Week 2 Lec: Renal Function and Renal Tests Flashcards
1
Q
The ability of the kidneys to clear waste products selectively from the blood and simultaneously to maintain the body’s essential water and electrolyte balances is controlled in the _________.
A
nephron
2
Q
The ability of the kidneys to clear waste products selectively from the blood and simultaneously to maintain the body’s essential water and electrolyte balances is controlled in the nephron by the following renal functions?
A
- Maintaining homeostasis
- Excretion of waste products
- Concerned with the maintenance of blood pressure and erythropoiesis
3
Q
Renal function consists of 4 main components?
A
A. Renal Blood Flow
B. Glomerular Filtration
C. Tubular Reabsorption
D. Tubular Secretion
4
Q
Which artery supplies blood to the kidney?
A
Renal artery
5
Q
The kidneys receive a large blood flow by how many percent?
A
25%
6
Q
Based on the average body size of 1.73m², what is the total renal blood flow?
A
approx. 1200 mL/min
7
Q
Based on the average body size of 1.73m², what is the total renal plasma flow?
A
600 to 700 mL/min
8
Q
Flow of blood in the kidneys?
A
renal artery
afferent arteriole
glomerulus
efferent arteriole
peritubular capillaries
vasa recta
renal vein
9
Q
Main function of glomerulus?
A
filtration
10
Q
Main function of peritubular capillaries?
A
immediate reabsorption
11
Q
Main function of vasa recta?
A
water and salt exchange
12
Q
The glomerulus consists of approximately how many capillary lobes?
A
8
13
Q
The 8 capillary lobes in the glomerulus is referred to as _________.
A
capillary tuft
14
Q
It serves as a sieve or a filter of plasma substances with molecular weight of <70,000.
A
Glomerulus
15
Q
The glomerulus is located within the ______, which froms the beginning of the renal tubule.
A
Bowman’s capsule
16
Q
Factors that influence the actual filtration process?
A
◦ cellular structure of the capillary walls and Bowman’s capsule
◦ hydrostatic and oncotic pressures
◦ feedback mechanisms of the renin angiotensin-aldosterone system
17
Q
3 cellular layers of the glomerulus?
A
- capillary wall membrane
- basement membrane (basal lamina)
- visceral epithelium of Bowman’s capsule
18
Q
The capillary wall membrane contain pores and are referred to as ______.
A
fenestrated
19
Q
The pores increase __________ but do not allow the passage of ____________________.
A
capillary permeability; large molecules and blood cells
20
Q
Role of the basement membrane/basal lamina in the cellular structure of the glomerulus?
A
restriction of large molecules occurs as the filtrate passes
21
Q
The thin membranes covering the filtration slits formed by the intertwining foot processes of the podocytes of the inner layer of Bowman’s capsule.
A
Visceral epithelium of Bowman’s capsule
22
Q
The intertwinning foot processes are found in?
A
podocytes
23
Q
Necessary to overcome the opposition of pressure from the fluid from the Bowman’s capsule and the oncotic pressure of unfiltered plasma protein.
A
hydrostatic pressure
24
Q
By increasing or decreasing the size of the afferent and efferent arterioles, an ___________________ maintains the glomerular blood pressure at a relatively constant rate regardless of fluctuations in systemic blood pressure.
A
autoregulatory mechanism within the juxtaglomerular apparatus
25
BP drops: _____ of the afferent arterioles and _____ of the efferent arterioles
dilation, constriction
26
BP rises: _____ of the afferent arterioles and _____ of the efferent arterioles
constriction, dilation
27
It regulates the flow of blood to and within the glomerulus. This system respond to changes in blood pressure and plasma sodium content.
RAAS (Renin-Angiotensin-Aldosterone System)
28
RAAS (Renin-Angiotensin-Aldosterone System) is monitored by the?
juxtaglomerular apparatus
29
RAAS (Renin-Angiotensin-Aldosterone System) respond to changes in ______ and ______.
blood pressure and plasma sodium content
30
The juxtaglomerular apparatus consists of?
the juxtaglomerular cells in the afferent arteriole and the macula densa of the distal convoluted tubule
31
_______, an enzyme produced by the juxtaglomerular cells, is secreted and reacts with the blood-borne substrate angiotensinogen to produce the inert hormone angiotensin I.
Renin
32
Renin, an enzyme produced by the juxtaglomerular cells, is secreted and reacts with the blood-borne substrate ______ to produce the inert hormone ______.
angiotensinogen; angiotensin I
33
As angiotensin I passes through the alveoli of the lungs, _________ changes it to the active form _________.
angiotensin-converting enzyme (ACE); angiotensin II
34
Angiotensin II corrects renal blood flow in the following ways?
1. Vasodilation of afferent & vasoconstriction of efferent arteriole.
2. Stimulate Sodium reabsorption in the Proximal Convoluted Tubule (PCT).
3. Release of the hormone Aldosterone from adrenal cortex.
4. Release of Antidiuretic hormone from hypothalamus.
35
As a result of the RAAS mechanism, every minute approximately _________ glomeruli filter approximately _________ of water-containing low-molecular-weight substances.
two to three million; 120 mL
36
True or False: The body cannot lose 120 mL of water-containing essential substances every minute.
True
37
A type of transport wherein a substance to be reabsorbed must combine to a carrier protein contained in the membranes of the renal tubular cells.
Active Transport
38
Active transport is responsible for transporting what substances?
glucose, amino acids, salts, chloride, sodium
39
Active transport can be influenced by the ________________ being transported.
concentration of the substance
40
Defined as the plasma concentration at which active transport stops.
Renal threshold
41
Renal threshold for glucose is?
160 to 180 mg/dL
42
It is the movement of molecules across membrane as a result of differences in their concentration or electrical potential.
Passive Transport
43
(Passive Transport) These physical differences on opposite sides of the membrane are called _______.
gradients
44
Passive reabsorption of water takes place in all parts of the nephron except the ____________ because it is impermeable to water.
ascending loop of Henle
45
Exceeding the renal threshold of substances affects the _________________ of the tubules, leading to the appearance of the substance in the urine.
maximal reabsorptive capacity
46
Active transport of glucose, amino acids, and salts take place in the?
Proximal Convoluted Tubule (PCT)
47
Active transport of sodium takes place in the?
Proximal and Distal Convoluted Tubule (PCT/DCT)
48
Passive transport of water takes place in the?
Proximal Convoluted Tubule (PCT), Descending Loop of Henle, and Collecting Duct
49
Passive transport of urea takes place in the?
Proximal Convoluted Tubule (PCT) and Ascending Loop of Henle
50
Passive transport of sodium takes place in the?
Ascending Loop of Henle
51
Glucose appearing in the urine of a person with a normal blood glucose level is the result of ____________ and not diabetes mellitus.
tubular damage
52
Renal/tubular concentration begins in the _____________________.
descending and ascending loops of Henle
53
Water is removed by osmosis in the __________, and sodium and chloride are reabsorbed in the __________.
descending loop of Henle; ascending loop
54
A selective reabsorption process that serves to maintain the osmotic gradient of the medulla.
countercurrent mechanism
55
The final concentration of the filtrate through the reabsorption of water begins in the __________ and continues in the collecting duct.
late distal convoluted tubule
56
Reabsorption depends on the osmotic gradient in the medulla and the hormone?
vasopressin (ADH)
57
Production of vasopressin is determined by the ___________.
state of body hydration
58
The ___________ is actually the final determinant of urine volume and concentration.
chemical balance in the body
59
Relationship between body hydration, ADH, and urine volume?
↑Body Hydration = ↓ADH = ↑Urine Volume
↓Body Hydration = ↑ADH = ↓Urine Volume
60
Vasopressin - Antidiuretic hormone (ADH) = ?
water reabsorption
61
Tubular secretion serves two major functions?
1. eliminating waste products not filtered by the glomerulus
2. regulating the acid–base balance in the body through the secretion of hydrogen ions
62
Examples of waste products not filtered by the glomerulus?
urea and medications
63
The major site for removal of nonfiltered substances is the?
proximal convoluted tubule
64
True or False: As a result of its molecular size, hydrogen ion are readily filtered and absorbed.
True
65
Secretion of hydrogen ions by the renal tubular cells into the filtrate prevents the _____________ from being excreted.
filtered bicarbonate
66
It acts as a buffer to the blood maintaining normal pH.
Bicarbonate
67
The standard test used to measure the filtering capacity of the glomeruli.
Clearance Test
68
Measures the rate at which the kidneys are able to remove (to clear) a filterable substance from the blood.
Clearance Test
69
The substance analyzed for Clearance Test must be one that is neither _____ no _____ by the tubules.
reabsorbed nor secreted
70
Primary substances used in clearance tests?
creatinine, beta2-microglobulin, cystatin C
71
Other info for Clearance Test?
- Stability of substance in urine during 24-hour urine collection
- Consistency of plasma level
- Substances availability to the body
- Availability of tests for analysis of the substance
72
Unit of measurement for Clearance Test?
mL/min
73
Standard method for GFR/Glomerular Filtration Rate?
Urea Clearance Test
74
Clearance test to demonstrate progression of renal disease or response to therapy.
Urea Clearance Test
75
Type of clearance test that do not give reliable estimates of GFR (Approximately 40% of filtered urea is reabsorbed).
Urea Clearance Test
76
It is about 50% of creatinine clearance.
Urea Clearance Test
77
Reference method for GFR/Glomerular Filtration Rate?
Inulin Clearance Test
78
Not routinely done because of the necessity for continuous IV infusion.
Inulin Clearance Test
79
Type of clearance test that have higher values in male due to larger renal mass?
Inulin Clearance Test
80
Priming dose for inulin clearance test?
25 mL of 10% inulin solution
81
Continuous infusion dose for inulin clearance test?
500 mL of 1.5% inulin solution
82
Reference values for inulin clearance test?
127 mL/min (Male), 118 mL/min (Female)
83
Most commonly used; screening method of GFR.
Creatinine Clearance
84
A waste product of muscle metabolism.
creatinine
85
Excellent measurement of renal function – creatinine is freely filtered by the glomerulus but not reabsorbed.
Creatinine Clearance
86
A measure of the completeness of a 24 hour urine collection.
Creatinine Clearance
87
Reference values for creatinine clearance?
85-125 mL/min (Male), 75-112 mL/min (Female)
88
Formula for Creatinine Clearance?
C = UC/PC x UV (mL)/minutes x 1.73/A
UC = URINE CREA; PC = PLASMA CREA; UV = URINE VOLUME; MINUTES = 1440 (mins.); A = Body surface of patient; 1.73 = Standard body surface
89
CCT significance in GFR?
Determines the functional capacity of nephrons
90
Significance of creatinine clearance test?
- Determines the extent of nephron damage in known cases of renal disease
- Monitor the effectiveness of treatment
- Determines the feasibility of administering medications
91
Disadvantage of CCT?
◦ Some Creatinine is secreted by tubule
◦ Chromogens present in human plasma
◦ Some medications causes false decreased value
◦ Creatinine breakdown by some bacteria
◦ Influenced by heavy diet
◦ Interference by muscle wasting disease
92
The approximate amount of plasma filtrate produced per minute is ______.
120 mL
93
Normal creatinine clearance values?
120 mL/min
(men, 107 to 139 mL/min)
(women, 87 to 107 mL/min)
94
The normal reference range of plasma creatinine is ______.
0.5 - 1.5 mg/dL
95
An indirect estimate of GFR; good procedure for screening and monitoring GFR.
Cystatin C
96
A low molecular weight protease inhibitor.
Cystatin C
97
It is completely reabsorbed by the PCT, hence its presence in urine denotes damage to the tubules.
Cystatin C
98
Specimen for Cystatin C?
Serum or plasma (fasting is not required)
99
Increased levels of Cystatin C are seen in what conditions?
Acute & Chronic Renal failure, Diabetic nephropathy
100
Method used for Cystatin C?
Immunoassay
101
Dissociates from human leukocyte antigens at constant rate and is rapidly removed from the plasma by glomerular filtration.
Beta2-Microglobulin
102
A rise in Beta2-Microglobulin has been shown to be a more sensitive indicator of _________ than creatinine clearance.
decrease in GFR
103
Beta2-Microglobulin is not reliable in patients who have?
history of immunologic disorders
104
Method used for Beta2-Microglobulin?
enzyme immunoassay (EIA)
105
Used for routinely screening patients as part of a metabolic profile.
Estimated Glomerular Filtration Rates (eGFR)
106
Used to monitor patients already diagnosed with renal disease or at risk for renal diseas.
Estimated Glomerular Filtration Rates (eGFR)
107
The formulas of this test are valuable when medications that require adequate renal clearance need to be prescribed.
Estimated Glomerular Filtration Rates (eGFR)
108
Most frequently used formula for Estimated Glomerular Filtration Rates (eGFR)?
Modification of Diet in Renal Disease (MDRD)
109
Current formula recommended for Estimated Glomerular Filtration Rates (eGFR)
MDRD-IDMS (Isotope Dilution Mass Spectrometry) traceable formula by the National Kidney Disease Education Program (NKDEP)
110
Enumerate the Glomerular Filtration tests.
- Clearance Test (Urine CT, Inulin CT, Creatinine Clearance Test)
- Estimated Glomerular Filtration Rates
- Cystatin C (Beta 2 Microglobulin)
111
Test measuring the ability of the tubules to reabsorb the essential salts and water that have been nonselectively filtered by glomerulus.
Concentration Test
112
The specific gravity of urine before entering the renal tubules is _____, the specific gravity will vary when the urine _______________ for the reabsorption process.
1.010; enters the renal tubules
113
2 methods of concentration test to measure specific gravity?
1. Fishberg Test
2. Mosenthal Test
114
Patients were deprived of fluids for 24 hours prior to measuring specific gravity.
Fishberg Test
115
Compare the volume and specific gravity of urine of day and night urine samples.
Mosenthal Test
116
It measures only the number of particles in a solution.
Osmolality
117
It is influenced by the number and density (molecular weight) of the particles.
Specific Gravity
118
It is concerned with small particles, primarily sodium and chloride molecules.
Renal concentration
119
These do not contribute to the evaluation of renal concentration.
Large molecular-weight molecules such as glucose and urea
120
It is performed for a more accurate evaluation of renal concentrating ability.
Osmolality
121
2 types of osmometers used for measuring osmolality?
1. Freezing Point Osmometers
2. Vapor Pressure Osmometers
122
Principle of Freezing Point Osmometers?
Measurement of freezing point depression
123
Temperature at which water and ice are in equilibrium and is related to solute concentration.
Freezing point
124
Standard reference for Freezing Point Osmometers?
NaCl
125
Principle of Vapor Pressure Osmometers?
Measurement of dew point
126
Temperature at which water vapor condenses to a liquid.
dew point
127
Standard reference for Vapor Pressure Osmometers?
NaCl
128
Enumerate the Tubular Reabsorption Tests.
- Concentration Test (Specific Gravity; Fishberg & Mosenthal)
- Osmolality (Freezing Point and Vapor Pressure Osmometers)
129
Tests to measure tubular secretion of nonfiltered substances and renal blood flow.
Tubular Secretion and Renal Blood Flow Tests
130
Test most commonly associated with tubular secretion and renal blood flow.
p-aminohippuric acid (PAH) test
131
The ability of the kidney to produce an acid urine depends on the tubular ___________ and ___________ by the cells of the distal convoluted tubule.
secretion of hydrogen ions; production and secretion of ammonia
132
A normal person excretes approximately 70 mEq/day of acid in the form of _____, _____, or _____.
- titratable acid (H+)
- hydrogen phosphate ions (H2PO4–)
- ammonium ions (NH4+)
133
A normal person excretes approximately _____ of acid.
70 mEq/day
134
In normal persons, a diurnal variation in urine acidity consisting of alkaline tides appears shortly after arising and postprandially at approximately what times?
2 p.m. and 8 p.m.
135
At what time of day is the pH lowest?
at night
136
The inability to produce an acid urine in the presence of metabolic acidosis.
renal tubular acidosis
137
Renal tubular acidosis may result from ______________ associated with the proximal convoluted tubule or ______________ associated with the distal convoluted tubule.
impaired tubular secretion of hydrogen ions; defects in ammonia secretion
