BIL360 | FE | L7 Kidneys & Excretion
Terms in this set (77)
despite their diverse morphology and physiology, all kidneys have:
1. tubular structures that open directly or indirectly to outside world
2. produce and eliminate soln derived from blood or extracellular fluid
3. fxn to regulate body fluid volume and composition by controlling water/solute excretion
kidneys mainly control:
composition of blood plasma
blood plasma reg
what comprises urine?
- nitrogenous wastes
- inorganic ions
- organic compounds
fxn served by urine excretion
maintain osmotic P, [ion], pH
2 basic steps of urine formation
1. primary urine
2. definitive urine
filtered material that enters tubules of kidney
urine modified in kidneys and then released from the body
in most verts, primary urine is formed by:
What drives the process of urine formation?
blood P drives plasma fluids over "filter" epithelial tissues to produce capsular fluid/primary urine
- nephron ends in boman's capsule bowl
What separates lumen of capillary and lumen of Bowman's capsule
2 cell layers
net filtration pressure
hydrostatic P + colloid osmotic P
in verts, primary urine formation is termed:
glomerular filtration rate (GFR)
Which is greatest: blood P, colloid osmotic P, and capsular fluid P?
How often is all the plasma water in a person's body is filtered?
which rate is higher: filtration or urine production?
most of the water filtered will be:
reabsorbed, will NOT produce urine
filtration rate if affected by:
- # of active nephrons
- level of reabsorption in each nephron
major regulatory processes occur:
after primary urine formation as it flows thru excretory system to form definitive urine
initial filtration creates urine that is ____osmotic to blood plasma
units of the kidney
amphibian nephron urine flow
proximal convoluted tubule -> intermediate segment -> distal convoluted tubule -> collecting tube -> collecting duct
How does urine travel to bladder?
all collecting ducts combine into a single ureter
amphibian nephron diameter
small, but can be long length
kidneys filter ____ water/solutes than are excreted
more (much of filtrate is absorbed)
reabsorption begins in:
proximal convoluted tubule
reabsorption involves an active uptake of ___ and ___ as well as a passive uptake of ___ and ___
active: Na+, glu
passive: Cl-, water
reabsorbed fluid is ___osmotic
What solute is reabsorbed in proximal tubule?
glu (thanks to active Na+ transport)
reabsorption of Na starts in:
How is Cl reabsorbed?
conc gradient created by active Na+ transport
Where does the blood plasma composition change?
distal tubule fxn
- controls release of osmotically free water
- produce definitive urine
- reabsorb water/solutes
osmotically free water
water not needed to get rid of solutes
if there is no osmotically free water, U/P is
if there is osmotically free water, U/P is
puts aquaporins in kidneys for water reabsorption
- abundant urine
- low permeability to water, which remains in tubule and is excreted
- concentrated plasma
- U/P < 1
- low volume, concentrated urine
- high permeability to water, which is reabsorbed
- dilute plasma
- U/P = 1
mammalian kidneys are characterized by:
- gross structure
- loops of Henle
How are mammal nephrons arranged differently from amphibians?
loop of Henle parallel to collecting duct to create macrostructure with outer and inner layers to help make hyperosmotic urine
urine flow in mammals
renal corpuscle -> proximal tubule -> intermediate segment (loop of Henle) -> down -> up -> collecting duct -> bladder
How will a thicker medulla (inner layer) of the kidney affect urine concentration?
thick medulla = conc urine (less water excretion, more water retention)
Compare medulla thicknesses of FW spp, desert spp, and intermediate spp
- FW: barely any
- int: small
- desert: thick
part of medulla that goes into the renal pelvis that houses loops of Henle
renal papilla contains:
long loops of Henle
renal papilla are more dev in which kind of spp?
What is the key to producing more conc urine?
how does interstitial fluid conc change with depth into the medulla?
When/where is water removed from urine?
as it passes thru collecting ducts
- bowman's capsule
- proximal tubule
- collecting duct
- loop of henle
when does water leave collecting duct?
antidiuresis due to high salt conc in medullary interstitial fluids
salt conc generated in:
loop of Henle
ascending limb fxn
- active transport of NaCl to interstitial fluid (w/o water following bc of wall types)
- impermeable to water (inc interstitial fluid osmotic P)
descending limb fxn
- more permeable, higher osmotic P than ascending limb
- reaches eql with interstitial fluids
- generates difference in osmotic P
- differences b/w fluids in ascending and interstitial, descending limb
- active transport of Na and differences in permeability
how does "single effect" change osmotic P
difference of 200mOsm from side to side of loop of Henle
countercurrent multiplier system
- generates gradient, w/ end-to-end difference of 600mOsm+
- close together w/ opposite fluid movement + single effect = multiplies effect of single effect over length of loop of henle
the longer the loop of the Henle:
the greater the effect of countercurrent multiplier system and thus more conc urine
where are interstitial fluids located
b/w ascending and descending limbs
multiplication effect ultimately causes water flow:
to move into salty interstitial fluids, developing increasingly greater osmotic P at end of the loop
the point of the countercurrent multiplier system is:
- renal tissue and blood become increasingly more hyperosmotic in deeper regions of the kidney
- favor reabsorption of water from collecting ducts (antidiuresis)
how does the osmotic P of the descending limb change towards the base of the loop?
which animal group can adjust the conc and volume of their urine over broad ranges?
mammals (human U/P = 0.2-4)
What controls the switch b/w antidiuresis and diuresis?
high ADH will ___ volume of plasma and ____ ions with ____ U/P ratio
on the cellular level, ADH modulates:
aquaporins in apical collecting duct epithelium, inc/dec permeability to water
(antidiuresis: conc urine)
urine leaving loop of henle is hyp___osmotic
(antidiuresis: conc urine)
urine conc occurs during:
final pass thru medulla via collecting ducts
which is NOT permeable to water: descending limb, ascending limb, collecting ducts
why does the conc of urine inc as it travels along the collecting duct?
fluids are around it
(diuresis: dilute urine)
- dec permeability of collecting duct to water
- actively absorb NaCl from collecting duct lumen
What makes collecting duct product more dilute?
- reabsorption of NaCl
- lack of ADH (less aquaporins)