DIGESTIVE SYSTEM
 Digestive System – also known as
gastrointestinal system
 Function: Physical and chemical breakdown
of food so it can be taken into the
bloodstream and used by the body’s cells and
tissues.
 Digestive Systems consists of the Alimentary
Canal and accessory organs:
 Alimentary canal – long, muscular tube that
includes the mouth, pharynx, esophagus,
stomach, small intestine, large intestine, and
anus.
 Accessory organs – salivary glands, tongue,
teeth, liver, gallbladder and pancreas
Parts of Alimentary Canal
 Mouth - also called buccal cavity or oral
cavity
 Food intake
 Tasted
 Broken down physically (teeth)
 Lubricated and partially digested by saliva
 swallowed
Teeth
 Teeth - physically break down food by
mastication (chewing and grinding).
Tongue
 Tongue – muscular organ containing special
receptors called taste buds. Taste buds allow
a person to taste sweet, sour, salty, bitter
sensations
 Aids in chewing and swallowing food.
Hard Palate
 Bony structure that forms the
roof of the mouth and
separates the mouth from the
nasal cavities
 http://www.youtube.com/watch?v=KIPL52w
Gu0Q
Soft Palate
 Separates the mouth from the nasopharynx
 Uvula – cone shaped muscular structure that
hangs from the middle of the soft palate
 Function of uvula – to prevent food from entering
nasopharynx during swallowing
Salivary Glands and Saliva
 3 Pairs of Salivary Glands (parotid, sublingual,
submandibular) produce saliva.
 Saliva – lubricates mouth during speech and
chewing, and moistens food so it can be
easily swallowed.
 Saliva contains enzyme (a substance that
speeds up a chemical reaction) called salivary
amylase. This begins the chemical
breakdown of carbohydrates, or starches,
into sugars that can be taken into the body.
 After food is chewed and mixed with saliva it
forms a bolus.
 When bolus swallowed – enters the pharynx
Pharynx
 Pharynx is a tube that carries both air and
food
 Carries air to the trachea (windpipe)
 Food to the esophagus
 When bolus is swallowed, muscle action causes
epiglottis to close over the larynx to prevent bolus
from entering respiratory system and causes it to
enter esophagus.
Esophagus
 Esophagus – approx. 10 inch long muscular
tube dorsal (behind) the trachea.
 Receives bolus from mouth and carries it to
the stomach
 Food is moved in a forward direction through
the alimentary canal by peristalsis
 Peristalsis – rhythmic, wavelike, involuntary
movements
 http://www.youtube.com/watch?v=vItktDQo-
mE
 http://www.youtube.com/watch?v=8V6VsNk
GfTQ
Stomach
 J-shaped muscular organ that acts as a bag or
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sac to collect, churn, digest and store food.
Receives food from the esophagus
Composed of 3 parts: fundus (upper region),
body (main portion), antrum (lower region).
Mucous membrane lining of stomach
contains folds called rugae. Rugae disappear
as the stomach fills with food and expands.
Stomach is about the size of your fist, but can
expand to hold up to a quart of food.
Sphincters of Stomach
 Stomach contains muscular valves called
sphincters.
 Sphincters control the flow of food in one
direction only.
 Cardiac sphincter (or lower esophageal
sphincter) – circular muscle between
esophagus and stomach. Closes after food
enters stomach and prevents food from going
back into esophagus. Prevents regurgitation.
Stomach Sphincters cont’d
 Pyloric sphincter – located at lower end of
stomach and controls passage of food into
duodenum of small intestine.
 Keeps food in stomach while being mixed
with gastric juices that aid digestion until
ready to be released into small intestine.
 Food remains in stomach for 1-4 hours
Med Tip
 When the pyloric sphincter becomes
abnormally narrow, a condition called pyloric
stenosis results in which food is unable to
pass from the stomach to the small intestine.
Emesis (vomiting) is the main symptom.
Chemical Digestion in
Stomach
 While food is in stomach, chemical digestion
occurs. Gastric juices are produced by gastric
glands in the stomach.
 Gastric juices such as hydrochloric acid and
enzymes are released to convert the food
into a semifluid substance called chyme.
Functions of Gastric Juices
 Hydrochloric acid – kills bacteria, facilitates
iron absorption, actives the enzyme pepsin.
 Enzymes in gastric juices – lipase helps break
down fats and pepsin starts protein digestion.
 In infants, the enzyme rennin is released to
aid in the digestion of milk. Rennin is not
present in adults.
 g tube placement
 g tube feeding demonstration
Myth or Fact about your Stomach?
 1. Myth or Fact: Digestion takes place
primarily in the stomach.
Answer: Myth. The major part of the
digestive process takes place in the small
intestine. The stomach takes in the food, then
churns it and breaks it into tiny particles called
"chyme." The chyme are then released in
small batches into the small intestine, where
most digestion occurs, he says.
Contrary to popular belief, foods do not
digest in the order they are eaten. Everything
lands in the stomach where it's all churned
together, and when it's ready it's released into
the small intestines together.
2. Myth or Fact: If you cut down on
your food intake, you'll eventually
shrink your stomach so you won't be
as hungry
Answer: Myth
Once you’re an adult, your stomach remains the
same size.
 3. Myth or Fact: Thin people have
naturally smaller stomachs than
people who are heavy.
