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PowerPoint® Lecture Slides
prepared by
Barbara Heard,
Atlantic Cape Community
College
CHAPTER
23
The Digestive
System: Part B
© Annie Leibovitz/Contact Press Images
© 2013 Pearson Education, Inc.
Pharynx
• Food passes from mouth  oropharynx 
laryngopharynx
– Allows passage of food, fluids, and air
– Stratified squamous epithelium lining; mucusproducing glands
– Skeletal muscle layers: inner longitudinal,
outer pharyngeal constrictors
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Esophagus
• Flat muscular tube from laryngopharynx to
stomach
• Pierces diaphragm at esophageal hiatus
• Joins stomach at cardial orifice
• Gastroesophageal (cardiac) sphincter
• Surrounds cardial orifice
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Homeostatic Imbalance
• Heartburn
– Stomach acid regurgitates into esophagus
– Likely with excess food/drink, extreme
obesity, pregnancy, running
– Also with hiatal hernia - structural
abnormality
• Part of stomach above diaphragm
• Can  esophagitis, esophageal ulcers,
esophageal cancer
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Esophagus
• Esophageal mucosa contains stratified
squamous epithelium
– Changes to simple columnar at stomach
• Esophageal glands in submucosa secrete
mucus to aid in bolus movement
• Muscularis externa - skeletal superiorly;
mixed in middle; smooth inferiorly
• Adventitia instead of serosa
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Figure 23.12a Microscopic structure of the esophagus.
Mucosa
(stratified
squamous
epithelium)
Submucosa
(areolar
connective
tissue)
Lumen
Muscularis
externa
• Circular layer
• Longitudinal
layer
Adventitia
(fibrous
connective
tissue)
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Figure 23.12b Microscopic structure of the esophagus.
Mucosa
(stratified
squamous
epithelium)
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Esophagus-stomach
junction
Simple columnar
epithelium of stomach
Figure 23.13 Deglutition (swallowing).
Slide 7
Bolus of food
Tongue
Uvula
Pharynx
Bolus
Epiglottis
Epiglottis
Glottis
Trachea
Esophagus
1 During the buccal phase, the upper
esophageal sphincter is contracted.
The tongue presses against the hard
palate, forcing the food bolus into the
oropharynx.
2 The pharyngeal-esophageal phase
begins as the uvula and larynx rise to prevent
food from entering respiratory passageways.
The tongue blocks off the mouth. The upper
esophageal sphincter relaxes, allowing food
to enter the esophagus.
4 Peristalsis moves
food through the
esophagus to the
stomach.
Relaxed muscles
Circular muscles
contract
Upper
esophageal
sphincter
3 The constrictor muscles of the
pharynx contract, forcing food into
the esophagus inferiorly. The upper
esophageal sphincter contracts
(closes) after food enters.
Relaxed
muscles
5 The gastroesophageal
sphincter surrounding the
cardial orifice opens, and
food enters the stomach.
Bolus of food
Longitudinal muscles
contract
Circular muscles contract
Gastroesophageal
sphincter closed
Gastroesophageal
sphincter opens
Stomach
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Bolus
Stomach: Gross Anatomy
• In upper left quadrant; temporary storage;
digestion of bolus to chyme
• Cardial part (cardia)
– Surrounds cardial orifice
• Fundus
– Dome-shaped region beneath diaphragm
• Body
– Midportion
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Stomach: Gross Anatomy
• Pyloric part
– Antrum (superior portion)  pyloric canal 
pylorus
– Pylorus continuous with duodenum through
pyloric valve (sphincter controlling stomach
emptying)
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Figure 23.14a Anatomy of the stomach.
Cardia
Fundus
Esophagus
Muscularis
externa
• Longitudinal layer
• Circular layer
• Oblique layer
Serosa
Body
Lumen
Lesser
curvature
Rugae of
mucosa
Greater
curvature
Duodenum
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Pyloric sphincter
(valve) at pylorus
Pyloric
canal
Pyloric
antrum
Figure 23.14b Anatomy of the stomach.
Liver
(cut)
Fundus
Body
Spleen
Lesser
curvature
Greater
curvature
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Stomach: Gross Anatomy
• Greater curvature - convex lateral
surface
• Lesser curvature - concave medial
surface
• Mesenteries tether stomach
– Lesser omentum
• From liver to lesser curvature
– Greater omentum – contains fat deposits &
lymph nodes
• Greater curvature  over small intestine  spleen
& transverse colon  mesocolon
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Figure 23.30a Mesenteries of the abdominal digestive organs.
Falciform ligament
Liver
Gallbladder
Spleen
Stomach
Ligamentum teres
Greater omentum
Small intestine
Cecum
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Figure 23.30b Mesenteries of the abdominal digestive organs.
Liver
Gallbladder
Lesser omentum
Stomach
Duodenum
Transverse colon
Small intestine
Cecum
Urinary bladder
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Figure 23.30c Mesenteries of the abdominal digestive organs.
Greater omentum
Transverse colon
Transverse
mesocolon
Descending colon
Jejunum
Mesentery
Sigmoid
mesocolon
Sigmoid colon
Ileum
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Stomach: Gross Anatomy
• ANS nerve supply
– Sympathetic from thoracic splanchnic nerves
via celiac plexus
– Parasympathetic via vagus nerve
• Blood supply
– Celiac trunk (gastric and splenic branches)
– Veins of hepatic portal system
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Stomach: Microscopic Anatomy
• Four tunics
• Muscularis and mucosa modified
– Muscularis externa
• Three layers of smooth muscle
• Inner oblique layer allows stomach to churn, mix,
move, and physically break down food
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Figure 23.15a Microscopic anatomy of the stomach.
Surface
epithelium
Mucosa
Lamina
propria
Muscularis
mucosae
Submucosa
(contains
submucosal
Oblique
plexus)
layer
Muscularis
Circular
externa
layer
(contains
Longitudinal
myenteric
layer
plexus)
Stomach wall
Serosa
Layers of the stomach wall
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Stomach: Microscopic Anatomy
• Mucosa
– Simple columnar epithelium composed of
mucous cells
• Secrete two-layer coat of alkaline mucus
– Surface layer traps bicarbonate-rich fluid beneath it
– Dotted with gastric pits  gastric glands
• Gastric glands produce gastric juice
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Figure 23.15b Microscopic anatomy of the stomach.
Gastric pits
Surface epithelium
(mucous cells)
Gastric
pit
Mucous neck cells
Parietal cell
Gastric
gland
Chief cell
Enteroendocrine cell
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Enlarged view of gastric pits and
gastric glands
Gastric Glands
• Cell types
– Mucous neck cells (secrete thin, acidic
mucus of unknown function)
– Parietal cells
– Chief cells
– Enteroendocrine cells
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Figure 23.15c Microscopic anatomy of the stomach.
Pepsinogen
Pepsin
HCI
Mitochondria
Parietal cell
Chief cell
Enteroendocrine
cell
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Location of the HCl-producing parietal cells
and pepsin-secreting chief cells in a gastric
gland
Gastric Gland Secretions
• Glands in fundus and body produce most
gastric juice
• Parietal cell secretions
– Hydrochloric acid (HCl)
•  pH 1.5–3.5 denatures protein, activates pepsin,
breaks down plant cell walls, kills many bacteria
– Intrinsic factor
• Glycoprotein required for absorption of vitamin B12
in small intestine
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Gastric Gland Secretions
• Chief cell secretions
– Pepsinogen - inactive enzyme
• Activated to pepsin by HCl and by pepsin itself (a
positive feedback mechanism)
– Lipases
• Digest ~15% of lipids
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Gastric Gland Secretions
• Enteroendocrine cells
– Secrete chemical messengers into lamina
propria
• Act as paracrines
– Serotonin and histamine
• Hormones
– Somatostatin (also acts as paracrine) and gastrin
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Mucosal Barrier
• Harsh digestive conditions in stomach
• Has mucosal barrier to protect
– Thick layer of bicarbonate-rich mucus
– Tight junctions between epithelial cells
• Prevent juice seeping underneath tissue
– Damaged epithelial cells quickly replaced by
division of stem cells
• Surface cells replaced every 3–6 days
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Homeostatic Imbalance
• Gastritis
– Inflammation caused by anything that
breaches mucosal barrier
• Peptic or gastric ulcers
– Erosions of stomach wall
• Can perforate  peritonitis; hemorrhage
– Most caused by Helicobacter pylori bacteria
– Some by NSAIDs
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Figure 23.16 Photographs of a gastric ulcer and the H. pylori bacteria that most commonly cause it.
