Transcript Chapter 26-Part 2-Digestive System

Chapter 26
Digestive System
Part 2, Stomach, Intestines, Rectum
Fig. 26.12 (a) Stomach regions, anterior view
Stomach
Fundus
Esophagus
• Entryway to stomach is
cardia
Cardia
• Opening between
esophagus and cardia is
cardiac orifice
Pyloric
orifice
• Fundus is lateral and
superior to cardiac orifice
Longitudinal
layer
Circular
layer
Oblique
layer
Body
Pyloric
sphincter
Pyloric
canal
Pylorus
Duodenum
Pyloric
antrum
Gastric folds
Muscularis
Fig. 26.12 (a) Stomach regions, anterior view
Stomach
• Largest part of stomach is
body
• Pyloris is funnel-shaped
pouch
• Pyloric antrum is near
body of stomach
• Pyloric canal attaches to
duodenum
• opening to duodenum
called pyloric orifice, ringed
by pyloric sphincter
Fundus
Esophagus
Cardia
Pyloric
orifice
Longitudinal
layer
Circular
layer
Oblique
layer
Body
Pyloric
sphincter
Pyloric
canal
Pylorus
Duodenum
Pyloric
antrum
Gastric folds
Muscularis
Fig. 26.12
Stomach
• Gastric folds (AKA rugae) stretch
to accommodate meal
• increase surface area for digestion
Gastric folds
Lesser curvature
Diaphragm
Liver (cut)
Esophagus
Cardiac orifice
Gastric folds
Body of stomach
Pylorus of stomach
Greater curvature
(c) Gross anatomy of stomach (cut open)
Fig. 26.12
Stomach
Esophagealstomach
border
Stratified
squamous
epithelium
Simple
columnar
epithelium
Gastric
pits
• Lining is simple columnar
epithelium
• little absorption in stomach
• Mucous cells secrete mucin
• Gastric pits are indentations in
lining
LM 50x
(b) Esophageal-stomach border
Fig. 26.13
Stomach
Gastric pit
• Muscularis has 3
muscle layers
Simple columnar
epithelium
• inner oblique layer
• middle circular
• outer longitudinal
• Ensures plenty of
churning
Stomach lumen
Mucosa
Lamina propria
Muscularis mucosae
Artery
Vein
Submucosal
nerve plexus
Submucosa
Oblique layer
Muscularis
Blood vessel
Lymph vessel
Circular layer
Longitudinal
layer
Serosa
Myenteric
nerve plexus
(a) Stomach wall, sectional view
Fig. 26.13
Stomach lumen
Stomach
Gastric pit
• At base of gastric pits are gastric
glands
Gastric glands
• release gastric juices
• 5 types of gastric gland cells
LM 60x
(b) Stomach mucosa
Fig. 26.13
• Mucin prevents
ulceration of lining of
stomach
• Other cells in gastric
gland produce acid,
enzymes, etc. to aid
digestion
Surface mucous cell
(secretes alkaline fluid
containing mucin)
Simple
columnar
epithelium
Gastric pit
Gastric gland
(c) Gastric pit and gland
Page 794
Gastric
Duodenal ulcer ulcers
Mucosa
Submucosa
Muscularis
Serosa
Duodenum
(a) Common locations of gastric and duodenal ulcers
• Ulcers most often caused by
bacterium Helicobacter pylori
• However, H. pylori probably protects
against reflux
(b) Perforated gastric ulcer
Fig. 26.14
Small intestine
Liver
Accessory
organs
• About 6m (20ft) in
unembalmed cadaver
• Extends from pyloris
of stomach to cecum
of large intestine
Gallbladder
Pancreas
Duodenojejunal flexure
Duodenum
Large intestine
Ileocecal valve
Cecum
Jejunum
Ileum
Small
intestine
Fig. 26.14
Small intestine
• Duodenum is first segment;
25cm long
• Curves around pancreas
• Joins jejunum at duodenojejunal
flexure
• Mostly retroperitoneal
Duodenojejunal flexure
Duodenum
Jejunum
Ileum
Small
intestine
Fig. 26.14
Small intestine
• Jejunum is 2.5 m long (2/5 total
length of small intestine)
• Primary site of absorption and
chemical digestion
• Intraperitoneal; suspended by
mesentery proper
Duodenojejunal flexure
Duodenum
Jejunum
Ileum
Small
intestine
Fig. 26.14
Small intestine
• Ileum is 3.6 m long (3/5 total
length of small intestine)
• Ends at ileocecal valve
• Intraperitoneal; suspended by
mesentery proper
Ileocecal valve
Cecum
Duodenojejunal flexure
Duodenum
Jejunum
Ileum
Small
intestine
Fig. 26.15
(a) Small intestine tunics
Small intestine
Muscularis
• Circular folds inside small
intestine
Circular folds
Mucosa
Submucosa
Inner circular layer
Outer longitudinal layer
Serosa
Circular fold
• add surface area
• act as “speed bumps” to
slow movement of chyme
• more numerous in
duodenum and jejunum
than in ileum
Intestinal villi
Mucosa
Submucosa
Inner circular layer
Muscularis
Outer longitudinal layer
Serosa
(b) Section of small intestine
Fig. 26.15
• Villi are microscopic,
fingerlike projections
on circular folds
• further increase surface
area
(c) Intestinal villus
Fig. 26.15
• Each villus contains
capillary bed and
lacteal
• Submucosa has lymph
vessels, arterioles and
venules
Epithelium
Goblet cells
Simple columnar
epithelial cells
Mucosa
Lamina propria
Capillary network
Lymphatic nodule
Lacteal
Muscularis mucosae
Lymph vessel
Submucosa
Venule
Arteriole
(c) Intestinal villus
Fig. 26.16
Large intestine
Transverse colon
Ascending colon
Descending colon
Cecum
Sigmoid colon
Transverse mesocolon
Right colic
flexure
Haustrum
Superior
mesenteric
artery
Omental appendices
Tenia coli
Descending
abdominal aorta
Inferior
mesenteric
artery
Ileocecal valve
Cecum
Left colic flexure
Ileum
Vermiform appendix
Rectum
Sigmoid mesocolon
Anal canal
(a) Large intestine, anterior view
• Total length 1.5m
• Diameter 6.5cm
• Receives about 1L of
3-4L that entered
small intestine
Fig. 26.16
Large intestine
Transverse colon
• Cecum is first region
Ascending colon
Descending colon
Cecum
Sigmoid colon
Ileocecal valve
Vermiform appendix
• extends inferiorly from
ileocecal valve
• Vermiform appendix (AKA
appendix)
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Appendicitis
• Inflammation of the appendix,
usually because fecal matter
obstructs appendix
• If appendix bursts, contents
causes infection called peritonitis
• Spasms of smooth muscle in
appendix cause pain, often
referred to T10 dermatome
around umbilicus
• More advanced appendicitis felt in
lower right quadrant of torso
Inflamed appendix
Mesentery for appendix
Inflamed appendix
© Medicimage/Phototake
Fig. 26.16
Large intestine
Transverse colon
Ascending colon
Descending
colon
Cecum
Ileocecal valve
Vermiform appendix
Sigmoid
colon
• Colon begins at ileocecal valve
• 4 segments of colon
•
•
•
•
ascending (retroperitoneal)
transverse (intraperitoneal)
descending (retroperitoneal)
sigmoid (intraperitoneal)
Fig. 26.16
Transverse mesocolon
Right colic
flexure
Superior
mesenteric
artery
Left colic
flexure
Descending
abdominal aorta
Ileum
(a) Large intestine, anterior view
Inferior
mesenteric
artery
• Ascending colon
becomes transverse
colon at right colic
flexure
• Transverse colon ends
at left colic flexure
• Transverse colon is held
to posterior abdominal
wall by mesentery
called transverse
mesocolon
Fig. 26.16
Transverse mesocolon
Right colic
flexure
Superior
mesenteric
artery
Left colic
flexure
Descending
abdominal aorta
Inferior
mesenteric
artery
Sigmoid
mesocolon
(a) Large intestine, anterior view
Sigmoid
flexure
• Descending colon
becomes sigmoid colon
at sigmoid flexure
• Sigmoid colon is held in
place by mesentery
called sigmoid
mesocolon
Fig. 26.16
• Longitudinal muscles of
colon form 3 thin bundles
called teniae coli
Haustra
Teniae coli
(a) Large intestine, anterior view
• cause colon to bunch into
haustra
Page 799
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Diverticula
• Diverticula are outpockets of intestinal wall
• most common in sigmoid
colon
• likely caused by low-fiber
diet causing strain on
colon
• presence of diverticula
called diverticulosis
• inflammation called
diverticulitis
(a)
(b)
Diverticulosis (a) An external view of the sigmoid colon showing
diverticula. (b) An endoscopic view of diverticula.
b: Photo courtesy Interactive Atlas of Gastrointestinal Endoscopy by Edgar Jaramillo, available free of charge at www.gastrosource.com
Fig. 26.16
• Rectum is retroperitoneal
• Muscular tube that stretches to
accommodate fecal matter
Rectum
Anal canal
(a) Large intestine, anterior view
Fig. 26.16
• Rectal valves ensure fecal
matter stays put during farts
• Fecal matter leaves body
through anal canal
• Anal canal has internal and
external anal sphincters
(b) Anal canal
Rectum
Rectal valve
Levator ani muscle
Anal canal
Veins
Internal anal sphincter
Anus
Anal columns
Anal sinuses
External anal sphincter
Fig. 26.17
(a) Large intestine tunics
• Mucosa of colon is simple
columnar epithelium
(absorb nutrients) and
goblet cells (secrete
Opening to intestinal gland
mucin)
Simple columnar epithelium
• No villi
Intestinal gland
• Numerous glands
Goblet cells
Mucosa
Lamina propria
Lymphatic nodule
Muscularis mucosae
Inner circular layer
of muscularis
Serosa
(or adventitia)
Nerves Arteriole Venule
Submucosa
Muscularis
Outer
longitudinal
layer of
muscularis
(tenia coli)
Fig. 26.17
Opening to
intestinal gland
Goblet cells
Simple columnar
epithelium
Mucosa
Intestinal gland
Submucosa
Muscularis
mucosae
LM 80x
(b) Large intestine mucosa and submucosa
Page 800
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• Colorectal cancer most
common in descending colon
• Arises from polyps, outgrowths
of colon mucosa
Polyps
Colorectal
cancer
• most polyps never become
cancerous
• Linked to low-fiber diets
• Often without symptoms;
sometimes rectal bleeding,
constipation, abdominal pain,
unexplained weight loss
Polyp
Large intestine, frontal section
Polyps in the large intestine sometimes lead to colorectal cancer.
Liver celebrates New Year’s Eve
Fig. 26.18
Right lobe
Inferior
vena cava
Liver
Left lobe
• Produces bile
• greenish fluid that breaks down fats
• stored in gallbladder
Falciform ligament
Round ligament
of liver
Gallbladder
(a) Anterior view
• Detoxifies drugs, metabolites, and
poisons
• Stores excess nutrients (especially fats)
and vitamins
• releases as needed by body
• Synthesizes blood plasma proteins
• Helps recycle old red blood cells
Fig. 26.18
Right lobe
Inferior
vena cava
Liver
Left lobe
• 4 incompletely separated lobes
• right lobe and left lobe are major lobes
• Supported by ligaments
Falciform ligament
Round ligament
of liver
Gallbladder
(a) Anterior view
• falciform ligament separates right and left
lobes and secures liver to anterior
abdominal wall
• inferior edge is round ligament of the
liver (AKA ligamentum teres) is remnant
of umbilical vein
Normal, healthy liver
Fatty liver
Page 804
Fibrous scar tissue
(a) Nodular cirrhosis of the liver
LM 100x
(b) Histology of liver cirrhosis
Normal hepatocytes
(a) This gross specimen depicts a type of nodular cirrhosis of the liver. (b) A photomicrograph shows how
scar tissue infiltrates and replaces hepatocytes.
