Urinary System 2

Question 1

what is paracellular transport

Answer 1

movement of substances between epithelial cells within tubule

Question 2

what is transcellular trasnport

Answer 2

movement of substances from one end of a cell to the other
must cross both luminal and basolateral membrane

Question 3

what do transport proteins embedded within luminal and basolateral membranes do

Answer 3

control movement of various substances
can have pumps, carriers, and channels

Question 4

what are the pressures like in the peritubular capillaries after glomerular filtration

Answer 4

low hydrostatic pressure and high colloid osmotic pressure
both facilitate reabsorption of substances from filtrate back into the peritubular capillaries

Question 5

where does most reabsorption occur and why

Answer 5

in the proximal convoluted tubule (PCT)
this portion of the tubule has lots of microvilli on the cells’ luminal surfaces (created more surface area for absorption)

Question 6

what is the transport maximum (Tm)

Answer 6

maximum rate of substance that can be reabsorbed or secreted across tubule epithelium per a certain time
if you have more substance than transport proteins, excess is excreted in the urine

Question 7

explain how glucose is reabsorbed at the proximal converted tubule

Answer 7

sodium moves down its concentration gradient through a sodium/glucose symporter
it moves from tubular fluid into tubule cell, creating energy
this energy moves glucose up its concentration gradient into the cell through that same symporter
glucose moves down its concentration gradient by facilitated diffusion through a glucose uniporter
moves into blood

Question 8

what is renal threshold

Answer 8

maximum plasma concentration value where the transport maximum is not exceeded

Question 9

what is glucosuria

Answer 9

excretion of glucose in the urine
occurs when amount of glucose in the tubule is more than the transport maximum
glucose pulls water into tubular fluid with it which causes loss of fluid in urine
ex. diabetes

Question 10

what two substances are typically 100% reabsorbed into the blood

Answer 10

nutrients
filtered plasma proteins

Question 11

explain how filtered plasma proteins are reabsorbed

Answer 11

proteins are moved into tubular cell by receptor-mediated endocytosis
proteins are digested by lysosomes into amino acids
amino acids are released by exocytosis into the blood

Question 12

what is renal disease

Answer 12

when kidney is not degrading or reabsorbing proteins

Question 13

what would higher than normal filtration of plasma proteins indicate

Answer 13

damage to filtration membrane or high systemic blood pressure
too much protein, left over lost in urine (proteinuria)
blood concentration of plasma proteins decreases

Question 14

what would lower than normal filtration of plasma proteins indicate

Answer 14

changes that accompany chronic kidney disease
results in a decrease in filtration of small proteins and their degradation within tubules
too many in the blood

Question 15

which substances undergo regulated reabsorption

Answer 15

sodium
water
potassium
biocarbonate
calcium

Question 16

how is sodium reabsorbed into the blood in the proximal convoluted tubule

Answer 16

sodium moves down its concentration gradient from the tubular fluid into the cell through a sodium transport protein
it then moves through sodium/potassium pump into the interstitial fluid
finally it moves into the blood

Question 17

how does aldosterone effect sodium reabsorption into the blood in the collecting tubules and ducts

Answer 17

produced by adrenal cortex
stimulates making of sodium channels and sodium potassium pumps
increase sodium reabsorption

Question 18

how does atrial natriuretic peptide effect sodium reabsorption into the blood in the collecting tubules and ducts

Answer 18

inhibits reabsorption of sodium by inhibiting release of aldosterone
more sodium excreted in urine, increases GFR

Question 19

explain how water is reabsorbed in the proximal convoluted tubule

Answer 19

water follows sodium and moves from tubular fluid into cell by aquaporin
it then moves by osmosis through another aquaporin to the blood
ADH would increase water absorption

Question 20

explain how water is reabsorbed in the nephron loop

Answer 20

water follows sodium and moves from tubular fluid into cell by aquaporin
it then moves by osmosis through another aquaporin to the blood
water moves from the descending limb of loop into vasa recta

Question 21

which portions of the system are impermeable to water

Answer 21

ascending limb and distal convoluted tubule

Question 22

explain how water is reabsorbed in the collecting tubules and ducts

Answer 22

controlled by aldosterone and antidiuretic hormones
aldosterone: increases sodium/potassium channels which increase sodium and water reabsorption
antidiuretic hormone: binds to ADH receptors, increases migration of vesicles containing aquaporins which adds channels to increase water reabsorption, less urine produced

Question 23

what is obligatory water reabsorption

Answer 23

water follows sodium by osmosis

Question 24

what is facultative water reabsorption

Answer 24

tubular reabsorption of water in response to ADH

Question 25

what happens during dehydration

Answer 25

more ADH causes more water reabsorption
less urine, darker yellow

Question 26

what happens during overhydration

Answer 26

less ADH, less water being reabsorpbed
more urine, less concentrated, paler color

Question 27

how is potassium moved in the proximal convoluted tubule

Answer 27

sodium is reabsorbed with water to create a gradient
potassium moves down the gradient from fluid into the blood by the paracellular route

Question 28

how is potassium moved in the nephron loop

Answer 28

intercalated cells reabsorb potassium
principals cells secrete potassium

Question 29

what is the most powerful stimulant for aldosterone

Answer 29

elevated potassium

Question 30

what regulates the absorption of calcium and phosphate

Answer 30

parathyroid hormone
inhibits potassium reabsorption in PCT
stimulates calcium reabsorption in DCT