Honors Anatomy & Physiology
AKA alimentary canal
or gut
 Continuous muscular
digestive tube
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Mouth
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
Anus
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Ingestion
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Propulsion
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Catabolic break down by enzymes
Absorption
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Chewing, mixing w/saliva by tongue, churning food in
stomach
Segmentation – constriction of intestines mixes food
w/juices (see fig b)
Chemical Digestion
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Swallowing -voluntary
Peristalsis – waves of involuntary contractions (see fig
a)
Mechanical Digestion
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Taking food in
Chemical building blocks, vitamins, minerals, and
water from lumen of GI into blood & lymph
Defecation
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Eliminates indigestibles
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Lines w/stratified squamous
epithelium
Labia (lips) – orbicularis oris
(poorly keratinized)
Cheeks – buccinators for chewing
Hard Palate – rigid surface for
tongue to mash food
Soft palate – skeletal muscle w/
uvula
Tongue- skeletal muscle fibers in
various directions, repositions
food and mixes w/saliva to form
bolus lingual frenulum attaches
to floor
1,000 – 1,500 mL per day!
Regulated by parasympathetic division of
ANS
 Functions:
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Composition
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Cleanses mouth
Dissolves food chemicals for taste
Moistens food to compact into bolus
Amylase breaks down starch
97% water, electrolytes
pH 6.75
Amylase, mucin (forms mucus), lingual lipase
Antimicrobials: lysozyme, IgA, defensins
Multiple Locations:
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Extrinsic salivary glands
Intrinsic salivary glands – continuous secretion
Buccal galnds
Paratid gland
Submandibular gland
Sublingual gland
Function: Masticate (Chew) voluntary &
reflexive
 20 Primary (deciduous) or milk teeth by
24 months
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Roots reabsorbed as adult teeth develop
causing them to fall out between 6-12 yrs
32 Permanent teeth (including wisdom
teeth)
 Types:
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Incisors - cutting
Canines – tear/pierce
Premolars (bicuspids) – grinding & crushing
Molars (4-5 cusps)
Structure:
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Enamel – acellular hardest substance in body
(Ca and hydroxyapatite), cannot be replaced
Gingiva recedes w/age
Dentin – bonelike but avascular
Cementum – Ca connective tissue covers
root
Peridontal liagment anchors to alveolus
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Oropharynx &
laryngopharynx
Stratified squamous
epithelium w/mucus
producing glands
2 skeletal muscle layers:
 inner layer longitudinal
 Constrictor muscles
encircle
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Peristalsis propels food
into esophagus
Collapsed 10” muscular tube
Pierces diaphragm to join to
cardiac sphincter of stomach
 Takes 2 (liquids) -8 (solids)
seconds
 4 layers:
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 Nonkeratinized stratified
squamous epithelium
 Longitudinal folds when empty,
flatten when food is in transit
 Esophageal glands – secrete
mucus as bolus moves thru
 Skeletal & smooth muscle
Storage tank where bolus +
enzymes = chyme
 6-10” long, ‘J’ shaped
 Mechanical digestion
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 Vigorous peristalsis
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Chemical digestion
 HCl denatures proteins
 Chief cells secrete pepsin & lipase
 rennin (milk proteins)
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Absorption
 Alcohol & aspirin (lipid soluble)
pass through stomach mucosa into
blood (can cause gastric bleeding)
 Secretes intrinsic factor to absorb
vitamin B12 in small intestine
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Mucus barrier
Rugae – fold when empty
Omentum –mesenteries that
tether digestive organs to body
wall (fat & lymph)
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20 ft long, 1.5” diameter, complete trip about 2 hours
Simple columnar epithelium w/goblet cells and T cells
Intestinal crypts w/defensins & lysozyme & stem cells
2 layers of muscle for segmentation
Peyer’s patches
Huge SA for absorption
 Villi – 1mm fingerlike projections w/capillary bed &
lacteal (lymph)
 Microvilli – brush border projections of plasma
membrane w/ bound enzymes to complete carb &
protein digestion
3 subdivisions:
 Duodenum - 10” curves around pancreas
▪ Bile duct
▪ Pancreatic duct
▪ Duodenal glands produce bicarbonate mucus to
neutralize acidic chyme
 Jejunum – 8’ long
 Ileum – 12’ long
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Liver
 Largest gland in body (3lbs), 4
primary lobes
 Produces 500-1,000 mL
bile/day – fat emulsifier
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Gallbladder
 4” long, inferior surface of
right lobe
 Store bile (yellow-green
alkaline solution)
 Salts, pigments (bilirubin),
cholesterol, triglycerides,
phospholipids & electrolytes
Pancreatic juice (12001500mL/day) released via
pancreatic duct which fuses w/bile
duct as enters duodenum
 Acini – clusters of secretory cells
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 Pancreatic proteases: trypsin,
carboxypeptidase, chymotrypsin
 Amylase, lipases, nucleases
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Islets of Langerhans
 β cells secrete – insulin (↓ blood
glucose)
 α cells secrete – glucagon ( blood
glucose)
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Bicarbonate ions – pH 8
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7cm diameter, 1.5 meters
Function: reabsorb remaining water from
indigestible food residue & eliminate as feces
12-24 hours to reclaim water & electrolytes
Simple columnar epithelium
Deep crypts w/goblet cells to ease passage of feces
Mass movements: slow powerful contractive
waves, fiber increases strength contractions
Subdivisions:
 Cecum - pouch
 Appendix – lymph tissue
 Colon – ascending, transverse, descending and
sigmoid
 Rectum – has valves to separate feces from
flatus!
 Anal Canal – 2 sphincters (1 involuntary & 1
voluntary), stratified squamous epithelium
Over 700 species!
Survivors from small intestine or
enter via anus
 Ferment indigestible carbs
(cellulose, xylan)
 Metabolize proteins (mucin, heparin,
hyaluronic acid)
 Release 500mL gasses/day (H2, N2,
CH4, CO2, and smelly dimethyl
sulfide)
 Synthesize vitamin B & K
 Lymph cells moniter to ensure they
do not stray
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Catabolic process: polymers hydrolyzed
monomers
Complete Enzyme Chart:
 Carbs: Amylase, dextrinase, glucoamylase,
maltase, sucrase, lactase
 Proteins:Pepsin, trypsin, chymotrypsin,
carboxypeptidase, aminopeptidase, dipeptidase
 Lipids: bile, lipase
 Nucleic Acids: ribonuclease, deoxyribonuclease,
phosphatases
Endoderm
forms lining GI
tract
 Rest develops
from mesoderm
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Nutrients – promote growth, maintenance & repair
Carbohydrates
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Lipids
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Organic compounds function as coenzymes
Classified as fat or water soluble
Minerals
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Structural uses: keratin, collagen, elastin, muscle proteins, etc
Functional uses: enzymes, hormones, pigments, and transport
Can be oxidized for energy in liver
RDA: 0.8%g/kg of body weight
Vitamins
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Utilized for phospholipids, myelin, insulation, cushion, stored energy, steroid hormones, absorb
fat-soluble vitamins
RDA: 80-100g plant/animal fats; <250mg cholesterol
Proteins
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Glucose oxidized to ATP (mitochondria)
Energy measured in kilocalories or Calories (heat energy required to raise 1kg of water 1OC)
RDA: 130g digestible, 25-30g of fiber
Inorganic
Ionized or bound to organic compounds
Water