BUNDLE 8: DIGESTIVE SYSTEM, METABOLISM, ENDOCRINE &
INTEGUMENTARY SYSTEMS
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PART A: DIGESTIVE SYSTEM
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INTRODUCTION
The digestive system = alimentary canal + accessory organs + digestive processes
preparing food for absorption.
GI tract: 23-26 feet long; from mouth to esophagus, stomach, small intestines, rectum, to
anus.
Accessory organs: teeth and gums, tongue, salivary glands, liver, gall bladder, pancreas.
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ANATOMIC AND PHYSIOLOGIC OVERVIEW
Mouth: Contains tongue and teeth (chewing, swallowing); salivary glands (digestion).
Esophagus:
• In mediastinum; anterior to spine, posterior to trachea and heart
• ~25 cm long
• Passes through diaphragm at diaphragmatic hiatus
Stomach:
• Left upper abdomen; under left lobe of liver and diaphragm
• Overlying most of pancreas
• Four regions: cardia, fundus, body, pylorus
Small intestine:
• Longest segment; 2/3 total length
• Three sections: duodenum, jejunum, ileum
Large intestine:
• Ascending (right), transverse (right to left), descending (left)
• Terminal: sigmoid colon, rectum, anus
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,DEFINITIONS IN ALIMENTARY TRACT
Ingestion: Taking food into alimentary tract (eating, drinking).
Propulsion: Mixes and moves contents along tract.
Digestion:
• Mechanical breakdown (e.g., mastication/chewing)
• Chemical digestion into small molecules by enzymes
Absorption: Digested substances pass through walls into blood/lymph capillaries.
Elimination: Undigested/unabsorbed substances excreted as feces by defecation.
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ORGANS OF THE DIGESTIVE SYSTEM
Alimentary Canal (GI Tract)
Long tube from mouth to anus:
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large intestine
• Rectum and anal canal
Accessory Organs
Secretions pass through ducts into tract:
• Three pairs of salivary glands
• Pancreas
• Liver and biliary tract
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BASIC STRUCTURE OF ALIMENTARY CANAL
Four layers (from esophagus onwards):
1. Adventitia or outer covering
2. Muscle layer
3. Submucosal layer
4. Mucosa lining
, Adventitia or Serosa
Outermost layer.
• Thorax: loose fibrous tissue
• Abdomen: serous membrane (peritoneum)
Peritoneum
Largest serous membrane; closed sac with small amount of serous fluid.
• Richly supplied with blood/lymph vessels; many lymph nodes
• Physical barrier to local infection spread
• Can isolate infective focus (e.g., appendicitis)
Two layers:
• Parietal peritoneum: Lines abdominal wall
• Visceral peritoneum: Covers organs within abdominal and pelvic cavities
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MOUTH (ORAL CAVITY)
Bounded by:
• Anteriorly: Lips
• Posteriorly: Continuous with oropharynx
• Laterally: Muscles of cheeks
• Superiorly: Bony hard palate and muscular soft palate
• Inferiorly: Muscular tongue and soft tissues of floor
Tongue
Functions:
• Chewing (mastication)
• Swallowing (deglutition)
• Speech
• Taste
Nerve endings of taste in papillae; widely distributed in epithelium of tongue, soft palate,
pharynx, epiglottis.
Teeth
Embedded in alveoli/sockets of alveolar ridges of mandible and maxilla.
• Two sets: temporary (deciduous) and permanent
• At birth, both present in immature form in mandible and maxilla
Functions by shape:
INTEGUMENTARY SYSTEMS
__________________________________________________
PART A: DIGESTIVE SYSTEM
__________________________________________________
INTRODUCTION
The digestive system = alimentary canal + accessory organs + digestive processes
preparing food for absorption.
GI tract: 23-26 feet long; from mouth to esophagus, stomach, small intestines, rectum, to
anus.
Accessory organs: teeth and gums, tongue, salivary glands, liver, gall bladder, pancreas.
__________________________________________________
ANATOMIC AND PHYSIOLOGIC OVERVIEW
Mouth: Contains tongue and teeth (chewing, swallowing); salivary glands (digestion).
Esophagus:
• In mediastinum; anterior to spine, posterior to trachea and heart
• ~25 cm long
• Passes through diaphragm at diaphragmatic hiatus
Stomach:
• Left upper abdomen; under left lobe of liver and diaphragm
• Overlying most of pancreas
• Four regions: cardia, fundus, body, pylorus
Small intestine:
• Longest segment; 2/3 total length
• Three sections: duodenum, jejunum, ileum
Large intestine:
• Ascending (right), transverse (right to left), descending (left)
• Terminal: sigmoid colon, rectum, anus
__________________________________________________
,DEFINITIONS IN ALIMENTARY TRACT
Ingestion: Taking food into alimentary tract (eating, drinking).
Propulsion: Mixes and moves contents along tract.
Digestion:
• Mechanical breakdown (e.g., mastication/chewing)
• Chemical digestion into small molecules by enzymes
Absorption: Digested substances pass through walls into blood/lymph capillaries.
Elimination: Undigested/unabsorbed substances excreted as feces by defecation.
__________________________________________________
ORGANS OF THE DIGESTIVE SYSTEM
Alimentary Canal (GI Tract)
Long tube from mouth to anus:
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large intestine
• Rectum and anal canal
Accessory Organs
Secretions pass through ducts into tract:
• Three pairs of salivary glands
• Pancreas
• Liver and biliary tract
__________________________________________________
BASIC STRUCTURE OF ALIMENTARY CANAL
Four layers (from esophagus onwards):
1. Adventitia or outer covering
2. Muscle layer
3. Submucosal layer
4. Mucosa lining
, Adventitia or Serosa
Outermost layer.
• Thorax: loose fibrous tissue
• Abdomen: serous membrane (peritoneum)
Peritoneum
Largest serous membrane; closed sac with small amount of serous fluid.
• Richly supplied with blood/lymph vessels; many lymph nodes
• Physical barrier to local infection spread
• Can isolate infective focus (e.g., appendicitis)
Two layers:
• Parietal peritoneum: Lines abdominal wall
• Visceral peritoneum: Covers organs within abdominal and pelvic cavities
__________________________________________________
MOUTH (ORAL CAVITY)
Bounded by:
• Anteriorly: Lips
• Posteriorly: Continuous with oropharynx
• Laterally: Muscles of cheeks
• Superiorly: Bony hard palate and muscular soft palate
• Inferiorly: Muscular tongue and soft tissues of floor
Tongue
Functions:
• Chewing (mastication)
• Swallowing (deglutition)
• Speech
• Taste
Nerve endings of taste in papillae; widely distributed in epithelium of tongue, soft palate,
pharynx, epiglottis.
Teeth
Embedded in alveoli/sockets of alveolar ridges of mandible and maxilla.
• Two sets: temporary (deciduous) and permanent
• At birth, both present in immature form in mandible and maxilla
Functions by shape:
