Intro to GIT physiology Flashcards
where is the start to the end of GIT
oral cavity to the anus
what long is the GIT as well as:
pharynx/oesohagus/stomach
small bowel
large bowel
about 8/9 metres
1m
6m
1.5m
what are the 6 functions of the GIT
ingestion mechanical processing digestion secretion absorption excretion
what is the role of the peritoneum
visceral and parietal
forms mesenteries which suspends them and support them
secretes peritoneal fluid which provides lubrication
which organs lie retroperitoneally and therefore no surround by peritoneum
kidneys, pancreas and part of the duodenum
what do mesenteries do
suspend organ and stop them from getting tangled - carry nerves, blood vessels and lymphatics as well as fat pads to cushion and protect organs
what are the three arteries than stem from the abdominal aorta
coeliac
superior mesenteric
inferior mesenteric
what vessels go into the liver and why
hepatic portal vein which comes from various abdominal organs and sites
hepatic artery stemming from the coeliac artery which is its main supply of oxygen
what does the coeliac artery supply
stomach, spleen, gall bladder, pancreas as well as forms the hepatic artery
what does the superior mesenteric artery supply
pancreas, small intestine and large intestine
what does the inferior mesenteric artery supply
large intestine and rectum
what are the general layers of the digestive tract from innermost to outermost
mucosa
submucosa
muscalris externa
serosa
what is the difference between epithelia and glands
epithelia are layers of cells covering internal or external surfaces
glands are structures than produce secretions
how does sheet of epithelial cells become and epithelial tube
sheet of epithelial cells are invaginated by an organised tightening of adhesion belts in sleeted regions of the cell sheet
the adhesion belt with associated actin filaments
epithelial tube pinches off from overly sheet of cells and becomes the tube
what is special about epithelia cells and polarisation
epithelial cells are polarised which allows them to determine the ultimate site of expression of proteins
ie they are polarised and protein form at certain areas within the cell
what are the four types of junctions between cells from apical to basal
apical side
occluding junction - tight junction sealing gaps between cells
cell-cell anchoring - adherent junction connects actin filament bundle in one cell with the next - desmosome
channel forming junctions - gap junction allows passage of small water soluble molecules from cell to cell
cell matrix anchoring junction - anchors celll to ECM (hemidesmosome)
what are the two movements of solutes and water across epithelia
1) from external compartment (lumen) to the internal compartment (blood) - absorption
2) from internal compartment to external - secretion such as protons and potassium/phosphate
what is net flux
absorptive flux - from lumen to capillary = Jabs
secretory flux - from capillary to lumen = Jsec
net flux = Jabs - J sec
what are the three transcellular pathways
transcellular absorption
transcellualr secretion
paracellular secretion/absoprtion
what are the barrier to trasncellular routes
basal and apical membrane
what are the types of passive transport across membranes
non-coupled - solutes moving down their electrochemical gradient
can occur via pores or channels
transporters - facilitate diffusion of small non-electrolytes
what are the two types of active transport
primary - energy to drive transport comes directly from ATP - substrate moves against an electrochemical gradient
secondary - energy to drive AT comes from electrochemical gradient which is set up by primary action - second substrate moves against electrochemical gradient
describe the process of sugar absorption from the lumen of the intestine
glucose/Na co transporters on apical side work via secondary active from an area of low to high glucose inside the cell
glucose then passively moves out the basal surface from high to low conc - Na/k primary active trasnporter on basal side pumps na out basal and K+ into the cell
what is the osmotic movement of water
water moves from an area of low osmotic pressure to areas of high osmotic pressure via para/trans routes or diffusion through aquaporins in lipids
what is the vagus nerves role in the GIT
controls foregut and midgut derivatives
what is the role of the splanchnic nerve
supply hindgut components
how does the sympathetic system affect the GIT
inhibits gut activity due to fight or flight
where do the vagus/splanchinic nerves stem from and innervate
vagus from medulla and stimulates parts of small/large intestine, stomach and oesophagus
splanchnic stems from s2 - s4 which stimulates some of the large intestine and anus
where does sympathetic innervation stem from in the GIT
T5 - L1
what is the enteric nervous system
gut autonomic control which lies underneaths the submucosa and controls most of gut motility
describe the two types of extrinsic nerve supply to the GIT
check the home screen
what are depolarisation sin the pacemaker cells of the submucosa
periodic shifts which provide underlying structure to the activity of smooth muscle
3-12 per minute
what are interstitial cells of cajal
mediators of slow waves which conduct to smooth muscle cells
3-12 per minute
