Renal Phys -McCormick Flashcards
explain the third space concept
the idea behind transcellular fluid which can occupy other spaces besides the normal ICF, ECF compartments. For example, CSF, synovial space, epithelial spaces etc. It’s considered the 3’rd ECF fluid compartment
1/3 of TBW is _
2/3 of TBW is _
ECF
ICF
what is the normal effective circulating volume? what is effective circulating volume?
.7L (20%). It is the volume of blood that is effectively perfusing organs. if the organs does not that get volume, the organ sense it as hypoperfusion.
In terms of 1. ECV (effective circulating volume), 2. ECF volume, 3. plasma volume and 4. CO, indicate how they're changed during A. Hypovolemia due to vomiting B. Heart failure C. Arteriovenous fistula D. Severe hepatic cirrhosis
A. All decreased
B. 1 and 4 decreased. 2 and 3 increased
C. 1 about normal; 2 increased; 3. increased; 4. increased
D. 1 decreased; 2 and 3 increased. 4 normal or increased
what electrolytes is major component in ICF, and which ones are in ECF/
ICF: K, Mg, PO4 and other organic anions, and proteins;
ECF; Na, Cl, HCO3
For each of each cases indicated how osmolarity and volume changes.
A. Diarhea/hemorrhage B. Water deprivation/dehydration C. Diuretics/adrenal insufficiency D. Infusion of isotonic NaCl E. High NacL intake F. SIADH
A. Oms remains about the same, but volume from ECF decreases
B. OSM increase. volume decrease from both ECF and ICF
C. Volume and osm of ECF decrease; ICF osm decrease but volume increase
D. only change is ECF volume expansion
E. ECF volume and osm increase. ICF osm increase but volume decrease
F. Volume in both increase and osm in both decrease.
Distribution of fluid between ICF and ECF is determined by _
ion distribution (Na) and ATpase activity
Distribution of ECF betwen plasma and intersitital compartments is determined by:
- balance of hydrostatic vs oncotic pressures.
- intravascular pressure in capillaries vs plasma protein and solute concentration
Edema is caused by
- alteration in capillary hemodynamics (altered starling forces with increased net filtration pressure) fluid moves from vascular space into the intersitium due to decreased capillary oncotpic pressure
- renal retention of dietary Na and water- expansion of ecf volume.
Edema does not become apparent until interstitial volume is increased by _
2.5-2 L
A diuretic will be useful in treating
A. non-pitting edema
B. pitting edema
B.
not-pitting edema is swollen cesll sude to increased ICF volume and does not respond to diuretics.
what are the two types of nephrons and what are their independent role?
Cortical nephrons = filtration
Juxtamedullary nephrons = concentration of urine
There are two sets of arterioles and 2 sets of capillaries in renal microcirculation. are these positioned in series or parallal?
In series.
First capillary network (glomerular caps): high hydrostatic pressure; large fluid volume filtered into bowmans capsule
Second capillary network (peritubular caps): low hydrostatic pressure; large amounts of water and solute reabsrobed
when the bladder fills, sensory fibers from bladder wall, posterior urethra are activated by stretch. Parasymp fibers (cholinergic-Ach) from micturition center S2-S4 via _ 1_nerve stimulates 2 muscles, inhibits contraction of internal urethral sphincter
Sympathetic fibers via _ 3_nerve inhibits detrusor constriction, constricts internal urethral sphincters
Somatic motor neurons via 4 nerve constrict external urthral sphincter
- pelvic nerve
- detrusor
- hypogastric nerve
- pudendal nerve
what are the three distinct layers of the glomerular membrane?
- fenestrated caps: highly permeable to water and dissolved solutes
- Glomerular basement membrane: collagen, proteolgycan contain anionic (negative charge)
- Podocyte epithelium: slit pores between podocytes restricts molecules.
GFR is product of 3 physican factors. name:
- hydraulic conductivity (Lp) of glomerular membrane
- Surface area for filtration
- capillary ultrafiltration pressure (Puf)
product of 1 and 2 = ultrafiltration coefficient Kf
GFR = Kf x Puf
Net filtration pressure (Puf) =
P(GC) - ((Pbc + n GC))
glomerular hydrostatic pressure - the total of bowman’s capsule pressure and oncotic pressure of the glomerulus)
usually Puf is 10 mmHg
How can GFR be altered?
you can alter Kf: mesangial cell contraction which will shorten capillary loops, lower Kf and thus lower GFR
2. You can altered ultrafiltration pressure: which changes glomerular hydrostatic pressure which can be done via changes in renal artery blood pressure, afferent arteriolar resistance or eferent arteriolar resistance
In audoregulation: why would afferent arterial wanna constrict? why would efferent arteriole consstrict?
during hyperperfusion constrict afferent arteriole to protect Glomeruli and maintain GFR.
DUring hypoperfusion, constrict efferent arteriole to maintain GFR
Explain why giving an ACE inhibitor to a patient with hypertension secondary to renal artery stenosis will lead to kidney damage.
ACEI will decrease BP, RBF and intraglomerular pressure below normal due to the stenosis. Although autorgulationnormally maintains glomerular pressure/GFR by increasing efferent arteriolar constriction, an ACEI decreases formation of ang II and blunts this response with a net effect of lowered GFR. GFR below a certain point will lead to GFR damage and thus kidney damage.
explain how the sympathetic nervous system and autoregulation maintains GFR and raise blood pressure during hypoperfusion.
sympathetics will constrict afferent and to a lesser extend, efferent arteiroles which will decrease RBF, and thus decrease and divert blood to other vital organs. THis will increase renin secretion by granular cells and angII will be produced to restore blood pressure. AngII promotes arteriole constriction more so on efferent and raise blood presure and stabize GFR.
Na reabsorption will also be stimulated in PCT and TAL, DCT and CT.
What counters the actions of sympathetics and renin in the kidney?
Prostaglandins which dampens vasoconstriction done by ang II and sympathetic activity.
What is the clinical significance of high doses of chronic use of NSAIDS for a patient who is hypertensive?
Pt with hypertension have increased activity of the sympathetic activity and ang II activity on kid. these actions are usually countered by prostaglandins to maintain a balance. With high dose NSAIDS, prostaglandins production is diminished and thus the constriction of renal vasculature goes on unimpeded leading to hypoperfusion, decreased GFR and kidney damage.
What is renal clearance?
the volume of plasma from which a substance is completely removed by the kidney in a given time period. Units are volume/time e..g ml/min, l/hr
what is the equation for clearance?
Clearance of substance X = (concentration of X in urine x Urine volume) / ( conc of X in plasma)
Clx = (Ux)(V) / Px
calculate the clearance of urea, given Plasma ura = 20mM; urine urea = 400 mM; Volume = 1mL/min
C(urea) = 400 x 1 ml/min/ 20mM
= 20ml/min
In theory, if a patient with plasma creatinine of 1.0 mg/dL develops kidney issues such that their GFR drops from 100mL/min to 50 ml/min, what is their creatinine level in plasma likely to be over the next several days?
It should be 2.0 mg/dL.
The idea here is that creatinine is inversely related to GFR. if GFR decreases by 50% creatinine level in plasma should increase by 50% in a few days.
For each of these BUN:Cr reation indicate if it’s prerenal, post or intra
A. 25/1
B. 15/1
C. 5/1
A. prerenal
B. normal or post renal
C. intrarenal
What is filtration fraction and how do you calculate it?
FF = fraction of total renal plasma flow which is filtered through glomerular membrane. FF = GFR/RPF
what happens to FF during an renal artery stenosis?
FF is increased. FF = GFR/RPF and since we’re lowering the denominator the answer should increase.
Clinically this makes sense, since with decreased RBF the kidney now has lower blood to work with to get rid of the same about of toxins from the body and and so the kidney has to increase FF to get that same end result.
