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structures involved in increasing the surface area in the GI tract

folds of kerckring, villi, and microvilli


Fold of kerckring

the first absorptive surface of the small intestine mucosa, well developed in the duodenum and jejunum protrudes into the lumen and increase absorption by 3 folds



located on the epithelial surface of the small intestine all the way down to the ileocecal value, present on the folding of kerckring and increase absorption by 10 folds



each intestinal epithelial cell on each villus has a brush boarder containing characteristic consisting of many microvilli


central lacteal

stucture in the villus involved in the absorption of lymph


pinocytic vesicles

are vesicles that pinch off in the portion of infold in the enterocytes membrane forming vesicle of absorbed fluids that have been entrapped


Transcellular transport

this is transport require the movement of molecule through the cell from passing through apical membrane and basalateral membrane. and this usually require energy.


water is transport entirely by ----- give example

simple diffusion moving from high concentration to lower concentration of water example when chyme is diluted enough water absorbed though the intestinal mucosa into the blood and the reverse can occur when there is an hyperosmotic solution in the small intestine (chyme)


The absorption of sodium ion is by

carrier mediated transport ( primary active transport) in the gallbladder and renal tubules


transport of Na+

the transport of Na is done through primary active transport from the epithelial cells through the basal and side walls of the cell into paracellular spaces.


with the transportation of na into the paracellular the drag of other ion occurs

Chloride ions.


the function of Aldosterone in the intestinal tract is the same as the effect of aldosterone in the

renal tubules, where in both case it serves to conserve NaCl and water.


how do the absorption of Na cause the reabsorption of water

with the primary active transport of Na into the Paracellular space, the osmotic gradient changes between the cell and the paracellular space which leads to the movement of water from a area of high concentration to an area of low concentration. ( simple diffusion)


Absorption of Chloride ions in the duodenum and jejunum

is mainly by diffusion due to electrical gradient to follow Na because the epithelial cells has become electronegative due to the movement of Na and the paracellular space has become electropositive


Ion are usually absorbed in what part of the intestine

the upper part of the intestine duodenum and jejunum


absorption of calcium

this is usually by active transport and the parathyroid hormone is important in its reabsorption by activating vitamin D which enhances the absorption of ca


the two forms of pinocytosis

fluid endocytosis and receptor mediated endocytosis


receptor mediated endocytosis

the molecule comes in contact with protein at the membrane of the cell, this result in the invagination of the cell into pinocytic vesicles


fluid endocytosis

it is the nonspecific invagination of specific molecule into the cell. it is a type of pinocytosis


paracellular tansport

the transport of molecules through intercellular space and between the cells. this is important in the renal physiology ( kidneys)


the absorption of bicarbonate ( active absorption of bicarbonate)

this is in a indirect way, when na is absorbed moderate amount of H ion is secreted into the lumen this thus combine with bicarbonate to form carbonic acid which then dissociate to h20 and co2, co2 is taking to the lung


Transport of glucose

this is by secondary active transport apical part then facilitated diffusion at the basolateral membrane into the paracellular space and into the blood


the first stage of glucose transport

there is a active transport of na the basolateral membrane of the intestinal cell into the blood causing the decrease of Na


second stage of transporting glucose

the na that has been transported to the lumen binds with transport protein that also bind to the glucose ( GLUT) in this case thus transporting glucose and Na into the cells


the transport protein that carries out the transport of Glucose into the cells

is a co-transport protein.


absorption of fructose

it uses facilitated diffusion all through and does not us na - co-transport mechanism.


absorption of galactose and animo acid

the same as glucose is absorbed


the absorption of fats

the end product of fat which is fatty acid and monoglyceride dissolve in the bile mycelles, the mycelles are highly charge so they are soluble in chyme, the free fatty acid diffuse from the mycells into the epithelia cell were they are also soluble. then are taken up by the SER to form chylomicron released at the base of the cell to the lymph duct and into the blood.


the bacteria in the colon are important for

forming vitamin K and vitamin B12


vitamin k is important for

blood coagulation.