intestines Flashcards
what is the small intestine the major site of
digestion and absorption
what kind of process if absorption and how does it occur
selective occurring via specific transporter proteins by diffusion and secondary active transport
what are the 2 phases of digestion
luminal - enzymes secreted by salivary glands/pancreas
membranous- enzymes attached to epithelial
surface of intestinal cells
what happens to anything that remains undigested in the SI
passed onto LI for microbial fermentation
what are the 4 types of intestinal epithelial cells
goblet
enteroendocrine
paneth
enterocytles
what do goblet cells do
secrete mucous for lubrication and protection of mucosa and HCO3+ for neutralisation of stomach acid
function of enteroendocrine cells
control digestion function via sensory mechanisms and release hormones
function of paneth cells
defence against microbial penetration
function of enterocytes
responsible for absorption via transporter proteins
what does SI motility do
mix luminal contents due to segmental contractions
propel contents down SI at appropriate rate to allow maximum digestion and absorption due to peristaltic contractions
effect of stomach motility after feeding
increases
what are segmental contractions
circular contractions along distended intestine
divide intestinal contents into small segments
mixes contents with digestive juices
moves contents towards mucosal surface for digestion/absorption
what is the main type of contraction when digestion is occurring
segmental
strength of segmental contractions when emptying of stomach
intense
what is the main type of contraction when digestion/absorption complete
peristaltic
what is motility regulated by
pacemaker cells
what provides most energy in herbivores/omnivores
carbohydrates
what type of maltose is starch
straight chained
what type of maltose is amylopectin
branched chained
what type of glucose is glycogen
branched chained
what bonds are digestible by mammalian enzymes
alpha-glycosidic
what type of bonds are in starch, amylopectin and glycogen
beta-glycosidic
what type of bonds are in cellulose
beta-glycosidic
what type of maltose is cellulose
straight chained
what are disaccharides
attached to enterocyte brush border
what are monosaccharides
glucose
fructose
galactose
what are the only carbohydrates that can be absorbed
monosaccharides
what is the luminal digestive phase
amylase converts starch to maltose
salivary amylase continues digestion in stomach until acid inhibits/destroys it
amylase digestion continues in SI with pancreatic amylase
what co-transporter is glucose and galactose absorbed by and type of transport
sodium-glucose = SGLT1
secondary active transport
what is fructose absorbed by and type of transport
facilitative transporter = GLUT5
passive transport
where is fructose transferred to and via what
liver via hepatic portal vein
what is fructose stored as in the liver
glycogen
what cannot be digested in neonates and why
proteins as the they are regarded as foreign material and evoke an immune reaction
what enzyme breaks down tri-glycerides into mono-glycerides and free fatty acids
lipase
what do bile salts do
reduce fat droplets to a smaller size = emulsification
what are the 2 roots water transport occurs via
para-cellular = across tight junctions between epithelial cells
trans-cellular = across cell membrane via transporter proteins
major functions of large intestine
absorption
fermentation
purpose of glands in LI
secrete mucous for protection/lubrication
what are the 4 layers of the LI
mucosa
submucosa
muscularis
serosa
does the LI contain digestive enzymes
no - purely microbial
what are the 2 major cell types in the LI and functions
colonocytes - absorption
goblet - secrete mucous
anatomy of LI
Caecum
colon
rectum
what is absorbed in the LI
VFAs
Na
Cl
water
what is diarrhoea
water lost in faeces due to increased secretion and decreased absorption
causes of diarrhoea
microbial imbalance - overload of guts capacity to absorb causes osmotic flow of water into gut lumen
infections
stress - activation of parasympathetic system increases secretion and motility
treatments of diarrhoea
intravenous fluids
oral rehydration therapy
large intestine contractions
segmental
peristaltic
anti-peristaltic
mass movement
what is constipation
abnormal accumulation of food material in gut usually in colon
treatments for constipation
oral fluids to soften faecal material
paraffin oils to lubricate
drugs eg enemas to strengthen contractions
