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PowerPoint® Lecture Slides
prepared by Vince Austin,
Bluegrass Technical
and Community College
CHAPTER
Elaine N. Marieb
Katja Hoehn
23
PART A
Human
Anatomy
& Physiology
SEVENTH EDITION
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
The Digestive
System
Digestive System: Overview



The alimentary canal or gastrointestinal
(GI) tract digests and absorbs food
Alimentary canal – mouth, pharynx,
esophagus, stomach, small intestine, and
large intestine
Accessory digestive organs – teeth,
tongue, gallbladder, salivary glands, liver,
and pancreas
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 23.1
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Figure 23.2
Gastrointestinal Tract Activities
Ingestion – taking food into the digestive
tract
1.
2. Propulsion – swallowing and peristalsis

Peristalsis – waves of contraction and
relaxation of muscles in the organ walls
3. Mechanical digestion – chewing,
mixing, and churning food
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Gastrointestinal Tract Activities
4. Chemical digestion
– catabolic
breakdown of food
5. Absorption – movement of nutrients
from the GI tract to the blood or lymph
6. Defecation – elimination of indigestible
solid wastes
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GI Tract
Regulation of digestion involves
1.
Mechanical and chemical stimuli – stretch
receptors, osmolarity (solute concentration) , pH
of contents and presence of substrate in the
lumen
2.
Controls (Enteric Nervous System)

Extrinsic by CNS centers (ACh; nitric oxide)

Intrinsic by local centers- within the walls of the
canal
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Nervous Control of the GI Tract
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Figure 23.4
Peritoneum and Peritoneal Cavity

Peritoneum – serous membrane of the abdominal
cavity



Visceral – covers external surface of most
digestive organs
Parietal – lines the body wall
Peritoneal cavity – fluid space between the two

Lubricates digestive organs

Allows them to slide across one another
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Peritoneum and Peritoneal Cavity
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Figure 23.5a
Peritoneum and Peritoneal Cavity



Mesentery – double layer of peritoneum that
provides:

Vascular and nerve supplies to the viscera

Hold digestive organs in place and store fat
Retroperitoneal organs – organs outside the
peritoneum (pancreas, parts of SI and LI)
Peritoneal organs (intraperitoneal) – organs
surrounded by peritoneum (stomach)
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Peritoneum and Peritoneal Cavity
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 23.5b
Blood Supply: Splanchnic Circulation

Arteries that branch from the
abdominal aorta and the hepatic portal
system

The hepatic, splenic, and left
gastric branches of the celiac trunk:
spleen, liver, and stomach
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Blood Supply: Splanchnic Circulation

Hepatic portal circulation:
Collects venous blood from the
digestive viscera and delivers to the
liver for metabolic processing and
storage
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Histology of the Alimentary Canal
4 layers (tunics) of the AC
1.Mucosa
2. Submucosa
3. muscularis externa
4. serosa
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Histology of the Alimentary Canal
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Figure 23.6
Mucosa

Three major functions:

Secretion of mucus

Absorption of end products of digestion

Protection against infectious disease
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Mucosa: Other Sublayers



Submucosa –containing elastic fibers,
blood and lymphatic vessels, lymph
nodes, and nerves
Muscularis externa – responsible for
segmentation and peristalsis
Serosa – the protective visceral
peritoneum
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Functional
Anatomy of the
Digestive System
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Mouth

Oral or buccal cavity:
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Anatomy of the Oral Cavity: Mouth
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Figure 23.7a
Lips and Cheeks

Have a core of skeletal muscles

Lips: orbicularis oris

Cheeks: buccinators

Vestibule

Oral cavity proper

Labial frenulum
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Oral Cavity and Pharynx: Anterior View
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Figure 23.7b
Palate

Hard palate

Soft palate
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Tongue

Occupies the floor of the mouth and
fills the oral cavity when mouth is
closed
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Tongue

Superior surface bears three types of
papillae

Filiform

Fungiform

Circumvallate
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Tongue
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Figure 23.8
Salivary Glands

Cleanses the mouth

Moistens and dissolves food
chemicals

Aids in bolus formation

Contains enzymes that break down
starch
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Salivary Glands
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Figure 23.9a
Saliva: Source and Composition

Secreted from serous and mucous cells of salivary
glands

97-99.5% water, hypo-osmotic, slightly acidic
solution containing

Electrolytes – Na+, K+, Cl–, PO42–, HCO3–

Digestive enzyme – salivary amylase

Proteins – mucin, lysozyme, defensins, and IgA

Metabolic wastes – urea and uric acid
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Teeth



Primary and permanent dentitions have formed by
age 21
Primary – 20 deciduous teeth that erupt at intervals
between 6 and 24 months
Permanent – enlarge and develop causing the root
of deciduous teeth to be resorbed and fall out
between the ages of 6 and 12 years

All but the third molars have erupted by the end of
adolescence

Usually 32 permanent teeth
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Permanent Teeth
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Figure 23.10.2
Dental Formula: Permanent Teeth
 A shorthand way of indicating the number and
relative position of teeth
2I
2I
1C
1C
2PM
2PM
3M
3M
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X
2 (32 teeth)
Tooth Structure
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Figure 23.11
Tooth and Gum Disease: Periodontitis
 Gingivitis – as plaque accumulates, it calcifies and
forms calculus, or tartar



Accumulation of calculus:

Disrupts the seal between the gingivae and the
teeth

Puts the gums at risk for infection
Periodontitis – serious gum disease resulting from
an immune response
Immune system attacks intruders as well as body
tissues, carving pockets around the teeth and
dissolving bone
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings