5 Renal Concentration Flashcards
Control of Body Water by Renal Excretion
- Normal plasma osmolarity is _________ mOsm/L
- Kidney varies solutes and water in the urine to maintain body fluid osmolarity.
- Normal urine is slightly ______tonic
- Osmolality = concentration of osmotically active particles per unit _________ (kg).
- Osmolarity = concentration of osmotically active particles per unit _________ (L).
- 285-295 mOsm/L
- hypertonic
- solvent
- solution
Control of Body Water by Renal Excretion
- When body fluids are hyperosmotic (water excess), the kidneys excrete a _______ urine.
- When body fluids are hyperosmotic (water deficit), the kidneys excrete a ________ urine
- The kidneys can regulate water excretion __________ of solute excretion.
- dilute (as low as 50 mOsm/L - water diuresis)
- concentrated ( up to 1400 mOsm/L - antidiuresis)
- independently
The counter-current multiplier creates a large overall _______ from the corticomedullary border to the tiip of the papilla by multiplying a small local gradient by the length of the counter-currnet system.
Ranges from ______ to ______.
The countercurrent multipllier takes place in the __________.
gradient
300 (cortex) - 1200 (papilla)
long loops of Henle
Loop of Henle Characteristics
- The osmotic gradient from the cortex to medulla in the interstitial space is used to ________ in the collecting duct.
- Descending limb
- NaCl transport?
- Water permeability?
- Ascending limb
- NaCl transport?
- water permeability?
- No active transport of NaCl
- high water permeability –> descending limb just secretes water
- Actively reabsorbs NaCl
- impermeable to water
Loop of Henle Characteristics
Fluid is proggressively _________ as it flows down the descending limb.
Fluid is progressively ________ as it flows up the ascending limb.
The largest osmotic gradient that can be maintained across the wall of the ascending limb is __________.
concentrated (descending limb; NaCl in and H20 out )
diluted (ascending limb; Active transport of Na+ and Cl-, water diffuses in)
200 mOsm/L
The Countercurrent Multiplier
The countercurrent “multiplier” because 200 mOsm/L created by _____________ has been multiplied to _____________.
The “countercurrent” multiplier because flow in __________ drections through the two liimbs.
What is the essential component?
active transport; 1200 mOsm/L
opposing
active transport
The Active Transport Mechanism in the Ascending Thick Limb
The NKCC2 transporter transports 3 types of ions (total of 4 ions) from the ___________ into the ___________.
What drug blocks the NKCC2 transporter?
What substance stimulates it?
Na+, K+, and 2Cl-
tubular flluid; tubule cell
Furosemide (lasix)
ADH
Why doesn’t the renal blood flow wash away the solutes in the medullary ISF and bring osmolality back to isosmotic?
Countercurrent exchange by the Vasa Recta “protects” the corticomedullary gradient
Vasa Recta as Countercurrent Exchangers
Vasa Recta characterized by ____________ loops.
As blood flows down the capillary, _______ diffuses in and _______ diffuses out.
As blood flows up the capillary, the reverse occurs.
This serves to ________ the ISF gradient.
The process is entirely __________.
hairpin
NaCl; H20
protect
passive
Medulllary Interstitial Fluid: Importance of Urea
Urea is generated by hepatic _______ _________.
Urea contributes to _____________ renal ISF and to a ____________ urine.
Urea is recycled in the ________ of the kidney.
Permeability of the inner medullary portion of the collecting duct is controlled by _______.
People on ____________ diets cannot concentrate urine as well (reduced urea formation).
protein catabolism
hyperosmotic; concentrated
medulla
ADH
kiw protein
Early Distal Convoluted Tubule
The Na+, K+, 2Cl- transporter is ____ present.
There is a ___________ in the luminal membrane which is blocked by ________ _______.
The early portion of the distal tubule is ___________ to water (continues to dilute the tubular fluid) - thus referred to as the _______ __________ (osmolarity ≈ 50 mOs/L)
not
NaCl transporter (NCC); thiazide diuretics
impermeable
diluting segment
Late Distal Tubule and Collecting Duct
Composed of ___ cell types:
-
Principal cells
- Reabsorb _____ and secrete _____
- Site of ___________ action
-
Intercalated cells (Type A)
- Secrete ____ and reabsorb _____.
- Na+ reabsorption and K+ secretion depend on the __________ in the basolateral membrane and the ______ channels for both ions.
2
Na+ K+
aldosterone
H+ K+
Na+, K+-ATPase apical
Late Distal Tubule and Collecting Duct
Principal cells
- reabsorb ____ and secrete ____.
- Aldosterone increases # of ______________ and ______________
- ENaC (epithelial Na+ channel) - blocked by ____________
Apha-intercalated cells
- have _______ and _________
- important for _________ balance.
Na+ K+
Na+ channels; Na+,K+-ATPase
Amiloride
H+-ATPase
H+,K+-ATPase
acid/base
The Collecting Duct (CD)
Water and urea permeability of the CD is controlled by __________
Water permeability can be high or low:
- Dependent on ________ in the apical membranes of the CD cells
- ______ causes the insertion of aquaporins into the apical membrains of CD cells.
The CD is impermeable to water and urea in the absence of _________.
ADH
water channels (aquaporins)
ADH
ADH
Mechanism for Increasing Water Channels in the Membrane
- Vasopressin (ADH) binds to the __________ side of the the distal tubular cell.
- ADH activates the _____________ in the cell
- cAMP increases the # of water channels (aquaportins) in the membrane (which increases H20 permeability)
basolateral
cAMP second messenger system
