Renal Flashcards
(190 cards)
1
Q
What is homeostasis?
A
tendency of the body to seek and maintain a condition of balance or equilibrium within its internal environment, even when faced with external changes
2
Q
The total body water (TBW) makes up how much of the body weight?
A
60%
3
Q
ICF
A
Intracellular Fluid
4
Q
ECF
A
Extracellular Fluid
5
Q
How much of the body fluid is ICF?
A
2/3 of body fluid
6
Q
How much of the body weight is ICF?
A
40% of body weight
7
Q
How much of the body fluid is ECF?
A
1/3 of body fluid
8
Q
How much of the body weight is ECF?
A
20% of body weight
9
Q
What 3 things make up the ECF?
A
- Interstitial fluid (ISF)
- Intravascular fluid (IVF)
- Transcellular fluid (TCF)
10
Q
What percentage of body weight is ISF?
A
15% of body weight
11
Q
What percentage of body weight is IVF?
A
5% of body weight
12
Q
What is one of the most important functions of the kidney?
A
maintain composition and vol. of the ECF
13
Q
Na+ in plasma?
A
142 mEq/L
14
Q
Na+ in ISF?
A
145 mEq/L
15
Q
Na+ in ICF?
A
12 mEq/L
16
Q
K+ in plasma?
A
4.3 mEq/L
17
Q
K+ in ISF?
A
4.4 mEq/L
18
Q
K+ in ICF?
A
150 mEq/L
19
Q
Ca2+ in plasma?
A
5 mEq/L
20
Q
Ca2+ in ISF?
A
2.4 mEq/L
21
Q
Ca2+ in ICF?
A
4 mEq/L
22
Q
Mg2+ in plasma?
A
3 mEq/L
23
Q
Mg2+ in ISF?
A
1.5 mEq/L
24
Q
Mg2+ in ICF?
A
34 mEq/L
25
Cl- in plasma?
104 mEq/L
26
Cl- in ISF?
117 mEq/L
27
Cl- in ICF?
4 mEq/L
28
HCO3- in plasma?
24 mEq/L
29
HCO3- in ISF?
27 mEq/L
30
HCO3- in ICF?
12 mEq/L
31
Phosphates in plasma?
2 mEq/L
32
Phosphates in ISF?
2 mEq/L
33
Phosphates in ICF?
40 mEq/L
34
Proteins in plasma?
14 mEq/L
35
Proteins in ISF?
0 mEq/L
36
Proteins in ICF?
54 mEq/L
37
What is osmotic pressure?
the force that a dissolved substance exerts on a semipermeable membrane, through which it cannot penetrate, when separated by it from pure solvent
38
With osmotic pressure, the vol of a given compartment depends on what?
number of solute particles in that compartment
39
With osmotic pressure, the vol of a given compartment does NOT depend on what?
any specific property of the solute, such as charge, size, or shape
40
2 ways water crosses cell membranes
- between lipids of bilayer
| - through specialized channels called aquaporins
41
Is it fast or slow for water to cross between lipids of the bilayer?
slow
42
Is it fast or slow for water to cross through aquaporins?
fast
43
T/F: An osmotic gradient is required to govern water movement across a membrane.
True
44
What is oncotic pressure?
osmotic pressure that is exerted by large molecules in a solution
AKA "colloid osmotic pressure'
45
How does the body govern how much fluid is in a particular compartment? (3 things)
- osmotic pressure
- hydrostatic pressure
- oncotic pressure
46
What is the impact of oncotic pressure for trans-membrane water flux?
negligible
47
What is the impact of oncotic pressure for trans-capillary fluxes?
significant
48
How is homeostasis maintained when conditions change/
Concept of "Set Point"
- system requires sensors/ detectors
- coordination of sensed signals
- feedback and adjustment mechanisms: effectors
49
Functions of the Kidney (7 things)
- regulation of water and electrolyte balance
- excretion of metabolic waste
- excretion of drugs and hormones
- regulation of arterial blood pressure
- production of erythropoietin
- conversion of vit. D to active form
- gluconeogenesis
50
What is the basic functional unit of the kidney?
nephron
51
3 Generally Categories of Kidney Functions
- Filtration
- Absorption/Reabsorption
- Secretion
52
T/F: Secretion is not the same thing as excretion
True
53
What causes the production of erythropoietin?
decrease in oxygen tension
54
In the renal corpuscle,what things are used for solute discrimination?
- size
- shape
- charge
55
Where are the bulk of filtered solutes reabsorbed?
proximal tubule
56
What are the juxtamedullary nephrons important for?
concentrating mechanisms
57
Thick ascending limb (Loop of Henle)
- high ACTIVE transport of NaCl - REQUIRES ATP
| - No H2O permeability
58
Thin descending limb (Loop of Henle)
- High H2O permeability
| - No NaCl permeability
59
Thin ascending limb (Loop of Henle)
- High NaCl permeability
| - No H2O permeability
60
How is the medullary hypertonicity established and maintained?
By the selective permeabilities of loop of Henle segments
61
What is the medullary hypertonicity necessary for?
concentrating mechanism
62
Tubular fluid in the distal tubule is ____________.
hypotonic
63
Role of macula densa cells?
-sense salt load = very sensitive to NaCl concentrations
64
Tubuloglomerular feedback?
mechanism by which both renal blood flow and glomerular filtration rate are controlled
65
What cells make up the juxtaglomerular apparatus?
- mesangial cells
| - granular cells of the afferent arteriole
66
Absorption of what happens in the distal convoluted tubule?
- Na+
- Ca2+
- Cl-
67
What are the cells of the connecting tubule like?
mix of DCT- and CD-like cells
68
How much of the cardiac output do the kidneys receive?
1/5
69
What is the percentage of plasma in the blood received by the kidneys?
50-55%
70
How much of the plasma delivered to the kidneys crosses into Bowman's capsule?
20-35%
71
How much of the filtered plasma is excreted?
less than 1%
72
Where does filtration occur?
interface between vascular and epithelial structures
73
What determines the permeability across the glomerular filtration barrier?
- size
- charge
- shape
74
In health, the oncotic pressure in the lumen of Bowman's capsule should equal?
0 mmHg
75
How can the glomerular filtration be regulated?
- hormonal
- autoregulation
- tubuloglomerular feedback
76
What is the stimulus for the renin-angiotensin-aldosterone system?
drop in blood pressure
77
What is the response for the renin-angiotensin-aldosterone system?
adjust vascular resistance and circulating blood vol.
78
Where is renin made?
granular cells of afferent arterioles
79
What is angiotensin?
- peptide
- circulates
- made by liver
80
Where is ACE made?
endothelial cells of lungs and kidneys
81
What is aldosterone?
- steroid
| - made in adrenal cortex
82
What does excessively high GFR result in?
elevated tubular flow rates and inefficient removal of NaCl by TALH
83
What cells sense the high tubular NaCl?
macula densa cells
84
After sensing high tubular NaCl, the macula densa cells release ATP and adenosine. What does that do?
- INCREASES glomerular mesangial cell constriction
| - DECREASES available glomerular capillary filtration area, and hence, Kf
85
What is clearance?
the volume of plasma from which a substance is completely removed by the kidney in a given amount of time (usually a minute)
86
How can clearance be a measure of GFR?
clearance of a special substance can be used to measure GFR
87
Why is inulin ideal for measuring GFR?
- freely filtered
- non-toxic
- not secreted
- not absorbed
- not metabolized
- Cin = GFR
88
T/F: GFR and inulin clearance do NOT depend on [Pin}
True
89
As inulin needs to be infused constantly to measure GFR, what is another substance that can be used?
creatinine
90
Characteristics of creatinine
- normal product of protein metabolism
| - production does not vary sig. w/ time
91
Pro of using inulin?
Cin = GFR
92
Cons of using inulin?
- requires IV and constant infusion
- requires complete bladder emptying before and after the test
- urine flow must be high to obtain enough urine sample
93
Pros of using creatinine?
- Ccr ~ GFR
- endogenous; no need for IV or infusion
- can collect urine sample over longer period of time
94
Con to using creatinine?
secretion can produce an overestimate of GFR
| - gen. doesn't d/t limitations of test
95
Transcellular transport
through the cell
96
Paracellular transport
between cells
97
Absorption
- endocytosis
| - transcytosis
98
Secretion
exocytosis of stored or newly synthesized proteins
99
Types of transport proteins
- pumps
- carriers
- channels
100
Types of carriers
- symporters = cotransporters
- antiporters = exchangers = countertransporters
- uniporters
101
Transport processes
- active
- secondary active (coupled carriers)
- passive (channels, some carriers)
102
How many sodium does the Na+/K+ pump move out of the cell?
3
103
How many potassium does the Na+/K+ pump move into the cell?
2
104
In a healthy individual, how much of the filtered glucose is reclaimed in the PT?
virtually ALL of it!
105
Why is glucosuria seen in diabetes mellitus?
The PT glucose transport rate is exceeded
106
Diabetes Mellitus Type I
insulin deficient = inability of pancreas to secrete insulin
107
Diabetes Mellitus Type II
insulin resistant = target tissues do not respond to insulin
| may also be insulin-insufficient
108
What mediates the proximal tubular reabsorption of HCO3-?
sodium gradient
109
T/F: HCO3- reabsorption does not rely on the gradient maintained by the Na+/K+ ATPase
False.
It does rely on the gradient.
110
What does the PT efficiently recover? (3)
- filtered amino acids
- oligopeptides
- low molecular weight proteins (LMPs)
111
How does Cl- mediated Na+ transport work? (3)
- early PT, lumen (-) potential difference; late PT, luminal [Cl-] increased
- "leaky" tight junctions
- sodium follows chloride
112
Percentage of filtered Na+ (re)absorbed in the PT?
~65%
113
Recovery of filtered LMPS via transcytosis in the proximal tubule (4 steps)
1. endocytosis of LMPs
2. fusion w/ lysosome
3. lysosomal degradation and fusion w/ multivesicular body
4. transport of amino acids to interstitial space
114
Transport by the thin segments of the Loop of Henle are ______________.
passive
115
NaCl transport by TAL is _______.
active
116
The active transport of NaCl by the TAL reclaims how much more of the filtered NaCl load?
25%
117
K+ and Cl- move __ their concentration gradients in TAL.
UP
118
As the TAL is not permeable to water, what happens to the luminal fluid?
It is diluted
119
What do loop diuretics affect? Examples?
Affect TAL
Examples
- bumetanide (bumex)
- furosemide (lasix)
120
What is Bartter syndrome?
human dz d/t loss of function mutation
121
Symptoms of Bartter syndrome? (5)
- present w/ hypotension and salt wasting
- NaCl absorption is impaired
- insufficient dilution of luminal fluid results
- high medullary interstitial tonicity cannot be achieved
- overall renal concentration mechanism is compromised!
122
T/F: Na+ gradient also drives NaCl uptake by the distal tubule (DT)
True
123
T/F: the apical transporter in the DT depends on the presence of K+
FALSE
Apical transporter in the DT does NOT depend on the presence of K+
124
What do thiazide diuretics affect? Example?
Affect DT
Example
-chlorothiazide (diuril)
125
What is DT Ca2+ absorption regulated by?
parathyroid hormone (PTH)
126
Cells of the Collecting Duct System (2 categories)
- Intercalated
| - Principle
127
Types of intercalated cells
- alpha
| - beta
128
What do alpha intercalated cells secrete?
acid
129
What do beta intercalated cells secrete?
base
130
What intercalated cells are found more in carnivores?
alpha
131
what intercalated cells are found more in herbivores?
beta
132
What type of cells predominate throughout all segments of the CD?
priniciple cells
133
What is the function of epithelial Na+ channels (ENaC)?
permits downhill movement of Na+ from tubular lumen and into cell
134
ENaC abundance and activity is regulated by?
aldosterone
135
How is the ENaC put together?
assembly of 3 subunits encoded by 3 genes belonging to a large cation channel gene family
136
what is something that inhibits ENaC, therefore blocking Na+ absorption?
amiloride
137
PHA Type I (humans)
- loss of function mutations in ENaC (alpha, beta, and gamma)
- leads to renal salt wasting
138
Liddle Syndrome (humans)
- gain of function mutations in ENaC (beta and gamma)
- increased renal Na+ uptake
- hypertension
139
The water permeability of the collecting duct principle cells is modulated by?
ADH (anti-diuretic hormone)
140
How does ADH affect water permeability of CD principle cells?
- binding of circulating ADH to its basolaterally-localized receptor increases intracellular cAMP
- this then stimulates the fusion of vesicles to the apical membrane
- water exits via aquaporins 3 and 4
141
Aquaporin 2 contains __________ and is regulated by __________.
pre-synthesized water channels; ADH
142
As aquaporins 3 and 4 are always around, do they need ADH stimulation?
no
143
AQP2 and CD ADH-regulated water permeability
| Loss of Function Mutation
- NEPHROGENIC diabetes insipidus (DI)
- inability to concentrate urine
- massive water diuresis
144
3 things that facilitate absorption by the PT
- subcellular specializations
- secondary structural features
- tertiary structural features
145
PT erubcellular specializations
- mitochondria rich
| - wide range of specialized transporters
146
PT secondary structural features
-brush border membrane
147
PT tertiary structural features
- convolutions of early proximal tubule
| - proximity of all nephronal segments to the vasa recta
148
In relation to substances being IN THE URINE, what is the role of filtration, absorption, and secretion?
