Grand Tour Of The Alimentary Canal Flashcards
What is the digestive system made up of?
GI tract & Accessory Organs
Salivary Gland
Liver
Pancreas
Gallbladder
What are the solid organs of the digestive system?
Accessory organs
Salivary gland
Liver
Pancreas
Gallbladder
What are the main functions of the digestive system?
Digestion
Absorption
Secretion
Motility
What is the flow of food through the GI system
Esophagus > Stomach > Small intestine > Colon > Rectum > Anus
Where does absorption and secretions take place?
Mostly small intestine and a little bit in the colon
What happens at the mouth?
Foodstuff broken down by chewing; saliva added as lubricant
What is the oesophagus
Conduit between mouth and stomach
What happens in the stomach
Digestion of proteins, foodstuffs reduced to semi liquid form, storage and sterilisation
What happens at the pancreas
Digestive enzymes for digestion of fats, carbs and proteins
What happens at the liver?
Bile salts for digestion/absorption of fats in small intestine
What is the purpose of the gallbladder
Stores and concentrates bile
What happens at the small intestine
Final stages of chemical digestion and nutrient absorption
What happens large intestine
Water absorption, bacterial fermentation and formation of faeces
What is the general structure of the alimentary canal
Continuous hollow tube that runs from oseophagus to rectum made up of 4 distinct layers (tunics)
What are the 4 distinct layers
Mucosa
Submucosa
Muscularis externa
Serosa/adventitia
What is serosa/adventitia?
Connective tissue sheet
Known as serosa in peritoneal cavity and adventitia if outside the peritoneal cavity
What is mucosa composed of?
3 distinct layers
Epithelium
Lamina proprietor
Muscularis mucosae
What is the purpose of epithelium in GI tract
Barrier separating lumen of alimentary canal from body
Synthesis and secretion of digestive enzymes, hormones, mucus
Absorbs products of digestion
Epithelium differs along length of gut tube - it adapts depending on function
What is the lamina proprietor
Lose CT found in glands, blood/lymph vessels
What is the Muscularis muscosae
Thin smooth muscle layer
What is submucosa composed of?
Thick, irregular CT
Contains neurones, blood vessels
These neurones form extensive network called submucosal meissners plexus (parasympathetic)
Submucosal glands in oesophageal and duodenum
How does adventitia occur outside the peritoneal cavity
Adventitia attaches oesophagus and rectum to surrounding structures
How does serosa occur outside the peritoneal cavity
Surrounds stomach, small intestine and large intestine
What is the Muscularis externa composed of?
Two concentric thick layers of smooth muscle
Inner layer - circular muscle which constricts lumen
Outer layer - longitudinal muscle which shortens tube
Motility produced by peristalsis and segmentation
Myenteric plexus between circular and longitudinal muscle
Submucosal + myenteric plexuses = enteric nervous system - independent control of gut function
How is the alimentary system autonomically controlled
By long - parasympathetic and;
Short - ENS - reflexes
What is the parasympathetic innervation of alimentary function?
Vagal Nerve CX
Except salivation - facial VII and glossopharyngeal (IX)
Stimulatory
- secretion
- motility
What is the sympathetic innervation of alimentary function
Splanchnic nerve
Inhibitory (except salivation)
- secretion
- motility
