Human Biology
Sylvia S. Mader
Michael Windelspecht
Chapter 8
Digestive
System and
Nutrition
Lecture Outline
Part 1
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Digestive System and Nutrition
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Points to ponder
• What are the digestive system structures and their
functions?
• Where does carbohydrate, protein, and fat digestion
and absorption occur?
• What are proteins, lipids, carbohydrates, minerals
and vitamins needed for?
• What is an essential vs. a nonessential nutrient?
• What are the 3 accessory organs of digestion?
• What is obesity and why is it a problem?
• What is LDL and HDL?
• What are the components of a healthy diet?
• Name and explain 4 eating disorders.
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8.1 Overview of Digestion
What are the main steps in the
digestive process?
•
________ – intake of food via the mouth
•
Digestion – mechanically or chemically breaking
down foods into their subunits
•
Movement – food must be moved along the GI
tract in order to fulfill all functions
•
_________ – movement of nutrients across the GI
tract wall to be delivered to cells via the blood
•
_________ – removal of indigestible molecules
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8.1 Overview of Digestion
What are the 4 major layers that
make up the wall of the GI tract?
• ________ – innermost layer that produces mucus to
protect the lining and also produces digestive
enzymes
• __________ – 2nd layer of loose connective tissue
that contains blood vessels, lymphatic vessels, and
nerves
• __________ – 3rd layer made of 2 layers of smooth
muscle that move food along the GI tract
• ________ – outer lining that is part of the
peritoneum
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8.1 Overview of Digestion
Visualizing the layers of the
GI tract
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nerve
supply
lymph
vessel
Lumen
central space containing
food being digested
Mucosa
inner mucous membrane
layer modified according
to the digestive organ
Submucosa
broad band of loose
connective tissue that
contains nerves, blood,
and lymphatic vessels
artery
vein
Muscularis
two layers of
smooth muscle
Serosa
thin, outermost tissue
that is the visceral
peritoneum
Figure 8.2 The layers of the gastrointestinal
tract wall.
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8.1 Overview of Digestion
An overview of the digestive system
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Accessory organs
Salivary glands
secrete saliva which contains digestive
enzyme for carbohydrates
Digestive tract organs
Mouth
teeth chew food; tongue tastes and
pushes food for chewing and swallowing
Pharynx
passageway where food is swallowed
Esophagus
passageway where peristalsis pushes
food to stomach
Liver
major metabolic organ ;
processes and stores nutrients;
produces bile for emulsification of fats
Gallbladder
Stomach
secretes acid and digestive enzyme
for protein; churns, mixing food with
secretions, and sends chyme to
small intestine
stores bile from liver; sends it to
the small intestine
Pancreas
produces pancreatic juice ; contains
digestive
enzymes, and sends it to the small intestine;
produces insulin and secretes it into the
blood after eating
Small intestine
mixes chyme with digestive enzymes
for final breakdown; absorbs nutrient
molecules into body; secretes
digestive hormones into blood
Large intestine
absorbs water and salt to form feces
Rectum
stores and regulates elimination
of feces
Figure 8.1 Organs of the GI tract and
accessory structures of digestion.
Anus
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8.1 Overview of Digestion
What is the pathway that food
follows?
mouth
pharynx
esophagus
stomach
small intestine
large intestine
rectum
anus
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8.2 The Mouth, Pharynx, and Esophagus
The mouth
• 3 pairs of ___________ secrete salivary amylase that
begins carbohydrate digestion.
• Tonsils at the back of the mouth are lymphatic tissues,
important in fighting _______.
• The mouth contains teeth that begin the __________
breakdown of food.
• The tongue is covered in taste buds and also assists in
the mechanical breakdown and movement of food.
• The tongue forms a ______ (mass of chewed food)
and moves it toward the pharynx.
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8.2 The Mouth, Pharynx, and Esophagus
Anatomy of the mouth
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hard palate
soft palate
uvula
tonsil
molars (3)
premolars (2)
canine (1)
incisors (2)
Figure 8.3a The functions of the
different teeth.
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8.2 The Mouth, Pharynx, and Esophagus
Teeth
• There are 32 teeth in adults (20 deciduous teeth
in babies).
• Teeth are used for mechanical breakdown of
food.
• Each tooth is made of a crown and a root.
• A hard covering of ______ and ______ covers
the crown.
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8.2 The Mouth, Pharynx, and Esophagus
Teeth
• An inner pulp area has nerves and blood
vessels.
• ____________ (cavities) occurs when bacteria
metabolize sugars and produce acids; limiting
sugar intake and brushing teeth reduces tooth
decay.
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8.2 The Mouth, Pharynx, and Esophagus
Anatomy of a tooth
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enamel
crown
dentin
pulp
gum
jawbone
root canal
root
periodontal
membrane
cementum
Figure 8.3b A cross section of a
tooth showing the crown and root.
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8.2 The Mouth, Pharynx, and Esophagus
The pharynx and esophagus
• The pharynx is a cavity between the mouth
and esophagus that serves as a passageway
for food (and air).
• The __________ is a long, muscular tube
that carries food to the stomach.
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8.2 The Mouth, Pharynx, and Esophagus
How do we swallow food?
• Voluntary phase
– In the beginning, when food is being
swallowed from the mouth into the pharynx
is a voluntary act.
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8.2 The Mouth, Pharynx, and Esophagus
How do we swallow food?
• Involuntary phase
– Once the food is in the pharynx, swallowing
becomes a reflex.
– The ___________ covers the voice box to
make sure food is routed into the
esophagus.
– Food moves down the esophagus through
____________ (rhythmic contraction).
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8.2 The Mouth, Pharynx, and Esophagus
How do we swallow food?
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hard palate
food bolus
nasopharynx
Soft palate closes
off nasopharynx.
soft
palate
bolus
peristaltic
wave
epiglottis
glottis
Esophagus
is closed.
trachea
(airway)
open
a. Swallowing
Larynx rises and
epiglottis covers
glottis.
esophagus
opens
Lower gastroesophageal
esophagus sphincter relaxes and
food enters stomach.
stomach
b. Peristalsis
Figure 8.4 The process of swallowing.
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