 Answer: Myth. While it may seem hard to
believe, the size of the stomach does not
correlate with weight or weight control. People
who are naturally thin can have the same size or
even larger stomachs than people who battle
their weight throughout a lifetime. Weight has
nothing to do with the size of the stomach. In
fact, even people who have had stomachreducing surgeries, making their tummy no
larger than a walnut, can override the small size
and still gain weight.
 4. Myth or Fact: Exercises like sit-ups or
abdominal crunches can reduce the size of
your stomach
 Answer: Myth. No exercise can change the size
of an organ, but it can help burn the layers of fat
that can accumulate on the outside of your body.
Plus it can help tighten the muscles in the
abdomen, the area of the body lying just south
of the diaphragm, that houses the stomach and
many other internal organs.
 Interestingly, the part of your "belly fat" that can
do you the most harm may actually be the fat
you don't see. It resides in the "omentum," a kind
of internal sheet that lies over and around your
internal organs.
 5. Myth or Fact: One way to reduce acid
reflux is to lose as little as 2 to 3 pounds.
 Answer: Fact. The less acid that flows back up
into your esophagus, the fewer problems you will
have clearing it. And believe it or not, losing just
2 pounds of weight from the abdominal area can
make a difference -- and pregnancy is about the
best example of this. As the baby grows and
pushes against the internal organs, heartburn
increases; but once the baby is born and the
pressure is relieved, the heartburn is, too. In
much the same way, losing even a little bit of
belly fat can provide similar relief
 6. Myth or Fact: Beans cause everyone to
make excess gas, and there's nothing you
can do about it.
 Answer: Myth ... sort of! Beans are high in a kind of
sugar that requires a certain enzyme to properly
digest. Some people have more if it, some people
less. And the less you have, the more gas that will be
produced during digestion of beans. What can help:
Studies show that over-the-counter products that
add more of the enzyme needed to break down the
sugar in beans as well as other traditionally gassy
vegetables can help if taken before you eat. After the
fact, you can reduce the gas that forms by taking a
product containing simethicone, which is a true
bubble buster, releasing the surface tension on gas
bubbles that form as a result of eating foods that are
hard to digest.
Small Intestine
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Food in the form of chyme enters the small
intestine.
 Small intestine
 Coiled
 Approx. 20 feet long and 1 inch in diameter
 Divided into 3 sections: duodenum, jejunum, and
ileum
Duodenum
 First 10 inches of small intestine
 Bile from gallbladder and liver and pancreatic
juice from pancreas enter small intestine
through ducts, or tubes.
Jejunum
 Middle portion of small intestine
 About 8 feet long
Ileum
 Last portion of small intestine
 12 feet long and is the longest portion of
small intestine
 Joins the large intestine at the ileocecal valve
 Ileocecal valve is a muscular valve which prevents
food from returning to the ileum
 Attaches to cecum of large intestine
Digestive Process of Small
Intestine
 Process of digestion is completed in small
intestine
 Products of digestion absorbed into bloodstream
for use by body’s cells
 Walls of small intestine are lined with villi which
contain blood capillaries and lacteals.
 Blood capillaries carry digested nutrients to liver
where they are stored or released to body cells
 Lacteals absorb most digested fats into
lymphatic system released to circulatory system
Large Intestine
 Final section of alimentary canal
 Approx 5 feet and 2 inches in diameter
 Only waste, indigestible materials, and
excess water go to large intestine
Functions of Large Intestine
 Absorption of water and any remaining
nutrients
 Storage of indigestible material before
eliminated by body
 Synthesis (formation) and absorption of
some B-complex vitamins and vitamin K
 Transportation of waste products out
Sections of Large Intestine
 Cecum
 Connected to ileum of SI
 Contains vermiform appendix
 Colon
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Ascending colon
Transverse colon
Descending colon
Sigmoid colon
 Rectum
 Final 6-8 inches of LI
 Storage for indigestables and waste
 Rectum – Anal Canal – Anus
 Fecal material (stool, waste, feces) - the final
waste product of digestion is expelled
through this opening (bowel movement BM)
 Polypectomy
 colon cancer
 parasite in colon
 colostomy care
Accessory Organs
 Pancreas
 Gallbladder
 Liver
Liver
 Largest gland in body
 Located in RUQ
 Function:
 secretes bile which aids in digestion of fats
 Stores sugar in form of glycogen
 Stores iron and vitamins
 Produces heparin – prevents blood clotting
 Detoxifies substances such as alcohol, pesticides,
and destroys bacteria
Gallbladder
 Small, muscular sac located under liver
 Stores and concentrates bile which it receives
from the liver
 When the bile is needed to emulsify fats in
the digestive tract, the gallbladder contracts
and pushes the bile through the common bile
duct and into the duodenum.
Pancreas
 Glandular organ behind the stomach
 Produces pancreatic juices which contain
enzymes to digest food
 Juices enter duodenum through pancreatic
duct
 Amylase or amylopsin – sugar
 Trypsin and chymotrypsin – proteins
 Lipase and steapsin – fats
Pancreas
 Produces insulin
 Insulin: Regulates the metabolism, or
burning of carbohydrates to convert glucose
(sugar) to energy.
What happens to a hamburger?
 You are getting ready to eat a hamburger
which contains a buttered bread bun, a meat
patty, and cheese.
 What will happen to the hamburger at each
stage of the digestive process: mouth,
pharynx, esophagus, stomach, small
intestine, large intestine, rectum