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Digestive System- Anatomy
Alimentary canal- open tract of major
organs through which food travels
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Mouth
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
Anal canal
Accessory organs- organs that aide in
digestion process
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Salivary glands
Tongue
Teeth
Liver
Gallbladder
Pancreas
Vermiform appendix
Mouth/Oral Cavity- beginning of
alimentary canal
• 3 major pairs salivary glands- secrete 1 liter of
saliva per day
– Parotid: largest
– Submandibular: Wharton
ducts beside frenulum
– Sublingual: below
floor of mouth
• Secrete mucous/serous saliva to aid in
digestion
Teeth
• Used for mastication/chewing– increases surface
area of food for more enzyme access
– Deciduous= baby teeth-20
– Permanent= adult – 32
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Incisors- bite into food
Canines/cuspids -tear
Premolars- grind & crush
Molars- grind & crush
3 Main Parts of Tooth
• 1. crown- exposed top
covered with
– enamel= 97% calcified
material
– dentin= softer, more elastic
than enamel, yellow
• 2. neck- narrow,
surrounded by gums and
cementum
• 3. root- fits into jaw,
anchors tooth, surrounded
by cementum
Interior of tooth= pulp cavity
• Contains:
connective tissue,
blood, lymph,
nerves
Swallowing
• After food leaves mouth it’s called a bolusgoes through pharynx
• Pharynx=throat
• Oropharynx= 2nd division
of pharynx through
which food is passed
 connects to
esophagus
GI tract- layers of
gastrointestinal tract
• 1. Mucosa- mucous lining the interior
• 2. Submucosa- CT tissue with blood vessels
Layers of GI
• 3. Muscularis- muscle with plexus of nerves
• 4. Serosa- fibroserous layer, includes
mesentery (later in GI)
Esophagus
Esophagus- beginning of GI proper
• 10 inches long- takes about 7 seconds for food
to pass through to stomach
• Normally flat at rest—expands during
peristalsis
• Lined with stratified squamous epithelium–
resists abrasion
Stomach
• Volume about 1-1.5 liters– large
size after big meal interferes
with diaphragm– located to left
side
• 3 major divisions:
– Fundus– goes above level of
esophagus
– Body
– Pylorus
Stomach
• Destroys most bacteria swallowed in food or
with mucus from resp. tract
• Stores food, churns food
• Limited amount of absorption– some drugs,
alcohol, some fats
Gastric Mucosa
• Lining with folds= rugae, and
depressions= gastric pits
• Gastric glands below pits– secrete
gastric juice
– Have 2 main secretory cells:
• 1. chief cells- secrete enzymes
• 2. parietal cells- secrete HCl and
“intrinsic factor”– binds to vitamin B1 to
protect it from HCl before intestine, aids
in absorption
Gastric Muscle
• 3 layers of smooth muscle running at different
angles--longitudinal, circular, oblique-- so it can
contract multiple directions
Small intestine
• Villi located on folds called
plicae
• Each villi has arteriole,
venule, and lymph vessel and
have “brush border”–
microvilli on columnar
epithelium
• Crypts- depressions where
mitosis is rapid
Parts of Large intestine
• Cecum- 1st few cm—pouch which appendix
attaches to
• Ascending colon- goes up right side where ileum
attaches- ileocecal valve allows material in (1
way)
• Transverse-horizontal
• Descending-goes down left side
• Sigmoid- S curve, joins rectum
• Rectum- last few inches