The genitourinary system, urinalysis, renal clearance Flashcards
1
Q
Functions of kidney?
A
Excretion of metabolic products and foreign substances (drugs). Homeostasis of electrolytes and acid base balance. Regulates blood pressure. Secretes hormones (e.g renin and EPO).
2
Q
What capillaries surround the nephron?
A
Peritubular capillaries.
3
Q
Arteriole arriving to the glomerulus?
A
Afferent arteriole.
4
Q
Arteriole leaving glomerulus?
A
Efferent arteriole.
5
Q
Glomerulus surrounds what blood vessels?
A
Glomerular cappilaries.
6
Q
What does the detrusor muscle do?
A
Contracts to build pressure in urinary bladder to support urination.
7
Q
What triangular region in the bladder signals need for urination?
A
Trigone.
8
Q
What does the bulbourethral gland do?
A
Produces thick lubricant for semen.
9
Q
Internal sphincter in bladder role?
A
Involuntary control to prevent urination.
10
Q
External sphincter in bladder role?
A
Voluntary control to prevent urination.
11
Q
What is the structural and functional unit of a kidney?
A
Nephron.
12
Q
Where are principal and intercalated cells found?
A
Late distal convoluted tube and collecting duct.
13
Q
Which parts of a nephron are rich in mitochondria?
A
Proximal convoluted tube, thick ascending loop of henle, distal convoluted tube and intercalated cells.
14
Q
Which parts of a nephron are low in mitochondria?
A
Thin descending and ascending loop of henle, principal cells.
15
Q
What is a superficial nephron?
A
Loop of henle only extends into outer medulla.
16
Q
What is a juxtamedullary nephron?
A
Loop of henle extends deep into inner medulla.
17
Q
Most common type of nephron in kidney?
A
Superficial nephron.
18
Q
What cells are present in the juxtaglomerular apparatus?
A
Juxtaglomerular cells, extraglomerular mesangial cells, macula densa.
19
Q
What are the macula densa cells part of?
A
Distal convoluted tube
20
Q
Where are juxtaglomerular cells?
A
Mostly in the walls of the afferent arteriole.
21
Q
Function of juxtaglomerular apparatus?
A
Glomerular filtration rate and blood pressure regulation.
22
Q
How is does the juxtaglomerular apparatus regulate blood pressure?
A
By secreting renin.
23
Q
What does the efferent arteriole branch out into?
A
Peritubular capillaries.
24
Q
What are the 4 main renal processes that occur in a nephron?
A
Glomerular filtration, tubular reabsorption, tubular secretion and excretion.
25
What is tubular reabsorption
Movement of solute and water from tubule to blood
26
What is tubular secretion
Movement of solute and water from blood to tubule
27
What moves fluid from glomerular capillaries into bowman's capsule space?
Hydrostatic pressure of the heart.
28
Where is the filtration barrier for glomerular filtration?
In-between glomerulus and bowman's capsule.
29
Examples of what the filtration barrier is impermeable to?
Cells and proteins.
30
2 factors that affect if a molecule can cross over filtration barrier?
Size. Charge.
31
What are the pores in the glomerular capillaries called?
Fenestrae.
32
Specialised epithelial cells that are in bowmans capsule that cover the glomerular capillaries?
Podocytes.
33
What lines the glomerular basement membrane?
Negatively charged proteins.
34
Why can't negatively charged proteins pass through the filtration barrier?
Get repelled by negatively charged proteins in glomerular basement membrane.
35
What are the cell junctions between podocytes in the bowman's space called? What can pass through these junctions?
Slit diaphragm. Water and small solutes.
36
What results in oncotic pressure in glomerular capillaries?
Solute (mainly protein) in blood results in fluid being drawn into capillaries.
37
What pressure results in solute and fluid being moved out into bowman's space?
Hydrostatic pressure.
38
What are the three pressures that occur in glomerular filtration?
Hydrostatic pressure in glomerular capillaries, hydrostatic pressure in bowman's capsule, oncotic pressure due to protein in glomerular capillaries.
39
How to calculate net ultrafiltration pressure?
Hydrostatic pressure in glomerular capillaries - [hydrostatic pressure in bowman's capsule + oncotic pressure due to plasma proteins]
40
What is the glomerular filtration rate?
Amount of fluid filtered from glomeruli into bowman's capsule per unit time. Sum of filtration rate of all functions nephrons.
41
How to calculate glomerular filtration rate?
Net ultrafiltration pressure x ultrafiltration coefficient (membrane permeability and surface area available for filtration).
42
Difference between glomerular filtration rate and net ultra filtration pressure?
Glomerular filtration rate is a rate while net ultra filtration pressure is just net pressure across filtration barrier. Glomerular filtration rate takes into account all functioning nephrons.
43
Glomerular filtration rate units?
mL/min
44
What is a key feature of renal disease?
Fall in GFR.
45
What are the two ways in which GFR is regulated?
Myogenic mechanism and tubulo-glomerular feedback mechanism.
46
How does myogenic autoregulation regulate GFR if arterial pressure increases?
Afferent arteriole experiences stretch. Smooth muscle in afferent arteriole contracts and resistance in blood vessel increases. Blood flow reduces and so GFR stays the same.
47
How does tubulo-glomerular feedback mechanism regulate GFR if GFR rises?
Increase in GFR. Increase in sodium chloride in loop of henle. Change detected by macula densa. Increase in ATP release. Adenosine removed from ATP and so increase in adenosine released. This signal results in constriction of afferent arteriole. Blood flow reduces and GFR therefore stays the same.
48
What is renal clearance?
Rate of removal of a substance from blood and excretion through urine.
49
What are the units of renal clearance?
mL/min
50
How to calculate renal clearance?
[Concentration of substance in urine x rate of urine production] / concentration of substance in plasma
51
What does a molecule need to fulfill to be used to measure GFR?
Freely filtered. Neither reabsorbed or secreted.
- Molecule is completely filtered from blood and excreted.
52
What molecules are used to calculate GFR?
Inulin and creatinine.
53
What is the problem with using inulin to calculate GFR?
Needs to be transfused as not present in mammals.
54
Why is creatinine a convenient way to calculate GFR?
Doesn't need to be transfused as its a waste product from creatine.
55
Creatinine levels that can indicate renal failure?
High plasma creatinine or low creatinine clearance.
56
Why is creatinine not as good as inulin?
Small amount of creatinine is secreted into nephron. Needs to be adjusted when calculating GFR.
57
What does a molecule need to fulfil to be used for renal plasma flow?
Molecule is removed from plasma via filtration and secretion.
58
What molecule is used for renal plasma flow?
Para aminohippurate
59
How to calculate filtration fraction?
GFR / RPF
60
What is filtration fraction?
Ratio of plasma which is filtered.
61
What will be the concentration of creatine in the efferent arteriole if the concentration in the afferent arteriole is 1.5 mmol/L?
1.5 mmol/L.
62
In renal tubules how is ONLY water moved into the blood?
Movement of aquaporins to the apical cell surface. These move only water into blood.
63
What substances via paracellular junctions in renal tubules?
Water, calcium, potassium, chloride and urea.
64
What maintains sodium gradients in duct cell?
Lack of sodium in duct cell created by Na+K+ATPase pump on basolateral surface that is pumping 3 sodium ions into blood for every 2 potassium ions into duct cell. This allows sodium to move from tubular fluid down a concentration gradient.
65
How does sodium and bicarbonate reabsorption occur in early proximal convoluted tube?
Carbonic acid converted to carbon dioxide and water by carbonic anhydrase in tubular fluid. CO2 enters duct cell by diffusion. Carbon dioxide and water in duct cell is converted to H+ and bicarbonate in cell by carbonic anhydrase. H+ diffuses out into tubular fluid and sodium diffuses into cell by Na+H+ antiporter. Sodium and bicarbonate enter blood by sodium bicarbonate symporter.
66
What substances are fully reabsorbed into blood?
Glucose and amino acids.
67
How does angiotensin increase sodium reabsorption?
Increases Na+H+ antiporters on apical membrane of duct cell.
68
How is glucose reabsorbed in early proximal convoluted tube?
Glucose enters via sodium glucose cotransporter 2. Glucose exits into blood via basolateral membrane via GLUT2.
69
What allow for passive movement of water into medullary interstitum in descending portion of henle's loop?
Descending portion of henle's loop is impermeable to salt. Hyperosmotic medullary interstitum allows water to move out via osmosis.
70
Osmotic nature of fluid entering loop of henle?
Isosmotic.
71
Osmotic nature of fluid in tip of loop of henle?
Hyperosmotic.
72
Osmotic nature of fluid in ascending portion of loop of henle? Why?
Hypoosmotic as only sodium moves out into medullary interstitum as ascending portion is impermeable to water.
73
What ions are reabsorbed in the thick ascending limb?
Sodium and chloride ions.
74
How is sodium and chloride reabsorbed in the thick ascending limb?
Sodium, chloride and potassium ions enter via symporter into duct cell. Potassium and chloride exit into blood via symporter on basolateral membrane. Sodium reabsorbed into blood via sodium potassium atpase.
75
What ions enter blodo via paracellular pathways in the thick ascending limb?
Na+, Ca2+, K+, Mg2+.
76
What ions get reabsorbed in the early distal convoluted tube?
Sodium, chloride and calcium.
77
How is the distal convoluted tube different to the proximal convoluted tube?
Distal convoluted tube is highly water impermeable.
78
How are sodium and chloride reabsorbed in early distal convoluted tube?
Sodium and chloride enter duct cell from tubular fluid via a symporter. Sodium enters blood via sodium potassium atpase on basolateral membrane. Chloride enter blood via potassium chloride symporter.
79
How is calcium absorbed in the early distal convoluted tube?
Calcium diffuses into duct cell via tubular fluid. Calcium pumped into blood by active transport using Ca2+ ATPase and sodium calcium antiporter on basolateral membrane.
80
What pumps reabsorbs chloride ions into blood in early distal convoluted tube?
Potassium chloride symporter.
81
What is the function of principal cells?
Sodium reabsorption and potassium secretion.
82
How is water reabsorbed in principal cells?
Via aquaporins.
83
What are the two ways in which aldosterone increase sodium reabsorption in principal cells?
Increasing apical sodium channels and basolateral sodium potassium ATPase pumps.
84
How does avp increase water reabsorption in principal cells?
Increase apical aquaporins.
85
What is the function of intercalated cells?
Maintaining acid-base balance
86
What is the function of alpha intercalated cells?
Bicarbonate reabsorption and H+ secretion.
87
What is the function of beta intercalated cells?
Bicarbonate secretion and H+ reabsorption.
88
What pumps are involved in intercalated cells?
Chloride bicarbonate antiporter and H+ ATPase.
89
What part of nephron is the filtrate most concentrated?
Tip of loop of henle.
90
What part of nephron is the filtrate least concentrated?
Distal convoluted tube and collecting duct.
91
How does amount of inulin change throughout the nephron?
Stays the same.
92
When does the amount of water and sodium in the filtrate decrease the fastest?
Proximal convoluted tube.
93
How does amount of sodium in filtrate change when moving down descending loop of henle?
Stays the same. Impermeable to sodium.
94
How does amount of water in filtrate change when moving up ascending loop of henle?
Stays the same. Impermeable to water.
95
Leukocytes detected in dipstick test indicate what?
UTI.
96
Nitrite detected in dipstick test indicate what?
Gram-negative bacteria in large number, e.g., E. Coli.
97
Ketones in dipstick test indicate what?
Starving or fasting or diabetic ketoacidosis
98
Glucose in dipstick test indicate what?
Diabetes Mellitus
99
What does low specific gravity mean?
Urine is too diluted.
100
What does low specific gravity in dipstick test indicate?
Diabetes Insipidus.
101
What is diabetes insipidus?
Decreased release of AVP or decreased response to AVP.
102
Protein in dipstick indicates what?
Nephrotic syndrome
103
Blood in dipstick indicates what?
Nephritic syndrome or kidney stones or UTI
104
Bilirubin in dipstick indicates what?
Liver disease or gallstones
105
Urobilinogen in dipstick indicates what?
Liver disease or haemolysis
106
What does freely filtered mean?
Same concentration in glomerular filtrate as in plasma.
107
What conclusions can you draw about a substance whose renal clearance is higher than that of inulin?
Secretion of that substance occurs.
108
What conclusions can you draw about a substance that is freely filtered and whose renal clearance is lower than that of inulin?
Reabsorption of that substance occurs.
109
Why can para aminohippurate be used for renal plasma flow?
All the para aminohippurate is removed from the plasma passing through filtration and secretion and all the PAH arriving at the kidneys in the plasma appears in the urine, and virtually none leaves in the renal vein. Renal clearance of this molecule equals the renal plasma flow.
110
Disadvantage of para aminohippurate?
Has to be infused.
111
When can para aminohippurate not be used to calculate RPF?
If too high of a concentration has been infused. Results in some leaving in the renal vein instead of all being in the urine.
112
Arterial plasma inulin concentration were 1 mmol/L, what would be the plasma inulin concentration in the efferent arteriole if 20% of inulin was filtered??
1mmol / L
113
the arterial plasma inulin concentration were 1 mmol/L, what would be the plasma inulin concentration in the renal vein if 20% of inulin was filtered?
0.8 mmol/L
114
Why is measurement of PAH clearance rarely performed clinically when renal disease is suspected
Incomplete secretion and issues with renal plasma flow.
115
Why is bladder catheterisation required for measurement of inulin clearance but not for creatinine?
Inulin is transfused and so you don't want to miss the opportunity of getting the inulin in the urine. Creatinine is released into the blood at a relatively constant rate so is always going to be present in urine.
116
Why is inulin not given orally when measuring inulin clearance?
Digested by bacteria in our gut instead so can't be used.
117
A small amount of creatinine enters the urine by secretion into the proximal tubule. Why is this not too big of a problem to use creatinine for GFR?
Creatinine measurement in plasma, measures creatinine and non-creatinine chromogens. This means the excess creatinine present in urine due to secretion and the excess creatinine in plasma due to non creatinine chromogens cancel each other out.
118
How does the gradient of Log plasma 51Cr EDTA activity change in someone with renal failure?
Less steep gradient.