```
filtration = input
absorption = output
secretion = additional input
```
149
Why is it important to understand clearance?
- Inulin/creatinine clearance measures GFR
- Regular GFR monitoring can help time when dialysis is NECESSARY
- Chronic kidney dz is not curable
150
Why is knowledge of renal functions essential and critical ?
For safe and proper drug dosage
151
What is PAH?
para-aminohippurate
152
What is PAH a useful indicator of?
renal plasma flow (RPF)
153
In a healthy individual, with normal plasma glucose levels, how much of the glucose is reabsorbed in the PT?
100%
154
How can glucose end up in the urine?
When the level of plasma glucose exceeds the PT glucose transport maximum (Tm)
155
How the medullary interstitial hypertonicity generated?
- Active NaCl absorption by TALH
| * role of urea recycling
156
How is the medullary interstitial hypertonicity maintained?
differential NaCl and H2O permeabilities of all segments of the Loop of Henle
157
Thin descending limb (DTL)
- H2O permeable
| - NOT NaCl permeable
158
Thick ascending limb (TALH)
- ACTIVE NaCl transport
| - NOT H2O permeable
159
Thin ascending limb (ATL)
- PASSIVE NaCl transport
- NOT H2O permeable
- UREA SECRETION
160
Where does urea secretion occur?
thin ascending limb
161
Medullary Collecting Duct
- REGULAR permeability to NaCl and H2O
| - UREA REABSORPTION
162
Where does urea reabsorption occur?
medullary collecting duct
163
What maintains the vertical gradient in the medullary interstitium?
countercurrent exchange between the descending and ascending vasa recta
164
T/F: Vasa recta are not freely permeable to both NaCl and H2O
False.
They are freely permeable to both NaCl and H2O.
165
What is the importance of medullary interstital hypertonicity?
required for urine concentration
166
Urea (7 things)
- small
- highly polar
- protein metabolite
- highly H2O soluble
- freely filtered
- major product for removal of free ammonia in vivo
- contributes to medullary hypertonicity
167
Can urea pass through pure lipid bilayers?
No; needs urea transporters
168
Urea transports in the ATL do what?
mediate secretion
169
Urea transports in the IMCD do what?
fascilitate reabsorption
170
IMCD stands for?
Inner Medullary Collecting Duct
171
ADH
Anti-diuretic Hormone
172
Effect of ADH
- induction of thrist
| - pressor effects = aid in maintaining perfusion during vol. depletion
173
T/F: A change in osmolarity will overrule a change in blood vol.
True.
174
Primary action of ADH in kidney?
increase H2O permeability of cells in the CD
Ultimately leads to H2O reabsorption and excretion of concentrated urine
175
How does ADH also increase urea recycling?
promoting urea transport in CD
176
Disruptions to ADH reaching its target cells?
nephrogenic DI
177
Diuresis
- removal of ADH leads to endocytosis of AQP2 from apical membrane
- decreases H2O permeability of CD, therefor decreases reclamation of H2O from urine
- excreted urine is therefore very dilute
178
Central diabetes insipidus
- ADH RELEASE is impaired
| - defect is at the SOURCE
179
Nephrogenic diabetes insipidus
- ADH SIGNALING is impaired
| - defect is at the TARGET
180
Why do you perform a water deprivation test?
H2O deprivation should stimulate an ADH response and increase H2O reabsorption (concentrate urine) in ANY non-DI subject
181
Why do you perform an ADH Response Test?
Administration of ADH should increase H2O reabsorption in non-DI AND CENTRAL DI subjects, but NOT in nephrogenic DI subject
182
What is the outcome for both water deprivation test and ADH Response Test?
increase in urine specific gravity for positive response
183
Who should not increase H2O absorption with a dose of ADH?
nephrogenic DI subjects
184
T/F: The concentration of Na+ in the ECF is a good indicator of ECF volume.
False.
[Na+] in ECF is not a good indicator of ECF volume.
185
Aldosterone
- released by zona glomerulosa cells of adrenal cortex
- stimulated by angiotensin II
- also stimulated by elevated plasma K+ and ACTH
186
What is ACTH?
adrenalcoricotrophic hormone
| stress increases this one
187
How does aldosterone relate to Na+ absorption?
increases sodium absorption from luminal fluid in CD
This causes Na+ to be retained
188
T/F: Increased Na+ intake decreases aldosterone synthesis
True
189
Amiloride
- binds to apically located ENaC
| - blocks Na+ conduction by that protein = INHIBITS Na+ REABSORPTION
190
What increases the production of epithelial sodium channels (ENaC)?
aldosterone
