Intestines Flashcards
what enzymes of found in the brush border of the intestines
amylase, maltase, isomaltose
describe the structure of starch
made up of chains of glucose connected by alpha 1-4 bonds (amylose) which are joined to other amylose chains by alpha 1-6 bonds (amylopectin)
describe the uptake of glucose in the intestines
Na/K/ATPase on the basolateral membrane gives a low Na conc inside the enterocyte
glucose then diffuses in with glucose through the SGLT 1
glucose then moves into the blood via GLUT 2
how do oral rehydration fluids work
they contain both Na and glucose which move into the enterocyte, water then follows
what does vitamin B12 require for absorption
intrinsic factor
how does autoimmune disease cause megaloblastic anaemia
as it destroys the parietal cells - therefore, no intrinsic factor is produced so vitamin B12 can’t be reabsorbed
when calcium levels are low, how is it absorbed in the intestines
actively
Ca ATPases on the basolateral membrane create a concentration gradient to allow facilitated diffusion on the apical membrane
in high calcium levels, how is it absorbed in the intestines
passively
through paracellular transport
how is iron absorbed
co-transported with H+
why do PPIs affect iron absorption
as gastric acid is important in iron absorption
what is coeliac disease
immune response against the gliadin in gluten
what affect does coeliac disease have on the intestines
damages mucosa, lengthens crypts, less villi and give lymphocytes in epithelium
this causes malabsorption
what are the symptoms of coeliac disease
diarrhoea, weight loss and sensory loss
how is sodium absorbed through the apical membrane in the small intestine
SGLT 1
how is sodium reabsorbed through the apical membrane in the large intestine
Na channels induced by aldosterone
what digest proteins in the intestines
pepsinogens from the stomach
proteases from the pancreas
what cells produce pepsinogen
chief cells
what convertors pepsinogen into pepsin
HCl
what converts trypsinogen into trypsin
enteropeptidase
what do exopeptides do
cleave the ends of proteins to produce small molecules
what do end-peptides do
cleave the middle of proteins to reduce protein lengths
how are amino acid absorbed
co-transporters with Na
how are tripeptides/dipeptides absorbed
through peptide transporter 1
what happens to tripeptides/dipeptides once they are absorbed
converted into amino acids by cytosolic peptidases
what is the role of the large intestines
absorb water
how is water absorbed in the large intestines
water follows sodium which moves through ENaC channels
what causes an increased amount of ENaC channels to be opened
aldosterone
what vitamin is produced in the large intestines
vitamin k
what is the gastro-colic reflex
when theres mass movement of contents from the distal colon to the rectum stimulated by eating
what are haustrau
the sacculations of the large intestine
what are teniae coli
the bands which make up the outer layer of incomplete muscle of the large intestine
contractions of these give the sacculations
how does crohns present
right lower quadrant pain
weight loss
mild anaemia
non bloody stools
what can be seen in crohns disease
fistulae strictures cobblestone appearance mucosal oedema skip lesions
how much of the GI tract does crohns affect
anywhere in the GU tract
how deep does the inflammation in crohns extend
all the way through the GI wall (transmural)
how deep does the inflammation in UC extend
only to the mucosa - superficial
do you see granulomas in UC or crohns
crohns
why are there strictures seen in crohns
the repeated inflammation and healing causes fibrosis
what is the presentation of UC
lower abdominal pain
bloody stools
weight loss
what is seen in UC
pseudopolyps
continuous inflammation
loss of haustra
where does UC affect
colon - starting in the rectum
what non-intestinal problems can also be seen in UC and crohns
uveitis, erythema nodosum, arthritis, gall bladder problems
are crypt abscesses seen in UC or crohns
UC
what is the treatment for UC
colectomy
