Test 4 Lecture 2 Flashcards
Water accounts for how much of body weight?
50-70% (average 60%)
What causes variations in total body water?
Gender and amount of adipose tissue
correlates INVERSELY with fat, and women have lower water content, thin men have highest, fat women have lowest
How much of total body weight is ECF and ICF?
ICF = two thirds of total body water (40% of body weight) ECF = one third of total body water (20% of body weight)
What are the divisions within the ECF?
3/4 of ECF is in interstitial fluid (16%)
1/4 of ECF is in plasma (4%)
Composition of ICF
Cations = K, Mg Anions = proteins, organic phosphates like ATP, ADP, AMP
What is plasma?
the fluid the circulates in the blood vessels
What is interstitial fluid?
bathes the cells
Composition of ECF
Cation = Na Anion = CL and HCO3
What is the composition of blood volume?
55% plasma (93% plasma water, 7% plasma proteins), 45% blood cells (hematocrit, higher in males than females)
Gibbs-Donnan Effect
predicts that plasma will have a slightly higher concentration of small cations than ISF and slightly lower concentration of small anions
What are the 4 steps for measuring volumes of body fluid compartments by the dilution method?
1) Identify an appropriate marker
2) Injection of a known amount of the marker substance
3) Equilibration and measurement of plasma concentration
4) Calculation of the volume of the body fluid comparment
What is the marker for total body water?
D20, THO, antipyrine
What is the marker for ECF?
Sulfate, mannitol, inulin
What is the marker for ICF?
TBW - ECF
What is the marker for plasma?
RISA, Evan’s Blue
What is the marker for ISF?
ECF - plasma
The volume of a body fluid compartment depends on the amount of _________ it contains.
solute (example, ECF volume is determined by amount of NaCl and NaHCO3 it contains)
Osmolarity is the concentration of ____________.
Osmotically active particles
Volume contraction means a ______ in ______ volume.
decrease, ECF
Volume expansion means an ______ in ______ volume.
increase, ECF
What is clearance?
General concept that describes the rate at which substances are removed from plasma
Renal clearance is the ratio between ______ to ______.
Urinary excretion to plasma concentration
What is the clearance for albumin?
zero (not filtered across glomerular capillaries)
What is the clearance for glucose?
zero (filtered then reabsorbed)
What is the clearance for Na, urea, phosphate and Cl?
higher than zero, they are filtered and then partially reabsorbed
What is the clearance for para-amniohippuric acid?
highest clearance, filtered and secreted
What is the clearance for inulin?
clearance measures the glomerular filtration rate (freely moves across glomerular capillaries, but neither reabsorbed or secreted)
Cx/Cinulin = 1
also a glomerular marker
Cx/Cinulin = < 1
clearance of x is lower than inulin, either the substance is not filtered OR filtered and then reabsorbed (albumin, glucose, NA, urea, phosphate, Cl)
Cx/Cinulin = > 1
clearance of x is higher than inulin, substance is filtered and secreted (organic acids and bases, sometimes K)
How much CO do the kidneys receive?
25% (1.25 L/min)
RBF is ______ proportional to the pressure gradient between the renal artery and vein.
Directly
RBF is _______ proportional to the resistance of the renal vasculature.
Inversely
What are the vasoconstrictors for RBF?
Sympathetic nerves (catecholamines), Angiotensin II, Endothelin
What are the vasodilators for RBF?
PGE2, PGI2, Nitric Oxide, Bradykinin, Dopamine
RAP can vary from ____ to ____ without a change to RBF.
80 to 200 mmHg
Resistance is controlled primarily by ________ arterioles in renal autoregulation.
Afferent
ANS is involved in renal autoregulation. (T/F)
False, denervated kidney transplants autoregulate
What are the 2 hypothesis for autoregulation of RBF?
Myogenic hypothesis and tubuloglomerular feeback
Explain the mechanism by which the myogenic hypothesis works.
Increases in RAP stretch the walls of afferent arterioles, which then contract. Contraction leads to increased resistance. Increased resistance balances increased pressure, RBF stays constant.
What are the unanswered questions with the tubuloglumerular feedback mechanism?
1) What component of the tubular fluid is sensed at the macula densa? (could be Na, Cl, Ca, osmolarity)
2) What vasoactive substance is secreted by the juxtaglomerular apparatus to act locally on the afferent arterioles? (could be adenosine, prostaglandins, kinins)
Renal plasma flow (RPF) can be estimated by clearance of ______.
organic acid PAH
Renal blood flow can be calculated by _______.
RPF and hematocrit
What is the fluid that is filtered into Bowman’s space?
ultrafiltrate
What is ultrafiltrate made up of?
water and small solutes of blood (DOES NOT contain blood cells, or proteins)
What are the forces responsible for glomerular filtration?
Starling Forces
What can pass through the endothelium? What cannot?
Fluid, dissolved solutes, and plasma proteins can filter through. Blood cells cannot.
What are the 3 layers of the basement membrane?
Lamina rara interna (fused to the endothelium) Lamina densa (middle) Lamina rara externa (fused to epithelial cell layer)
The basement membrane permits filtration of plasma proteins. T/F
False, does not, is the most significant barrier of the glomerular capillary
Where are the negative charges present?
Endothelium, lamina rar interna and externa, podocytes and food processes, and on the filtration slits of the epithelium
What is the consequence of the negatively charged barrier?
Provides an electrostatic component to filtration, negatively charged solute will be repelled from the barrier (does not apply to small solutes like Na, K, Cl or HCO3)
What causes proteinuria?
A removal of the negative charges on the barrier, which allows an increased filtration of plasma proteins
Which of the Starling forces is equal to zero?
ISF oncotic pressure
What two factors contribute to Kf (filtration coefficient)?
water permeability per unit of surface area
total surface area
How does Pgc (hydrostatic pressure in the glomerular capillaries) vary from system pressure?
Relatively higher and pressure (45 mmHg) does not fall along the length of the capillary
What role does Pbs (hydrostatic pressure in bowman’s space) play?
Force opposing filtration, origin if the fluid present in the lumen of the nephron (10 mmHg)
Which way does net ultrafiltration pressure favor?
always favors filtration so that the direction of fluid movement is out of the capillaries
Which starling pressure changed to make net ultrafiltration zero?
oncotic pressure of glomerular capillary blood
What are the 3 characteristics of a glomerular marker?
1) must be freely filtered across the glomerular capillaries with no size/charge restrictions
2) cannot be reabsorbed or secreted by renal tubule
3) when infused, cannot alter the GFR
Hypoxemia
decrease in arterial PO2
Hypoxia
decrease in O2 delivery to the tissues
What are some causes of hypoxemia?
High altitude, hypoventiliation, diffusion defect, V/Q defect, right-to-left shunt
What is the A-a gradient?
The difference between the PO2 of alveolar gas and the PO2 of systemic arterial blood
What are some causes of hypoxia?
Decreased CO, hypoxemia, anemia, Carbon monoxide poisoning, cyanide poisoning
