Grand tour of the alimentary canal Flashcards
What are the functions of the alimentary canal?
Digestion
Absorption
Secretion
Motility
Give an example of how digestion may be used to control osmolarity.
1000 glucose chain has same osmolarity as glucose monomer
Immediate breakdown of the chain massively changes osmolarity as there is 1000 fold increase in number of dissolved particles in the solution
Particles must be broken down gradually
What are the functions of the mouth?
Chews and lubricates food
Starts digestion with lingual lipase and salivary amylase
What is the function of the oesophagus?
Conduit between mouth and stomach
Works both ways
What are the functions of the stomach?
HCl digests protein
Stores food
Neutralises microbes in food
Food is reduced to liquid
What is the function of the pancreas?
Produces digestive enzymes for fats, carbs and proteins
What digestive function does the liver serve?
Produces bile salts for digesting fats
What does the gallbladder do?
Stores and concentrates bile
What is the function of the small intestine?
Final stage for chemical digestion and nutrient absorption
What are the functions of the large intestine?
Water absorption
Bacterial fermentation
Formation of faeces
What are the 4 distinct layers of the gut tube wall?
Mucosa
Submucosa
Muscularis externa
Serosa/adventitia
What are the 3 layers of the submucosa?
Epithelium
Lamina propria
Muscularis mucosa
What is the difference between the 2 layers of the muscularis externa?
The inside layer of fibres wrap around the tube
Outside layer runs along the tube
What does the duodenum secrete?
Bicarbonate to neutralise acid coming out of the stomach
What kind of epithelium lines the mouth, oesophagus and anal canal?
Stratified squamous
What kind of epithelium lines the stomach, small intestine and large intestine?
Simple columnar
What does the lamina propria consist of?
Loose connective tissue
What does the submucosa contain?
Thick irregular connective tissue Neurones Blood vessels Submucosal plexus Submucosal glands present in oesophagus and duodenum
What is peristalsis?
Series of involuntary wave-like muscle contractions of adjacent muscles which moves food along the digestive tract
What is segmentation?
Non-adjacent segments of alimentary canal contract and relax, moving food forward and back to break it down and mix it
What is the effect of parasympathetic innervation on the alimentary canal?
Increases secretion and motility
How is the alimentary canal mostly innervated?
Vagus nerve, parasympathetic is king
Except for salivation which is controlled by CN VII and CN IX
What is the effect of sympathetic innervation?
Decreases secretion and motility
What is the venous drainage of the stomach?
Gastric veins
What is the venous drainage of the pancreas?
Splenic vein
What does the hepatic portal vein do?
Moves blood from spleen and gut into liver
What is the venous drainage of the liver?
Hepatic vein
Do the gut and liver run in series or parallel?
Series
Which areas of the GI tract are drained by the superior mesenteric vein?
Small intestine
Caecum
Ascending colon
Transverse colon
Which areas of the GI tract are drained by the inferior mesenteric vein?
Descending colon
Sigmoid colon
Rectum
What does the jejunum do?
Responsible for about 95% of nutrient absorption
Usually empty
What is the duodenum responsible for?
NaCl/H2O reabsorption
What are plicae?
Corkscrew pattern of grooves aids mixing and contact with gut wall for foodstuffs
Describe the water secretion of the small intestine
Secretes about 1.5 litres per day
Comes from crypts of Lieberkuhn
Dilutes and washes away potentially injurious substances
What does adenylate cyclase do?
Regulates water secretion
Doesn’t work properly in CF
