Digestive System
KEY TERMS
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Alimentary Canal
Anus
Colon
Digestive System
Duodenum
Esophagus
Gallbladder
Hard Palate
Ileum
Jejunum
Large Intestine
Liver
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Mouth
Pancreas
Peristalsis
Pharynx
Rectum
Salivary Glands
Small Intestine
Soft Palate
Stomach
Teeth
Vermiform Appendix
Villi
Digestive System
• The digestive system (gastrointestinal
system) is responsible for:
1. The physical and chemical breakdown
of food
2. Absorption of nutrients
3. Elimination of wastes
• The digestive system consists of:
1. Alimentary canal
2. Accessory organs
Alimentary Canal
• A long, muscular tube that begins at the
mouth and includes the:
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large intestine
• Anus
Parts of Alimentary Canal
• Mouth – receives the food
• Teeth – help with the mastication of food
• Tongue – aids in chewing, swallowing, and
tasting of food
• Hard palate – bony structure that is the roof of
your mouth, separates the mouth from the
nasal cavities
• Soft palate – separates the mouth from the
nasopharynx, includes the uvula which helps
to prevent food from entering the nasopharynx
• Salivary glands – produces salivary amylase
which begins the chemical breakdown of
carbohydrates into sugars
Poly want a cracker??
• A cracker is mostly a carbohydrate (starch)
but if you leave it in your mouth long
enough it will become a sugar.
• TRY IT!!!!
• Chew up an unsalted cracker but don’t
swallow it!
• Keep the bolus (chewed up food) in
your mouth for 1 minute…
• After you notice the sweet taste you
may swallow!
YUMMY!!!!
Parts of Alimentary Canal (cont.)
• Pharynx (throat) – carries both food and air
(air to the trachea and food to the esophagus)
• Bolus (chewed food and saliva) enters the
esophagus
• Epiglottis is closed over the larynx to prevent
food from entering the respiratory tract
• Esophagus – muscular tube behind the
trachea that carries the bolus to the stomach
• Like all parts of the alimentary canal, it
relies on peristalsis (rhythmic, wavelike,
involuntary movement of muscles) to move
the food in a forward direction
Parts of Alimentary Canal (cont.)
• Stomach
• Receives the food from the esophagus
• Cardiac sphincter – muscle b/n the esophagus
and stomach that closes after food enters
• Pyloric sphincter – muscle b/n the stomach
and small intestine that keeps food in the
stomach until it is time to move on
• Food remains in the stomach for 2-4 hours
• Food is converted into chyme (semifluid
material) by gastric juices (hydrochloric acid
and enzymes)
• Food is then ready to move to the small
intestine
Parts of Alimentary Canal (cont.)
• Small intestine – accepts chyme from the
stomach
• Coiled section that is approx 20 feet in length
and 1 inch in diameter
• Divided into 3 sections:
• Duodenum (first 9-10 inches) – bile and
pancreatic juices enter this section
• Jejunum (8 ft in length) – forms the middle
section
• Ileum (final 12 ft) – connects with the large
intestine at the cecum
Parts of Alimentary Canal (cont.)
Small Intestine
• Process of digestion is completed here
• Products of digestion are absorbed into
the bloodstream
• Bile from the liver and gallbladder
physically breaks down fat
• Wall of small intestine is lined with villi
(fingerlike projections) – absorb the
digested nutrients and carry them to the
liver
• Once food has completed its trek through
the small intestine, only wastes,
indigestible materials, and excess water
remains
Parts of Alimentary Canal (cont.)
Large Intestine
• Last part of the alimentary canal
• Approx 5 feet in length and 2 inches in
diameter
• Functions:
• Absorption of water and any remaining
nutrients
• Storage of waste before elimination
• Transportation of waste out of the
alimentary canal
Parts of Alimentary Canal (cont.)
Large Intestine
• Divided into a series of connected sections:
• Cecum - connected to the ileum of the
small intestine (contains the appendix)
• Colon
• Ascending colon – continues up the
right side of the body
• Transverse colon – extends across the
abdomen
• Descending colon – extends down the
left side of the body
• Sigmoid colon – S-shaped section that
joins with the rectum
Parts of Alimentary Canal (cont.)
• Rectum – final 6-8 inches of the large
intestine
• Storage area for indigestibles and
wastes
• Has a narrow canal called the anal
canal which opens at the anus
• Anus – fecal material is expelled through
this opening
Accessory Organs
Liver
• The largest gland in the body
• Located under the diaphragm in the upper
right quadrant
• Secretes bile which breaks down fats and
makes them water soluble
• Stores sugar in the form of glycogen, iron,
and some vitamins
• Produces heparin (prevents clotting in the
blood)
• Detoxifies substances such as alcohol and
pesticides
Accessory Organs
Gallbladder
• Small, muscular sac located under the
liver and attached to it by connective
tissue
• Stores and concentrates bile which is
received from the liver
• Sends bile to the duodenum when needed
Accessory Organs
Pancreas
• Glandular organ located behind the
stomach
• Produces enzymes to digest food
• Produces insulin which regulates
metabolism (converting glucose into
energy)
Diseases and Abnormal Conditions
• Appendicitis
• Acute inflammation of the appendix
• Resulting from an obstruction and
infection
• Symptoms – abdominal pain that
localizes in the LRQ, nausea and
vomiting, mild fever, and elevated WBC
• Rupture of the appendix is a serious
condition (infection spills into the
peritoneal cavity)
• Treatment - appendectomy
Diseases and Abnormal Conditions
• Cholecystitis
• Inflammation of the gallbladder
• Symptoms occur after eating fatty foods and
include: indigestion, nausea and vomiting, pain
that starts under the rib cage and radiates to the
right shoulder
• Treatment: low-fat diet or a cholecystectomy
• Cirrhosis
• Chronic destruction of liver cells which leads to
scar tissue
• Some causes include hepatitis and alcoholism
• Some common symptoms: liver enlargement,
anemia, jaundice, and hematemesis
Diseases and Abnormal Conditions
• Constipation
• Causes include a diet low in fiber, dehydration,
or extended laxative use
• Usually self-corrected with diet, hydration, and
exercise
• Diarrhea
• Causes include infection, stress, and diet
• Treated by eliminating the infection and
modifying diet
• Hemorroids
• Painful dilated veins in the rectum
• Causes include constipation, laxative abuse, or
pregnancy
• Treatment includes a high fiber diet, increased
fluid intake, or a hemorrhoidectomy
Diseases and Abnormal Conditions
• Diverticulitis
• Inflammation of the diverticula (sacs
that form in the intestine as the mucosal
lining pushes through the surrounding
muscle)
• Occurs when fecal material or bacteria
become trapped in the diverticula
• Symptoms include: abdominal pain,
abdominal distention, low grade fever,
nausea and vomiting
• Treatment includes antibiotics, pain
medication, change in diet, or even
surgery to remove the affected section
of the colon
Diseases and Abnormal Conditions
• Gastroenteritis
• Inflammation of the mucous membrane
that lines the stomach and intestinal
tract
• Causes include food poisoning,
infection, and toxins
• Symptoms include abdominal
cramping, nausea, vomiting, fever, and
diarrhea
• Treatment includes rest, antibiotics, and
increased fluid intake