Transcript Digestive-2404digestivesystem12-04-06-1-

Overview of the Digestive System
Digestive Tract:
Mouth, pharynx, and
esophagus, stomach,
small intestine, and
large intestine (colon)
Accessory Organs:
Teeth, tongue, salivary
glands, pancreas, liver,
and gallbladder
Functions of the Digestive System
• Ingestion
• Mechanical
processing
• Chemical
digestion
• Secretion
• Absorption
• Excretion
Histology of the Digestive Tract
Mucosa
Submucosa
Muscularis
Externa
Serosa
Mucosa (Innermost Layer)
• Epithelium
• Connective
•
Tissue
(Blood
vessels,
lymphatic
vessels,
lymphatic
nodules)
Smooth
Muscle
Submucosa
Connective tissue
•
•
•
•
Blood vessels
Lymphatic
vessels
Nerve plexus
May have glands
and lymphatic
tissue
Muscularis Externa
Smooth or Skeletal Muscle
If smooth muscle, usually 2 layers (circular and
longitudinal)
Adventitia or Serosa
Adventitia
(organs
superior to
diaphragm)
Serosa =
visceral
peritoneum
Small Intestine: Peyer’s Patches
Components of the Digestive System
GI Tract:
•Oral Cavity
•Pharynx
•Esophagus
•Stomach
•Small
Intestine
•Large
Intestine
Oral Cavity
Oral Cavity
The Pharynx
• Nasopharynx
• Oropharynx
• Laryngopharynx
The Esophagus
The Esophagus
• Stratified
•
•
squamous
epithelium
Mucous glands
Muscularis
externa –
skeletal muscle
first third of
length
Peristalsis in Esophagus
LE 21-8
Muscles contract
Bolus of
food
Muscles
contract,
constricting
passageway
and pushing
bolus down
Muscles relax
Muscles relax,
allowing
passageway
to open
Stomach
Muscles contract
Muscles
relax
Stomach
• Site where
•
food is
churned into
chyme
Protein
digestion
begins
Stomach
Stomach
Stomach – Microscopic Anatomy
Stomach – Microscopic Anatomy
The Stomach – Microscopic Anatomy
Ulcers in stomach
Helicobacter pylori
Small Intestine – Gross Anatomy
• Longest portion of
•
•
the alimentary canal
Site of most
enzymatic digestion
and absorption
Three subdivisions
• Duodenum,
jejunum, and ileum
LE 21-11a
Duodenum and Related Organs
Liver
Bile
Gallbladder
Stomach
Bile
Acid chyme
Intestinal enzymes
Duodenum of
small intestine
Pancreatic
juice
Pancreas
Duodenum and Related Organs
Enzymes in Small Intestine
Small Intestine – Microscopic Anatomy
LE 21-11b
Lumen of intestine
Nutrient
absorption
Vein
with blood
en route to
the liver
Nutrient absorption
into epithelial cells
Microvilli
Epithelial
cells
Muscle
layers
Amino
acids
and
sugars
Lumen
Fats
Blood
capillaries
Large
circular folds
Blood
Villi
Lymph
vessel
Lymph
Nutrient
absorption
Epithelial cells
Villi
Intestinal wall
Fatty
acids
and
glycerol
Small Intestine: Duodenum
Br = Brunner glands
V = Villus
G = Goblet cells
Cr = Intestinal glands
MM = Muscularis
Mucosae
LP = Lamina Propria
The Small Intestine – Structural Features
Gross Anatomy of Large Intestine
•Cecum
•Appendix
•Ascending
•Transverse
•Descending
•Sigmoid colon
•Rectum
•Anus
LE 21-12
Large
intestine
(colon)
Small
intestine
Sphincter
End
of small
intestine
Rectum
Anus
Nutrient
flow
Appendix
Cecum
Gross Anatomy of Large Intestine
• Rectum – descends along the inferior half of the
•
sacrum
Anal Canal – the last subdivision of the large
intestine
Gross Anatomy of Large Intestine
Microscopic Anatomy of Large Intestine
•
•
•
•
•
Villi are absent
Contains numerous goblet cells
Intestinal crypts – simple tubular glands
Lined with simple columnar epithelial tissue
Epithelium changes at anal canal
• Becomes stratified squamous epithelium
Microscopic Anatomy of Large Intestine
Teeth
Salivary Glands
Pancreas
Exocrine Pancreas: Histology
Liver
•
•
•
•
Largest gland in the body
Performs over 500 functions
Digestive function – bile production
Performs many metabolic functions
Visceral Surface of the Liver
Microscopic Anatomy of Liver
Microscopic Anatomy of Liver
Gallbladder
• Stores and concentrates bile
• Expels bile into duodenum
• Bile emulsifies fats
Gallbladder
Enzymes in Small Intestine
The Peritoneal Cavity and Peritoneum
• Mesentery – a
double layer of
peritoneum
• Holds organs in
•
•
place
Sites of fat
storage
Provides a route
for circulatory
vessels and
nerves
Mesenteries
•
Superficial view of
the abdominal
organs
Mesenteries
•
Greater omentum and
transverse colon
reflected
Mesenteries
•
Sagittal section through
the abdominopelvic
cavity
Segmentation
•
•
Rhythmic local
contractions of the
intestine
Mixes food with
digestive juices
Disorders of the Digestive System
•
Intestinal obstruction
• Mechanical obstructions
• Adhesions, tumors, or foreign objects
• Nonmechanical obstruction
• Halt in peristalsis
• Trauma
• Intestines touched during surgery
Disorders of the Digestive System
•
Inflammatory bowel disease
• Inflammation of intestinal wall
• Crohn’s disease
• Ulcerative colitis
•
Viral hepatitis – jaundice and flu-like symptoms
• Major types – A, B, C, and G
•
Cystic Fibrosis and the Pancreas
The Digestive System in Later Life
•
•
Middle age – gallstones and ulcers
Old age – activity of digestive organs decline
•
•
•
•
Fewer digestive juices and enzymes produced
Absorption is less efficient
Dehydration of fecal mass leads to constipation
Diverticulosis and cancer of digestive organs