Renal Flashcards
1
Q
Kidneys are primarily responsible for..
A
maintaining the stability of ECF volume, water and electrolyte composition, blood pressure and osmolarity
2
Q
Kidneys are main route for..
A
eliminating potentially toxic substances, metabolic wastes, and foreign compounds from the body
3
Q
Kidney functions
A
- maintain water, salt and electrolytes balance in the body by urinary output e.g. maintain surplus and deficit for ECF constituents
- maintain the proper osmolarity of body fluids; primarily through regulating water balance (prevents disruption is osmosis)
- regulate and maintain the quantity and concentration of most ECF ions (Na+, Cl-, K+, HCO3-, Ca2+, Mg+, SO4-, PO4-2) e.g. minor changes in ECF K+ lead to fetal cardiac arrest or dysfunction
- maintain proper plasma volume to regulate long-term blood pressure
- help maintain proper acid-base balance in the body (urinary output of H+ and HCO-3) e.g. high H+= blood acidic= acidosis.
- excretion of the end products (wastes) of bodily metabolism e.g. urea, uric acid and creatinine
- excreting many foreign compounds (drugs, pesticides, food additives and other non-nutritive materials)
- produce erythropoietin to regulate RBC production
- produce renin (kidney enzyme) that triggers RAAS, important in salt conservation by the kidneys
- converting vitamin D into its active form (Calcitriol)
4
Q
Kidneys
A
- urine-forming organs
- located in the back of the abdominal cavity, each kidney is supplied with a renal artery and a renal vein
- acts on plasma flowing through it to produce urine
5
Q
Structures that carry urine from the kidneys to the outside for elimination from the body
A
- ureters
- urinary bladder
- urethra
6
Q
The outer surface of the kidney is called the __ __, the inner surface is the __ ___
A
The outer surface of the kidney is called the renal cortex, the inner surface is the renal medulla
7
Q
Formed urine drains into the __ __, located at the medial inner core of each kidney
A
Formed urine drains into the renal pelvis, located at the medial inner core of each kidney
8
Q
Ureters
A
- smooth muscle-walled duct
- exits each kidney at the medial border near renal artery and vein
- carry urine to the urinary bladder
9
Q
Urinary bladder
A
- temporarily stores urine
- periodically empties to the outside of the body through the urethra
10
Q
Urethra
A
- conveys urine to the outside of the body
- urethra is straight and short in females
- in males: longer and follows curving course from bladder to outside
11
Q
Dual function of the urethra
A
- provides route for eliminating urine from bladder
- passageway for semen from reproductive organs
12
Q
Nephron
A
- the functional unit of the kidney
- the smallest unit that can perform all the functions of the kidney
- approx. 1 million nephrons/kidney
- arrangement of nephrons gives rise to 2 distinct regions: outer region, inner region
13
Q
Outer region of nephron
A
renal cortex (granular in appearance)
14
Q
Inner region of nephron
A
renal medulla, made up of striated triangles called renal pyramids
15
Q
Parts of a nephron: vascular components
A
afferent arteriole, glomerulus, efferent arteriole, peritubular capillaries
16
Q
Parts of a nephron: tubular components
A
bowman’s capsule, proximal tubule, loop of Henle, distal tubule and collecting duct
17
Q
Afferent arteriole
A
carries blood to the glomerulus
18
Q
Glomerulus
A
a tuft of capillaries that filters a protein-free plasma into the tubular component
19
Q
Efferent arteriole
A
carries blood from the glomerulus
20
Q
Peritubular capillaries
A
supply the renal tissue; involved in exchanges with the fluid in the tubular lumen
21
Q
Bowman’s capsule
A
collects the glomerular filtrate
22
Q
Proximal tubule
A
uncontrolled reabsorption and secretion of selected substances occur here
23
Q
Loop of Henle
A
establishes an osmotic gradient in the renal medulla that is important in the kidney’s ability to produce urine of varying concentrations
24
Q
Distal tubule and collecting duct
A
variable, controlled reabsorption of sodium and water and secretion of potassium and hydrogen occur here; fluid leaving the collecting duct is urine, which enters the renal pelvis
25
Combined vascular/tubular component
Juxtaglomerular apparatus: produces substances involved in the control of kidney function
26
Each nephron consists of 2 components
vascular and tubular components
27
Vascular component
- ball-like tuft of capillaries (glomeruli)
- water and solutes are filtered through the glomerulus as blood passes through it--> the filtered fluid then passes through the nephron's tubular component
- From the renal artery inflowing blood passes through afferent arterioles, which deliver blood to the glomerulus
- Efferent arteriole transports blood from the glomerulus
- Efferent arteriole breaks down into peritubular capillaries, which surround the tubular part of the nephron
- Peritubular capillaries join into venules which transport blood into the renal vein
28
2 types of nephrons
cortical and juxtamedullary
29
Cortical nephrons
lie in the outer layer of the cortex, 80% of nephrons
30
Juxtamedullary nephrons
lie in the inner layer of the cortex, performs most urine concentration
31
3 basic renal processes
glomerular filtration, tubular reabsorption, tubular secretion
32
Structures involved in glomerular filtration
glomerulus, bowman's capsule
33
Structures involved in tubular reabsorption
renal tubule (proximal, loop of Henle, distal), peritubular capillaries
34
Structures involved in tubular secretion
peritubular capillaries, renal tubule
35
Glomerular filtrate
filtrate protein free-plasma
36
Tubular reabsorption
- absorb nutrients, ions, and electrolytes from kidney tubules into peritubular capillaries
- all plasma constituents, except plasma proteins are at the same concentration in the glomerular filtrate (urine) as in the plasma
- the quantity of each reabsorbed material is the amount required to maintain the proper composition and volume of the ECF
- the tubules have a high absorptive capacity for substances needed by the body and little or no capacity for substances of no value
- only excess amounts of essential electrolytes are excreted in the urine
- the absorptive capacity may vary depending on the body's needs
- as the water and other valuable constituents are reabsorbed, the waste products remaining in the tubular fluid become highly concentrated, producing concentrated, less volume and yellowish urine
37
Tubular secretion
movement of non-filtered substances from peritubular capillaries into the kidney tubules
38
Fluid filtered from the glomerulus into Bowman's capsule passes through 3 layers of the glomerular membrane ...
1) Glomerular capillary wall
2) Basement membrane
3) The inner layer of Bowman's capsule
39
Glomerular capillary wall
- a single layer of endothelial cells
- more permeable to water and solutes than capillaries elsewhere in the body
40
Basement membrane
- acellular gelatinous layer
- composed of collagen and glycoproteins (discourage the filtration of small proteins)
41
Inner layer of Bowman's capsule
consists of podocyte foot processes that encircle the glomerulus tuft
42
Glomerular capillary blood pressure
- the pressure exerted by the blood within glomerular capillaries
- 55 mm Hg
- major force producing glomerular filtration- favors filtration
43
Glomerular capillary blood pressure depends on...
- contraction of the heart
- resistance to blood flow offered by afferent and efferent arterioles
- the smaller diameter of efferent arteriole
44
Forces involved in glomerular filtration
glomerular capillary blood pressure, plasma-colloid osmotic pressure and bowman's capsule hydrostatic pressure
45
Plasma-colloid osmotic pressure
- caused by the unequal distribution of plasma proteins across glomerular membrane (by osmosis)
- opposes filtration
- 30 mmHg
46
Bowman's capsule hydrostatic pressure
- pressure exerted by fluid in the initial part of the tubule
- tends to push fluid out of Bowman's capsule
- opposes filtration
- 15 mmHg
47
Forces involved in glomerular filtration that FAVOUR filtration
glomerular capillary blood pressure and net filtration pressure (GFR)
48
Forces involved in glomerular filtration that OPPOSE filtration
plasma-colloid osmotic pressure and bowman's capsule hydrostatic pressure
49
Glomerular filtration rate (GFR)
- the net (total force) difference favouring glomerular filtrate
= glomerular capillary blood pressure - (plasma-colloid osmotic pressure + Bowman's capsule hydrostatic pressure)
50
Glomerular filtrate rate (GFR) depends on..
- net filtration pressure
- glomerular surface area available for penetration
- permeability of the glomerular membrane
51
Blood flow and GFR when resistance is high in afferent arteriole
less blood flow into glomerulus, decreased GFR
52
Blood flow and GFR when resistance is low in afferent arteriole
more blood flow into glomerulus, increased GFR
53
Autoregulation
- prevents spontaneous changes in GFR
- automatically adjusted without knowledge
- myogenic mechanism
- tubuloglomerular feedback (TGF)
54
Mechanisms that regulate GFR and how they both do that
- autoregulation and extrinsic sympathetic NS
- they are directed towards adjusting glomerular blood flow by regulating caliber/diameter and resistance in the afferent arterioles
55
Extrinsic sympathetic NS
- regulates long-term blood pressure regulation
- mediated by sympathetic nervous system input to afferent arterioles
- baroreceptor reflex
56
If plasma colloid osmotic pressure and bowman's capsule hydrostatic pressure remains constant, GFR is ...
directly proportional to an increase in arterial blood pressure i.e. increase in afferent arterial BP= increase GFR, decrease in afferent arterial BP= decrease GFR
57
An increased GFR due to increased arterial pressure and net filtration pressure, can be normalized by ___ which will decrease blood flow into the glomerulus bringing the GFR back down
An increased GFR due to increased arterial pressure and net filtration pressure, can be normalized by vasoconstriction which will decrease blood flow into the glomerulus bringing the GFR back down
58
A decreased GFR due to decreased arteriolar pressure and net filtration pressure, can be normalized by ___ which will increase blood flow into the glomerulus bringing the GFR back up
A decreased GFR due to decreased arteriolar pressure and net filtration pressure, can be normalized by vasodilation which will increase blood flow into the glomerulus bringing the GFR back up
59
Intra-renal mechanisms of autoregulation
myogenic and tubuloglomerular feedback mechanism
60
Myogenic autoregulation
refers to the properties of arteriolar vasculature
(1) smooth muscles stretch automatically
(2a) if afferent arteriole's smooth muscle constricts= decrease blood to glomerulus= decrease GFR
(2b) if afferent arteriole's smooth muscle relax= increase blood to glomerulus= increase GFR
61
Purpose of juxtaglomerular apparatus
- tubuloglomerular mechanisms are initiated by the tubules to help each nephron regulate the rate of filtration through its own glomerulus
- it prevents dangerous imbalances of fluid, electrolytes and wastes
62
Extrinsic control of the GFR
- sympathetic nervous system (can override the autoregulatory responses)
- baroreceptors
- filtration coefficient
63
Parasympathetic NS does/does not exert any influence on the kidneys
DOES NOT
64
The rate of glomerular filtration depends on..
filtration coefficient and net filtration pressure
65
filtration coefficient (KF) depends on..
surface area and the permeability of the glomerular membrane
66
Podocytes and permeability of glomerular membrane
- contraction and relaxation of podocytes with foot processes increase or decrease the filtration slits in the inner membrane
- the number of slits determines the permeability; the more slits open, the greater the permeability
67
Transepithelial transport
involves the transfer of substances from the kidney/renal tubular lumen into peritubular capillaries
68
To be reabsorbed (move from the filtrate to the plasma i.e. transepithelial transport), a substance must transverse 5 distinct barriers...
1. the luminal cell membrane
2. the cytosol
3. the basolateral cell membrane
4. the interstitial fluid
5. the capillary wall
69
The 2 mechanisms to transport material across the tubules
passive and active
70
Passive transport
- no energy required
- substances move down the electrochemical and osmotic gradients (H--> L)
71
Active transport
- ATP used as an energy source
- substances move against the electrochemical gradient (L--> H_
- e.g. glucose, amino acids, sodium, potassium, chloride, electrolytes and phosphate
72
The average percentage of filtered substance reabsorbed/ excreted: Water
Reabsorbed= 99% (210 L/day)
Excreted= 1%
73
The average percentage of filtered substance reabsorbed/ excreted: Sodium
Reabsorbed= 99.5% (160g/day)
Excreted= 0.5%
74
The average percentage of filtered substance reabsorbed/ excreted: Glucose
Reabsorbed= 100% (1Kg/day)
Excreted= 0% (cannot afford to lose glucose, if >0 then diabetes/pancreas failed to produce insulin)
75
The average percentage of filtered substance reabsorbed/ excreted: Urea (a waste toxic product)
Reabsorbed= 50%
Excreted= 50%
76
Water reabsorption in the proximal tubule
- out of 125 ml/min of plasma filtered, 124 ml/min plasma is reabsorbed (99% reabsorption), leaving only 1ml/min of plasma filtered and become part of the urine
- water channels are always open in proximal tubules. However, water channels in the distal tubules of the nephron are regulated by the hormone vasopressin/ADH
77
Sodium reabsorption
- An active Na+- K+ ATPase pump in basolateral membrane is essential for Na+ reabsorption
- Of the total energy spent by kidneys, 80% is used for Na+ transport
- Na+ is not reabsorbed in the descending limb of the loop of henle
- water follows reabsorbed sodium by osmosis which has the main effect on blood volume and blood pressure
78
Tubule area: proximal tubule
% of Na+ reabsorbed: ___
Role of Na+ reabsorption: ____
% of Na+ reabsorbed: 67%
Role of Na+ reabsorption: Plays role in reabsorbing glucose, amino acids, water, chloride, and urea
79
Tubule area: ascending limb of the loop of Henle
% of Na+ reabsorbed: ___
Role of Na+ reabsorption: ____
% of Na+ reabsorbed: 25%
Role of Na+ reabsorption: Plays critical role in kidneys' ability to produce urine of varying concentrations
80
Tubule area: distal and collecting tubules
% of Na+ reabsorbed: ___
Role of Na+ reabsorption: ____
% of Na+ reabsorbed: 8%
Role of Na+ reabsorption: Variable and subject to hormonal control; plays role in regulating ECF volume
81
Glucose and amino acids reabsorption
- are reabsorbed back into the blood by energy and sodium-dependent mechanisms in the proximal tubules
- use secondary active transport by using co-transport carrier molecules within proximal tubules
- co-transport molecules simultaneously transport glucose and amino acids from the lumen to blood and vice-versa
82
Filtered load of glucose
100 mg/100 ml X 125 ml/min= 125 mg/min
doubling plasma glucose: 200mg/100ml X 125 ml/min= 250 mg/min
- at constant GFR, the filtered load of glucose is directly proportional to the plasma glucose concentration
83
Filtered load of a substance
plasma concentration x GFR
84
The tubular maximum (Tm) for glucose
- when the maximum reabsorption rate is reached, and when all carriers specific for a particular substance are fully "occupied/saturated", they cannot handle any additional glucose at that time
- Tm for glucose is 375 mg/min
- if more glucose is absorbed than it is filtered, this will happen when,
1. Tm will exceed above 375 mg/100ml
2. Plasma glucose concentration must not exceed more than 375 mg/100ml
3. It will spill into the urine
85
Reabsorption moves solutes from the ____ to the ___. Secretion moves solutes from the ___ to the ___
Reabsorption moves solutes from the lumen of the tubule to the blood. Secretion moves solutes from the blood to the lumen of the tubule
86
Passive reabsorption of urea at the end of the proximal tubule
- reabsorption of sodium in the proximal tubules follow water
- this reduces the original filtrate from 125 ml/min to only 44 ml/min at the end of the proximal tubule (i.e. 81 ml/min water is reabsorbed)
- sodium and water create the concentration gradient for urea to be passively diffused from the tubular lumen into the peritubular capillary plasma
87
One of the first chemical characteristics identified in the plasma of a patient with severe renal failure
elevated urea level
88
Tubular secretion
- transfer of substances from the peritubular capillaries into the kidney/renal tubules
- involves transepithelial transport but reversed
- provides a "second" route of entry into the tubule for selected substances (saves you from cardiac arrhythmia and hyperkalemia)
- includes: hydrogen, potassium, organic anions and cations (all of which escaped filtration (glomerular filtration) and are in high quantity in the peritubular capillary )
89
The most important secretory systems are for ..
hydrogen, potassium and organic ions
90
Hydrogen
- important in regulating acid-base balance
- secreted in proximal, distal and collecting tubules
91
Potassium
- keep plasma potassium concentration at an appropriate level to maintain normal membrane excitability in muscles and nerves
- secreted only in the distal and collecting tubules under the control of aldosterone
92
Organic ions
- accomplish more efficient elimination of foreign organic compounds from the body
- secreted only in the proximal tubule
93
Potassium is selectively reabsorbed in the __ tubules and is secreted in __ and __ tubules
Potassium is selectively reabsorbed in the proximal tubules and is secreted in distal and collecting tubules
94
Dual control of aldosterone secretion of potassium and sodium
(1) decrease sodium/decrease ECF volume/decrease arterial pressure
(2) increase renin
(3) increase angiotensin I
(4) increase angiotensin II
(5) stimulates aldosterone secretion
(6) increases tubular sodium reabsorption and decreases urinary sodium excretion
OR
(1) increase plasma potassium
(2) stimulates aldosterone secretion
(3) increases tubular potassium secretion and increases urinary excretion
95
Isotonic
solute concentration is equal to the water concentration
96
Hypotonic
otherwise known as the body fluid being dilute (dilute urine), happens when more water is present than the solute load
97
Hypertonic
otherwise known as the body fluid being too concentrated (concentrated urine), happens when there is less water than solute load
98
Excretion of urine in the face of water deficit
- vasopressin present: distal and collecting tubules permeable to water (allows water to leave)
- small volume of concentrated urine excreted, reabsorbed water picked up by peritubular capillaries and conserved for body
99
Excretion of urine in the face of water excess
- no vasopressin present: distal and collecting tubules impermeable to water (water doesn't leave)
- large volume of dilute urine, no water reabsorbed in distal portion of nephron, excess water eliminated
100
Countercurrent multiplication
passive exchange of solutes and water between the two limbs of the loop of henle
101
Descending vs ascending limbs of the Loop of Henle
- Descending limb is highly permeable to water but does not extrude (force out) sodium for reabsorption
- Ascending limb actively transports NaCl out of the tubular lumen into the surrounding interstitial fluid. It is impermeable to water. Therefore, water does not follow the salt by osmosis
102
Mechanism of action of vasopressin
- vasopressin-controlled variable water reabsorption occurs in the final tubular segments
- 65% of water reabsorption is obligatory in the proximal tubule. In the distal tubule and collecting it is variable based on the secretion of ADH/vasopressin
- the secretion of vasopressin increases the permeability of the tubule cells to water. An osmotic gradient exists outside the tubules for the transport of water by osmosis
- water deficit increases vasopressin release and more water reabsorbed
- excess water, decreases vasopressin release, and more water is released in urine
103
Effect of vasopressin/ADH on distal tubules and collecting tubules
posterior pituitary --> vasopressin/ADH --> blood --> kidney --> water
^controlled by negative feedback
104
Functions of renin-angiotensin-aldosterone system (RAAS)
1. aldosterone increases reabsorption in distal and collecting tubules
2. promotes salt retention and resultant water retention and elevation of arterial blood pressure
3. angiotensin-II is a potent constrictor of the systemic arterioles, thus increasing blood pressure and peripheral resistance
4. it also stimulates thirst and vasopressin release
105
Angiotensinogen
a plasma protein synthesized by
the liver, always present in the plasma in high concentration
106
Source and role of renin
source: kidney
role: acts as an enzyme to activate angiotensinogen into angiotensin I
107
Role of angiotensin I
On passing through the lungs via the pulmonary circulation, angiotensin I is converted into angiotensin II by
angiotensin-converting enzyme (ACE), which is abundant in
the pulmonary capillaries
108
Angiotensin II
Angiotensin II is the main stimulus
for secretion of the hormone aldosterone from the adrenal
cortex
109
Source and role aldosterone
Source: adrenal cortex
role: stimulates Na+ reabsorption by the kidneys. The resulting retention of Na+ exerts an osmotic effect that holds more H2O in the ECF. Together, the conserved Na+ and H2O help
correct the original stimuli that activated this hormonal system (low sodium/low ECF volume, low arterial blood pressure)
110
Aldosterone vs Vasopressin
Vasopressin: opens all water channels, recruits more water channels-- increases permeability and water reabsorption to prevent dehydration
Aldosterone: increases sodium reabsorption, passively reabsorbs water
111
What is NOT a function of the kidneys?
a. excretion of metabolic wastes
b. maintaining proper plasma volume
c. secreting aldosterone to regulate sodium
d. maintaining proper osmolarity of body fluids
C
112
What is the specialized nephron capillary bed where filtration occurs?
a. afferent arteriole
b. efferent arteriole
c. glomerulus
d. peritubular bed
C
113
Below is a listing of nephron components and associated structures:
1. descending limb of loop of Henle
2. Bowman's capsule
3. collecting tubule
4. ascending limb of loop of Henle
5. distal tubule
6. proximal tubule
What is the correct flow of filtrate through these structures?
a. 4,6,5,3,2,1
b. 2,6,1,4,5,3
c. 2,5,6,3,1,4
d. 3,2,6,1,4,5
B
114
Which nephron structure is especially important in the kidney's ability to produce urine of varying concentration?
a. Bowman's capsule
b. proximal tubule
c. distal tubule
d. loop of Henle
D
115
Which of the following is true about blood that flows through the kidneys?
a. normally about 20-25 percent of the total cardiac output
b. all filtered through the glomeruli
c. all used to supply the renal tissue with oxygen and nutrients
d. normally about 40% percent of the total cardiac output
A
116
Which statement is correct concerning glomerular filtrate?
a. it is a plasma-free blood
b. it is formed as a result of passive forces acting across the glomerular membrane
c. it does not contain foreign compounds because these substances are secreted by special transport mechanisms in the proximal tubule instead
d. its rate is increased by increased plasma protein level
B and C
117
The glomerular capillary blood pressure in the nephron is 78 mm Hg. The Bowman’s capsular hydrostatic pressure is 24 mm Hg. The colloidal osmotic pressure is 18 mm Hg. What is the net filtration pressure?
a. 18 mm Hg
b. 26 mm Hg
c. 36 mm Hg
d. 42 mm Hg
C
118
Which factor would reduce the net filtration pressure the most?
a. vasodilation of the afferent arteriole
b. vasocontraction of the efferent arteriole
c. It has a large increase in blood colloid osmotic pressure
d. It has a low capsular hydrostatic pressure
C
119
Which statement concerning the process of glomerular filtration is correct?
a. Bowman’s capsule hydrostatic pressure opposes filtration.
b. The glomerular filtration rate is limited by a Tm.
c. All of the plasma that enters the glomerulus is filtered.
d. All of the plasma that enters the glomerulus is reabsorbed.
A
120
What is NOT involved in autoregulation of the GFR?
a. a myogenic mechanism in which the afferent arteriole automatically constricts when it is stretched
b. a tubuloglomerular feedback mechanism in which vasoactive chemicals released from the juxtaglomerular apparatus bring about afferent arteriolar vasoconstriction
c. sympathetically induced vasoconstriction of the afferent arterioles
C
121
Afferent arteriolar vasoconstriction _____ blood flow into the glomerulus, which causes the glomerular-capillary blood pressure to _____, leading to a(n) _____ in the net filtration pressure and a resultant _____ in the GFR.
a. increases, increase, increase, increase
b. decreases, decrease, decrease, decrease
c. increases, increase, decrease, decrease
d. decreases, decrease, increase, increase
B
122
What occurs after stimulation of the macula densa cells?
a. vasodilation of the afferent arteriole
b. vasoconstriction of the afferent arteriole
c. increased GFR
d. secretion of erythropoietin
B
123
When arterial blood pressure is elevated above normal, which compensatory change in renal function occurs as a result of the baroreceptor reflex?
a. afferent arteriolar vasoconstriction
b. afferent arteriolar vasodilation
c. reduction in GFR
d. efferent arteriolar vasoconstriction
B
124
Which statement is NOT true concerning tubular reabsorption?
a. It refers to the movement of a substance from the peritubular capillary blood into the tubular fluid.
b. It occurs by either active or passive transport.
c. It involves the process of transepithelial transport.
A
125
Which statement is NOT a step in transepithelial transport?
a. movement of the substance through the cytosol of the tubular cell
b. movement of the substance across the glomerular capillary wall
c. movement of the substance across the luminal membrane of the tubular cell
d. movement of the substance through the interstitial fluid
B
126
Why is glucose NOT normally found in the urine?
a. Glucose does not get filtered out of glomerulus.
b. Glucose is not found in the blood.
c. Glucose is usually reabsorbed by renal tubule cells.
d. Glucose is kept in the blood.
C
127
Which statement regarding the proximal tubule is NOT true?
a. It reabsorbs about 65 percent of the filtered water.
b. It is the site of action of renin.
c. It is the location where glucose is reabsorbed.
B
128
Which statement regarding tubular maximum (Tm) is NOT true?
a. It is the maximum amount of a substance that the tubular cells can actively transport within a given time period.
b. It is the maximum rate at which a substance is filtered at the glomerulus.
c. It occurs when the membrane carrier becomes saturated.
B
129
Which plasma constituent is NOT regulated by the kidneys?
a. Glucose
b. Na+
c. H+
d. Phosphate
D
130
What is the major waste product of nitrogen metabolism?
a. plasma proteins
b. Urea
c. Glucose
d. amino acids
B
131
Given the following data for substance X (GFR = 125 mL/min, Tm = 125 mg/min, at a plasma concentration of 200 mg/100 mL), how much of substance X is filtered, reabsorbed, and excreted?
a. 125 mg/min filtered, 125 mg/min reabsorbed, 0 mg/min excreted
b. 200 mg/min filtered, 125 mg/min reabsorbed, 75 mg/min excreted
c. 250 mg/min filtered, 125 mg/min reabsorbed, 125 mg/min excreted
d. 250 mg/min filtered, 200 mg/min reabsorbed, 50 mg/min excreted
C
132
Which statement about Na+ reabsorption is INCORRECT?
a. It uses 80 percent of the energy requirement of the kidney.
b. It is under control of the hormone aldosterone in the distal portions of the nephron.
c. It is not linked to the reabsorption of amino acids and urea.
C
133
What happens when blood volume becomes abnormally low?
a. Sodium reabsorption is diminished.
b. Dilute urine is formed.
c. Renin catalyzes the conversion of angiotensinogen.
d. Aldosterone is secreted by the kidney.
C
134
What is the energy required for glucose reabsorption used for?
a. to run the Na+–K+ ATPase pump
b. to run the Na+-glucose co-transport carrier
c. to maintain the Tm for glucose
d. to produce aldosterone-induced protein, which increases the permeability of the proximal tubular cells to glucose
A
135
What are the distal and collecting tubules the site of?
a. the co-transport carriers for glucose and amino acid reabsorption
b. the organic ion secretory systems
c. aldosterone and vasopressin action
d. glucose reabsorption
C
136
Which statement regarding tubular secretion is NOT true?
a. It involves transepithelial transport.
b. It is the movement of a substance from the peritubular capillary blood into the tubular fluid.
c. It always occurs by active transport.
d. a and b.
C
137
Which statement with regards to plasma clearance is correct?
a. It is the time required to filter blood in the glomerulus.
b. It is the amount of a substance appearing in the urine in one minute.
c. It is the amount of a substance filtered in one minute.
d. It is the volume of plasma that is completely cleared of a substance by the kidneys in one minute.
D
138
What establishes the medullary vertical osmotic gradient by means of countercurrent multiplication?
a. loops of Henle of juxtamedullary nephrons
b. loops of Henle of cortical nephrons
c. vasa recta of juxtamedullary nephrons
d. vasa recta of cortical nephrons
A
139
Which of the following is true about the ascending limb of the loop of Henle?
a. NaCl passively leaves the tubular fluid down its concentration gradient.
b. NaCl is actively transported into the interstitial fluid, leaving water behind because the tubular cells are not permeable to water.
c. K+ is secreted.
d. aldosterone stimulates Na+ reabsorption.
B
140
Which statement with regards to vasopressin is correct?
a. It can completely halt urine production during periods of water deprivation to conserve water for the body.
b. It activates the cyclic AMP second-messenger system within the tubular cells.
c. It renders the distal and collecting tubules impermeable to water.
d. It increases Na+ reabsorption by the distal portions of the nephron.
B
141
What enable the kidneys to produce urine of varying concentrations and volumes depending on the body’s needs?
a. Na+–K+ ATPase pump and co-transport carriers
b. juxtaglomerular apparatus and vasa recta
c. podocytes and peritubular capillaries
d. medullary vertical osmotic gradient and vasopressin
D
142
What happens when the bladder of an infant is filled with urine?
a. Stretch receptors in the bladder wall are inhibited.
b. Parasympathetic nerve supplying the bladder is inhibited, allowing the bladder to relax.
c. A motor neuron supplying the external urethral sphincter is stimulated, causing the sphincter to open.
d. A motor neuron supplying the external urethral sphincter is inhibited, allowing the sphincter to open.
D
143
True/False: The kidneys are the organs that are primarily responsible for maintaining constancy of the volume and electrolyte composition of the internal fluid environment.
True
144
True/False: The afferent arteriole is the blood vessel that carries blood to the glomerular capillaries.
True
145
True/False: Glomerular filtration occurs primarily by active transport
False
146
True/False: The glomerular filtrate is almost identical in composition to the plasma
True
147
True/False: The glomerular filtrate contains only substances that are not needed by the body.
False
148
True/False: If a kidney stone blocked the renal pelvis and consequently caused a buildup of fluid pressure in the tubules and Bowman’s capsule, the net filtration pressure across the glomerular capillary membrane would increase.
False
149
True/False: The pores in the glomerular membrane are too small for albumin to pass through.
False
150
True/False: Contraction of mesangial cells closes off a portion of the filtering capillaries, which leads to a decrease in GFR if the filtration pressure remains unchanged.
True
151
True/False: Transepithelial transport occurs only for substances that are actively reabsorbed
False
152
True/False: The amount of glucose reabsorbed is directly proportional to the plasma glucose concentration at all plasma glucose concentrations.
False
153
True/False: The secretion of aldosterone stimulates the tubular reabsorption of sodium and the tubular secretion of potassium.
True
154
True/False: Water reabsorption cannot occur from any portion of the nephron in the absence of vasopressin.
False
155
True/False: Angiotensinogen is produced by the kidney.
False
156
True/False: A plasma clearance of 135 mL/min for a substance when the GFR is 125 mL/min indicates that net secretion of the substance occurs.
True
157
True/False: In the tubular segments permeable to H2O, solute reabsorption is always accompanied by comparable H2O reabsorption
True
158
True/False: When tubular fluid enters the distal tubule, it is hypotonic
True
159
True/False: A pure loss or gain of H2O that is not accompanied by comparable solute deficit or excess in the body leads to changes in ECF osmolarity.
True
160
The functional unit of the kidneys is the ____________________.
nephron
161
Tubular ____________________ and tubular ____________________ are selective processes that occur in the nephron
reabsorption, secretion
162
The specialized cells of the ____________________ within the ____________________ detect changes in the rate at which fluid is flowing past them through the tubule. In response, they secrete vasoactive chemicals that influence the GFR by making adjustments in the calibre of the ____________________ arterioles. This is known as the ____________________ feedback mechanism.
The specialized cells of the macula densa within the juxtaglomerular apparatus detect changes in the rate at which fluid is flowing past them through the tubule. In response, they secrete vasoactive chemicals that influence the GFR by making adjustments in the calibre of the afferent arterioles. This is known as the tubulo-glomerular feedback mechanism.
163
If the plasma concentration of substance X is 200 mg/100 mL and the GFR is 125 mL/min, the filtered load of this substance is ____________________.
250 mg/min
164
On average, of the 125 mL/min of plasma filtered, ____________________ mL/min is reabsorbed, and ____________________ mL/min is excreted as urine.
124 mL/min, 1 mL/min
165
____________________ percent of the filtered H2O is variably reabsorbed under the control of the hormone ____________________ in the distal and collecting tubules
20%, vasopressin/ADH
166
Two means by which substances can enter the renal tubules are ____________________ and ____________________. Two means by which substances can leave the kidney tubules are ____________________ and ____________________.
Two means by which substances can enter the renal tubules are glomerular filtration and tubular secretion. Two means by which substances can leave the kidney tubules are tubular reabsorption and urine excretion.
167
Match the renal function with the correct characteristic by using the answer code:
a. movement of substances from the peritubular capillary blood into the tubular lumen
b. movement of substances from the glomerular capillary blood into the tubular lumen
c. everything filtered or secreted that is not subsequently reabsorbed
d. movement of substances from the tubular lumen into the peritubular capillary blood
1. glomerular filtration
2. tubular reabsorption
3. tubular secretion
4. urine excretion
1. B
2. D
3. A
4. C
