Generation of Medullary Hypertonicity Flashcards
What is the loop of henle?
A renal paradox
What 2 types of creatures can concentrate urine?
Mammals and birds
What 2 types of creatures have loops of henle?
Mammals and birds
What is the loop vital for?
concentrating ability
What happens to the fluid leaving the loop compared to plasma?
Is dilute
What is medullary hypertonicity generated by?
Countercurrent multiplication of loops of henle, distal tubules and collecting ducts
What is handled in the collecting ducts?
Facultative water ADH
How is medullary hypertonicity generated?
Different H2O permeabilities - DL is permeable, AL is not
Ability of TAL to extrude NA to medullary interstitium - basolateral NaK ATPase
Transverse osmotic gradient - 200mosmol, for large longitudinal gradient
what does a 200 mosmol H2O difference between AL and DL create?
Small transverse osmotic gradient
how does countercurrent multiplication work?
Multiplied into longitudinal gradient - counterflow of tubular fluid as result of hairpin bend in loop
What is facultative H20 handle according to?
DCT and collecting ducts
What are the 2 sections of the collecting duct?
Cortical collecting duct CCD
Medullary collecting duct MCD
What is the DCT,CCD,MCD impermeable to?
H2O,UREA,NaCl
What does anti-diuretic hormone ADH do?
Increase H2o permeability of the segments DCT,CCD,MCD according to need
What happens in the cortical CD with ADH?
Increased h2o reabsorption - fluid osmolality increases from 90 to 290 mosmol
What happens to the remaining fluid in presence of ADH?
5% of total glomerular filtrate, enters medullary CD for more H2o reabsorption
What would too much reabsoprtion in the medulla cause?
Medullary hypertonicity
Where does more H2O reabsorption take place?
Cortical CD
Where is Urea freely filtered?
Glomerulus
How and how much urea reabsorped in PCT?
50% passively reabsorbed
Where does Urea conc increase in DL to?
Along loop to passive diffusion from interstitium
What is impermeable to urea?
DCT, Cortical CD
What is permeable to H20 ADH?
DCT, cortical CD
What happens when H2o leaves cortical CD?
Urea conc rises
What does ADH activate?
urea uniporter in medullary CD
Where does Urea diffuse?
Along gradient from medullary CD to interstitium into TAL//DL
Where does Urea travel along tubule to?
DC/Cortical CD - cycle repeats
What area has high urea conc?
Interstitium
What is 50% of medullary hypertonicity due to?
urea recycling
What percentage of nephrons are Juxtamedullary long?
15%
What percentage of nephrons are cortical short?
85%
Where do all nephrons drain into?
Collecting ducts which pass through the medulla - possible to gain conc of urine from all nephrons
