Transcript Alimentary Canal Notes

DIGESTIVE
SYSTEM
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Peritoneum: Membrane of the abdominal cavity
 Parietal Peritoneum covers
the abdominal wall
 Visceral Peritoneum covers
the inner organs
Branching from the peritoneum:
 Lesser omentum—
attaches the liver to the
lesser curvature of
stomach
 Greater omentum:
(Apron) Contains fat to
insulate, cushion, and
protect abdominal organs
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
The Digestive System Functions
 Ingestion—taking in food
 Digestion—breaking food down both physically
and/or chemically
 Absorption—movement of nutrients into the
bloodstream
 Defecation—rids the body of indigestible waste
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Organs of the Digestive System
 Two main groups of organs
 Alimentary canal (gastrointestinal or GI
tract)—continuous coiled hollow tube from
mouth to anus
 Accessory digestive organs (aid in digestion
but food does not pass through)
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Layers of Alimentary Canal Organs
 Four layers
 Mucosa
 Submucosa
 Muscularis externa
 Serosa
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Layers of Alimentary Canal Organs
 Mucosa
 Innermost, moist membrane , smooth muscle
layer
 Submucosa
 Just beneath the mucosa, contains blood
vessels and nerve endings
 Muscularis externa—smooth muscle
 Inner circular layer and outer longitudinal
layer
 Serosa—outer membrane
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Organs of the Alimentary Canal
 Mouth
 Pharynx
 Esophagus
 Stomach
 Small intestine
 Large intestine
 Anus
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Mouth (Oral Cavity) Anatomy
 Lips (labia)—protect the
anterior opening
 Cheeks—form the lateral
walls
 Hard palate—forms the
anterior roof
 Soft palate—forms the
posterior roof
 Uvula—fleshy projection of
the soft palate
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Mouth Physiology
 Ingestion
 Mastication (chewing) of food
 Mixing masticated food with saliva
 Initiation of swallowing by the tongue
 Allows for the sense of taste
 Enzymes from salivary glands are secreted here
 Digestion begins here
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Pharynx Anatomy (REVIEW)
 Nasopharynx—not part of
the digestive system
 Oropharynx—posterior to
oral cavity
 Laryngopharynx—below
the oropharynx and
connected to the
esophagus
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Pharynx Physiology
 Serves as a passageway for air and food
 Food is propelled to the esophagus by two
muscle layers
 Longitudinal inner layer
 Circular outer layer
 Food movement is by alternating contractions of
the muscle layers (peristalsis)
http://www.nlm.nih.gov/medlineplus/ency/anatomyvi
deos/000097.htm
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Esophagus Anatomy and Physiology
 Anatomy
 About 10 inches long
 Runs from pharynx to stomach through the
diaphragm
 Physiology
 Conducts food by peristalsis (slow rhythmic
squeezing; a wave-like movement of smooth
muscles)
 Passageway for food only (respiratory system
branches off after the pharynx)
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Stomach Anatomy
 Located on the left side of the abdominal cavity
 Food enters at the cardioesophageal sphincter
 Contain Rugae—internal folds of the mucosa
 Food empties into the small intestine at the pyloric
sphincter (valve)
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Stomach Physiology
 Temporary storage tank for food
 Enzymes released here
 Digestion occurs here
 Hydrochloric Acid produced here
 Delivers chyme (processed food) to the small
intestine
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Subdivisions of the Small Intestine
 Duodenum
 Attached directly to the stomach
 Jejunum
 Attaches anteriorly to the duodenum
 Ileum
 End portion of the small intestine extends
from jejunum to large intestine
http://nutrition.jbpub.com/resources/animations.
cfm?id=1&debug=0
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Small Intestine Anatomy
 Structural modifications
that increase surface area
 Microvilli—tiny
projections of the
plasma membrane
(create a brush border
appearance)
 Villi—fingerlike
structures formed by
the mucosa
 Circular folds (plicae
circulares)—deep folds
of mucosa and
submucosa
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Small Intestine Anatomy
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Large Intestine
 No digestion here
 Absorption occurs here
 Larger in diameter, but shorter in length, than the
small intestine
 Frames the internal abdomen
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Large Intestine Anatomy
 Cecum—saclike first part of the large intestine
 Appendix
 Accumulation of lymphatic tissue that
sometimes becomes inflamed (appendicitis)
 Hangs from the cecum
 Nursery for important digestive bacteria
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Large Intestine Anatomy
 No villi present
 Goblet cells produce alkaline mucus which
lubricates the passage of feces
 Muscularis externa layer is reduced to three
bands of muscle called teniae coli
 These bands cause the wall to pucker into haustra
(pocketlike sacs)
 Bacteria produce Vitamins
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Large Intestine Anatomy
 Colon
 Ascending—travels up
right side of abdomen
 Transverse—travels
across the abdominal
cavity
 Descending—travels
down the left side
 Sigmoid—enters the
pelvis
 Rectum and anal canal—
also in pelvis
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Large Intestine Anatomy
 Anus—opening of the large intestine
 Double sphincter
 These sphincters are normally closed except
during defecation
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings