Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Year 1 NME > The Formation of Urine > Flashcards

The Formation of Urine Flashcards

1
Q

What are the 5 stages of filtration that producd urine?

A

1 - glomerulus = filtration of blood

2 - proximal tubule = reabsorption of filtrate and secrete into tubule

3 - loop of henle = concentration of urine

4 - distal tubule = modification of urine

5 - collecting duct = final modification of urine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

In order for filtrate to be created in the glomerulus there needs to be a pressure gradient with good renal blood flow. There are 3 types of pressure with their normative values:

1 - hydrostatic pressure in glomerular capillaires = 45mmHg

2 - osmotic plasma pressure (albumin etc in plasma) = 25mmHg

3 - hydrostaric pressure in bowmans capsule = 10mmHg

What would be the net filtration rate at the glomerular with the above pressures?

A
  • 45 - 25 -10 = 10mmHg
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

In order for GFR to be maintained even if blood pressure rises or falls the kidneys must autoregulate even in changes in blood pressure. Generally autoregulation will occur when systematic arterial blood pressure reaches what levels?

A
  • 90 - 200mmHg
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

In order for GFR to be maintained even if blood pressure rises or falls the kidneys must autoregulate even in changes in blood pressure. Generally autoregulation will occur when systematic arterial blood pressure reaches 90-200mmHg. There are 2 processes that have been identified that contribute to autoregulation, namely myogenic and metabolic. What is the myogenic autoregulation?

A
  • myogenic autoregulation is due to response of renal arterioles to stretch (Starling’s Law)
  • if BP decreases there is no stretch in efferent arterioles
  • in response efferent arterioles constrict to maintain a constant renal blood flow (1,200mL/min) and GFR (~125 mL/min)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

In order for GFR to be maintained even if blood pressure rises or falls the kidneys must autoregulate even in changes in blood pressure. Generally autoregulation will occur when systematic arterial blood pressure reaches 90-200mmHg. There are 2 processes that have been identified that contribute to autoregulation, namely myogenic and metabolic. What is metabolic autoregulation?

A
  • renal metabolites modulate afferent and efferent arteriolar contraction and dilation (e.g. adenosine, nitric oxide)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

When thinking about metabolic autoregulation, if the GFR reduces, what happens to the afferent and efferent arterioles that feed into the glomerulus?

A
  • afferent arterioles are dilated by nitric oxide, prostoglandins or dopamine. Blood flow is increased into glomerulus
  • efferent arterioles are constricted by angiotensin II, which stops blood leaving the glomerulus
  • overall increased blood for filtration in glomerulus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

When thinking about metabolic autoregulation, if the GFR increases, what happens to the afferent and efferent arterioles that feed into the glomerulus?

A
  • afferent arterioles are constrcited by noradrenalin from sympathetic nervous system or anti diuretic hormone. Blood flow is reduced into glomerulus
  • efferent arterioles dilated by adenosine and nitric oxide, which increases blood leaving the glomerulus
  • overall reduces blood for filtration in glomerulus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What can a drop in blood pressure do to GFR and how does the kidney respond to this?

A
  • could cause a reduced GFR and Na+ in proximal tubules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

A drop in blood pressure reduce GFR and Na+ levels in the proximal tubules. What cells in the proximal tubules are able to detect changes in Na+ levels and what do these cells do in response?

A
  • macula densa cells
  • stimulate juxtaglomerular cells to release renin into the blood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

A drop in blood pressure reduce GFR and Na+ levels in the proximal tubules. Macula densa cells in the proximal tubules are able to detect changes in Na+ levels and stimulate the juxtaglomerular cells to release renin into the blood. What does this then cause?

A
  • renin converts angiotensinogen into angiotensin I
  • angiotensin converting enzyme converts angiotensin I into angiotensin II
  • angiotensin II causes vasoconstriction and increases BP
  • GFR returns to normal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Angiotensin II (Ang II) has a number of effects on the body, which are importabnt for maintaining GFR. What does Ang II do to the sympatheitc system?

