Digestive System
The Gastrointestinal System
Digestive System
Alimentary Canal
Long, muscular organ
that includes the mouth
(oral cavity), pharynx,
esophagus, stomach,
small intestine, large
intestine & anus
Buccal Cavity
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Mouth – receives food
as it enters the body
Teeth - Food in the
mouth is tasted, broken
down physically by the
teeth, digested, by
saliva & swallowed
Mastication – Chewing
& grinding of food by
the teeth
Buccal Cavity
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Tongue – Muscular organ
with special receptors –
taste buds
Hard Palate – bony
structure that forms the
roof of the mouth
Soft Palate – Separates the
mouth from the
nasopharynx
Uvula – hangs from the
soft palate & keeps food
from entering the
nasopharynx during
swallowing
Buccal Cavity
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3 pairs of salivary glands
Parotid
Sublingual
Submandibular
Produce saliva to lubricates
the mouth during speech &
chewing and moistens food
so that it can be swallowed
easily
Salivary Glands
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Saliva contains the
enzyme salivary amylase
(ptyalin)
Begins the chemical
breakdown of
carbohydrates (starches),
into sugars that can be
used by the body
Bolus – food that has
been chewed & mixed
with saliva
Pharynx
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The Throat
A tube that carries the air
to the trachea & food to the
esophagus
When a bolus is being
swallowed muscle action
causes the epiglottis to
close over the larynx,
preventing the bolus from
entering the respiratory
tract causing it to enter the
esophagus
Esophagus
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Muscular tube dorsal to
the trachea
Receives the bolus from
the pharynx & carries it
to the stomach
Relies on a rhythmic,
wavelike involuntary
movement of its muscles
called peristalsis
Stomach
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Enlarged part of the
alimentary canal.
Receives food from the
esophagus
Rugae – folds inside the
stomach
Cardiac Sphincter –
between esophagus &
stomach
Pyloric sphincter –
between stomach &
small intestine
Stomach
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Food in stomach 1-4
hours
Chyme – food is
converted into a semifluid material
Gastric Juices – contain
hydrochloric acid &
enzymes
Stomach Enzymes
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Hydrochloric Acid – kills
bacteria, facilitates iron
absorption & activates
the enzyme pepsin
Lipase – starts the
chemical break down of
fats
Pepsin starts protein
digestion
Rennin aids in the
digestion of milk (found
only in children)
Small Intestine
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Coiled section of alimentary
canal 20 feet long
Divided into the:
duodenum (9-10 in.) jejunum (8
ft.) ileum (12 feet)
Cecum – place that the small
intestine connects to the large
intestine.
Ileocecal valves – separates the
ileum & cecum
Small Intestine
Enzymes in the Small Intestine
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Duodenum – Bile (from the
gallbladder & liver) and
pancreatic juice enter
through ducts
Process of digestion is
completed in the small
intestine
The products of digestion
are absorbed into the blood
stream for use by body
cells
Small Intestine Enzymes
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Maltase, sucrase & lactase
break down sugars into
simpler forms
Peptidases – completes the
digestion of proteins
Steapsin – aids in the
digestion of fats
Bile – from liver &
gallbladder emulsifies fats
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Pancreatic enzymes
complete digestion
Pancreatic amylase or
amylopsin acts on sugars
Trypsin and chymotrypsin
act on proteins
Lipase or steapsin acts on
fats
Absorption
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After food is digested it is absorbed into the
bloodstream
Walls of small intestine are lined with fingerlike projections called villi
Villi contain blood capillaries & lacteals
Blood capillaries absorb the nutrients & carry
them to the liver
Absorption
Large Intestine
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5 ft. in length & 2 in. in
diameter
Functions include:
absorption of water &
remaining nutrients,
storage of indigestible
materials before
elimination
Synthesis of some B
complex vitamins &
vitamin K
Transportation of waste
products from the body
Large Intestine
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Cecum – first section
& is connected to the
ileum of the small
intestine. It contains a
small projection called
the veriform appendix
Large Intestine
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Colon has several
divisions:
Ascending colon – up the
right side of body from the
cecum to the lower part of
the liver
Transverse Colon –
Extends across the
abdomen, below the liver
& stomach and above the
small intestine
Large Intestine
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Descending Colon –
extends down the left
side of the body.
