Lecture 1: Renal Phys Intro and Clearance Flashcards
Where is the hilium?
Middle of the kidney
What is in the hilium?
Renal artery, vein, and ureter.
What is the function unit of the kidney?
Nephron
What does the nephron do? Vaguely
Filters blood to make urine
What are the 2 general renal functions of the kidney?
Regulation of water balance
Maintain normal electrolyte concentrations and content in plasma
Other functions of the kidney
Conserve nutrients
Excrete wastes
Regulate cardiac output and BP
Control hematopoiesis
How does the kidney control hematopoiesis?
Release erythropoetin in times of renal/circulatory hypoxia (makes RBCs)
How does the kidney regulate CO and BP?
Through RAAS (renin angiotensin aldosterone system)
What are the two kinds of nephrons and how are they categorized?
Cortical (superficial) and Juxtamedullary
Location within the kidney
Where/what are the cortical nephrons?
Mostly out of the medulla, dips into medulla. Mostly in cortex
Has a short loop of Henle
Where/what is the juxtamedullary nephron?
Can go down to the Papilla, mainly in the medulla, small portion is in the cortex
The Juxtamedullary nephron has a specialized peritubular capillary called the…
Vasa recta
-very slow moving blood supply that helps nephron do its job
Which nephron is there more of?
Cortical (superficial) - 80%
Juxtamedullary- 20%
What are the 2 capillary beds of the nephron?
Glomerular capillaries and peritubular capillaries
What/where are the golmerular capillaries?
Found in the glomerulus
1st step in urine formation, filters plasma into nephron making tubular fluid
The glomerular capillaries receive blood from __________ ___________ and drained into __________ _________.
They can also control the ___________ of each arteriole.
Afferent arteriole
Efferent arteriole
Diameter
Where/what are the peritubular capillaries?
Normal capillaries, that wrap around the rest of the nephron.
Peritubular nephrons are fed by the __________ arteriole and are required for what 2 functions?
Efferent
Reabsorption and secretion
Where does filtration occur and what does it filter and form?
At the glomerulus
Filters plasma
Forms tubular fluid/urine
Define excretion/
What is removed from the body via urine
Equation for urinary excretion rate
Filtration rate - reabsorption rate + secretion rate
What is reabsorption?
Moves solutes/water from tubular fluid back to blood
“Reabsorbed into the blood”
What is secretion?
Moves solutes from blood into the tubular fluid
“Secreted into nephron”
Order of Nephron Structures
- Glomerulus
- Proximal Conv. Tubule
- Loop of Henle
3a. Macula densa - Distal Conv. Tubule
- Collecting Duct
Capillary bed that filters blood to produce urine
Glomerulus
Cup-shaped entrance to nephron and surrounds the glomerulus
Bowman’s capsule
Has arterioles on both sides
Area between Bowman’s capsule and capillary bed of glomerulus
Bowman’s space
1st step in urine production
Filtration
What is reabsorbed into the PCT?
67% of ions
- Na, K, and Ca
Water
ALL glucose and AA’s
Most transport mechanisms are dependent on __________ in the PCT?
Na/K ATPase
Makes sense because 67% of ions are filtered here, including Na and K (plus Ca and Water)
What drugs have diuretic effects in the PCT?
Ex?
Carbonic hydrate inhibitor
Acetazolamide
What mainly happens in the Loop of Henle?
Reabsorption and dilution of urine.
Sets up gradient used to alter urine concentration
In the Loop of Henle, water reabsorption occurs in the ______________ limb and solute reabsorption occurs in the. ______________ limb.
Descending (H2O)
Ascending (solute)
Specialized part of the Loop of Henle that senses tubular fluid flow and renal blood flow
Macula Densa
Part of the Juxtaglomerular appartus
What drugs act at a diuretic in the Loop of Henle?
Ex?
Loop diuretics
Lasix (furosimide)
What happens isn’t he DCT?
Reabsorption and secretion of ions, fine-tuning of urine solute amounts.
Site of pH balancing
What ions are moved in the DCT for pH balancing?
H+ and HCO3+
What drugs work in the DCT?
Ex?
Thiazides (-like diuretics)
What is the main function of the collecting duct?
To reabsorb water to concentrate urine
Final control of urine osmolality!
Collecting ducts are the site of _________________ function.
What does this drug do?
Anti-Diuretic Hormone (ADH)
Makes ya not pee a lot.
Adds aquaporins to collecting ducts membranes to make them permeable to water
Reabsorb water!
What diuretics work in the collecting ducts?
K-sparing diuretics
Spirolactone
Amiloride
Glucose is removed from the tubular fluid by active transport and returned to the blood. This is an example of what kind of renal process?
Reabsorption
In periods of hyperglycemia (high blood sugar) like in Diabetes Mellitus, some filtered glucose is lost to the urine. This is an example of what kind of renal process?
Excretion
The most water is reabsorbed in which segment of the nephron?
PCT (67% of ions and water)
What is the 1 way and 2 ways out of the Kidney?
In: Renal artery
Out: ureter and renal vein
Kidney only filters:
Blood plasma
Not RBCs WBCs etc
Equation for blood volume, in relation to plasma volume and filtration
BV = PV/(1-hematocrit)
Plasma volume is about ______ of total blood volume
Half…about 40%ish
PV= 0.5TBV
Equation for input of solute to the kidney
RPF * Xa
RPF=renal plasma flow
Xa= concentration in blood plasma
Equation for output, solute leaving the kidney in urine AND renal vein
(RPF * Xv) + (Xu + V)
RPF = renal plasma flow
Xv = concentration in renal vein
Xu= concentration in urine
V = urine volume
Equation for Renal Function Determination
Input = Output
RPF * Xa = (RPF * Xv) + (Xu * V)
Determines the clearance of a solute!
How much plasma the kidney is able to clear
Or
Volume of plasma that has had a solute removed from it in one minute
Clearance
Solutes removed from the plasma
Equation for Clearance
Units?
Cx= (Xu * V)/ Xa
Cx= clearance (units are mLs/min)
Xu= Conc. Urine
V= urine volume
Xa= conc. Blood plasma
What is the basis for determining renal function?
Clearance.
Can determine the amount of plasma filtered AND the amount of blood delivered to the kidney
Clearance of ______ can determine the glomerular filtration rate.
What will this tell you?
Inulin
The amount of plasma filtered by the kidneys
Clearance of _____ determines renal plasma flow (RPF)
What will this tell you?
Para-aminohippuric acid (PAH)
Every bit of PAH is pulled out of blood and put into urine (100% filtered and secreted)
Will tell you how much plasma is moved through the kidney
Filtration Fraction
FF = GFR/RPF
Amount of plasma that is filtered by the kidney
tells us how much water we are excreting.
Free Water Clearance
If plasma osmolarity were too high, what would we want?
Excrete minimum amount of H2O to dilute solutes.
If plasma osmolarity were too low, what would we want?
Excrete H2O
Equation for Clear water clearance
Cosm = (Uosm * V) / Posm
Tells us the volume from which ALL solutes have been removed
If osmolarity clearance is 1ml/min, but our urine flow is 3ml/min, where does the extra 2 mls come from?
Free water, water that has no dissolved substances
If free water is negative…
More solute cleared than water.
If free water clearance is positive….
More water cleared than solutes.
If Uosm > Posm, then you should have:
Negative Cwater
If Uosm < Posm, then you will have:
Positive Cwater
What is normal Uosm?
Posm?
100-1000 (Uosm)
265-320 (Posm)
Consider the following information:
Posm=335 mOsm/L
Uosm= 156 mOsm/L
Flow = 4 mls/min
Is this an appropriate free water clearance?
NO because both Posm and Uosm should be high for a low Uflow, and vice versa.
Uflow is too high for the high Posm
