Kidney Pt2- Filtration Flashcards
1
Q
Renal corpuscles is made of:
A
glomerular capillaries + Bowman’s capsule
2
Q
_______ filters blood to produce a large volume (~150-200 L/day) of filtrate that is similar in composition to plasma minus most plasma proteins
A
Renal corpuscles
3
Q
glomerular capillaries + Bowman’s capsule, which make up the _____ _______, produce _____L/day of filtrate
A
150-200 L/day
4
Q
the nephron processes the filtrate to produce a small volume _______L/day of excreted urine of varying composition
A
~1.5 L/day
5
Q
produces 20 - 25% of the cardiac output which flows through the kidneys
A
Renal Blood Flow (RBF)
6
Q
is the portion of blood that is filtered. It ranges from 10-25% of renal blood flow.
A
Filtration Fraction (FF)
7
Q
at rest RBF is about ____ L/min
A
1.2
8
Q
_________ is the rate at which filtrate enters Bowman’s capsule
A
Glomerular Filtration Rate (GFR)
9
Q
the glomerular filtration rate for males is about ______.
the glomerular filtration rate for females is about ____.
A
90 - 140 mL/min
80-125 mL/min
10
Q
Glomerular Filtration Rate (GFR) equation is:
A
RBF x (1 – Hct) x FF
RBF = Renal Blood Flow Hct = Hematocrit/100 FF = Filtration Fraction
11
Q
Clinically GFR is usually estimated from blood _____ values and is sometimes used to adjust the dosage of medications
A
creatinine
12
Q
_______is equal to the total of the filtration rates of the functioning
nephrons in the kidney.
A
GFR
13
Q
How was GFR measured before?
A
The urinary or plasma clearance of an ideal filtration marker, such as inulin, iothalamate or iohexol, is the gold
standard for the measurement of GFR
14
Q
How is GFR measured now
A
serum levels of endogenous
filtration markers, such as creatinine, have traditionally been used to estimate GFR, along with
urinary measurements in some cases
15
Q
______ is accepted as the best overall index
of kidney function.
A
GFR
16
Q
A clinician or medical laboratory
can estimate GFR from a person’s serum
creatinine level and some or all of the following
variables: (4)
A
gender, age, weight, and race
17
Q
In most healthy people, the normal GFR is
___ mL/min/1.73 m2 or higher.
A
90
18
Q
Why are GFR estimates adjusted for body
surface area?
A
Adjustment for body surface
area is necessary when comparing a patient’s
estimated GFR to normal values or to the levels
defining the stages of CKD.
19
Q
How does age affect GFR?
A
GFR declines gradually with age, even in people
without kidney disease. However, decreased GFR
in the elderly is an independent predictor of
adverse outcomes, such as death and cardiovascular disease.
20
Q
_____ clearance exceeds GFR because it
is secreted by the proximal tubule as well as
filtered by the glomerulus. It can be measured from serum creatinine and creatinine
excretion, or estimated from serum creatinine
using estimating equations
A
Creatinine
21
Q
What is the CKD-EPI equation?
A
The CKD-EPI equation was developed in 2009
to estimate GFR from serum creatinine, age, sex,
and race.
22
Q
What is the currently recommended
method to estimate GFR?
A
serum creatinine
23
Q
Two commonly used
equations when estimating GFR is
A
Modification of Diet in Renal Disease (MDRD) Study equation and
Cockcroft-Gault equation
24
Q
What factors affect the creatinine assays?
A
Proteins in the serum, as well as glucose and
ketoacids in high levels (as occurring in diabetic
ketoacidosis), interfere with the alkaline picrate
assay, giving rise to false elevations in serum
25
What factors affect creatinine secretion?
Some medications inhibit tubular secretion of
creatinine, thereby decreasing creatinine clearance
and increasing serum creatinine without a
change in GFR
26
medications that affect creatinine secretion are:
* cephalosporin and aminoglycoside antibiotics
* flucytosine
* cisplatin
* cimetidine
* trimethoprim
27
________ is a break-down product of creatine/creatine phosphate, mainly from muscle, and is usually produced at a fairly constant rate
Creatinine
28
Creatinine is eliminated by kidney _____, it is slightly secreted but not ______ so serum creatinine levels give a fairly good estimate of GFR
filtration
| reabsorbed
29
Typical reference ranges for serum creatinine are ______ mg/dL, for women and ______ mg/dL for men.