Connects with the
sigmoid colon
Sigmoid Colon, an S
shaped section that
joins the rectum
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Rectum – final 6 – 8 in.
of the large intestine &
is a storage area for
indigestible & waste
The narrow anal canal
opens at a hole called
the anus
Fecal material or stool,
the final waste product
is expelled
Liver
Liver
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Largest Gland
Secretes Bile which emulsifies fats & makes them
water soluble
Stores Sugar in the form of glycogen
Stores Iron & Vitamins
Produces heparin, fibrinogen, prothrombin &
Cholesteral
Detoxifies substances
Destroys bacteria taken into the blood from the
intestine
Liver
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Heparin: Prevents clotting
Fibrinogen: Blood Protein aids in clotting
Prothrombin: Blood Protein aids in clotting
Gallbladder
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Small, muscular sac
located under liver
Stores & concentrates
bile
Bile needed to emulsify
fats
Pancreas
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Glandular organ
Produces pancreatic
juices & enzymes
Produces insulin
Diseases
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Appendicitis – Acute inflammation or
infections of the appendix
Symptoms: RLQ abdominal pain,
nausea/vomting, mild fever, elevated WBC.
Danger- peritonitis
Diseases
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Cholecystitis- inflammation of the
gallbladder, characterized by formation of
cholelithiasis (gallstones, which are
crystallized cholesterol, bile salts, and bile
pigments)
Symptoms- pain under the rib cage radiating
to the right shoulder, indigestion, n/v occurs
after eating fatty meal.
continued
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Cholecystitis- if a gallstone blocks the bile
duct, it can rupture causing peritonitis
Treatment-low fat diet, lithotripsy, and
possible cholecystectomy
Diseases
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Constipation-when fecal material stays in the
large intestine too long causing excessive
reabsorption of water. Stool becomes hard,
dry, and difficult to eliminate.
Causes- low fiber diet; chronic laxative use
makes the bowel “lazy”
Treatment- high fiber diet; fluids, and
exercise (avoid laxatives if possible)
Diseases
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Diarrhea- frequent water stools caused by
infection, stress, diet, irritated colon, or toxic
substances. Can be dangerous in infants and
small children.
Treatment is directed at eliminating the cause,
modifying diet, and adequate fluids.
Diseases
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Diverticulitis- inflammation of the diverticula
(sacs) that form in the lining of the intestine.
Occurs when fecal material or bacteria
become trapped in the “sacs”. Can result in
abscess or rupture and cause peritonitis.
Symptoms- abdominal pain, gas, abdominal
distention, constipation, diarrhea
Treatment-antibx, pain med, surgery
Diseases
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Gastroenteritis- inflammation of the mucosal
membrane lining the GI tract.
Cause-food poisoning, infection, toxins
Symptoms- abdominal cramping, n/v,
diarrhea
Treatment- replace fluids, rest, antibiotics, IV
fluids if severe.
Diseases
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Hemorrhoids- painful dilated or varicose
veins of the rectum or anus.
Symptoms- pain, itching, bleeding
Treatment- high fiber diet, stool softeners,
sitz baths, warm moist compresses.
If severe, hemorrhoidectomy.
Diseases
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Hepatitis- inflammation of the liver
A- infectious hepatitis- transmitted in food or
water that has been contaminated by feces of
an infected person. Most benign type.
B- transmitted by all body fluids including
breast milk, saliva, and urine. (vaccine)
C- also transmitted through blood and body
fluids but more likely to cause cirrhosis.
Hepatitis continued
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C-no vaccine
Symptoms- fever, fatigue, anorexia, n/v,
mylagia, dark urine, clay colored stool,
enlarged liver and jaundice.
Treatment- rest, diet high in protein and
calories but low in fat. If severe, liver
transplant.
Diseases
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Hernia- a rupture that occurs when an internal
organ pushes through a weakening or natural
opening in a body wall.
hiatal hernia- when the stomach protrudes
through the diaphragm into the chest cavity
through the opening for the esophagus.
If a hernia cannot be reduced, then a
herniorraphy is performed.
Diseases
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Ulcer – open sore on the lining of the
digestive tract. Peptic ulcers include stomach
and duodenal ulcers.
Causes- H. pylori bacteria is most common
cause (infection) by burrowing into the lining
allowing gastric juices to create an ulcer.
Symptoms- burning pain, indigestion, melena,
and hematemesis.
Ulcers cont.
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Treatment- bland diet, decreased stress,
avoiding irritants. Bismuth medications (pepto
bismol is used) If H. Pylori is the cause, this is
an infection that should be treated with
antibiotics.
Diseases
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GERD (gastroesophageal reflux disease)occurs when stomach contents and acid leak
back into the esophagus and there are visible
signs of irritation to the lining of the esophagus.
Many people have acid reflux, heartburn, and
indigestion but that doesn’t mean they have
GERD.
GERD cont.
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Symptoms- burning pain in your lower chest,
tasting acid in your mouth, throat.
Treatment- dietary and lifestyle changes;
avoiding irritation to the esophagus
(chocolate, peppermint, alcohol, fatty foods,
coffee, citrus fruits and juices)