Human Biology
Sylvia S. Mader
Michael Windelspecht
Chapter 8
Digestive
System and
Nutrition
Lecture Outline
Part 2
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8.2 The Mouth, Pharynx, and Esophagus
Heartburn
• This occurs when acids from the stomach
pass into the esophagus (acid reflux).
• There is a burning sensation in the
esophagus.
• Chronic heartburn is called gastroesophageal
reflux disease (GERD).
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8.2 The Mouth, Pharynx, and Esophagus
Heartburn
• The following are tips for decreasing
heartburn.
– Avoid high fat meals.
– Do not overeat.
– Eat several small meals rather than the
standard 3 larger meals each day.
– Exercise lightly.
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8.3 The Stomach and Small Intestine
The stomach
• It functions to store food, start digestion of proteins,
and control movement of chyme into the small
intestine.
• The ________ is a J-shaped organ with a thick
wall.
• There are 3 layers of muscle in the muscularis
layer of the stomach wall to help in mechanical
digestion and allow it to stretch.
• The mucosa layer has deep folds called _______,
and gastric pits that lead into gastric glands that
secrete gastric juice.
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8.3 The Stomach and Small Intestine
The stomach
• Gastric juice contains _______, an enzyme that
breaks down proteins, plus HCl and mucus.
• HCl gives the stomach a ______, which activates
pepsin and helps kill bacteria found in food.
• A bacterium, ______________, lives in the mucus
and can cause gastric ulcers.
• The stomach empties chyme into the small intestine
after 2-6 hrs.
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8.3 The Stomach and Small Intestine
Anatomy of the stomach
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esophagus
lower gastroesophageal
sphincter
pyloric
sphincter
muscularis layer
has three layers
of muscle.
mucosa layer
has rugae.
c. Gastric pits in mucosa
gastric pit
SEM 3,260x
lower gastroesophageal
sphincter
a. Stomach
gastric pit
gastric gland
cells that secrete
gastric juice
b. Gastric glands
pyloric
sphincter
d. How the stomach empties
c: © Dr. Fred Hossler/Visuals Unlimited
Figure 8.5 The layers of the stomach.
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8.3 The Stomach and Small Intestine
The small intestine
• The small intestine averages 6 m (18 ft) in
length.
• Enzymes secreted by the __________ into the
small intestine digest carbohydrates, proteins,
and fats.
• Bile is secreted by the _____________ into the
small intestine to emulsify fats.
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8.3 The Stomach and Small Intestine
The small intestine
• The absorption of digested food depends on
the large surface area created by numerous
villi (finger-like projections) and microvilli.
• Amino acids and sugars enter the capillaries
while fatty acids and glycerol enter the lacteals
(small lymph vessels).
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8.3 The Stomach and Small Intestine
Anatomy of the small intestine
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Small intestine
Section of intestinal wall
villus
lumen
lacteal
blood
capillaries
villus
microvilli
goblet
cell
lymph
nodule
venule
lymphatic
vessel
Villi
arteriole
(villi): © Kage Mikrofotografie/ Phototake; (microvilli): Reprinted from Medical Cell Biology, Charles Flickinger, copyright 1979, with permission from Elsevier
Figure 8.6 Absorption in the small intestine.
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8.3 The Stomach and Small Intestine
How are nutrients digested and
transported out of the small intestine?
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
carbohydrate
protein
pancreatic amylase
+
bile salts fat globules
trypsin
emulsification
droplets
peptides
maltase
cell of
intestinal
villus
peptidase
lipase
glucose
monoglycerides
and free
fatty acids
amino acids
pH = basic
pH = basic
pH = basic
blood capillary
blood capillary
a. Carbohydrate digestion
b. Protein digestion
chylomicron
lymphatic
capillary
c. Fat digestion
Figure 8.7 Digestion and absorption of organic nutrients.
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8.3 The Stomach and Small Intestine
What are the major digestive enzymes?
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8.4 The Accessory Organs and Regulation of Secretions
The 3 accessory organs
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bile canals
• Pancreas
bile
• Liver
branch of
hepatic
artery
central
vein
common hepatic duct
pancreatic duct
pancreas
pancreatic
juice
gallbladder
b.
• Gallbladder
bile duct
branch of
hepatic
portal vein
common bile duct
duodenum
a.
Figure 8.8 Accessory organs of the digestive system.
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8.4 The Accessory Organs and Regulation of Secretions
The pancreas
• __________ spongy organ behind the stomach
• Functions of the pancreas
1. Secretes enzymes into the small intestine
• Trypsin digests proteins
• Lipase digests fats
• Pancreatic amylase digests carbohydrates
2. Secretes bicarbonate into the small intestine to
_______________________
3. Secretes _______ into the blood to keep blood
sugar levels under control
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8.4 The Accessory Organs and Regulation of Secretions
The liver and gallbladder
• The liver is a large metabolic organ that lies under
the diaphragm and is made of 100,000 lobules.
• It filters blood from the GI tract, thus acting to
remove poisons and detoxify the blood.
• The liver removes iron, vitamins A, D, E, K, and B12
from the ______ and stores them.
• It stores glucose as glycogen and breaks it down to
help retain ______________ levels.
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8.4 The Accessory Organs and Regulation of Secretions
The liver and gallbladder
• The liver makes plasma proteins and helps
regulate cholesterol levels by making bile salts.
• It makes ____ that is then stored in the _________
to be secreted into the small intestine to emulsify
fats.
• The liver also breaks down hemoglobin.
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8.4 The Accessory Organs and Regulation of Secretions
Liver disorders
• Hepatitis
– Hepatitis is _____________ of the liver.
– It is caused by Hepatitis A, B, and C.
– This disease can lead to liver damage,
cancer, and/or death.
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8.4 The Accessory Organs and Regulation of Secretions
Liver disorders
• Cirrhosis
– The liver becomes fatty and eventually the
liver tissue is replaced by fibrous scar
tissue.
– It is seen in _________ and _____ people.
– Cirrhosis can lead to liver failure in which
the liver cannot regenerate as fast as it is
being damaged.
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