Abdomen and Digestive
system
Thursday, 21 October 2021 10:31 AM
Overview of our digestive system
- Digestive tract (Alimentary tract / canal)
- Gi tract
○ Stomach and intestines
- Accessory organs
○ Not part of canal but they provide enzymes / fluids etc to
supplement digestion
○ Primarily glands
○ Secrete fluids into the tract
- Regions
○ Oral cavity
○ Pharynx
○ Esophagus
○ Stomach
○ Small intestines
§ Duodenum / ileum / jejunum
§ liver, gallbladder and pancreas as major accessory organs
○ Large intestines
§ Cecum, colon, rectum and anal canal with mucous glands
○ Anus
Major functions
- Ingestion
- Mastication
- Propulsion
○ Deglutition
§ Swallowing
○ Peristalsis
§ Moves material through digestive tract
§ Unidirectional movement of food
○ Mass movement
§ In large intestines
- Secretion
○ Lubricate, liquefy, digest
○ Mucus, water, bile, enzymes
- Digestion
, ○ Mass movement
§ In large intestines
- Secretion
○ Lubricate, liquefy, digest
○ Mucus, water, bile, enzymes
- Digestion
○ Mechanical and chemical
- Absorption
○ Movement from tract into circulation or lymph
○ Most in small intestines
- Elimination
○ Waste products removed from body
○ Feces - defecation
Digestive tract histology
- Layers
○ Mucosa
§ In contact with food
§ Mucous membrane
§ Epithelium
§ Lamina propria
□ Loose connective tissue
□ Provides vascular support for the epithelium
□ Often contains mucosal glands
§ Muscularis mucosae
□ Thin double layer of smooth muscle
□ For local movement of the mucosa
§ Lymphatic nodule intestinal gland
○ Submucosa
§ Loose connective tissue layer
§ Mucous secreting glands
□ And their Ducts
§ Plexus to control the secretion from glands
□ Submucosal plexus
□ The nerves are derived from the myenteric nerve plexus
® Nerves from myenteric perforate the muscle fibres
to reach the submucosa
□ Innervates cells in the epithelial layer and the smooth
muscle of the muscularis mucosae
□ Involuntarily induce secretion of enzymes from mucous
○ Muscularis
§ 2 layers
□ Circular inner muscle layer
□ Longitudinal outer muscle layer
§ Segmentation / peristalsis
§ Myenteric plexus
□ Bundle of nerves between the 2 layers of muscle
, § 2 layers
□ Circular inner muscle layer
□ Longitudinal outer muscle layer
§ Segmentation / peristalsis
§ Myenteric plexus
□ Bundle of nerves between the 2 layers of muscle
□ Regulates peristalsis in the GI tract
○ Serosa
§ Provides protection layer to reduce friction when visceral
moves around in abdomen
□ Surrounded by visceral peritoneum
§ Serous membrane
§ Connective tissue
- Structure of the wall
○ Distinct epithelium in different parts of GI tract
○ Small intestines
§ Microvilli
§ Simple epithelium that allows efficient diffusion of nutrients
General characteristics of alimentary canal
- Muscular tube about 8 meters long
- Innervation of tube
○ Branches of sympathetic and parasympathetic divisions of
autonomic nervous system innervate alimentary canal
§ Submucosal plexus
□ Controls secretion
□ In submucosa
§ Myenteric plexus
□ Controls gastrointestinal mobility
○ Parasympathetic increases the activity of the digestive system
○ Sympathetic inhibits certain digestive actions
Oral cavity
- Bound by lips anteriorly and fauces (opening into pharynx) posteriorly
○ Vestibule
§ Space between lips / cheeks and alveolar processes with teeth
§ Kept moist by secretions from parotid gland
§ Alveolar processes
□ Thick ridge of bone which contains the tooth sockets
□ Holds the teeth
○ Oral cavity proper
§ Medial to alveolar processes
- Many layers of epithelium
○ Lined with moist stratified squamous epithelium
○ Moist
§ To protect
- Tongue
system
Thursday, 21 October 2021 10:31 AM
Overview of our digestive system
- Digestive tract (Alimentary tract / canal)
- Gi tract
○ Stomach and intestines
- Accessory organs
○ Not part of canal but they provide enzymes / fluids etc to
supplement digestion
○ Primarily glands
○ Secrete fluids into the tract
- Regions
○ Oral cavity
○ Pharynx
○ Esophagus
○ Stomach
○ Small intestines
§ Duodenum / ileum / jejunum
§ liver, gallbladder and pancreas as major accessory organs
○ Large intestines
§ Cecum, colon, rectum and anal canal with mucous glands
○ Anus
Major functions
- Ingestion
- Mastication
- Propulsion
○ Deglutition
§ Swallowing
○ Peristalsis
§ Moves material through digestive tract
§ Unidirectional movement of food
○ Mass movement
§ In large intestines
- Secretion
○ Lubricate, liquefy, digest
○ Mucus, water, bile, enzymes
- Digestion
, ○ Mass movement
§ In large intestines
- Secretion
○ Lubricate, liquefy, digest
○ Mucus, water, bile, enzymes
- Digestion
○ Mechanical and chemical
- Absorption
○ Movement from tract into circulation or lymph
○ Most in small intestines
- Elimination
○ Waste products removed from body
○ Feces - defecation
Digestive tract histology
- Layers
○ Mucosa
§ In contact with food
§ Mucous membrane
§ Epithelium
§ Lamina propria
□ Loose connective tissue
□ Provides vascular support for the epithelium
□ Often contains mucosal glands
§ Muscularis mucosae
□ Thin double layer of smooth muscle
□ For local movement of the mucosa
§ Lymphatic nodule intestinal gland
○ Submucosa
§ Loose connective tissue layer
§ Mucous secreting glands
□ And their Ducts
§ Plexus to control the secretion from glands
□ Submucosal plexus
□ The nerves are derived from the myenteric nerve plexus
® Nerves from myenteric perforate the muscle fibres
to reach the submucosa
□ Innervates cells in the epithelial layer and the smooth
muscle of the muscularis mucosae
□ Involuntarily induce secretion of enzymes from mucous
○ Muscularis
§ 2 layers
□ Circular inner muscle layer
□ Longitudinal outer muscle layer
§ Segmentation / peristalsis
§ Myenteric plexus
□ Bundle of nerves between the 2 layers of muscle
, § 2 layers
□ Circular inner muscle layer
□ Longitudinal outer muscle layer
§ Segmentation / peristalsis
§ Myenteric plexus
□ Bundle of nerves between the 2 layers of muscle
□ Regulates peristalsis in the GI tract
○ Serosa
§ Provides protection layer to reduce friction when visceral
moves around in abdomen
□ Surrounded by visceral peritoneum
§ Serous membrane
§ Connective tissue
- Structure of the wall
○ Distinct epithelium in different parts of GI tract
○ Small intestines
§ Microvilli
§ Simple epithelium that allows efficient diffusion of nutrients
General characteristics of alimentary canal
- Muscular tube about 8 meters long
- Innervation of tube
○ Branches of sympathetic and parasympathetic divisions of
autonomic nervous system innervate alimentary canal
§ Submucosal plexus
□ Controls secretion
□ In submucosa
§ Myenteric plexus
□ Controls gastrointestinal mobility
○ Parasympathetic increases the activity of the digestive system
○ Sympathetic inhibits certain digestive actions
Oral cavity
- Bound by lips anteriorly and fauces (opening into pharynx) posteriorly
○ Vestibule
§ Space between lips / cheeks and alveolar processes with teeth
§ Kept moist by secretions from parotid gland
§ Alveolar processes
□ Thick ridge of bone which contains the tooth sockets
□ Holds the teeth
○ Oral cavity proper
§ Medial to alveolar processes
- Many layers of epithelium
○ Lined with moist stratified squamous epithelium
○ Moist
§ To protect
- Tongue
