Download Digestive System Part Two

Digestive System
Part 2
Anatomy and Physiology of the Digestive System
 Small intestine
 Major organ of digestion and absorption
 2–4 m long; from pyloric sphincter to ileocecal valve
 Subdivisions
Duodenum
 Jejunum
 Ileum

Anatomy and Physiology of the Digestive System
 Small intestine
 Structural modifications
 Villi
 Intestinal glands
Mucosa
 Submucosa

Mouth (oral cavity)
Tongue
Esophagus
Liver
Gallbladder
Duodenum
Jejunum
Small
intestine Ileum
Anus
Parotid gland
Sublingual gland Salivary
Submandibular
glands
gland
Pharynx
Stomach
Pancreas
(Spleen)
Transverse colon
Descending colon
Ascending colon
Large
Cecum
intestine
Sigmoid colon
Rectum
Vermiform appendix
Anal canal
Figure 23.1
Vein carrying blood to
hepatic portal vessel
Muscle
layers
Circular
folds
Villi
Lumen
(a)
Figure 23.22a
Microvilli
(brush border)
Absorptive cells
Lacteal
Goblet cell
Blood
capillaries
Mucosa
associated
lymphoid tissue
Intestinal crypt
Muscularis
mucosae
Duodenal gland
(b)
Vilus
Enteroendocrine
cells
Venule
Lymphatic vessel
Submucosa
Figure 23.22b
Microvilli
(b)
Absorptive
cell
Figure 23.3b
Anatomy and Physiology of the Digestive System
 Chemical digestion in the small intestine
 Food entering SI = partially digested
 Intestinal juice
 Water, mucous
 Crypt cells produce lysozyme
Microvilli
(brush border)
Absorptive cells
Lacteal
Goblet cell
Blood
capillaries
Mucosa
associated
lymphoid tissue
Intestinal crypt
Muscularis
mucosae
Duodenal gland
(b)
Villus
Enteroendocrine
cells
Venule
Lymphatic vessel
Submucosa
Figure 23.22b
Anatomy and Physiology of the Digestive System
 Chemical digestion in the small intestine
 Pancreatic juice
 Enzymes
Amylase
o Carbohydates
 Lipase
o Fats
 Trypsinogen, chymotrypsinogen, carboxypeptidase
o Activated to digest protein
 Sodium bicarbonate
 Neutralize stomach acid

Stomach
Pancreas
Epithelial
cells
Membrane-bound
enteropeptidase
Trypsinogen
Trypsin
(inactive)
Chymotrypsin
Chymotrypsinogen
(inactive)
Carboxypeptidase
Procarboxypeptidase
(inactive)
Figure 23.27
Anatomy and Physiology of the Digestive System
 Chemical digestion in the small intestine
 Bile
 Emilsify lipids
 Disaccharides and peptidases
 Protective mucous secreted as well
Right and left
hepatic ducts
of liver
Cystic duct
Common hepatic duct
Bile duct and sphincter
Accessory pancreatic duct
Mucosa
with folds
Gallbladder
Major duodenal
papilla
Hepatopancreatic
ampulla and sphincter
Tail of pancreas
Pancreas
Jejunum
Duodenum
Main pancreatic duct
and sphincter
Head of pancreas
Figure 23.21
Anatomy and Physiology of the Digestive System
 Accessory digestive organs
 Liver
 Pancreas
 Gallbladder
Anatomy and Physiology of the Digestive System
 Accessory digestive organs
 Liver
 Largest internal surface area of any body organ
 Blood supply



Hepatic artery
Hepatic-portal vein
Hepatic vein
Inferior vena cava
(not part of hepatic
portal system)
Hepatic veins
Liver
Hepatic portal
vein
Small intestine
Gastric veins
Spleen
Inferior vena cava
Splenic vein
Right gastroepiploic
vein
Inferior
mesenteric vein
Superior
mesenteric vein
Large intestine
Rectum
(c) The hepatic portal circulation.
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Figure 19.29c
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
Portal vein
Hepatic
macrophages
in sinusoid walls
Bile duct
Portal venule
Portal arteriole
Portal triad
(c)
Copyright © 2010 Pearson Education, Inc.
Figure 23.25c
Anatomy and Physiology of the Digestive System
 Accessory digestive organs
 Liver
 Microscopic compartments = lobules

Lined by hepatocytes = screen blood
o Store nutrients
o Manage toxins
Sternum
Nipple
Liver
Bare area
Falciform
ligament
Left lobe of liver
Right lobe
of liver
Gallbladder
(a)
Round ligament
(ligamentum
teres)
Figure 23.24a
(a)
Lobule
Copyright © 2010 Pearson Education, Inc.
(b)
Central vein
Connective
tissue septum
Figure 23.25a, b
Anatomy and Physiology of the Digestive System
 Accessory digestive organs
 Liver
 Hepatocyte functions
 Process blood borne nutrients
 Store fat-soluble vitamins
 Perform detoxification
 Produce ~900 ml bile per day
 Glucose is stored as glycogen
Cystic, Hepatic and Bile ducts
Right and left
hepatic ducts
of liver
Cystic duct
Common hepatic duct
Bile duct and sphincter
Accessory pancreatic duct
Mucosa
with folds
Gallbladder
Major duodenal
papilla
Hepatopancreatic
ampulla and sphincter
Copyright © 2010 Pearson Education, Inc.
Tail of pancreas
Pancreas
Jejunum
Duodenum
Main pancreatic duct
and sphincter
Head of pancreas
Figure 23.21
Anatomy and Physiology of the Digestive System
 Accessory digestive organs
 Liver
 Bile
 Yellow-green, alkaline solution
 Bile salts
o Cholesterol derivatives that function in fat emulsification and
absorption
 Bilirubin
o Pigment formed from heme
 Metabolized to form urobilinogen → stercobilin
 Lack of bile = grayish stools with fatty streaks (Acholic feces)
Anatomy and Physiology of the Digestive System
 Accessory digestive organs
 Liver
 Other functions




Makes heparin and other plasma proteins
Stores vitamins, minerals and lipid soluble toxins
Stores nutrients
Catabolizes nitrogenous wastes
Anatomy and Physiology of the Digestive System
 Accessory digestive organs
 Liver
 Gallbladder
 Thin-walled muscular sac on the ventral surface of the liver
 Stores and concentrates bile by absorbing its water and ions
 Releases bile via the cystic duct
o Flows into the bile duct
Anatomy and Physiology of the Digestive System
 Accessory digestive organs
 Pancreas
 Function
 Delivers digestive fluids and NaHCO3 to duodenum via pancreatic duct
 Tissue types
 Endocrine
o Islets of Langerhans → insulin and glucagon
 Exocrine
o Acinar tissue → pancreatic juice
Mouth (oral cavity)
Tongue
Esophagus
Liver
Gallbladder
Duodenum
Jejunum
Small
intestine Ileum
Anus
Parotid gland
Sublingual gland Salivary
Submandibular
glands
gland
Pharynx
Stomach
Pancreas
(Spleen)
Transverse colon
Descending colon
Ascending colon
Large
Cecum
intestine
Sigmoid colon
Rectum
Vermiform appendix
Anal canal
Figure 23.1
Anatomy and Physiology of the Digestive System
 Accessory digestive organs
 Pancreas
 Secretion mediated by hormones
 Secretin
o Released in response to acid
o Stimulates release of base
 Cholecystokinin
o Released when protein and fat enter intestine
o Stimulates the release of bile and pancreatic juice
Right and left
hepatic ducts
of liver
Cystic duct
Common hepatic duct
Bile duct and sphincter
Accessory pancreatic duct
Mucosa
with folds
Gallbladder
Major duodenal
papilla
Hepatopancreatic
ampulla and sphincter
Tail of pancreas
Pancreas
Jejunum
Duodenum
Main pancreatic duct
and sphincter
Head of pancreas
Figure 23.21
Small
duct
Acinar cells
Basement
membrane
Zymogen
granules
Rough
endoplasmic
reticulum
(a)
Figure 23.26a
Slide 1
1
Chyme entering duodenum
causes release of
cholecystokinin
(CCK) and
secretin from
duodenal
enteroendocrine
cells.
2
CCK (red
dots) and
secretin (yellow
dots) enter the
bloodstream.
3
CCK induces
secretion of
enzyme-rich
pancreatic juice.
Secretin causes
secretion of
HCO3–-rich
pancreatic juice.
4
Bile salts and,
to a lesser extent,
secretin
transported via
bloodstream
stimulate liver to
produce bile
more rapidly.
5
CCK (via
bloodstream)
causes
gallbladder to
contract and
hepatopancreatic
sphincter to
relax; bile enters
duodenum.
6 During
cephalic and
gastric phases,
vagal nerve
stimulation
causes weak
contractions of
gallbladder.
Figure 23.28
Anatomy and Physiology of the Digestive System
 Large intestine
 About 1.5 meters in length in a cadaver (SI about 6m long)
 Functions
 Vitamins, water, and electrolytes are reclaimed
 Propulsion of feces toward the anus
 Colon is not essential for life
Left colic
(splenic) flexure
Transverse
mesocolon
Epiploic
appendages
Right colic
(hepatic)
flexure
Transverse
colon
Superior
mesenteric
artery
Haustrum
Descending
colon
Ascending
colon
IIeum
Cut edge of
mesentery
Teniae coli
IIeocecal
valve
Cecum
Vermiform appendix
Sigmoid
colon
Rectum
Anal canal
(a)
External anal sphincter
Figure 23.29a
Anatomy and Physiology of the Digestive System
 Regions
 Cecum
 Colon
 Rectum
 Anal canal
Anatomy and Physiology of the Digestive System
 Regions
 Cecum
 Blind pouch
 Appendix attaches to this area
 Bacteria
 Immune function
Anatomy and Physiology of the Digestive System
 Regions
 Colon
 Ascending
 Retroperitoneal
 Transverse
 Anchored via mesocolons (mesenteries)
 Descending
 Retroperitoneal
 Sigmoid
 Anchored via mesocolons (mesenteries)
Greater omentum
Transverse colon
Transverse
mesocolon
Descending colon
Jejunum
Mesentery
Sigmoid
mesocolon
Sigmoid colon
Ileum
(c)
Figure 23.30c
Liver
Lesser omentum
Pancreas
Stomach
Transverse
mesocolon
Duodenum
Transverse colon
Mesentery
Greater omentum
Jejunum
Ileum
Visceral peritoneum
Parietal peritoneum
(d)
Urinary bladder
Rectum
Figure 23.30d
Anatomy and Physiology of the Digestive System
 Regions
 Rectum
 Rectal valves stop feces from being passed with gas
 Anal canal
 Last segment of the large intestine
 Internal anal sphincter
 Smooth muscle (involuntary)
 Spinal reflex arcs
 External anal sphincter
 Skeletal muscle (voluntary)
Rectal valve
Rectum
Hemorrhoidal
veins
Levator ani
muscle
Anal canal
External anal
sphincter
Internal anal
sphincter
Anal columns
Pectinate line
Anal sinuses
Anus
(b)
Figure 23.29b
Anatomy and Physiology of the Digestive System
 Defectation
 Mass movements force feces into rectum
 Distension initiates spinal defecation reflex
 Parasympathetic signals
 Stimulate contraction of the sigmoid colon and rectum
 Relax the internal anal sphincter
 Conscious control allows relaxation of external anal sphincter
 Valsalva’s maneuver
Impulses from
cerebral cortex
(conscious
control)
1
Sensory
nerve fibers
Distension, or stretch, of the
rectal walls due to movement
of feces into the rectum
stimulates stretch receptors
there. The receptors transmit
signals along afferent fibers to
spinal cord neurons.
2
Voluntary motor
nerve to external
anal sphincter
Sigmoid
colon
A spinal reflex is initiated in
which parasympathetic motor
(efferent) fibers stimulate
contraction of the rectal walls
and relaxation of the internal
anal sphincter.
Stretch receptors in wall
Rectum
External anal
sphincter
(skeletal muscle)
Involuntary motor nerve
(parasympathetic division)
Internal anal sphincter
(smooth muscle)
3
If it is convenient to defecate, voluntary motor
neurons are inhibited, allowing the external anal
sphincter to relax so that feces may pass.
Figure 23.31
Questions?