Bacteria
Mucosa
layer of
stomach
A gastric ulcer lesion
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H. pylori bacteria
Digestive Processes in the Stomach
• Mechanical breakdown
• Denaturation of proteins by HCl
• Enzymatic digestion of proteins by pepsin
(and milk protein by rennin in infants)
• Delivers chyme to small intestine
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Digestive Processes in the Stomach
• Lipid-soluble alcohol and aspirin absorbed
into blood
• Only stomach function essential to life
– Secretes intrinsic factor for vitamin B12
absorption
• B12 needed  mature red blood cells
• Lack of intrinsic factor causes pernicious anemia
• Treated with B12 injections
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Regulation of Gastric Secretion
• Neural and hormonal mechanisms
• Gastric mucosa  up to 3 L gastric
juice/day
• Vagus nerve stimulation  secretion 
• Sympathetic stimulation  secretion 
• Hormonal control largely gastrin
–  Enzyme and HCl secretion
– Most small intestine secretions - gastrin
antagonists
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Regulation of Gastric Secretion
• Three phases of gastric secretion
– Cephalic (reflex) phase – conditioned reflex
triggered by aroma, taste, sight, thought
– Gastric phase – lasts 3–4 hours; ⅔ gastric
juice released
• Stimulated by distension, peptides, low acidity,
gastrin (major stimulus)
• Enteroendocrine G cells stimulated by caffeine,
peptides, rising pH  gastrin
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Stimuli of Gastric Phase
• Gastrin  enzyme and HCl release
– Low pH inhibits gastrin secretion (as between meals)
• Buffering action of ingested proteins  rising pH
 gastrin secretion
• Three chemicals - ACh, histamine, and gastrin stimulate parietal cells through secondmessenger systems
– All three are necessary for maximum HCl secretion
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HCl Formation
• Parietal cells pump H+ (from carbonic acid
breakdown) into stomach lumen
– K+ goes into cells to balance charge
– HCO3– from carbonic acid breakdown
•  blood (via Cl– and HCO3– antiporter)
•  blood leaving stomach more alkaline 
Alkaline tide
– Cl– (from blood plasma via antiporter) follows
H+ HCl
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Figure 23.18 Mechanism of HCl secretion by parietal cells.
Gastric gland
Blood
capillary
Chief cell
CO2
CO2 + H2O
H2CO3
Stomach lumen
Carbonic
anhydrase
H+
K+
HCO3−
Alkaline
tide
Parietal cell
H+-K+
ATPase
H+
K+
HCI
HCO3−
Cl−
HCO3−- Cl−
Interstitial antiporter
fluid
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Cl−
Cl−
Regulation of Gastric Secretion
• Intestinal phase
– Stimulatory component
• Partially digested food enters small intestine 
brief intestinal gastrin release
– Inhibitory effects (enterogastric reflex and
enterogastrones)
• Chyme with H+, fats, peptides, irritating substances
 inhibition
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Enterogastric Reflex
• Three reflexes act to
– Inhibit vagal nuclei in medulla
– Inhibit local reflexes
– Activate sympathetic fibers  tightening of
pyloric sphincter  no more food entry to
small intestine
•  Decreased gastric activity  protects
small intestine from excessive acidity
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Intestinal Phase
• Enterogastrones released
– Secretin, cholecystokinin (CCK),
vasoactive intestinal peptide (VIP)
• All inhibit gastric secretion
• If small intestine pushed to accept more
chyme  dumping syndrome
– Nausea and vomiting
– Common in gastric reduction for weight loss
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Figure 23.17 Neural and hormonal mechanisms that regulate release of gastric juice.
Inhibitory events
Stimulatory events
Cephalic
phase
Gastric
phase
1 Sight and thought
of food
Cerebral cortex
Conditioned reflex
2 Stimulation of
taste and smell
receptors
Hypothalamus
and medulla
oblongata
1 Stomach
distension
activates
stretch
receptors
Vagovagal
reflexes
Intestinal
phase
Stimulate
Inhibit
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Vagus
nerve
Local
reflexes
2 Food chemicals
G cells
(especially peptides and
caffeine) and rising pH
activate chemoreceptors
1 Presence of
partially digested
foods in duodenum
or distension of the
duodenum when
stomach begins to
empty
Medulla
Vagus
nerve
Lack of
stimulatory
impulses to
parasympathetic
center
Cerebral
cortex
Gastrin
secretion
declines
G cells
Overrides
parasympathetic
controls
Sympathetic
nervous
system
activation
1 Loss of
appetite,
depression
1 Excessive
acidity
(pH < 2)
in stomach
2 Emotional
stress
Gastrin
release
to blood
Intestinal
(enteric)
gastrin
release
to blood
Stomach
secretory
activity
Enterogastric
reflex
Brief
effect
Local
reflexes
Vagal
nuclei
in medulla
Pyloric
sphincter
Release of
enterogastrones
(secretin, cholecystokinin,
vasoactive intestinal
peptide)
1 Distension
of duodenum;
presence of
fatty, acidic, or
hypertonic
chyme; and/or
irritants in
the duodenum
2 Distension;
presence of
fatty, acidic,
partially
digested food
in the
duodenum
Response of the Stomach to Filling
• Stretches to accommodate incoming food
– Pressure constant until 1.5 L food ingested
• Reflex-mediated receptive relaxation
– Coordinated by swallowing center of brain stem
– Gastric accommodation
• Plasticity (stress-relaxation response) of smooth
muscle (see Chapter 9)
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Gastric Contractile Activity
• Peristaltic waves move toward pylorus at
rate of 3 per minute
– Basic electrical rhythm (BER) set by enteric
pacemaker cells (formerly interstitial cells of
Cajal)
– Pacemaker cells linked by gap junctions 
entire muscularis contracts
• Distension and gastrin increase force of
contraction
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Gastric Contractile Activity
• Most vigorous near pylorus
• Chyme is either
– Delivered in ~3 ml spurts to duodenum, or
– Forced backward into stomach
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Figure 23.19 Deglutition (swallowing).
Pyloric
valve
closed
1 Propulsion: Peristaltic
waves move from the fundus
toward the pylorus
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Pyloric
valve
slightly
opened
2 Grinding: The most
vigorous peristalsis and
mixing action occur close
to the pylorus. The pyloric
end of the stomach acts as a
pump that delivers small
amounts of chyme into the
duodenum.
Slide 1
Pyloric
valve
closed
3 Retropulsion: The peristaltic
wave closes the pyloric valve,
forcing most of the contents of
the pylorus backward into the
stomach.
Figure 23.19 Deglutition (swallowing).
Pyloric
valve
closed
1 Propulsion: Peristaltic
waves move from the fundus
toward the pylorus
© 2013 Pearson Education, Inc.
Slide 2
Figure 23.19 Deglutition (swallowing).
Pyloric
valve
closed
1 Propulsion: Peristaltic
waves move from the fundus
toward the pylorus
© 2013 Pearson Education, Inc.
Pyloric
valve
slightly
opened
2 Grinding: The most
vigorous peristalsis and
mixing action occur close
to the pylorus. The pyloric
end of the stomach acts as a
pump that delivers small
amounts of chyme into the
duodenum.
Slide 3
Figure 23.19 Deglutition (swallowing).
Pyloric
valve
closed
1 Propulsion: Peristaltic
waves move from the fundus
toward the pylorus
© 2013 Pearson Education, Inc.
Pyloric
valve
slightly
opened
2 Grinding: The most
vigorous peristalsis and
mixing action occur close
to the pylorus. The pyloric
end of the stomach acts as a
pump that delivers small
amounts of chyme into the
duodenum.
Slide 4
Pyloric
valve
closed
3 Retropulsion: The peristaltic
wave closes the pyloric valve,
forcing most of the contents of
the pylorus backward into the
stomach.
Regulation of Gastric Emptying
• As chyme enters duodenum
– Receptors respond to stretch and chemical
signals
– Enterogastric reflex and enterogastrones
inhibit gastric secretion and duodenal filling
• Carbohydrate-rich chyme moves quickly
through duodenum
• Fatty chyme remains in duodenum 6 hours
or more
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Figure 23.20 Neural and hormonal factors that inhibit gastric emptying.
Presence of fatty, hypertonic,
acidic chyme in duodenum
Duodenal enteroendocrine cells
Chemoreceptors and
stretch receptors
Secrete
Enterogastrones
(secretin,
cholecystokinin,
vasoactive intestinal
peptide)
Target
Via short
reflexes
Enteric
neurons
Duodenal
stimuli
decline
Via long
reflexes
CNS centers
sympathetic
activity;
parasympathetic
activity
Contractile force and
rate of stomach
emptying decline
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Initial stimulus
Stimulate
Physiological response
Inhibit
Result
Homeostatic Imbalance
• Vomiting (emesis) caused by
• Extreme stretching
• Intestinal irritants, e.g., bacterial toxins, excessive
alcohol, spicy food, certain drugs
• Chemicals/sensory impulses  emetic
center of medulla
• Excessive vomiting  dehydration,
electrolyte and acid-base imbalances
(alkalosis)
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Small Intestine: Gross Anatomy
• Major organ of digestion and absorption
• 2-4 m long; from pyloric sphincter to
ileocecal valve
• Subdivisions
– Duodenum (retroperitoneal)
– Jejunum (attached posteriorly by mesentery)
– Ileum (attached posteriorly by mesentery)
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Figure 23.1 Alimentary canal and related accessory digestive organs.
Mouth (oral cavity)
Tongue*
Parotid gland
Sublingual gland
Submandibular gland
Salivary
glands*
Pharynx
Esophagus
Stomach
Pancreas*
(Spleen)
Liver*
Gallbladder*
Transverse colon
Small
intestine
Anus
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Duodenum
Jejunum
Ileum
Descending colon
Ascending colon
Cecum
Sigmoid colon
Rectum
Appendix
Anal canal
Large
intestine
Duodenum
• Curves around head of pancreas; shortest
part – 25 cm
• Bile duct (from liver) and main pancreatic
duct (from pancreas)
– Join at hepatopancreatic ampulla
– Enter duodenum at major duodenal papilla
– Entry controlled by hepatopancreatic
sphincter
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Figure 23.21 The duodenum of the small intestine, and related organs.
Right and left
hepatic ducts
of liver
Cystic duct
Common hepatic duct
Bile duct and sphincter
Accessory pancreatic duct
Mucosa
with folds
Tail of pancreas
Pancreas
Jejunum
Gallbladder
Major duodenal
papilla
Hepatopancreatic
ampulla and sphincter
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Main pancreatic duct and sphincter
Duodenum
Head of pancreas
Jejunum and Ileum
• Jejunum
– Extends from duodenum to ileum
– About 2.5 m long
• Ileum
– Joins large intestine at ileocecal valve
– About 3.6 m long
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Gross Anatomy of Small Intestine
• Vagus nerve (parasympathetic) and
sympathetics from thoracic splanchnic
nerves serve small intestine
• Superior mesenteric artery brings blood
supply
• Veins (carrying nutrient-rich blood) drain
into superior mesenteric veins  hepatic
portal vein  liver
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Structural Modifications
• Increase surface area of proximal part for
nutrient absorption
– Circular folds (plicae circulares)
– Villi
– Microvilli
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Structural Modifications
• Circular folds
– Permanent folds (~1 cm deep) that force
chyme to slowly spiral through lumen  more
nutrient absorption
• Villi
– Extensions (~1 mm high) of mucosa with
capillary bed and lacteal for absorption
• Microvilli (brush border) – contain
enzymes for carbohydrate and protein
digestion
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Figure 23.22a Structural modifications of the small intestine that increase its surface area for digestion and
absorption.
Vein carrying
blood to
hepatic portal
vessel
Muscle
layers
Circular
folds
Villi
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Lumen
Figure 23.22b Structural modifications of the small intestine that increase its surface area for digestion and
absorption.
Microvilli
(brush border)
Absorptive
cells
Lacteal
Goblet
cell
Blood
capillaries
Mucosaassociated
lymphoid
tissue
Intestinal
crypt
Muscularis
mucosae
Duodenal
gland
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Villus
Enteroendocrine
cells
Venule
Lymphatic vessel
Submucosa
Figure 23.22c Structural modifications of the small intestine that increase its surface area for digestion and
absorption.
Absorptive cells
Goblet
cells
Villi
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Intestinal crypt
Figure 23.23 Microvilli of the small intestine.
Mucus
granules
Microvilli
forming the
brush border
Absorptive cell
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Intestinal Crypts
• Intestinal crypt epithelium renewed every
2-4 days
– Most - secretory cells that produce intestinal
juice
– Enteroendocrine cells  enterogastrones
– Intraepithelial lymphocytes (IELs)
• Release cytokines that kill infected cells
– Paneth cells
• Secrete antimicrobial agents (defensins and
lysozyme)
– Stem cells divide to produce crypt cells
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Homeostatic Imbalance
• Chemotherapy targets rapidly dividing
cells
– Kills cancer cells
– Kills rapidly dividing GI tract epithelium 
nausea, vomiting, diarrhea
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Mucosa
• Peyer's patches protect especially distal
part against bacteria
– May protrude into submucosa
• B lymphocytes leave intestine, enter
blood, protect intestinal lamina propria with
their IgA
• Duodenal (Brunner's) glands of the
duodenum secrete alkaline mucus to
neutralize acidic chyme
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Intestinal Juice
• 1-2 L secreted daily in response to
distension or irritation of mucosa
• Slightly alkaline; isotonic with blood
plasma
• Largely water; enzyme-poor (enzymes of
small intestine only in brush border);
contains mucus
• Facilitates transport and absorption of
nutrients
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The Liver and Gallbladder
• Accessory organs
• Liver
– Many functions; only digestive function  bile
production
• Bile – fat emulsifier
• Gallbladder
– Chief function  bile storage
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Liver
• Largest gland in body
• Four lobes—right, left, caudate, and
quadrate
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Liver
• Falciform ligament
– Separates larger right and smaller left lobes
– Suspends liver from diaphragm and anterior
abdominal wall
• Round ligament (ligamentum teres)
– Remnant of fetal umbilical vein along free
edge of falciform ligament
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Figure 23.24a Gross anatomy of the human liver.
Sternum
Nipple
Bare area
Liver
Falciform
ligament
Left lobe of
liver
Right lobe of liver
Gallbladder
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Round ligament
(ligamentum
teres)
Figure 23.24b Gross anatomy of the human liver.
Lesser
omentum
(in fissure)
Left lobe
of liver
Porta hepatis
containing
hepatic
artery (left)
and hepatic
portal vein
(right)
Quadrate
lobe of liver
Ligamentum
teres
Bare area
Caudate lobe
of liver
Sulcus for
inferior
vena cava
Hepatic vein
(cut)
Bile duct
(cut)
Right lobe
of liver
Gallbladder
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Liver: Associated Structures
• Lesser omentum anchors liver to stomach
• Hepatic artery and vein enter at porta
hepatis
• Bile ducts
– Common hepatic duct leaves liver
– Cystic duct connects to gallbladder
– Bile duct formed by union of common hepatic
and cystic ducts
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Figure 23.21 The duodenum of the small intestine, and related organs.
Right and left
hepatic ducts
of liver
Cystic duct
Common hepatic duct
Bile duct and sphincter
Accessory pancreatic duct
Mucosa
with folds
Tail of pancreas
Pancreas
Jejunum
Gallbladder
Major duodenal
papilla
Hepatopancreatic
ampulla and sphincter
© 2013 Pearson Education, Inc.
Main pancreatic duct and sphincter
Duodenum
Head of pancreas
Liver: Microscopic Anatomy
• Liver lobules
– Hexagonal structural and functional units
– Composed of plates of hepatocytes (liver
cells)
• Filter and process nutrient-rich blood
– Central vein in longitudinal axis
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Figure 23.25a–b Microscopic anatomy of the liver.
Lobule
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Central Connective
vein tissue septum
Liver: Microscopic Anatomy
• Portal triad at each corner of lobule
– Branch of hepatic artery supplies oxygen
– Branch of hepatic portal vein brings nutrient-rich
blood
– Bile duct receives bile from bile canaliculi
• Liver sinusoids - leaky capillaries between
hepatic plates
• Stellate macrophages (hepatic
macrophages or Kupffer cells) in liver
sinusoids remove debris & old RBCs
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Figure 23.25c Microscopic anatomy of the liver.
Interlobular veins
(to hepatic vein)
Central vein
Sinusoids
Bile canaliculi
Plates of
hepatocytes
Bile duct (receives
bile from bile
canaliculi)
Fenestrated
lining (endothelial
cells) of sinusoids
Stellate macrophages
in sinusoid walls
Portal vein
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Bile duct
Portal venule
Portal arteriole
Portal triad
Liver: Microscopic Anatomy
• Hepatocytes – increased rough & smooth
ER, Golgi, peroxisomes, mitochondria
• Hepatocyte functions
– Process bloodborne nutrients
– Store fat-soluble vitamins
– Perform detoxification
– Produce ~900 ml bile per day
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Liver
• Regenerative capacity
– Restores full size in 6-12 months after 80%
removal
– Injury  hepatocytes  growth factors 
endothelial cell proliferation
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Homeostatic Imbalance
• Hepatitis
– Usually viral infection, drug toxicity, wild
mushroom poisoning
• Cirrhosis
– Progressive, chronic inflammation from
chronic hepatitis or alcoholism
– Liver  fatty, fibrous  portal hypertension
• Liver transplants successful, but livers
scarce
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Bile
• Yellow-green, alkaline solution containing
– Bile salts - cholesterol derivatives that
function in fat emulsification and absorption
– Bilirubin - pigment formed from heme
• Bacteria break down in intestine to stercobilin 
brown color of feces
– Cholesterol, triglycerides, phospholipids, and
electrolytes
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Bile
• Enterohepatic circulation
– Recycles bile salts
– Bile salts  duodenum  reabsorbed from
ileum  hepatic portal blood  liver 
secreted into bile
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The Gallbladder
• Thin-walled muscular sac on ventral
surface of liver
• Stores and concentrates bile by absorbing
water and ions
• Muscular contractions release bile via
cystic duct, which flows into bile duct
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The Gallbladder
• High cholesterol; too few bile salts 
gallstones (biliary calculi)
– Obstruct flow of bile from gallbladder
• May cause obstructive jaundice
– Gallbladder contracts against sharp crystals
 pain
– Treated with drugs, ultrasound vibrations
(lithotripsy), laser vaporization, surgery
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