Download Chapter 23 Digestive System

Chapter 23
Digestive System
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.
Slide 1
Overview of the Digestive System
• Functions of the Digestive System
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Ingestion (eating)
Digestion
Absorption
Elimination
• The Wall of the Digestive Tract and Membranes
– Four layers: mucosal, submucosa, muscle, serosa
– Peritoneal membranes: mesentery, mesocolon, greater and lesser
omentum
Slide 2
Structures and Organs of the Digestive
System
• Mouth
– Teeth and tongue
– Salivary glands: parotid,
submandibular, and sublingual
• Pharynx (Throat)
Slide 3
Structures and Organs of the Digestive
System - cont’d
• Esophagus
– The esophagus is a long tube that connects the
pharynx to the stomach.
– There are two sphincters.
• Stomach
– The three parts of the stomach are the fundus,
body, and pylorus.
– The stomach functions in digestion; its most
important role is regulate the rate at which chyme
is delivered to the small intestine.
Slide 4
Structures and Organs of the Digestive
System - cont’d
• Small Intestine
– The three parts of the small intestine are the
duodenum, jejunum, and ileum.
– Most of the digestion and absorption occurs within
the duodenum.
– The end-products of digestion are absorbed into
villi.
Slide 5
Structures and Organs of the Digestive
System - cont’d
• Large Intestine
– The large intestine consists of the cecum,
ascending colon, transverse colon, descending
colon, sigmoid colon, rectum, and anus.
– The large intestine functions in absorption of
water and electrolytes.
Slide 6
Accessory Digestive Organs
• Liver
– The liver has many functions; its most important
digestive function is the secretion of bile.
– The liver receives blood from the portal vein;
portal blood is rich in digestive end products.
Slide 7
Accessory Digestive Organs - cont’d
• Biliary Tree
– The biliary tree is composed of the bile ducts that
connect the liver, gallbladder, and duodenum.
– The common bile duct empties into the
duodenum.
Slide 8
Accessory Digestive Organs - cont’d
• Gallbladder
– The gallbladder functions to store and concentrate
bile.
– The gallbladder contracts and releases bile in
response to the hormone cholecystokinin (CCK).
Slide 9
Accessory Digestive Organs - cont’d
• Pancreas
– The pancreas secretes the most important
digestive enzymes.
– The pancreatic enzymes empty into the
duodenum.
Slide 10
Digestion and Absorption
• Carbohydrate Digestion
– To be absorbed, carbohydrates must be broken
down into glucose.
– Carbohydrates are digested by enzymes called
amylases and disaccharidases.
Slide 11
Digestion and Absorption - cont’d
• Protein Digestion
– To be absorbed, proteins must be broken down
into amino acids.
– Proteins are broken down by proteolytic enzymes
or proteases.
Slide 12
Digestion and Absorption - cont’d
• Fat Digestion
– To be absorbed, fats must be broken down into
fatty acids and glycerol.
– Fats are digested by enzymes called lipases.
Fats are first emulsified by bile.
Slide 13
Nutrition and Body Energy
• Carbohydrates
– Carbohydrates are either simple or complex.
– Glucose, the simplest carbohydrate, is the major
fuel used by the body for energy.
Slide 14
Nutrition and Body Energy - cont’d
• Protein
– The body needs essential amino acids, which it
cannot synthesize, and nonessential amino acids,
which it can synthesize.
– Dietary proteins are complete or incomplete.
Slide 15
Nutrition and Body Energy - cont’d
• Fats (Lipids)
– Most dietary lipids are triglycerides.
– Fats are either saturated fats (like butter) or
unsaturated fats (like oils).
Slide 16
Nutrition and Body Energy - cont’d
• Vitamins
– Vitamins are small organic molecules that help
regulate cell metabolism. Dietary vitamin
deficiencies give rise to many diseases
(see Table 23-2).
– Vitamins are either water soluble (vitamins B and
C) or fat soluble (vitamins A, D, E, and K).
Slide 17
Nutrition and Body Energy - cont’d
• Minerals
– Minerals are inorganic substances necessary
for normal body function.
– Mineral deficiencies can cause serious health
problems.
Slide 18
Nutrition and Body Energy - cont’d
• Body Energy
– The body needs energy to do its work and
maintain body temperature.
– The basal metabolic rate (BMR) is the amount of
energy the body requires per unit time to perform
essential activities at rest.
– Metabolism is determined by many factors,
including age; gender; surface area; emotional
state; overall health status; and hormones
(especially thyroxine).
Slide 19