Urinary System Flashcards
Lec 33, 34, & 35
1
Q
What do the kidneys do (simple)?
A
form urine and regulate the composition of blood plasma.
2
Q
What are the components of the urinary system?
A
kidney, nephron, structures that support urine transport - renal pelvis, ureters, urinary bladder, urethra.
3
Q
What are the functions of the kidney?
A
- maintain plasma vol and therefore bp/MAP. 2. regulate ion concentrations (na, k, etc) and water balance/concentration. 3. acid-base balance 4. eliminate waste, drugs, hormones. 5. endocrine - renin (regulates bp) and erythropoietin (affects rbc production).
4
Q
What is the nephron?
A
the functional unit of the kidney.
5
Q
What are the different parts of the nephron?
A
- renal capsule - glomerulus and renal/bowmans capsule surrounding it 2. tubule - proximal convoluted tubule, descending and ascending loop of henley/nephron loop, distal convoluted tubule, and collecting duct.
6
Q
What are the processes in the nephron that lead to urine formation?
A
- glomerular filtration - water and small solutes are forced out of the blood in the glomerulus to the bowmans capsule due to pressure differences across the filtration membrane. 2. tubular reabsorption - substances like water, glucose, and ions are transported from the filtrate into the nephron back into the bloodstream/capillaries. 3. tubular secretion - additional waste products and excess ions are actively transported from the peritubular caps into the lumen of the nephron tubules to be excreted in urine.
7
Q
What is glomerular filtration?
A
20% of plasma in glomerulus is filtered into the bowmans capsule via bulk flow due to change in pressure across the filtration membrane.
8
Q
What does the filtration membrane consist of?
A
- fenestrated (holey) endothelium thats part of the glomerulus. 2. podocytes (a layer of bowmans capsule cells) with filtration slits btwn, 3. fused basement membranes
9
Q
What is the composition of filtrate?
A
- identical to plasma except that theres no large proteins. 2. H2O, glucose, aas, vitamins, ions, urea, some small proteins. 3. pH is around 7.45.
10
Q
What is the net filtration pressure btwn the glomerulus capillaries and the capsule?
A
- glomerular hydrostatic pressure - 55mmHg, promotes filtration. so from bl to capsule. 2. blood osmotic pressure - 30mmHg, opposes filtration. so its the OP in the blood meaning it pushes fluid from the capsule into the capillaries. 3. capsular hydrostatic pressure - 15mmHg, opposes filtration. so from capsule to blood. 4. capsular osmotic pressure - 0mmHg, promotes filtration. so the OP in the capsule. would be fluid from blood to capsule. NFP= 55 + 0 - 30 + 15= 10mmHg.
11
Q
What is the glomerular filtration rate?
A
around 180 L/day filtrate from both kidneys = 125 mL/min, so the entire plasma volume is filtered around 65 times per day. however, less than 1% of filtered volume remains at the end of collecting duct bc it is reabsorbed into the body.
12
Q
Why is GFR regulated?
A
to ensure that kidneys filter blood a consistent and appropriate rate for the conditions of the body, and helps to maintain a constant pressure in the glomerulus despite changes in MAP.
13
Q
What happens if GFR is too high?
A
valuable nutrients and water may be lost in the urine (the filtrate passes through too quickly for proper reabsorption).
14
Q
What happens if the GFR is too low?
A
the blood is not being filtered fast enough and wastes may accumulate in the blood.
15
Q
What’s the relationship btwn GFR changes and BP?
A
regulation helps to keep the GFR from changing when bp changes. if not, an increase in MAP would result in an increase in GFR and vice versa.
16
Q
What are the processes of regulation of the GFR? (list)
A
- intrinsic regulation - autoregulation, for. bps in resting to moderate exercise range. a. myogenic response b. juxtaglomerular apparatus response 2. extrinsic regulation - SNS and endo.
17
Q
What is the myogenic response?
A
increase in MAP means get stretch of smooth mm of afferent arteriole, so it contracts, which prevents an increase in bp in the glomerular capillaries (and vice versa).
18
Q
What is the juxtaglomerular apparatus response?
A
decrease in bp means decrease in GFR, so flow of filtrate past the macula densa cells decreases, causing the release of local factors (proteins that initiate a response) and the afferent arteriole dilates, therefore the GFR increased to resting.
19
Q
What is the extrinsic regulation of the GFR?
A
primarily SNS, arteriole vasoconstriction. constriction of the afferent arteriole causes a decrease in flow into the glomerulus, so GHP decreases and so does GFR. constriction of the efferent arteriole causes blood to back up in the glomerulus, so GHP increases and so does GFR.
20
Q
What is the extrinsic regulation of the GFR during moderate SNS activation?
A
constriction of the afferent and efferent arterioles is balanced. so GFR doesnt change much.
21
Q
What is the extrinsic regulation if the GFR during extreme stress?
A
during things like heavy exercise or hemorrhage where losing fluids, there is more vasoconstriction if the afferent arteriole which causes GFR to decrease which helps the body to conserve fluid and redirect blood to critical organs.
22
Q
How can the NFP change?
A
- blood OP (proteins). dehydration causes an increase in BOP which decreases the GFR bc more absorption from BOP. burns decrease BOP which means get increase in GFR from less absorption. 2. capsular HP - urinary tract obstruction like kidney stones causes an increase in CHP which decreases GFR bc its more absorption.
23
Q
What is tubular reabsorption?
A
get 1-1.5 L/day urine but 180 L/day filtered therefore 99% of filtrate is reabsorbed from the tubules into the peritubular and vasa recta capillaries. transport may be: active (requires nrg) - Na, other ions, glucose, aa. passive (no nrg) - CL, H2O, urea.
24
Q
What is reabsorbed in the proximal convoluted tubule (unregulated) during tubular reabsorption?
A
- glucose, aas - 100% reabsorbed via active transport. 2. Na - 65% reabsorbed via active transport. 3. small proteins by endocytosis into tubule cell to become aas and go into blood 4. vitamins 5. obligatory/unregulated reabsorption of H2O via osmosis bc it follows the increase solute conc from solutes going into the capillaries.
25
What is the result of reabsorption via the PCT?
large amount of solute removed and the volume of the filtrate is reduced, filtrate is now isotonic to plasma = 300mOsmoles/L.
26
What reabsorption happens in the loop of henley during tubular reabsorption?
descending limb - unregulated/obligatory absorption of water only. ascending limb - impermeable to water, but get active transport of Na and Cl.
27
What reabsorption happens in the distal convoluted tubule?
reabsorbs NA, CL, CA. impermeable to H2O.
28
What reabsorption happens in the late distal convoluted tubule and collecting duct?
1. reabsorbs Na, caused by; aldosterone which increase NA reabsorption, or ANP which decreases Na reabsorption. 2. facultative/regulated reabsorption of H2O: ADH increases (ANP inhibits ADH).
29
What do the nephrons normally reabsorb?
99% of filtered H2O, 99.5% of filtered NaCl, 100% of filtered glucose, 50% of filtered urea. filtrate may contain trace aa and small proteins but no glucose or blood.
30
What happens during tubular secretion?
mvmt of substances from the peritubular capillary blood into the filtrate in the lumen nephron. main substances secreted are; 1. wastes ie urea, uric acid, some hormones. 2. K (increased by aldosterone) 3. H or NH4 which maintains bl plasma pH
31
What does the countercurrent multiplier mechanism create and why?
a conc grad/vertical osmotic gradient (a progressive increase in [solute] in the ISF as move deeper into medulla) in the kidney medulla by moving NaCl out of the ascending limb and water out of the descending limb of the nephron loop. conc grad allows the kidneys to produce a urine that is either concentrated (1200 mOsm/L or dilute 100 mOsm/L, helping to regulate water balance and bp.
32
CMM within the loop of henle.
fluid flows in parallel tubes (DL and AL) in oppo directions. DL - permeable to water but impermeable to NaCl. AL - impermeable to water but permeable to NaCl. NaCl is pumped actively out of the AL making the ISF more concentrated. this leads to osmosis from the DL which gets more and more concentrated as filtrate descends bc its losing water. at bottom of loop the filtrate is at its highest concentration. then when start to go into AL, NaCl starts to leave (200 mOsm/L) and the filtrate becomes more and more dilute as filtrates ascends. NaCl leaving the filtrate is what makes the ISF more concentrated. when the filtrate leaves the AL at 150 mOsm/L it has a lower osmolarity than the plasma due to the AL being impermeable to water, and actively transporting NaCl out into the ISF.
33
CMM within the early DCT.
more salt removed from filtrate (reabsorbed), no h2o removed, therefore 100mOsm/L when enters late DCT.
34
What are the different kinds of urine that can be produced?
Concentrated - dehydrated, low bp. Dilute - excess plasma h2o, high bp
35
What produces concentrated urine?
in late DTC, CD: a. aldosterone increases Na reabsorption. b. ADH increases facultative/regulated h2o reabsorption.
36
What produces dilute urine?
in late DCT, CD: ANP inhibits ADH and aldosterone so impermeable to Na and h2o.
37
What are the kinds of regulation of [urine]?
hormonal - renin-angiotensin system, ADH, Aldosterone, ANP. SNS impulses.
38
When does renin increase during regulation of [urine]?
decreased bp or blood vol. increased SNS activity. decreased NaCl in filtrate (detected at macula densa).
39
When does renin decrease during regulation of [urine]?
increased bp or blood vol. increased NaCl in filtrate. increase in ADH and angio II.
40
What processes does an increase in renin act on?
increase in renin --> increase in angio II --> adrenal cortex --> increases aldosterone --> kidney --> increased Na reabsorption into cap and increased K secretion from cap. increase in arteriolar vasocon --> increased systemic bp and decrease in GFR if triggered by large decrease in bp. brain --> increases thirst and increases ADH--> kidney --> increases facultative H2) reabsorption. Summary: increase in renin = increased Na reabsorp and K secretion, increased vasocon, increased thirst and h2o reabsorp.
41
What does ADH do?
facultative reabsorption of water in late DCT and CD.
42
When does ADH increase?
increases water going back into body so; if low bp or blood vol, increased plasma osmolarity/concentration. increase in angio II, nicotine and nausea.
43
When does ADH decrease?
would decrease water going back into body so; if high bp or blood vol, decreased plasma osmolarity, decreased angio II, increased ANP, alcohol.
44
What is diabetes insipidus?
body does not produce ADH hormone or kidneys do not respond to ADH hormone. results in large amount of dilute hormone and increased thirst (bc wouldnt have body reabsorbing water before its pissed out)
45
What does aldosterone do?
steroid hormone that increases when angio II increases and theres high plasma K. turns on genes that increase the number of Na/K ATPase pumps in DCT and CD. Na reabsorption in late DCT and collecting duct increases, h2o follows bc of osmosis and Cl follows bc of charge. get increased K secretion. Summary: increased Na reabsorp (so leaving the filtrate), and increased K secretion (so entering the filtrate)
46
What does ANP do?
release of anp caused by an increase in bp. Effects of ANP; decreased renin and therefore angio II, decreased ADH, decreased aldosterone, decreased vasocon. all of the above lead to an increase in urine vol (more water out, reduces bp).
47
How does the SNS regulate [urine]?
(no PSNS). increase in SNS impulses; afferent and efferent arterioles constrict. decrease in SNS impulses; afferent and efferent arterioles relax. BUT the myogenic response in the kidneys is powerful, meaning if theres an increase in MAP this increases flow to kidneys which causes vasocon in spite of the decrease in SNS, renin, angio II, and an increase in ANP (result of these decrease vasocon), so the GFR returns to resting. the lack of ADH and aldosterine means the urine will be dilute (bc no water reabsorption, or Na reabsorption), therefore blood vol will decrease and so will MAP. hormones correct bp and GFR is kept constant.
48
What happens with the GFR if theres a large decrease in bp or vol?
vasocon signals are stronger than intrinsic mechanisms/regulation so GFR doesnt stay as normal and decreases bc of vasocon.
49
What are the normal urine constituents?
1. h2o 2. nitrogenous wastes; a. urea - from metabolism of aa around 50% reabsorbed. b. uric acid - from nucleic acid metabolism, secreted, only 10% reabsorbed. uric acid is poorly water soluble and an accumulation results in gout in joints and kidney stones. c. creatinine - from creatine metabolism in skel mm. production/excretion is constant and theres no reabsorption. used to estimate GFR and can indicate kidney disease before it occurs. 3. regulated substances - ions. 4. pH 4.5 - 8.0
50
What is the abnormal urine constituents?
1. protein - proteinuria or albuminuria. due to increased permeability of glomerulus, makes it so that theres proteins leaving the glomerulus and entering into capsule/filtrate. due to heavy metals or glomerulonephritis (inflammation of glomerulus). 2. glucose - glycosuria. temporary; IV glucose. pathological; diabetes mellitus - high bl glucose bc no insulin or receptors not responding.
51
What is the micturition/bladder reflex?
involuntary reflex in response to bladder stretching that causes the bladder to contract and internal urethral sphincter to relax, initiating the urge to urinate. peeing reflex.
52
What is the pathway of the micturition reflex?
kidney --> ureters --peristalsis and gravity mover urine--> urinary bladder --> stretch receptors --> sacral spinal cord and micturition centre --> PSNS --> detrusor contracts, internal urethral sphincter opens. at same time stretch receptors --> cortex and get gotta pee feeling --> external urethral sphincter relaxes --couples with int urethral sphincter opening and allows for --> urine expelled. OR cortex --> gotta wait --> external urethral sphincter contracts --> no micturition.
53
What is renal plasma clearance?
the volume of plasma that is completely cleared of a substance in 1 minute.
54
What does renal plasma clearance estimate?
the time a substance such as a drug will remain in the blood.
55
What is the equation for plasma clearance?
PC of substance A = vol urine/min x [A] in urine/ [A] in arterial plasma.
56
How is inulin used to estimate GFR?
inulin is a polysacc that is completely filtered, but not reabsorbed, secreted, or metabolized. so wtv is put into the body all comes out in the urine. therefore the amount of inulin in the urine = the amount filtered. PC of inulin is 125 ml/min so thats the GFR.
57
If the PC is less than the GFR what does that mean?
substance is reabsorbed from filtrate. ie urea PC is 75 ml/min so 50% reabsorbed. ie glucose PC is 0 so 100% reabsorbed.
58
If the PC is greater than the GFR what does that mean?
substance is secreted into the filtrate. ie penicillin and H.
59
What is acid-base balance?
regulation of free H+ in the ECF. H is normally produced by metabolism. H+ is buffered and the eliminated by the respiratory system and the renal system.
60
What are the different body pHs?
normal = 7.35-7.45. acidosis = 6.8-7.35 (below that is death). alkalosis = 7.45-8.0 (above that is death).
61
What are buffer systems?
pairs of chemicals. bases take up H (remove them from solution). acids give up H (add it to solution). balance of the two minimizes pH changes.
62
What is a major buffer in the blood?
the bicarbonate system= CO2 + H2O --> H2CO3 --> H+ + HCO3-.
63
What are some other buffers?
1. Hb + H+ --> HbH in rbcs only. 2. proteins --> cells. plasma. (uptake and release H ions).
64
How does the respiratory system control acid-base balance?
acts within minute so is short term. H + HCO3 --> H2CO3 --> CO2 + H2O. CO2 is removed and therefore also removes H. if H increases get hyperventilation (trying to get it out). if H decreases get hypoventilation (trying to keep it in).
65
How does the renal system control acid-base balance?
longer term. 1. eliminates H+ from metabolically produced acids (FAs, lactic acid, etc). 2. secretes H into tubule 3. conserves and increases blood HCO3-.
66
What are the kinds of acid-base imbalances (list)?
1. acidosis - respiratory and metabolic. 2. alkalosis - respiratory and metabolic.
67
How does acidosis affect the CNS, and what will the urine contain?
CNS depressed --> coma, irregular heart beat. urine = H, HPi, NH4, no/little HCO3-.
68
What is the cause of respiratory acidosis?
Hypoventilation which causes an arterial Pco2 increase, increasing H and therefore decreasing pH. ie lung disease, depression of medulla respiratory centre.
69
What is the compensation for respiratory acidosis?
lungs cannot compensate bc of poor fxn. so kidneys do by increasing secretion of H and increasing HCO3 into blood to buffer.
70
What is the cause of metabolic acidosis?
an increase in H from any source other than CO2. ex: diarrhea - loss of HCO3-, uncontrolled diabtes mellitus - increase fat metabolism (bc glucose not going into tissues) and get keto acids. strenuous exercise - lactic acid, renal failure.
71
What is the compensation for metabolic acidosis?
lungs: increase ventilation due to increase in H at peripheral chemoreceptors which decreases H. but central chemoreceptors will eventually increase ventilation due to decreased CO2. kidneys: increase H secretion and increase HCO3 uptake into blood.
72
How does alkalosis affect the CNS, and what will the urine contain?
CNS is overexcited, spasms in skel mm. urine: HCO3-, no HPi, no NH4, no/little H.
73
What is the cause of respiratory alkalosis?
hyperventilation which causes a decreased in arterial Pco2, therefore decreased H and increased pH. can be bc of an anxiety attack.
74
What is the compensation for respiratory alkalsosis?
lungs: cannot compensate unless hyperventilation is voluntary. kidneys: decrease H secretion and decrease HCO3 into blood.
75
What is the cause of metabolic alkalosis?
a decrease in H for any reason other than respiratory. ex: excess vomiting - loss of stomach acid, ingestion of alkaline drugs - antacids.
76
What is the compensation for metabolic alkalosis?
lungs: decrease ventilation so increase arterial Pco2, and therefore increased H. Kidneys: decrease H secretion and decrease HCO3 into blood.