Steatohepatitis image by Nephron
Fig. 26.21
Left and right hepatic ducts
Common hepatic duct
• Stores and concentrates bile secreted
by hepatocytes
• 3 regions
Cystic duct
Neck
Body
Gallbladder
Stored bile
Fundus
Minor duodenal papilla
Hepatopancreatic ampulla
with hepatopancreatic
sphincter
Major duodenal
papilla
Duodenum
Gallbladder
Common
bile duct
• Neck; sphincter controls flow into and
out of gallbladder
• Body
• Fundus
Fig. 26.21
Left and right hepatic ducts
Common hepatic duct
Cystic duct
Neck
Body
Common
bile duct
Gallbladder
Stored bile
Fundus
Minor duodenal papilla
Hepatopancreatic ampulla
with hepatopancreatic
sphincter
Major duodenal papilla
Duodenum
Gallbladder
• Bile flows out of liver through left and
right hepatic ducts, then common
hepatic duct
• Bile flows into and out of gallbladder
through cystic duct then into
common bile duct to duodenum
• Enters duodenum at major duodenal
papilla
Page 806
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Gallstones
• Caused by high concentrations
of certain materials
• More common in women,
Caucasian people, and in
developed countries
• Linked to obesity, age, female
sex hormones, lack of physical
activity
• Treatment: removal of
gallbladder (cholecystectomy)
• liver continues to produce bile
Photo of gallstones in a gallbladder.
© Gladden Willis/Visuals Unlimited
Fig. 26.20
(a) Duodenum
and pancreas,
anterior view
Pancreas
Main pancreatic duct
Body of pancreas
Common bile duct
Tail of
pancreas
Duodenum
Accessory
pancreatic duct
Hepatopancreatic
ampulla
Duodenojejunal
flexure
Major duodenal
papilla
Jejunum
Head of pancreas
• Sits above and behind stomach
• Retroperitoneal
• Wide head, long body, small tail
touches spleen
Fig. 26.20
(a) Duodenum
and pancreas,
anterior view
Pancreas
Main pancreatic duct
Body of pancreas
Common bile duct
Tail of
pancreas
Duodenum
Accessory
pancreatic duct
Hepatopancreatic
ampulla
Duodenojejunal
flexure
• Endocrine function:
Major duodenal
papilla
Jejunum
Head of pancreas
• produces insulin to help some
tissues take up glucose
• Exocrine function:
• produces enzymes for digestion
Fig. 26.20
(a) Duodenum
and pancreas,
anterior view
Pancreas
Main pancreatic duct
Body of pancreas
Common bile duct
Tail of
pancreas
Duodenum
Accessory
pancreatic duct
Hepatopancreatic
ampulla
Duodenojejunal
flexure
Major duodenal
papilla
Jejunum
Head of pancreas
• Creates pancreatic juice
(digestive enzymes and
bicarbonate)
• released into duodenum
Fig. 26.20
(b) Histology of pancreas
Pancreatic
ducts
Main
pancreatic
duct
Pancreas
• Acinar cells are modified simple
cuboidal epithelial cells
Pancreatic
acini
Pancreatic
islet
LM 75x
Acinar cell
LM 200x
Pancreatic acinus
• organized into clusters called acini
(AKA lobules)
• secrete mucin and digestive enzymes
into pancreatic ducts
• Unite to form main pancreatic duct
• Cells lining ducts produce
bicarbonate (alkaline)
Fig. 26.20
Pancreas
(a) Duodenum
and pancreas,
anterior view
Main pancreatic duct
Common bile duct
Duodenum
Accessory
pancreatic duct
Minor duodenal
papilla
Hepatopancreatic
ampulla
Major duodenal
papilla
• Pancreatic juices and
bicarbonate flow into
duodenum
• Main pancreatic duct drains into
main duodenal papilla
• combines with common bile duct at
hepatopancreatic ampulla
• Accessory pancreatic duct drains
into minor duodenal papilla
Fig. 26.21
Left and right hepatic ducts
Common hepatic duct
Cystic duct
Neck
Body
1 Left and right hepatic ducts merge
to form a common hepatic duct.
2 Common hepatic and cystic ducts
merge to form a common bile duct.
Gallbladder
Stored bile
Fundus
Minor duodenal papilla
Hepatopancreatic ampulla
with hepatopancreatic
sphincter
Major duodenal
papilla
Duodenum
Common bile duct
Accessory
pancreatic duct
Main pancreatic duct
Main pancreatic duct merges with common
bile duct at the hepatopancreatic ampulla,
which extends into the duodenum.
4 Bile and pancreatic juices enter
duodenum at the major duodenal papilla.
3