0. 5 to 1.0
| 0. 7 to 1.2
30
Creatinine production is related to _____ _____, so a serum creatinine of 1.2 mg/dL may indicate normal kidney function in a male body builder, while a serum creatinine of 1.2 mg/dL can indicate significant renal disease in an elderly female.
muscle mass
31
Part of nephron that collects the filtrate produced by filtration of the blood
Bowman’s capsule
32
the _____ _____ of Bowman’s capsule is continuous with and conducts filtrate to the proximal convoluted tubule
parietal layer
33
In the glomerulus, the network of glomerular capillaries are covered by the _______ of the _____ _____ of Bowman’s capsule
podocytes
| visceral layer
34
In the glomerulus, fluid is forced from the glomerular capillaries into the lumen of Bowman’s capsule by the ______ blood pressure inside the capillaries
hydrostatic
35
The renal corpuscles filter ~ _____ liters of blood to produce ~ 180 liters of filtrate per day. Only about ____ liters is excreted as urine, the rest of the filtrate is reabsorbed back into the blood.
1500L
180L (48 gal)
1.5L
36
Capillary wall consists almost entirely of _______ cells and basement membrane
endothelial
37
3 types of capillaries
continuous
fenestrated
sinusoidal
38
______ capillaries contain ______ _____, and do not have fenestrae. they also have lowest prmeability and more pericytes.
Continuous
39
Have fenestrae (pores that may or may not be covered by membranes, or fenestral diaphragms); Highly permeable
Fenestrated capillaries
40
Large diameter with large fenestrae and leaky junctions; very highly permeable
Sinusoidal capillaries
41
The Filtration Membrane has 3 layers:
```
Endothelial cells (fenestrated)
Basement membrane
Podocytes of bowman’s capsule
```
42
Water and small molecules can easily pass through the filtration membrane but ____ cells and most ____ _____ cannot
blood
| plasma proteins
43
________ in the visceral layer of Bowman’s capsule are packed closely together to form filtration slits which work with the basement membrane to help prevent plasma proteins from entering the filtrate
pedicels (podocytes)
44
_____ _____ help prevent the filtration slits from enlarging under pressure
Slit diaphragms
45
The endothelial cell glycocalyx, basement membrane and podocyte slit membrane contain several charged ______ that influence the filtration of charged molecules
glycoproteins
46
____ and ____ of a molecule determines its filterability
Size and charge
47
______ interacts with actin in the podocyte cytoskeleton and is essential in formation of normal filtration slits
nephrin
48
Mutations of nephrin or basement membrane proteins can cause renal pathologies ____ and _____
congenital nephrotic syndrome
| proteinuria
49
heterogenous conditions characterized by structural abnormalities in the glomerular basement membrane (GBM) due to mutations in type IV collagen. Both conditions typically present with hematuria.
Alport syndrome
| Nephropathy (thin glomerular basement membrane)
50
Glomerular Filtration Rate (GFR) and Net filtration Equation
GFR = Kf [(PGC – PBS) – σ(πGC – πBS)]
```
Kf= Ultrafiltration coefficient
PGC= Hydrostatic pressure in glomerular capillary
PBS= Hydrostatic pressure in bowman’s space
σ= Reflection coefficient for protein
πGC= Oncotic pressure in glomerular capillary
πBS = Oncotic pressure in bowman’s space
```
51
______ filtration is produced by the blood pressure in the glomerular capillaries
Glomerular
52
______ _____ _____= total pressure that promotes filtration minus opposing forces
Net filtration pressure (NFP)
53
Forces Producing Filtration , pushing water out of the capillary
Hydrostatic Blood Pressure
| Interstitial Osmotic Pressure
54
Hydrostatic Blood Pressure:
About _____ mmHg at arteriole end of most systemic capillaries
About ____ mmHg at venule end of most systemic capillaries
About _____ mmHg in glomerular capillaries
30-35
13-16
40-70
55
Interstitial Osmotic Pressure:
```
About ____ mmHg
Filtrate osmotic (oncotic) pressure in Bowman’s capsule is normally considered to be near ___ mmHg
```
1-8
| 0
56
Forces Opposing Filtration Keeping water in the capillary
```
Blood Osmotic (oncotic) Pressure
Bowman’s capsule Hydrostatic Pressure
```
57
Blood Osmotic (oncotic) Pressure:
About ____ mmHg mainly due to serum albumin & other serum proteins
25 - 30
58
Bowman’s capsule Hydrostatic Pressure:
About ____ mmHg; may be increased by renal obstruction (i.e., kidney stone)
10
59
The blood osmotic pressure in the afferent arterioles is _____ than the efferent arteriole
higher
60
What determines filterability?
size and charge
61
Size of particle:
_____ nm filters easily, water is ~ 0.3 nm)
< ____ kDa proteins filter easily
> ____ kDa proteins do not filter
2 - 4.2
10
100
62
Charge of particle:
______ is faster & ______ slower
_____ (~70kDa, negatively charged) does not readily cross the filtration membrane
positive
negative
Albumin
63
Filterability ratio of Water = ___
1
64
Exogenous carbohydrate polymers that can be produced with different sizes or charge
Dextran
65
High molecular weight dextrans are sometimes used therapeutically as a “______ ______”
plasma extender
66
osmotic action helps _______ to hold water in the blood vessels
albumin
67
_______ charges inhibit filtration
Negative
68
Filterability = 1, for substances < 2 nm dependent on _______
charge
69
Filterability of a Polyanionic Dextran if Negative Charges in the filtration barrier are neutralized cause the curve to shift to the _____, which represents increased permeability
right
70
If GFR too high:
useful substances are lost due to the speed of fluid passage through nephron (diabetes or diuresis)
71
If GFR too low:
sufficient waste products may not be removed from the body (renal failure)
72
The Kidneys are able to maintain a fairly constant GFR over a range of systemic blood pressures by ________ regulation of the afferent and efferent arterioles to maintain GCHP
independent
73
in the absence of external neural and humoral factors, the kidney will maintain GFR and RBF relatively constant in the face of changes in arterial pressure within range of _____mmHg
80-200
74
Mechanisms to maintain a functional GFR despite changes in systemic arterial BP:
myogenic mechanisms
| tubuloglomerular feedback
75
Changes in blood pressure (BP) or blood flow via this mechanism, cause immediate compensatory responses by the glomerular vasculature
myogenic mechanisms
76
Changes in BP or tubular fluid flow via this mechanism, cause both local and systemic compensatory responses
tubuloglomerular feedback
77
tubuloglomerular feedback cause local regulation of the afferent and efferent arterioles to adjust ____ & ____
GCHP
| GFR
78
tubuloglomerular feedback cause systemic effects on BP by _______ ________ & other chemical messengers
Renin-angiotensin- aldosterone system
79
Myogenic Mechanism:
systemic increase in BP, stretches the wall of the afferent arteriole stimulating smooth muscle contraction which ____ the diameter of the afferent arteriole decreasing _____ _____ and pressure returning the GFR to its previous level in seconds
reduces
| glomerular flow
80
Myogenic Mechanism:
systemic decrease in BP, decreases the tension in wall of the afferent arteriole stimulating smooth muscle _____ which increases the diameter of the afferent arteriole increasing glomerular flow and pressure returning the GFR to its previous level in seconds
relaxation
81
The ______ cells lining the arteriole may release chemicals that contribute to myogenic mechanism
endothelial
82
_______ cells are sensitive to pressure and blood flow rate
Endothelial
83
chemical messengers of endothelial cells:
NO & prostaglandins → _________
Endothelin & others → _________
vasodilation
| vasoconstriction
84
Afferent arteriole and efferent arteriole vascular smooth muscle respond differently to the various chemical messengers produced by
```
endothelial cells
mesangial cells
podocytes
juxtaglomerular cells
neurons and other tissues
```
85
_______ arteriole dilation and/or ______ arteriole constriction will increase glomerular capillary hydrostatic pressure and increase GFR
Afferent
| efferent
86
_______ arteriole constriction and/or ______ arteriole dilation will decrease glomerular capillary hydrostatic pressure and decrease GFR
Afferent
| efferent
87
The cells of the _____ ______ are sensitive to the concentration of sodium chloride in the late thick ascending limb. A decrease in sodium chloride concentration initiates a signal from the macula densa that has two effects:
macula densa
1) it decreases resistance to blood flow in the afferent arterioles via vasodilation, which increases glomerular hydrostatic pressure and helps return glomerulus filtration rate (GFR) toward normal
(2) it increases renin release from the juxtaglomerular cells of the afferent and efferent arterioles
88
which are the major storage sites for renin
juxtaglomerular cells
89
increase in sodium chloride concentration would result in _______ of afferent arterioles, and reduced paracrine stimulation of juxtaglomerular cells. This demonstrates the macula densa feedback, where compensatory mechanisms act in order to return GFR to normal.
vasoconstriction
90
Elevated systemic BP raises the GFR so that fluid flows too rapidly through the renal tubule & ____ and ____ are not adequately reabsorbed.
The macula densa detects that difference & releases vasoconstrictors (_____?) from the juxtaglomerular apparatus causing the afferent arterioles to constrict & reduce GFR
Na+, Cl- and water
| adenosine
91
Decreased systemic BP lowers the GFR so that fluid flows too slowly through the renal tubule and _____ ____ is reabsorbed. The juxtaglomerular apparatus detects the decreased tubular flow and releases a vasodilator (______) causing the afferent arterioles to ____ increasing glomerular blood flow, pressure and the GFR
excess water
prostaglandin
dilate
92
Vasoconstrictor Chemicals
```
Norepinephrine & Epinephrine: alpha1 receptors
Serotonin
Thromboxane A2 & other prostaglandins
Substance P
Endothelin
Angiotensin II
Vasopressin (Anti-Diuretic Hormone)
ATP (P2 receptors)
Adenosine (P1A1A receptors) (vasoconstriction in the kidney)
```
93
Vasodilator Chemicals
```
Adenosine (P1A2 receptors)
low O2, ^CO2, ^H+, ^K+
Nitric Oxide (NO)
Bradykinin {via NO}
Acetylcholine {via NO}
Histamine
Prostacyclin & other prostaglandins
Epinephrine &NE: {Beta-2 receptors}
Dopamine (D1 receptors)
Natriuretic Peptides (ANP & BNP)
Vasoactive Intestinal Peptide
```
94
Adenosine binds to ___ _______ receptors, which activate G proteins
P1 purinergic
95
ATP binds to ___ ________ receptors
P2 purinergic
96
Half-life of adenosine is ~_______, taken up by erythrocytes and endothelial cells
1 second
97
inhibits adenylcyclase which decreases intracellular cAMP (vasoconstriction)
P1A1
98
stimulates adenylcyclase which increases intracellular cAMP (vasodilation)
P1A2
99
```
P1A1 effect on:
Heart:
Vessels:
Bronchi:
CNS:
```
Heart: Slowing of the rhythm
Vessels: Vasoconstriction
Bronchi: constriction
CNS: Sedation
100
```
P1A2 effect on:
Heart:
Vessels:
Bronchi:
CNS:
Platelets:
Mast Cells:
Intestinal Secretion:
```
```
Heart: Negative inotropic effect
Vessels: Vasodilation
Bronchi: dilation
CNS: Stimulant
Platelets: Inhibits aggregation
Mast Cells: Degranulation
Intestinal Secretion: Inhibition
```
101
receptors mediate ATP induced vasoconstriction
P2
102
______ receptors have been cloned in humans
12 P2Y
103
_______ receptor is the target of the anti-platelet drug clopidogrel
P2Y12
