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Introduction
The digestive system consists of the muscular digestive tract and
various accessory organs.
Functions of digestive system:
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Ingestion
Mechanical processing
Digestion
Secretion
Absorption
Excretion
Compaction
An Overview of the Digestive System
Major layers of the digestive tract include
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Mucosa
Submucosa
Muscularis externa
Serosa
The Oral Cavity
 The oral cavity includes:
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The tongue
Salivary glands
Teeth
Mastication
 Functions of the oral cavity:
 Analyzes material before swallowing
 Mechanical processing of food through the actions of teeth, tongue, and palatal
surfaces
 Lubrication
 Limited digestion of carbohydrates by a salivary enzyme
The Pharynx
 Muscles involved in swallowing:
 Pharyngeal constrictors push the bolus toward theesophagus.
 Palatopharyngeus and stylopharyngeus muscles elevate the larynx.
 The palatal muscles raise the soft palate.
 The swallowing process:
 Buccal phase
 Pharyngeal phase
 Esophageal phase
The Esophagus
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Muscular tube that transports food and liquid to the stomach
Connects the pharynx to the stomach
Superior portion is skeletal muscle
Inferior portion is smooth muscle
The Stomach
 Three major functions:
 Stores bulk amounts of ingested food
 Mechanically breaks down ingested food
 Chemically digests ingested food
 Four regions:
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Cardia
Fundus
Body
Pylorus
 Three layers of muscle
 Highly specialized mucosa
The Small Intestine
 Plays primary role in the digestion and absorption of food
 Three anatomical regions:
 Duodenum— the “mixing bowl”
 Jejunum— where the bulk of digestion and absorption occurs
 Ileum— materials flow through here into large intestine
The Large Intestine
 Often called the large bowel
 Functions include:
 Reabsorb water and compact feces
 Absorption of important minerals by bacteria
 Storage site for feces before defecation
 Three regions:
 The cecum
 The colon
 The rectum
Accessory Glandular Digestive Organs
 Liver
 Bile production
 Gallbladder
 Bile storage and concentration
 Pancreas
 Enzyme production and secretion
Aging and the Digestive System
 The rate of epithelial stem cell division declines.
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Smooth muscle tone decreases.
The effects of cumulative damage become apparent.
Cancer rates increase.
Changes in other systems have direct or indirect effects on the
digestive system.