Digestion and absorption Flashcards
What is the difference between the luminal and membranous phase of digestion?
Luminal phase:
- action of enzymes of food particles
- initial breakdown of proteins into smaller peptides
- in lumen
Membranous phase:
- at brush border of SI
- enzymes of the enterocyte membrane further break down peptides into amino acids for absorption
Describe the absorption mechanism of carbs
What is secretory diarrhoea?
increase in active secretion or inhibition of absorption
little to no structural damage
What is osmotic diarrhoea
when too much water drawn into bowels
What is motility-related diarrhoea
caused by rapid movement of food through intestines - hypermotility
What is inflammatory diarrhoea?
damage to mucosal lining or brush border => loss of protein-rich fluids and decreased ability to absorb lost fluids
What diseases can result in diarrhoea?
Infection and inflammation - disrupts absorption
Malabsorption disorders e.g., coeliac, Crohns
Disruption of brush border enzymes e.g., lactose intolerance
Altered ion transport e.g., inflammatory bowel disease
Increased permeability e.g., inflammatory bowel disease
Neurological disorders effecting ENS
Medication-induced
How can infection and inflammation lead to diarrhoea?
infection can directly effect GIT lining
inflammation disrupts normal absorption => impaired nutrient absorption and influx of water into lumen
How do malabsorption disorders e.g. coeliac, lead to diarrhoea?
reduces absorption of nutrient => osmotic imbalance in lumen
unabsorbed nutrients and water increase osmotic pressure => draws more water into intestine
How does disruption of brush border enzymes cause diarrhoea?
indigested carbs reaching colon can serve as substrates for bacterial fermentation => production of osmotically active substances => diarrhoea
How can altered ion transport cause dairrhoea?
dysregulation of ion transport, including increased secretion of Cl ions impaires water absorption => diarrhoea
How can increased permeability cause diarrhoea?
allows leakage of water and electrolytes from bloodstream into intestinal lumen => diarrhoea
How can neurological disorders cause diarrhoea?
dysregulation of intestinal motility and secreted can result in accelerated transit of contents through intestine => less time for absorption => diarrhoea
How can medication cause diarrhoea?
Medication can alter gut microbiota, motility or absorptive capacity
Describe the permeability of the GIT in neonates
permeable to large molecules, including proteins and immunoglobulins
crucial for absorption of maternal antibodies present in colostrum
