S 10
Secretion
Reabsorption
Filtration
Drink plenty of water the day of lab;
Avoid coffee, caffeine, salty foods
60 min
1 Hr
before Lab
Empty
bladder;
note time
Drink
Test
Beverage
30 min
800 ml tap water
800 ml tap water + 7 g NaCl
80 ml tap water + 7 g NaCl
30 min
30 min
At 30 min
interval,
collect urine
measure V
and [NaCl]
Beginning of Lab:
Collect Urine, measure V and [NaCl]
30 min
30 min
S 11
Renal Physiology
• Structures of the kidney
• Four fundamental renal mechanisms
–
–
–
–
Filtration
Reabsorption
Secretion
Metabolism
• Functions of the kidneys
– Homeostasis
• Fluid balance (blood pressure)
• Electrolyte balance (blood pressure, membrane excitability)
• Acid-base balance (in concert with lungs)
Table 14.02
Lab: Extra 800 ml intake!
Sidebar: some desert animals never drink
and must obtain all their water in the diet.
Table 14.04
Lab: Extra 7 g intake!
Kidneys are source of 3 hormones: Renin, EPO, and Vit D.
Kidneys are targets of 3 hormones: ADH, Aldosterone, ANH
S 15
Nephron = tubule
Tubular fluid vs urine
Topics discussed: cortex, medulla, kidney stones, micturition (detrussor, internal and external
urethra sphincters and innervation), incidence of bladder infections by gender, urethral sphincters
Renal artery = One way in. Two ways out of kidney (renal vein or ureter)
S 16
S 19
Juxtamedullary and Cortical Nephrons
Fig. 14.02a
Renal
corpuscle
Peritubular Capillaraies and branch
thereof called vasa recta
S 20
The nephron
S 21
Fig. 14.03a
Fig. 14.05
Glomerular Filtration Rate
is 180 L/day
Three stimuli for secretion
of renin from JGC
Ultrafiltrate of plasma enters
Bowman’sFigure
space 14.03
Composition same as plasma
except no formed elements
and no proteins and no
substances bound to proteins
Starling
Fig. 14.08
Forces
variable
What substances can cause this constriction?
Ways to alter GFR
Fig. 14.09
What happens during
hemorrhage?
Fig. 14.02a
Membrane proteins are
segregated into apical (luminal)
and basolateral membranes.
Figure 14.10
reabsorption
secretion
Amino acid
metabolism
glucose
Special terms
• Filtration: movement of fluid from blood into
the lumen of the nephron
• Reabsorption: the movement of specific
compounds from the lumen back into the blood
(peritubular capillaries)
• Secretion: the transport of specific compounds
from blood into the lumen
• Excretion: elimination from the body in urine
Reabsorption and secretion in
proximal tubule is NOT under
hormonal control.
Primary active transport of
Na+ establishes a gradient for
reabsorption of glucose,
amino acids, etc.
Reabsorption and secretion in
DCT & CCD is under
hormonal control.
Hormones that act here:
ANH, ADH, Aldosterone.
Here, reabsorption of Na+ is
linked to the secretion of K+.
Effect of ADH: insertion of
more aquaporins in the
membranes
Effect: Increase H2O reabsorption
Normally, all14.31
filtered
Figure
bicarbonate is “reabsorbed”
Filtration is controlled by aa and ea diameters!
Consider a substance that in filtered only, no reabsorption, no secretion.
Excretion of this substance = GFR
Clearance of this substance = GFR
• Clearance = volume of plasma from which a
substance is completely removed (cleared) by the
kidneys per unit time.
• Clearance of Inulin is 120 ml/min
• Cinulin or Ccreatinine = Glomerular Filtration Rate
• If C x is greater than GFR ( which is Cinulin) then that
substance undergoes NET TUBULAR SECRETION
• If C x is less than GFR ( which is Cinulin) then that
substance undergoes NET TUBULAR REABSORPTION
Calculating clearance
Clearance of s = Urine concentration of s X Urine Volume
Plasma concentration of s
“24 hour urine catch” + blood sample
Special cases: Clearance of
•
Inulin and creatinine (filtered only; use to
measure Glomerular Filtration Rate.)
•
Para Amino Hippurate (filtered and completely
secreted, use to measure Renal Plasma Flow)
Renal Handling of Substances
Filtration +
complete Secretion
Ex: Para AminoHippurate (PAH)
Measure Renal Plasma Flow
Filtration + partial reabsorption
Filtration + 100 Reabsorption
Ex: Sodium
Ex: Water
Ex: Glucose
Ex: Amino Acids
A little more on Clearance:
Clearance of glucose = 0 ml/min which means….
Clearance of X = 120 ml/min which means….
Clearance of antibiotic XXX = 500 ml/min which means…
Who Cares?
S 17
pp
X
P?
S 18
Fluid-filled cysts
Polycystic
Kidney
Disease
Symptoms?
Genetics?
Prognosis &
Treament?
Fig. 14.04