Digestive tract and GI tract
Digestive tract = alimentary tract/canal
- GI tract = stomach + intestines
Digestion Function:
- Ingestion
- Mastication: chewing.
○ Chemical digestion
○ Mechanical digestion - Propulsion
○ Deglutition: Swallowing
○ Peristalsis: moves material - Secretion: lubricate, liquefy, digest
○ Mucus - lubricates, protects from digestion, acid, and digestive enzymes
○ Bile - emulsifies fats
○ Enzymes - chemical digestion - Digestion: Mechanical and Chemical
- Absorption: nutrients into circulation or lymph
- Elimination: waste products removed from body
Tunic of digestion
- Mucosa: innermost layer
- Submucosa: nerves, blood vessels, small glands, parasympathetic submucosal plexus
- Muscularis:
○ Circular and longitudinal
○ contains the myenteric plexus. The myenteric and submucosal plexi together are called the enteric or intramural plexus.
§ Controls movement and secretion - Serosa: visceral peritoneum
- Adventitia: c.t. blends w/ surrounding c.t.
Peritoneum of Digestive System
○ Visceral: Covers organs
○ Parietal: Covers interior surface of body wall
○ Retroperitoneal: Certain organs covered by peritoneum on only one surface and are considered behind the peritoneum; e.g., kidneys, pancreas, duodenum
Mesenteries of the digestive system
○ Greater omentum: connects greater curvature of the stomach to the transverse colon.
○ Lesser omentum: connects lesser curvature of the stomach and the proximal part of the duodenum to the liver and diaphragm.
○ Transverse mesocolon, sigmoid mesocolon, mesoappendix.
Ligaments of the digestive system
○ Coronary: between liver and diaphragm
○ Falciform: between liver and anterior abdominal wall
Function of Lips and Cheeks
Mastication
Function of Tongue
Moves food in mouth, participates in speech and swallowing
Function of Teeth
Two sets
○ Primary = Childhood
○ Permanent = Adult
Mastication and speech
Function of Saliva
Alveolar salivary gland produce saliva
Prevents infection, lubrication, amylase for breaking down starch, helps in swallowing, parasympathetic
Function of Salivary glands
- Parotid = Largest, Serous, parotid duct
- Submandibular = Mixed (more serous)
- Sublingual = smallest, mixed (more mucous)
Esophagus
Esophageal hiatus = opening of diaphragm and ends at stomach
Three phases of Swallowing
○ Voluntary = food moved by tongue, oral - pharynx
○ Pharyngeal = reflex lets food pass through larynx
○ Esophageal = reflex, initiate peristalsis in esophagus
Stomach Anatomy
- Gastric pits: hold gastric glands
- Cells of gastric pits
○ Surface mucus: mucus that protects stomach lining from acid and digestive enzymes
○ Mucous neck: mucus
○ Parietal: hydrochloric acid and intrinsic factor
○ Chief: pepsinogen
○ Endocrine: regulatory hormones
Secretions of the Stomach
- Chyme
- Mucus
- Intrinsic factor: absorption
- HCl: kills bacteria
- Pepsinogen: break down protein
Small intestine
- Primary function: absorb nutrients
- Secondary: absorption of water
Duodenum
§ Absorptive cells: cells with microvilli, produce digestive enzymes and absorb digested food
§ Goblet cells: produce protective mucus
§ Endocrine cells: produce regulatory hormones
§ Granular cells (paneth cells): may help protect from bacteria
Jejunum and Ileum
Major site of nutrient absorption
Liver Function
Bile production, Storage, Nutrient interconversion, Detoxification, Phagocytosis, Synthesis
Gallbladder Function
Concentrates and Stores Bile
Bile - emulsifies fats
Pancreas Function
Endocrine - produce pancreatic islets (insulin, glucose, somatostatin)
Exocrine - gives out secretions to outside world (pancreatic juice in stomach and large intestine)
- Acini glands are exocrine
- Alpha beta delta are endocrine