A
  • increases sympatheitc activity, specificallt a-1
  • a1 causes vasoconcstriction of blood vessels increasing BP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Angiotensin II (Ang II) has a number of effects on the body, which are importabnt for maintaining GFR. What does Ang II do to the tubules of the kidneys?

A
  • increases Na+ and H2O absorption
  • blood volume increases which increases BP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Angiotensin II (Ang II) has a number of effects on the body, which are importabnt for maintaining GFR. What does Ang II do to the suprarenal (adrenal glands)?

A
  • causes secretion of aldosterone
  • aldosterone increases Na+ and H2O re-absorption into the tubules of kidneys and then into the capillaires
  • increases blood volume and BP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Angiotensin II (Ang II) has a number of effects on the body, which are importabnt for maintaining GFR. What does Ang II do to the pituatory gland?

A
  • increase anti-diuretci hormone (ADH) which is made in the hypothalamus
  • causes increased thirst and increased fluid intake and increases reabsorption of H20 in tubules
  • increases blood volume and BP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Angiotensin II (Ang II) has a number of effects on the body, which are importabnt for maintaining GFR. What does Ang II do to the smooth muscles surround blood vessels?

A
  • increases Ca2+ secretion and vasoconstriction
  • increases BP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

In the RAAS system, if the increase in BP has returned GFR to within nromal levels, what does the kidney do in response?

A
  • macula densa cells detect increased Na+
  • juxtaglomerular cells stop producing renin into the blood
  • this is a negative feedback loop
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Once the filtrate has lef the glomerular it enters the proximal tubule where what electrolytes are reabsorbed?

A
  • Na+, HCO3-, Cl- and K+
  • urea is also reabsorbed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Once the filtrate has lef the glomerular it enters the proximal tubule where 60-70% of electrolytes (Na+, Cl-, HCO3- and K+ alongside urea are reabsorbed. What else is alsmost entirely reabsorbed in the proximal tubules?

A
  • glucose
  • amino acids
  • small amount of filtered proteins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Once the filtrate has lef the glomerular it enters the proximal tubule where 60-70% of electrolytes (Na+, Cl-, HCO3- and K+ alongside urea are reabsorbed. Glucose, amino acids and a small amount of filtered proteins are almost entirely reabsorbed in the proxiaml tubules. However, as these require active transport, what pump facilitates this?

A
  • Na+K+ATPase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Once the filtrate has lef the glomerular it enters the proximal tubule where electrolytes Na+, Cl-, HCO3- and K+ alongside urea are reabsorbed. What % of these are reabsorbed in the proximal tubules?

A
  • 60-70%
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How does the Na+/K+ ATPase pump Na+ from the tubules back into the pertibular capillaries?

A
  • this is an active transport so ATP is needed
  • 3 Na+ are pumped from tubules into capillaries and 2 K+ are pumped from capillaries into tubules
  • this lowers Na+ in tubules and Na+ moves from filtrate into tubules down concentration gradient and H2O follows due to osmossis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

The Na+/K+ ATPase pumps Na+ from the tubules back into the pertibular capillaries and K+ from the capillaries into the tubules. In addition to transporting Na+, what tends to follow Na+ into the pertibular capillaries?

A
  • glucose, especiallin the in the proximal tubule
  • Cl-, phosphate and sulphate are also co-transported with Na+
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

60-70 % filtered water is reabsorbed in the proximal tubules. What electrolyte facilitates this active transport and how does the H2O get reabsorbed in a process that does not require ATP?

A
  • Na+ via osmosis
  • paracellular is through osmosis
  • transcellular = aquaporin (AQP) channels located on apical and basolateral surfaces
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What helps glucose get reabsorbed and is glucose concentration highest in urine or capillaires around the proximal tubules?

A
  • Na+/K+ ATPase
  • glucose is higher in urine so moves down concetration gradient
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Is the amount of glucose that you can reabsorb from the tubules using the Na+/K+ ATPase pump unlimited, what can happen if the glucose is not absorbed?

A
  • no it can only reabsorb so much
  • if too much glucose is excreated, which is what happens in diabetes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How is K+ reabsorbed in the proximal tubules?

A
  • 70% is reabsorbed in proximal tubules
  • mostly passive via tight junctions paracellularly
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How is urea reabsorbed in the proximal tubules?

A
  • 40–50 % is absorbed passively down its concentration gradient
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

How are amino acids reabsrobed in the proximal tubules?

A
  • there are 7 independent transport processes for reabsorption of amino acids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How are proteins reabsrobed in the proximal tubules?

A
  • very little passes through glomerulus
  • what does pass is via receptor-mediated endocytosis
  • if protein is present indicates glomerular damage
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

There are some endogenous substances and drugs that cannot be filtered at the glomerulus due to size or protein that is bound to them. What does the proximal tubules do with these substances?

A
  • proximal tubule uses pumps to secrete them into the urine
  • organic acid pumps (e.g. uric acid, diuretics, antibiotics - penicillin)
  • organic base pumps (e.g. creatinine, procainamide)
31
Q

The third stage of urine formation is in the loop of henle, what occurs here?

A
  • concentration of urine
32
Q

In the loop of henle there are 2 major parts, what are they and what are their main roles?

A

1 - descending = extraction of H2O

2 - ascending = extraction of Na+ and Cl-

33
Q

In the loop of henle there are 2 major parts, the descending which extracts H2O and the ascending which extracts Na+ and Cl-. Is this extraction process more important in the cortical or juxtamedullary nepherons?

A
  • juxtamedullary nepherons
34
Q

In the loop of henle there are 2 major parts, the descending whicb mainly extracts H2O and the ascending which mainly extracts Na+ and Cl-. When looking at the thin descending limb of henle are the cells flat or tubular?

A
  • cells are flat
  • no active transport of Na+, Cl-
35
Q

In the loop of henle there are 2 major parts, the descending whicb mainly extracts H2O and the ascending which mainly extracts Na+ and Cl-. When looking at the thin descending limb of henle the cells are flat which means no active transport of salts (Na+ or Cl-) occurs. However, what is present on these cells that allows H2O to freely move from the loops of henle to the capillaries?

A
  • aquaporin-1 channels
36
Q

In the loop of henle there are 2 major parts, the descending whicb mainly extracts H2O and the ascending which mainly extracts Na+ and Cl-. When looking at the thick ascending limb of henle are the cells flat or tubular and what does this allow to be absorbed from the loops of henle into the capillaries?

A
  • walls of descending loop of henle have tubular walls
  • impermeable to water
  • contain specialised Na+/K+/2Cl- (NKCC2) co-transporters
37
Q

When fluid leaves the proximal tubule and enters the descedning loop of henle is the fluid isotonic, hypertonic or hypotonic?

A
  • fluid is isotonic, same as plasma
38
Q

When fluid leaves the proximal tubule and enters the descedning loop of henle it is isotonic. However by the time the filtrate reaches the descending loop of henle, is the filtrate still isotonic, hypertonic or hypotonic?

A
  • hypertonic
39
Q

When fluid leaves the proximal tubule and enters the descedning loop of henle it is isotonic. However by the time the filtrate reaches the descending loop of henle, due to H2O reabsorption by capillaries the filtrate when it enters the descending loop of henle is highly concentrated and hypertonic. By the end of the ascending loop of henle is the filtrate isotonic, hypotonic or hypertonic and why?

A
  • solutes (Na+, Cl-) are pumped out of the ascending loop of henle into the capillaries
  • leaves a hypotonic filtrate
40
Q

When fluid leaves the proximal tubule and enters the descedning loop of henle it is isotonic. However by the time the filtrate reaches the descending loop of henle, due to H2O reabsorption by capillaries the filtrate when it enters the descending loop of henle is highly concentrated and hypertonic. By the end of the ascending loop of henle is the filtrate is hypotonic. Why is this important?

A
  • creates large osmotic gradient within medulla
  • this is called the countercurrent multiplication
41
Q

What is the countercurrent multiplication?

A
  • ascending loop of henle lets Na+/K+/Cl- leave
  • creates a high concentration gradient in the the interstial space between ascending and descedning loop of henle
  • H2O follows Na+ and leves descending loop of henle to dilute and balance the Na+/K+/Cl- in the interstitial space
42
Q

The countercurrent multiplication is essentially where the ascending loop of henle lets Na+/K+/Cl- leave into the interstial space, creating a high concentration gradient between ascending and descedning loop of henle. H2O follows Na+ and leaves the descending loop of henle to dilute and balance the Na+/K+/Cl- in the interstitial space. Each loop therefore balances each other out. Why is this important?

A
  • ensures optimal H2O and electrolyte re-absorbtion into capillaries
43
Q

Urea is the chief nitrogenous end product of the metabolic breakdown of proteins in all mammals and some fishes. Is urea filtered in the glomerulas and proximal convoluted tubules?

A
  • yes
  • approximately 50% in the proximal convoluted tubules
44
Q

Urea is the chief nitrogenous end product of the metabolic breakdown of proteins in all mammals and some fishes. It is filtered by the glomerulas and a little is reabsorbed in the proximal convoluted tubules. Where does the majority of urea leave the tubulues and why?

A
  • high concentration of urea in collecting ducts
  • able to diffuse down concentration gradient from the collecting ducts and enter the interstial space in the medualla
45
Q

Urea is the chief nitrogenous end product of the metabolic breakdown of proteins in all mammals and some fishes. It is filtered by the glomerulas and around 50% is reabsorbed by the proximal convoluted tubules. It then remains in the tubules until it reaches the collecting ducts where there will be a high concentration of urea in collecting ducts. The urea is able to dissuse out of the colecting ducts and into the interstial space in the medualla. How does this contribute towards countercurrent multiplication?

A
  • increases concentration gradient in the interstial space in the medulla
  • more H2O diffuses out of tubules by osmosis to equalise the concentration between the tubules and interstitial space
46
Q

Where does further modification of urine happen following the loop of henle?

A
  • distal tubules
47
Q

In the distal tubules are Na+ and K+ actively or passively reabsorbed?

A
  • actively
48
Q

Which part of the distal tubules is Na+ reabsorbed and K+ secreted in exchange?

A
  • distal tubules
49
Q

What are the 2 cell types in the distal tubules that are responsible for Na+ and K+ transport?

A

1 - principle cells

2 - intercalated cells

50
Q

How do principle cells in the distal tubules Na+/K+ ATPase pump on the basal membrane (close to blood) faciliate Na+ reabsorption?

A
  • 3 Na+ are removed in exchange for 2 K+, reducing Na+ concentration in principle cells
  • K+ taken from plasma
  • Na+ moves down concentration gradient from lumen (tubule)
51
Q

The Na+/K+ ATPase pump in the distal tubules pump on the basal membrane (close to blood) of the principle cells faciliate Na+. As 3 Na+ are pumped out of the cell and into the plasma, and Na+ then moves down the concentration gradient from the tubules, what happens to the K+?

A
  • K+ can be reabsorbed into the blood down the conctration gradient
  • K+ can be pumped into the tubules
52
Q

In the principle cells of the distal tubules, in addition to Na+ being reabsorbed from the tubules, what else can be reabsrobed by principle cells?

A
  • Cl-
53
Q

Which cells in the distal tubules are sensitive to aldosterone?

A
  • principle cells
  • aldosterone increases Na+ reabsorption at expense of K+
  • H2O follows Na+ whcih increases blood volume and BP
54
Q

What would an aldosterone antagonist, such as spirolactone do to perincple cells in the distal tubules of the kidney?

A
  • bind and inhibit aldosterone receptors on distal cells in tubules
  • inhibit Na+ and H2O reabsorption
  • used to reduce BP and odeama
55
Q

What s the role of the intercalated cells of the distal tubules in the kidneys?

A
  • exchange Na+ for H+
  • important for acid-base homeostasis
56
Q

What are the 2 subtypes of intercalated cells of the distal tubules in the kidneys?

A

1 - alpha intercalated cells

2 - beta intercalated cells

57
Q

In the a and B intercalated cells of the distal tubule, which is responsible for secreting and reabsorbing H+?

A
  • alpha cells = secrete H+
  • beta cells = re-absorb H+
58
Q

How does carbonic anhydrase facilitate the reabsorption of HCO3- into capillaries via alpha intercalated cells?

A
  • Na+ enters intercalated cell in exchange for a H+
  • H+ combines with HCO3- in lumen forming carbonic acid
  • carbonic anhydrase converts this to CO2 and H2O which can move from the lumen into the intercalated cells
  • carbonic anhydrase the reverse reaction leaving HCO3- and H+
  • HCO3- with Na+ can then be reabsorbed into capillaries
59
Q

What do the beta Beta intercalated cells do in the distal tubules?

A
  • reabsorb H+in exchange HCO3-
  • used specialist transporters called pendrin channels
60
Q

If the alpha intercalated cells do not work what can this cause?

A
  • metabolic acidosis
61
Q

If the beta intercalated cells do not work what can this cause?

A
  • metabolic alkalosis
62
Q

The are 3 hormones that regulate the amount of Ca2+ that is reabsorbed in the kidneys. What is the function of calcitonin?

A
  • decreases Ca2+ reabsorption
  • inhibits osteoclasts (re-absorption of Ca2+ from bones)
63
Q

The are 3 hormones that regulate the amount of Ca2+ that is reabsorbed in the kidneys. What is the function of Parathyroid Hormone (PTH) and active vitamin D?

A
  • Parathyroid Hormone (PTH): increases Ca+
  • 1,25 Vit D: increases Ca+
64
Q

Where is the majority of Ca2+ reabsrobed in the nepheron?

A
  • proximal tubules
65
Q

Where does the final modiufication of urine take place?

A
  • collecting ducts
66
Q

In a healthy individual are the collecting ducts permeable to H2O and solutes?

A
  • no
  • generally impermeable to both
67
Q

What is the most important hormone for maintaing water balance in the body?

A
  • anti diuretic hormone (increases thirst and increaes aquaporin number in collecting ducts for H2O to leave and be reabsorbed)
  • also known as vasopressin
68
Q

Anti Diuretic Hormone (ADH) is released from the posterior pituitary in response to hypothalamic input. How does ADH increase the permeability in the distal tubules and the collecting ducts?

A
  • acts on vasopressin V2 receptors on principal cells in DT and collecting duct
  • intracellular activation of Aquaporin-2 (AQP2) water channels
  • increases H2O reabsorbtion from urine
69
Q

Anti Diuretic Hormone (ADH) is released from the posterior pituitary in response to hypothalamic input. When would ADH be released generally?

A
  • low H2O levels
  • stimulates thirst
  • reabsorbtion of H2O in kidneys
70
Q

If there is no anti-diuretic hormone in the circulation, what can happen in the kidneys?

A
  • H2O is absorbed as normal in nepheron
  • BUT can cause significant increase in urine output and reduce blood volume in body
71
Q

Diabetic insipidus can cause no or very low levels of anti-diuretic hormone (ADH) being present in the circulation, and what can this cause?

A
  • significant urine output
  • synthetic ADH can be given to treat this
72
Q

In the figure below, is A or B high or low levels of anti-diuretic hormone (ADH)?

A
  • A = maximum ADH where high osmolarity = high solute concentration so little urine secreted
  • B = minimum ADH where low osmolarity = low solute concentration so lots of urine secreted
73
Q

What can alcohol do to anti-diuretic hormone (ADH) levels?

A
  • decrease ADH levels
  • can make you urinate more often
74
Q

Once all the solutes and H2O have been reabsorbed from the tubules what capillaries do they enter and then feed into?

A
  • peritubular vessels
  • then feed into vasa recta which surrounds the tubules
  • vasa recta then feeds into the renal vein

Year 1 NME (61 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions