Digestive System
Digestive System
• Basic Divisions
– Digestive tract
– Accessory organs: various
exocrine glands
• Digestive Processes
– Ingestion
– Mechanical Processing
– Motility
•Peristalsis
• Digestive Processes
– Ingestion
– Mechanical Processing
– Motility
•Peristalsis
• Digestive Processes
– Ingestion
– Mechanical Processing
– Motility
•Peristalsis
•Segmentation movements
• Digestive Processes, continued
– Chemical digestion
– Secretion
– Absorption
– Excretion and defecation
• Non-Digestive Functions of
Digestive Tract
– Immunity
– Storage of iron
• Layers of the
digestive tract
– Mucosa
• Epithelium
• Lamina
propria
(areolar CT)
• Muscularis
mucosae
• Layers of the
digestive tract,
continued
– Submucosa
• includes the
submucosal
plexus
• Layers of the digestive tract,
continued
– Muscularis externa:
responsible for peristalsis and
segmentation movements
• longitudinal layer
• circular layer
• myenteric plexus
• Layers of the digestive tract,
continued
– Serosa (example of the
visceral peritoneum)
• Simple squamous
epithelium
• Areolar CT
Within peritoneal cavity
only
• Layers of the digestive tract,
continued
– Adventitia
• Dense irregular CT
Oral cavity, pharynx,
esophagus, rectum
• The Peritoneum
– Parietal p.
– Visceral p.
• The mesenteries
– Mesentery proper
– Mesocolon
– Greater omentum
– Lesser omentum
– Falciform ligament
• Oral (buccal) cavity
– Salivary Glands
• buccal glands
• lingual glands
• major salivary glands
– parotid
– sublingual
– submandibular
– Structure of salivary glands
• glandular epithelium
• merocrine cells
– Structure of salivary glands
• glandular epithelium
• merocrine cells
• compound tubularacinar
– Functions of saliva
• lubrication for swallowing,
speaking
• re-mineralizes tooth enamel
• buffer
• antibodies (IgA)
• dissolves food molecules
• some chemical digestion
• Pharynx
• Pharynx
– 3 divisions
• Nasopharynx
• Oropharynx
• Laryngopharynx
• Pharynx
– Structural features
• Lined with a stratified
squamous epithelium
• Skeletal muscle in wall
• Pharynx
– Structural features, continued
•eustachian tube opening
•uvula
•tonsils
• Pharynx
– Functions
• food and air pathways
•resonating chamber for voice
• swallowing
http://www.innerbody.com/ani
m/mouth.html
• Esophagus
– Structural features
• muscular tube about 25 cm
long
• posterior to larynx, trachea
• pierces diaphragm through
esophageal hiatus
• Esophagus
– Structural features, continued
• 2 sphincters:
– upper esophageal sphincter
– lower esophageal sphincter
• Esophagus
– Histology highlights
• mucosa: strat. sqaumous
• submucosa: lots of mucous
glands
• muscularis: from skeletal to
smooth
• adventitia (no serosa)
• Gastroesophageal Reflux
• Stomach
– Location
• Stomach
– Location: from
epigastric and
umbilical region
• Stomach
– Location: from
epigastric and
umbilical region to left
hypochondriac regions
• Gross
Structural
Features
– cardiac
region
– fundus
– body
– pylorus
– pyloric
sphincter
• Stomach Histology
– mucosa
• Stomach Histology
– mucosa: location of gastric glands
• Stomach Histology
– mucosa: location of gastric glands
• Stomach Histology
– mucosa: location of gastric glands
• gastric gland cells
– mucous cells
– parietal cells
– chief cells
– endocrine cells
• Stomach Histology, continued
– muscularis: three layers
• Stomach Functions
– food reservoir
– formation of chyme
– some chemical digestion
– regulation of chyme entry into
S.I.
– instrinsic factor production
– some absorption
Digestive System, review
• Basic Divisions
– Digestive tract
– Accessory organs: various
exocrine glands
• Pancreas
– Location
• Umbilical region
• Pancreas
– Location
• Umbilical region
• Retroperitoneal
• Pancreas Gross Structure
– Head
– Body
– Tail
– Ducts
• pancreatic
• accessory
– pancreas histology
• mostly glandular epithelium
– exocrine pancreas
– endocrine pancreas
– exocrine pancreas
• functions
– digestive enzymes
– sodium bicarbonate
– endocrine pancreas
• structure: thousands of islets
of Langerhans
– endocrine pancreas
• function: hormone secretion
– glucagon
– insulin
– somatostatin
• Liver
–Location: epigastric and right
hypochondriac regions
• Liver
–Location: epigastric and right
hypochondriac regions
• Liver
–Gross
structure: 2
major lobes
separated by
falciform
ligament
• Liver Blood
Supply
– Hepatic
portal vein
– Hepatic
arteries
• Liver Histology
– Functional unit:
• Liver Histology
– Functional unit: liver lobule
• Liver Histology
– Functional unit: liver lobule
– Liver cells
• Liver Histology
– Functional unit: liver lobule
– Liver cells
• hepatocytes
• Kupffer cells
– Each liver lobule supplied by
branches of:
• hepatic arteries
• hepatic portal veins
– Liver Functions
• Maintains blood glucose
levels
• Cholesterol synthesis
• HDL and LDL synthesis
• Plasma protein synthesis
– Liver Functions, continued
• Hormone and drug removal
• Phagocytosis
• Vitamin storage
• Iron storage
• Bilirubin excretion
– Liver Functions, continued
• Hormone and drug removal
• Phagocytosis
• Vitamin storage
• Iron storage
• Bilirubin excretion
– Liver Functions, continued
• Hormone and drug removal
• Phagocytosis
• Vitamin storage
• Iron storage
• Bilirubin excretion
• Bile salt secretion
• Gall Bladder
– Location: right lumbar region
• Liver Blood
Supply
– Hepatic
portal vein
– Hepatic
arteries
• Gross Structural Features of
Gall Bladder
– Muscular sac
– Mucosa folded into rugae
– Bile enters and leaves
through cystic duct
• Gall Bladder Function
– Stores and concentrates bile
– Contracts during meals to
force bile into SI
• Biliary Pathway
• Biliary Pathway: “plumbing”
which drains bile
• Small Intestine
– 1 inch diameter
– 10-20 ft. in length
• duodenum (10 in)
• jejunum (3-6 ft.)
• ileum (6-12 ft)
• Features of SI mucosa
– Plica circularis
• Features of SI mucosa
– Plica circularis
• Features of SI mucosa
–Plica circularis
–Villi
• Features of SI mucosa
–Plica circularis
–Villi
• Features of SI mucosa
–Plica circularis
–Villi
• Features of SI mucosa
–Plica circularis
–Villi
–Microvilli
• Features of SI mucosa
–Plica circularis
–Villi
–Microvilli
• Features of SI mucosa, cont’d
–Epithelial cell types:
•absorptive cells
•Goblet cells
•Endocrine cells
•Paneth cells
• Features of SI mucosa, cont’d
–MALT in lamina propria
• Features of SI mucosa, cont’d
–MALT in lamina propria
• Features of SI mucosa, cont’d
–MALT in lamina propria
–Intestinal glands (“crypts”)
• Features of SI submucosa
–Submucosal glands in
duodenum
• Motility of SI
–Segmentation movements
–Peristalsis
• Functions of small intestine
– Completion of chemical
digestion
• “brush-border” enzymes
required
– Absorption
– Endocrine control of some
digestive processes
Summary movie
• Large Intestine
• Large Intestine (large bowel)
• Large Intestine (large bowel)
–2.5 inches
in diameter
• 5-6 feet long
–Cecum
–Colon
• Ascending
• Transverse
• Descending
• Sigmoid
–Rectum
–Anal canal
• Features of LI
mucosa
– no villi
– numerous
intestinal glands
– goblet and
absorptive cells
in epithelium
– MALT in
lamina propria
• Structural
Features of
cecum and colon
– Taeniae coli
– Haustra
– Epiploic
appendages
• Other Structural Features
– Vermiform appendix
• Other Structural Features
– Vermiform appendix
• Other Structural Features
– Vermiform appendix
– Ileocecal valve
• Other Structural Features
– Vermiform appendix
– Ileocecal valve
• Other Structural Features
– Vermiform appendix
– Ileocecal valve
– Stretch receptors in rectum
• initiate defecation reflex
• Other Structural Features
– Vermiform appendix
– Ileocecal valve
– Stretch receptors in rectum
• initiate defecation reflex
– Anal sphincters of anal
canal
• Motility of Large Intestine
– From cecum to transverse
colon:
• peristalsis
– From transverse colon to
rectum:
• mass movements
• Functions of Large Intestine
– Water and electrolyte
absorption
– Feces formation
– Defecation
• Large Intestinal Bacteria
– Coat surface of mucosa
– Examples: E. coli
– Keep out pathogenic bacteria
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