Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Urinary System > 4. Basic tubular function > Flashcards

4. Basic tubular function Flashcards

(51 cards)

Start Studying
1
Q

What components of urine do we not have a method of transporting on their own?

A

Urea and Water: so these move in by passive transport

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

What percentage of the ultrafiltrate is reabsorbed?

A

99%

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

2 pathways once entering renal artery

A

Glomerular filtration

Directly into efferent arteriole

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

Define osmolarity.

A

A measure of osmotic pressure exerted by a solution across a perfect semi-permeable membrane.
Dependent on the number of particles not the nature.

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

How do you calculate osmolarity?

A

Add all the concentrations of the different solutes together (mmol/l)
Each ion is counted separately

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe the range for normal plasma osmolarity. What makes up the majority of this?

A

Tight range: 285-295 mosmol/L

Mainly consists of Na+ (140 mmol/L)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the range for normal urine osmolarity?

A

50-1200 mosmol/L

Can vary massively

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What effect will a solute present at equal concentrations either side of a semi-permeable membrane have on water movement?

A

No net effect on water movement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the 2 pathways for absorption and secretion through the urinary epithelium?

A

Transcellular

Paracellular (depending on how tight tight junctions are)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the difference between lipophilic passive transport and hydrophilic passive transport?

A

Lipophilic passive transport rate has a linear relationship with solute concentration
Hydrophilic passive transport rateis saturable because it is dependent on the availability of channel proteins.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the 2 routes for water to pass through the renal tubular wall?

A

Transcellular (through aquaporins)

Paracellular

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are primary active transport mechanisms rate limited by?

A

Availability of ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are secondary active transport mechanisms rate limited by?

A

Concentration gradient (of Na+ going in) across membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How can hydrophilic passive transport be upregulated or downregulated?

A

By changing the number of transporters available
Decrease: Store channels inside cell
Increase: Move channels to cell membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How does protein reabsorption normally happen?

A

Receptor mediated endocytosis:
Protein binds to a receptor and is endocytosed
Acidity of the endosome allows the complex to dissociate and the receptors are recycled

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Specificity and capacity of protein receptors on the membrane for binding proteins

A

Low specificity

High capacity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What happens if the concentration of a solute in the urine exceeds the transport maxima?

A

It is excreted in the urine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Above which plasma glucose concentration do we see glucose in the urine?

A

15 mmol/l

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Where are the majority of Na+ transporters found?

A

Proximal tubule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Describe secretion

A

Moves substances from peritubular capillaries into tubular lumen
Can occur by diffusion or by transcellular mediated transport

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the most important substances that are secreted?

22
Q

Describe the differences in sodium reabsorption throughout the nephron.

Study These Flashcards
A

PCT: 65%
Ascending loop of Henle: 25%
DCT: 8%

23
Q

Where is most bicarbonate reabsorbed?

Study These Flashcards
A

90% is reabsorbed in the PCT

24
Q

Where and how much glucose is reabsorbed?

25
Where, along the nephron, do you find cells that don't have that many mitochondria?
Descending loop of Henle and collecting duct | These areas are mainly involved in the passive transport of water
26
Describe the features of a cell in the PCT
Numerous mitochondria Brush border to increase SA Designed for lots of reabsorption
27
What is the most important protein of the cells lining the tubules throughout the nephron?
Na+/K+ ATPase: | responsible for the sodium gradient that drives the movement of most substances
28
Which substances move in or out with Na+ in the early proximal tubule?
H+ moves out into tubule (Na+/H+ countertransport) Glucose moves into cell (Na+/glucose cotransport) Amino acids move into cell (Na+/amino acid cotransport)
29
How is proton excretion linked to bicarbonate reabsorption?
H+ are pumped into the tubule via (Na+/H+ exchanger) H+ react with HCO3- to form H2CO3 H2CO3 is converted by carbonic anhydrase to CO2 + H2O CO2 + H2O moves into the cell and carbonic anhydrase converts it back to H2CO3, which dissociates to form H+ and HCO3-. HCO3- is passes into the blood, H+ moves out again via the Na+/H+ exchanger
30
Why is reabsorption of all solutes/ water sensitive to metabolic poisons?
Reabsorption is dependent on ATP production
31
Why is net secretion in the PCT important?
Route of excretion for some substances | Some drugs enter the tubular fluid here and act further down the nephron
32
Describe the differences between the ascending and descending loop of Henle.
``` Descending: Squamous epithelium Few mitochondria Water passively reabsorbed Draws in Na+ and K+ Ascending: Cuboidal epithelium Few microvilli but many mitochondria Cl- actively reabsorbed Na+ passively reabsorbed with it HCO3- reabsorbed Impermeable to water (very tight TJs and no aquaporins)§ ```
33
Describe the tubular fluid leaving the loop of Henle with respect to plasma
Hypo-osmolar (More salt than water has been reabsorbed) Water: 85% Na+: 90%
34
What do Loop diuretics block?
Na+/K+/Cl- co-transporter in ascending loop of henle
35
Which transporter is found on the apical membrane in cells in the DCT?
Na+/Cl- cotransporter
36
Which 3 ions are reabsorbed on the apical membrane of cells in the DCT?
Na+ Cl- Ca2+
37
Describe how thiazide diuretics would lead to increase in plasma Ca2+
If Na+/Cl- channel is blocked, there is only 1 passive route of entry for Na+: so more is brought in by the Na+/Ca2+ transporter, and more Ca2+ is exchanged out into the blood This decreases intracellular Ca2+, so more Ca2+ enters passively from the lumenal side of the membrane (thus more Ca2+ is reabsorbed)
38
List 5 features of the epithelium of the distal convoluted tubule.
``` Cuboidal epithelium Few microvilli Complex lateral membrane Interdigitations with Na+ pumps Numerous large mitochondria ```
39
What do the macula densa cells do?
Detect Na+ concentration in the filtrate | Can stimulate release of renin
40
What is the reabsorption of Na+ in the distal part of the DCT and the collecting duct dependent on?
Aldosterone
41
What is needed for reabsorption of water in the collecting duct?
ADH
42
What other ions are adjusted in the DCT and CT?
K+ H+ NH4+
43
What are the two types of cells in the collecting duct and how do their functions differ?
``` Principal cells: Have Na+ channel sensitive to aldosterone Regulate movement of Na+/K+/water Intercalated cells: Regulate acid-base balance ```
44
What are each of the cells pumps in the CT mediated by?
Principal: Na+/K+ ATP pump Intercalated: ATP dependent H+ pump
45
State 3 single gene defects that affect tubular function.
``` Renal tubule acidosis Bartter syndrome Fanconi syndrome (Dent's disease) ```
46
What is renal tubule acidosis? State 3 clinical features.
Metabolic acidosis caused by failure of the renal tubules. Hyperchloremia Hypokalemia Impaired growth
47
What is Bartter syndrome? State 6 clinical features.
``` Excessive electrolyte secretion Hypokalemia Premature birth Polyhydramnios Renin and aldosterone hypersecretion Moderate metabolic alkalosis Severe salt loss ```
48
What causes Bartter syndrome?
Mutation in the Na+/K+/Cl- triple transporter | This point is responsible for 25% of Na+ reabsorbtion
49
What is Fanconi syndrome? List 2 clinical features
Disease of the proximal tubules associated with renal tubular acidosis Increased excretion of low molecular weight proteins Increased excretion of uric acid, glucose, phosphate and bicarbonate
50
Describe how Dents disease is a cause of fanconi syndrome
Mutation in endosomal compartment of Cl- transporter The endosome never gets to the pH that allows dissociation of the protein from its carrier, so cant recirculate carrier, so excrete protein
51
Describe how a normal endosomal compartment of Cl- transporter would work
To acidify endosome, you have to pump H+ into it As you pump H+ in, pH decreases, +ve charge increases Becomes increasingly harder to pump H+ in, so have a transporter that lets some H+ out in exchange for bringing Cl- in (1 charge goes out, but neutralise 2 charges) net reduction in charge of -3 so more H+ can be pumped in

Urinary System (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions