particles
 Absorption: passage of molecules into the
body’s interior
 Elimination: remove waste

Where does it occur?
 The digestive system follows a tract starting
at the mouth and ending at the start of the
excretory system.
Digestive Tract
 1) Mouth
 2) Esophagus
 3) Stomach
 4) Small Intestine
 5) Large Intestine
Mouth
 The mouth is the very start of the digestive
system. It is the entrance for both food and
drink.
 The mouth performs mechanical
breakdown of food breaking it into smaller
particles by grinding, tearing, and chewing
with the teeth and jaws.
Mouth continued…
 Chemical breakdown occurs within the
mouth through the salivary glands. The
salivary glands produce salivary amylase
which break down starch.
 The one organ in the mouth, the tongue,
uses both mechanical and chemical
breakdown. The tongue manipulates food
particles and moves food to the back of the
mouth when swallowing.
Esophagus
 The esophagus is a long muscular tube that
extends from the pharynx to the stomach.
 The esophagus provides transportation for
food to get to the stomach. Muscles in the
esophagus propel a bolus (a mass of food)
down the tube to enter the stomach.
Stomach
 The stomach is a sac-like organ with
muscular walls. Epithelial cells line the
inner surface of the stomach.
 The food is churned in the stomach to
breakdown through mechanical breakdown.
It contains gastric juices made of
hydrochloric acid, pepsinogen and mucus
for chemical breakdown.
Gastric acids purposes
 Hydrochloric Acid (not directly involved)
kills microorganisms, lowers the stomach’s
pH level and activates pepsinogen.
 Pepsinogen starts protein digestion and
produces the enzyme pepsin
 Enzyme pepsin is an enzyme that breaks
down proteins and carbohydrates.
 Mucus sets up a protective barrier between
cells and the stomach acid.
Traveling through…
 When food particles have been broken
down enough in the stomach chyme ,a
mixture of food and acid, moves to the small
intestine.
Small Intestine
 The small intestine is a long loose tube
coiled in the abdomen. It is split into three
parts.
 The purpose of the small intestine is to
absorb nutrients through its villi that are
then transported by the bloodstream
throughout the body.
Small Intestine continued…
 Three parts:
 The first part the duodenum produces
mucus to protect the intestinal lining
from acid in entering chyme.
 Jejeunum is where the villi are in the small
intestines. The villi and microvilli absorb
nutrients in the chyme into capillaries
because they are connected.
 The ileum absorbs bile salts used to further
digestion of fats.
Small Intestine diagram
Large Intestine
 It is a 5-6 foot tube that encases the
surrounds the small intestine. Divided into
parts, it starts at the cecum and ends at the
rectum.
 The large intestine recovers water and
electrolytes from digested food, forms and
stores feces, performs microbial
fermentation, and contains microbes that
produce that digest indigestible molecules.
Other organs involved
 Liver
 Gall Bladder
 Pancreas
 Appendix
Liver
 Seated on the right side of the stomach is
the liver. It is a large, rubbery, reddish brown
organ.
 It produces and sends bile to the small
intestine to help with digestion.
 The bile contains bile salts and emulsify
fats.
Gall Bladder
 It is a pear-shaped organ positioned under
the liver.
 It stores excess bile.
 Do we need it?
 Many people have their gall bladder
removed. We are able to live without our gall
bladder but have to monitor what we eat
more.
Liver and gall bladder
Pancreas
 Located behind the stomach is the pancreas.
It is an elongated and tapered organ.
 The pancreas neutralizes chyme with
pancreatic juice sent to the small intestine,
by way of the pancreatic duct.
 It also produces glucagon and insulin.
Pancreas diagram
Appendix
 It is a small thin tube that sits in the lower
right abdomen.
 The function of the appendix is unknown.
There are only theories as to its function
 Theories
 It reboots the digestive system after
diarrheal diseases.
 It is a safehouse for beneficial bacteria.
 It once helped cavemen digest leaves.
Appendix diagram
How does this work with other
systems?
 The digestive system works with the
following systems:
 Circulatory system
 Endocrine system
 Excretory system
 Nervous System
How?
 The circulatory system transports nutrients
extracted during the digestive process
throughout the body.
 Part of the digestive system, the liver and
pancreas participate in the endocrine
system function by regulating glucagon
release and regulating the speed of
digestion.
Continued…
 The digestive system eventually leads to the
excretory system. After the nutrients have
been collected the waste is released through
the excretory system.
 The nervous system stimulates for us to
swallow our food.
Homeostasis
 The digestive system helps in homeostasis
by supplying nutrients to the bodies cells for
the cells to function correctly.
 Also the liver helps in digestion by breaking
down toxic substances such as alcohol by
producing urea.
Evolving…
 The digestive system for us has stayed
consistent over time minus the possibility of
the appendix once being useful.
Bibliography
 Body Systems and Homeostasis (n.d.). April 3, 2013. From




http://www.mhhe.com/biosci/genbio/maderbiology/supp/ho
meo.html
Digestive System (n.d.). National Geographic. April 2, 2013. From
http://science.nationalgeographic.com/science/health-andhuman-body/human-body/digestive-system-article/
McKie, Robin (March 3, 2012). Is the mystery of the appendix close
to being unravelled?. The Observer. April 3, 2013. From
http://www.guardian.co.uk/science/2012/mar/04
/appendixstore-beneficial-bacteria
Picture of the appendix (April 28, 2010). WebMD. April 2, 2013.
From http://www.webmd.com/digestive-disorders/pictureof-the-appendix
Picture of the liver (April 28, 2010). WebMD. April 2, 2013. From
http://www.webmd.com/digestive-disorders/picture-of-theliver?page=2
Continued…
 The Digestive System (March 12, 2007). Online Biology
Book. April 2, 2013. From
http://www2.estrellamountain.edu/faculty/farabe
e/biobk/biobooktoc.html
 The Pancreas: Anatomy and Functions (n.d.). Wexner
Medical System. April 2, 2013. From
http://medicalcenter.osu.edu/patientcare/healthc
areservices/liverbiliarypancreaticdisease/pancreas
anatomyfunction/Pages/index.aspx
 Your Digestive System (July 25 2012). WebMD. April 2,
2013. From http://www.webmd.com/heartburngerd/your-digestive-system?page=2
Picture Credits
 Picture of the appendix (April 28, 2010). WebMD. April 2, 2013.
From
http://www.webmd.com/digestive-disorders/picture-of-theappendix
 Picture of the liver (April 28, 2010). WebMD. April 2, 2013. From
http://www.webmd.com/digestive-disorders/picture-of-theliver?page=2
 The Digestive System (March 12, 2007). Online Biology Book. April 2, 2013. From
http://www2.estrellamountain.edu/faculty/farabee/biobk/biobooktoc.html
 The Pancreas: Anatomy and Functions (n.d.). Wexner Medical System. April 2,
2013. From http://medicalcenter.osu.edu/patientcare/healthc
areservices/liverbiliarypancreaticdisease/pancreas
anatomyfunction/Pages/index.aspx
 Your Digestive System (July 25 2012). WebMD. April 2, 2013. From
http://www.webmd.com/heartburn-gerd/your-digestive-system?page=2