Download 17.1: Introduction

17.1: Introduction
• Digestion is the mechanical and chemical breakdown of
foods into forms that cell membranes can absorb
• Organs of the digestive system carry out these processes, as
well as ingestion, propulsion, absorption and defecation
• The digestive system consists of the alimentary canal
extending from the mouth to the anus, plus accessory organs
that empty into the alimentary canal
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17.2: General Characteristics of the
Alimentary Canal
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• The alimentary canal
is a muscular tube about
8 meters long
Tongue
.5 meter (from tongue
to duodenum)
Esophagus
Duodenum
5.5 – 6.0 meters
(small intestine)
Gallbladder
Stomach
1.0m
Pancreas
Jejunum
(2.2 – 2.4 m)
Ileum
(3.3 – 3.6 m)
Appendix
1.5 meters
(large intestine)
Cecum
Large
intestine
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Anus
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Innervation of the Tube
• Branches of the sympathetic and parasympathetic divisions
of the autonomic nervous system extensively innervate the
alimentary canal, including:
• Submucosal plexus – controls secretions
• My enteric plexus – controls gastrointestinal motility
• Remember:
• Parasympathetic impulses – increase activities of
digestive system
• Sympathetic impulses – inhibit certain digestive actions
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