Flashcards in Digestive System Deck (33)
What are the four layers of the gut?
Mucosa, submucosa, external muscle layers, serosa
What are the three layers of the mucosa?
Epithelia, Lamina propria, muscularis mucosae
What is the submucosa?
A layer of connective tissue bearing glands, arteries, veins and nerves
What are the major functions of the gastrointestinal tract?
mechanically disrupt, temporarily store, chemically digest food
Kill pathogens in food, move food, absorb nutrients and eliminate waste
What is digestion?
The conversion of what we wet by physical and chemical disruption into a solution from which we can absorb our nutrients
What is saliva used for?
Starts digestion with amylase and lipase
Bacteriostatic, high in calcium, alkaline, assists swallowing, protects mouth
What does the mouth do to food?
By using teeth, tongue and saliva's enzymes forms a bolus
How does the oesophagus move food?
Rapid Peristaltic transport
What is the Muscularis externa?
smooth muscle layers which move food by peristalsis
What is the Adventitia?
Thin outermost layer of connective tissue
How does the stomach physically and chemically disrupt food?
Physically- By churning with the three muscle layers
Chemically- By acid and enzymes
What does the stomach do?
Store, initial disruption and disinfection
How does the stomach protect itself from the acid?
Secretes mucus which contains HCO3- which neutralise the stomach
What is Rugae?
Folds of gastric mucosa forming longitudinal ridges in empty stomach
What can damage mucus cells in the stomach?
Alcohol and aspirin
What is the duodenum?
Connects the liver and pancreas
Dilutes and neutralises chyme
Draws in water to make chyme isotonic otherwise would damage the liver
What do enzymes do from the pancreas and intestine?
Cleave peptides to amino acids
cleave polysaccharides to monosaccharides
Break down and re-form lipids
Break down nucleic acids
What does absorption require?
Lots of energy, large surface area, good blood supply
What are the three parts of the small intestine?
Duodenum- absorbs iron
Jejunum- absorbs most sugars, aa and fatty acids
Ileum- absorbs vitamin B12, bile acids and remain nutrients
What does the large intestine do?
continues water recovery so by the end is semi-solid
What does the bacteria in the large intestine do?
syntheisie vitamin K, B12, thiamine and riboflavine, breaks down 1 to 2 bile acids, converts bilirubin into non-pigmented metabolites
Where contains most bacteria in the GI tract?
How much food is converted not faeces?
1kg into 0.15kg of faeces via 14 litres of fluid
What is the problem with fluid balance?
delicate balance and gut is dealing with large quantities
How is the fluid balance controlled?
Neural, Paracrine and Endocrine systems
How is the fluid balance controlled neurally?
Somatic- ingestion and excretion
Autonomic- gut nervous system, neurotransmitters, post ganglion neurones
How is the fluid balance controlled by the paracrine system?
Substances act locally e.g. histamine (production of acid control) and Vasoactive substances(blood flow to gut control)
How is the fluid balance controlled by the endocrine system?
Range of hormones control the secretion of acid, alkali and enzymes
These are Secretin, Cholecystokinin and Gastrin
What does secretin do?
Promotes HCO3- secretion from duct cells of pancreas
Promotes bile production by the liver
inhibits secretion of acid by parietal cells of stomach