Kidney and Urinary EXAM III Flashcards
(148 cards)
1
Q
Where are the kidneys located?
A
retroperitoneal (towards the back)
located at the level of the 2nd to 4th lumbar vertebrae.
2
Q
Describe the blood supply to and from the kidneys.
A
the renal arters are specific branches off of the abdominal aorta.
The renal veins go to the inferior vena cava.
3
Q
Describe the weight of the kidney.
A
1% of the total body weight.
4
Q
How much cardiac output does the kidney receive?
A
20-25%
5
Q
What is the kidney covered by?
A
a fibrous capsule.
6
Q
What is the hilus?
A
The location where the renal artery, renal vein, and ureter attach.
7
Q
What is the renal cortex?
A
the outer layer of the kidney
8
Q
What is the renal medulla?
A
the inner layer of the kidney made up of renal pyramids.
9
Q
What is a nephron?
A
the function unit of the kidney. The smallest unit of the kidney that contains function.
10
Q
What is the glomerulus?
A
a ball shaped capillary bed located in the renal cortex.
11
Q
What are afferent arterioles?
A
bring blood into the kidneys, an dinto the glomerulus.
12
Q
What are efferent arterioles?
A
carries blood away from the glomerulus, yet parallels the tubular system.
13
Q
What is filtrate?
A
not urine, can still be modified.
Becomes urine once it enters the renal pelvis.
14
Q
What does dilation of afferent arteriole cause?
A
increased volume in glomerulus–>increased hydrostatic pressure–>filtration.
15
Q
What are peritubular capillaries?
A
tiny blood vessels that travel alongside nephrons allowing reabsorption and secretion between blood and the inner lumen of the nephron.
16
Q
In medullary nephrons, what are the peritubular capillaries called?
A
vasa recta.
17
Q
What does the Bowman’s capsule allow for?
A
increased SA.
18
Q
Describe the anatomy of bowman’s capsule.
A
surrounds the glomerulus.
has podocytes that wrap around the glomerulus
between the capillaries and podocytes is a basement membrane.
the spaces between the podocytes form the filtration slits.
the glomerular endothelium has extensive pores.
19
Q
What is the proximal tubule?
A
carries glomerular filtrate away from the glomerulus.
20
Q
What is the difference between juxtamedullary nephron and cortical nephrons?
A
the cortical nephrons only slightly enter the medulla, whereas juxtamedullary nephrons plunge into the medulla in order to be able to concentrate urine.
21
Q
What percentage of nephrons are juxtamedullary?
A
20%
22
Q
Where does the ascending limb of the loop of henle travel?
A
back up towards the cortex.
23
Q
What percentage of nephrons are cortical?
A
80%
24
Q
What are medullary pyramids composed of?
A
juxtamedullary loops of Henle and collecting ducts.
25
What do corticol nephrons function for?
not used to concentrate urine, help with solute movement and retention.
26
What is the function of the distal tubule?
receives filtrate from the loop of henle
27
what is the function of the collecting ducts?
to transport filtrate to the renal pelvis.
28
What does it mean that the endothelium of glomerular capillaries is fenestrated?
has holes or pores.
29
Describe the basement membrane.
noncellular--has a slight negative charge. This charge repels large, negatively charged protein molecules and prevents their loss in the urine.
30
What is the function of podocytes?
to form filtration slits that help control the size of the particles that can escape from circulation to the filtrate.
31
Describe the permeability of the filtration slits.
100X more permeable to water than other capillaries.
32
Describew glomerular capillary blood pressure.
favors filtration
| 55mmHg.
33
Describe plasma-colloid osmotic pressure
opposes filtration
| 30mmHG.
34
Describe Bowman's capsule hydrostatic pressure.
opposes filtration.
15mmHg.
a fluid pressure that is formed by the fluid as it resists flowing through the rest of the nephron.
35
Describe net flitration pressure.
the sum of the pressures: 50- (30+15)=10mmHg, therefore inward movement is favored from the capillaries into the Bowman's capsule.
36
What is the equation for glomerular filtration rate (GFR).
Kf*net flitration pressure=GFR
37
What is Kf?
the filtration coefficient. Describes how filterable something is.
38
What factors influence how filterable something is?
size, surface area, solubility.
39
What percentage of cardiac output goes to the kidneys each minute?
22%.
40
How much filtrate is formed each day in males and females?
180L in males.
| 160L in females.
41
How does vasoconstriction affect GFR?
decreases GFR
42
How does vasodilation affect GfR?
increases GFR
43
What are the average GFRs in males and females?
125ml/min in males
| 115ml/min in females.
44
How much urine is produced each minute?
1mL this is called obligatory water loss.
45
What is autoregulation of the kidneys?
maintenance of a constant blood pressure in the afferent arteriole by either reflex dilation in the case of pressure loss or reflex constriction in the case of increased pressure.
46
What is the myogenic mechanism?
smooth muscle in the wall of the afferent arteriole responds to stretch by contracting. This is intrinsic control.
47
In the myogenic mechanism, if pressure increases, the smooth muscle...
contracts decreasing the flow of blood.
48
In the myogenic mechanism, if pressure decreases, the smooth muscle....
relaxes increasing flow.
49
What is the tubuloglomerular feedback mechanism?
involves the juxtaglomerular apparatus.
specialized cells of the distal tubule called the macula densa monitor the rate at which filtrate is flowing via the salt content of the filtrate.
50
What are the components of the juxtaglomerular apparatus?
1. macula densa: tubular cells of the distal tubule that have salt sensors.
2. granular cells: special vascular cells at the afferent arteriorle. Have granules of renin.
51
Describe what occurs if there is a decrease in GFR.
decrease in filtrate flow in the loop of henle.
increase in the NaCl reabsorption in the ascending limb.
Decrease in NaCl in the filtrate at the distal convoluted tubule, sensed by the macula densa cells.
Stimulation of vasodilation of afferent arteriole.
Increase in hydrostatic pressure in glomerulus
Increase in GFR.
52
How do macula densa cells respond to a decrease in GFR?
stimulate vasodilation of afferent arteriole.
also stimulate Renin which leads to production of angiotensin II which causes vasoconstriction of the efferent arteriole which also increases hydrostatic pressure in glomerulus leading to an increase in GFr.
53
How does the extrinsic sympathetic system respond to decreases in blood volume?
increased sympathetic stimulation will decrease urine production. this is accomplished by arteriolar constriction.
Helps to retain fluid to increase blood volume (prohibiting loss of fluid in the urine).
54
Describe extrinsic alteration of the filtration coefficient.
occurs at the mesangial cells, which hold the glomerular capillary in position.
contraction of the mesangial cells can close off portions of the glomerulus, decreasing surface area and filtration.
55
What controls filtration slits?
contractile elements in the podocytes that can either enlarge or narrow the filtration pore, depending on the need.
56
What does filtration remove?
all constituents from the plasma except for cells and proteins. Loss of nutrients in the urine would be bad.
57
What is transepithelial transport?
places reabsorbed compounds back into the peritubular capillaries.
gaps filled with interstitial fluid between the tubules and capillaries must be cross and are called lateral spaces.
tight junction between the cells of the tubules prevent diffusion between the cells, requiring any reabsorbed materials to pass through the cells themselves.
58
what are the barriers involved in tubular reabsorption?
1. membrane of the tubular epithelial cell in the lumen of the tubule.
2. cytosol of the tubular cell.
3. membrane of the tubular epithelial cell on the side of the lateral spaces.
4. interstitial fluid in the lateral space.
5. capillary wall.
59
What are the types of transport in the kidneys?
active and passive depending on the substance being transported.
60
Describe the re-absorption of sodium.
An active process utilizing 80% of the total energy requirement of the kidneys.
61
How much sodium does reabsorption recover?
99.5%
62
Describe where sodium is reabsorbed and how much is reabsorbed.
67% is reabsorbed in the proximal tubule
25% is reabsorbed in the loop of henle
8% is reabsorbed in the distal and collecting tubules.
63
What does sodium play a major role in?
the reabsorption of glucose, amino acids, chlorine and urea
64
Describe reabsorption of sodium in the loop of henle.
establishes the concentration gradient in the medulla that is vital for the production of concentrated urine.
65
Describe reabsorption of sodium in the distal nephrons.
under hormonal control and important for regulation of ECF.
66
What does reabsorption of sodium rely on?
an energy-dependent sodium potassium pump located on the basolateral membrane.
This pump moves sodium against a concentration gradient into the lateral spaces. From there it diffuses down its concentration gradient into the plasma.
67
What provides hormonal influence on the reabsorption of sodium?
the RAAS system (renin-angiotensin-aldosterone system)
68
What happens as NaCl levels fall along with the blood pressure?
the granular cells of the juxtaglomular apparatus as as an intrarenal baroreceptor by sensing the drop in pressure in the afferent arteriole. When the granular cells are not stretched they secrete renin into the blood.
69
What are the macula desnse cells?
"internal baroreceptors"
| sense a decrease in NaCl and stimulate granular cells to secrete Renin.
70
What happens when the baroreceptors of the aorta and carotids sense a decrease in blood pressure (less stretch)?
they activate the sympathetic nervous system to stimulate the granular cells to secrete Renin.
71
What does renin do?
enzymatically cleaves angiotensinogen from the liver to angiotensin I.
72
What happens to angiotensin I?
converted by angiotensins-converting enzyme in the lungs to aldosterone.
73
What does aldosterone do?
increases the reabsorption of sodium at the distal and collecting tubules by stimuluating the production of aldosterone-induced proteins in th etubular cells. These proteins form channels in the luminal membrane of the cells, and also serve as sodium potassium ATPase carriers.
74
What does increased sodium reabsorption lead to?
increased chlorine reabsorption and an increased water retention.
75
Describe angiotensin II as a arteriolar constrictor.
increases total peripheral resistance. Also stimulates thirst and the release of vasopressin (ADH) to help retain water.
76
What is atrial naturetic peptide?
released from the heart when the ECF is expanded.
77
What induces ANP release?
the stretch of specialized cardiac atrial muscle cells
78
What does ANP do?
inhibits sodium reabsorption in the distal parts o the nephron and the RAAS system.
increases GFR by increasing blood pressure and relaxation of the glomerular mesangial cells.
inhibits sympathetic activity on the heart and blood vessels.
79
Describe what occurs during congestive heart failure.
they will retain sodium in order to expand their blood volume in the face of declining MAP. This is appropriate as increasing the ECF will put further load on the heart.
80
What are diuretics?
drugs that induce sodium loss.
81
Why must people who take ACE inhibitors be watched?
must be watched for sever decreases in GFR, especially if they also have renal artery stenosis due to arteriosclerosis.
82
How much sodium does a person need a day, and how much do they actually take in?
need 0.5g, typically ingest 10-15g
83
under normal circumstances, what is the recovery by reabsorption of glucose and amino acids?
100%
84
What is the means of transport of glucose and amino acids across membranes?
co-transported with sodium.
85
What is the transport maximum?
Because reabsorption of glucose and amino acids is mediated by a co-transport carrier, the carrier can be overloaded.
86
How much glucose is filtered?
125mg/minute
87
What is the tubular maximum for glucose?
375 mg/min.
88
What happens when the concentration of glucose reaches and exceeds 300mg/dL (3mg/mL)?
it begins to become lost in the urine. This is a diagnostic sign of diabetes mellitus.
89
What is the equation for tubular maximum?
filtration rate*GFR=Tm
90
What is renal threshold?
the plasma concentration that reaches the Tm, such that substances start to appear in urine.
91
What is the normal plasma concentration of glucose?
100mg/100mL
92
Describe the renal threshold of phasphate and calcium.
renal threshold is equal to normal plasma concentration.
93
What happens to excess calcium and phosphate?
excreted in the urine.
94
Describe the hormonal influences on phosphate and calcium.
parathyroid hormone (PTH) and calcitonin can alter reabsorption of these based upon the body's need.
95
What is PTH?
responds to low calcium and keeps kidneys from putting calcium into the urine.
96
What is Calcitonin?
responds to high Calcium and increases loss of calcium in urine.
97
Where else can PTH and calcitonin work?
in the bone tissue and GI trant.
98
Describe the reabsorption of clorine.
follows passively with sodium.
99
Describe the reabsorption of water.
water diffuses down its concentration gradient. As the glomerular filtrate becomes more dilute, the lateral spaces become more concentrated. Water diffuses by osmosis into these spaces and then into the plasma.
100
Describe the reabsorption of urea.
passive reabsorption is favored.
As water is reabsorbed, the concentration of urea in the glomerular filtrate increases.
compared to the plasma, urea is much higher concentration in the tubullar fluid.
only 50% of the urea is reabsorbed in the tubular epithelium.
101
Describe urea and uric acid.
```
when ammonium (toxic) is broken down, urea and uric acid are formed which are both less toxic nitrogen wastes.
Urea is water soluble, bur uric acid forms crystals which can cause gout.
```
102
Describe tubular secreation of hydrogen ions, potassium ions and organic ions.
involves transepithelial transport form the plasma to the tubular lumen.
may be active or passive
103
Describe the tubular secretion of hydrogen ions.
regulates acid-base
| secreted in the proximal, distal and collecting tubules.
104
Describe th elocation of reabsorption and secretion.
can be reabsorbed in the proximal tubule and secreted in the distal or collecting tubules.
105
What is loss or retention of potassium based upon?
the need to maintain an optimal plasma potassium concentration.
106
how does secretion of potassium occur?
using the same pump as used in sodium reabsorption.
107
What does aldosterone promote?
potassium secretion.
108
What will occur after increases in extracellular potassium?
drives excitable tissues closer to threshold.
| result: heart muscle-->increased heart rate--> fatal arrythmia.
109
What will occur after decreases in extracellular potassium?
drives excitable tissues away from threshold. Result: skeletal muscle weakness, smooth muscle problems (diarrhea and abdominal distension) and abnormal heart rhythm.
110
What are organic cations and anions mediated by?
independent carrier mechanisms.
111
What are some examples of organic cations and anions.
prostaglandins
food additives
pollutants
drugs.
112
What is the definition of plasma clearance?
the volume of plasma cleared per minute. shows how fast a substance is appearing in the urine.
113
What if a substance is filtered and not reabsorbed or secreted?
its clearance rate is equal to GFR.
| Inulin, creatine.
114
What if a substance is filtered and reabsorbed, but not secreted?
its clearance is less than GFR.
| Urea, glucose
115
What if a substance is filtered and secreted but not reabsorbed?
its plasma clearance is greater than GFr.
| hydrogen ions and para-aminohippuric acid.
116
What is the equation for the calculation of plasma clearance?
PC=([substance in urine]*urine flow rate)/[substance in plasma]
117
What is countercurrent multiplication?
establishes an osmotic gradient.
occurs in the medulla.
dependent upon selective permeability of the loop of Henle as well as the presence of the vasa recta.
118
Describe the medullary countercurrent system.
applies to juxtamedullary nephrons only..
| occurs at the loop of Henle.
119
What is the osmolarity of the filtrate in the tubular lumen?
300mosm/L
120
Describe the permeability of the descending limb.
tubules are highly permeable to water, but does not actively transport sodium into the plasma.
121
Describe the permeability of the ascending limb.
actively transports NaCl out of the lumen, into the surrounding interstitial fluid, yet is impermeable to water. (this maintains the concentration gradient in the interstitial fluid that is responsible for the production of concentrated urine).
122
What does the counter current mechanism do to the osmolarity?
brings it to 1200 mosm/L.
| this is also established by urea in addition to NaCl.
123
What occurs to prevent dilution of the medullary gradient?
the blood in the vasa recta (of the efferent arteriole) also increases osmolarity to 1200 mosm/L
124
What happens as water follows the salts into the interstitial spaces?
it is rapidly absorbed into the blood due to the increased osmolarity.
125
Where is ADH produced?
produced in the hypothalamus and stored in the posterior pituitary.
126
Where does ADH act?
at the level of the basolateral membrane in the distal and collecting tubules only.
127
What does the binding of ADH to the basolateral membrane do?
binding of receptors on this membrane open channels (via a cAMP second messenger system) for water to be reabsorbed from the tubular lumen (aquaporins).
128
What is the osmolarity of urine produced in the presence of ADH?
1200mosm/L
| this means the urine is hypertonic compared to plasma.
129
How much plasma is filtered with ADH present?
99.7% of the plasma filtered is returned to the blood.
130
What is the value of obligatory water loss?
500mls
131
What is osmotic diuresis?
when certain solutes are excreted or unreabsorbable, an obligatory water loss occurs too.
132
What are some famous osmotic diuretics?
glucose in diabetes and caffeine.
133
what is ADH inhibited by?
alcohol consumption.
134
What is diabetes insipidus?
when damage to the head and pituitary gland can result in loss of ADH.
135
What is micturition controlled by?
micturition reflex and voluntary control.
136
What are involved in micturition reflex?
1. spinal reflex (can occur without conscious input)
| 2. stretch receptors in the smooth muscle of the wall of the bladder. (travel via afferent neuron to the spinal cord).
137
When does micturition by stretch receptors occur?
when the volume of the bladder reaches 250mL.
138
How does micturition by stretch receptors occur?
stretch receptors initiate contraction of smooth muscle in the wall of the bladder (detrussor muscle) and relaxation of internal urethral sphincter. relaxation is caused by change in its shape during contraction.
inhibits motor input to the skeletal muscle of the external urethral sphincter.
filling of the bladder alsosends sensory information to the cortex, signaling desire to urinate.
139
What is the external urethral sphincter made of?
skeletal muscle.
140
Describe the control of the external urethral sphincter.
1. voluntary
2. can inhibit micturition reflex.
3. as the bladder fills, the IPSPs from the stretch receptors will eventually inhibit the motor input to the external urethral sphincter and urination will occur.
141
Describe loss of cortical input.
loss of control over when urination occurs.
Bladder empties when it reaches 250mL
can occur in a wide variety of severe spinal injuries.
142
Describe loss of sensory input.
signal to urinate is not transmitted.
over-filling of bladder with the inability to urinate.
can be managed by drugs.
only occurs in a few specific sacral injuries.
143
What are the causes of renal failure?
1. acute cessation of urine production (glomerular filtration).
2. pre-renal can be due to low blood to the kidneys.
3. renal is problems with filtration, reabsorption or secretion
4. post-renal is due to decreased outflow due to an obstruction.
144
Describe chronic renal failure.
usually characterized by an increase in urine production.
decrease in ability to filter appropriately, reabsorb completely, or secrete a variety of substances.
can have inappropriate substance in the urine such as protein, glucose, too much sodium, etc.
145
What are the consequences of renal failure?
1. retention of potassium increases ECF K+, moves resting membrane potential closer to threshold; heart arrhythmias can stop the heart.
2. retention of hydrogen, metabolic acidosis, decreases excitability of tissues.
146
What is uremia?
build up of nitrogenous wastes in the blood.
| problems with filtration.
147
describe sodium imbalances as an effect of renal failure.
primarily seen as osmotic problems.
may affect resting membrane potential.
sodium retention can lead to hypertenstion and may be caused by decreased filtration.
excess excretion of sodium may cause cerebral edema and be caused by decreased reabsorption.
148
What are other consequences of renal failure?
1. protein loss
2. calcium and phosphate imbalances
3. inability to form concentration urine
4. anemia
5. immunosupression.
