Kidney Function Flashcards
What is the clearance?
The volume of plasma cleared of a substance per unit of time
For which type of glomeruli does the loope of Henle penetrate deeper into the medulla?
Juxtamedullary
Where is Na and Water reabsorption regulated?
Collecting duct
What is the name of the Na transporters in the collecting duct?
ENaC - channel
What is a possible consequence of low [Ca++]
Bone fractures
What happens when ADH is high?
Water is reabsorbed in the collecting duct
Which part of the nephron abuts with the parent glomeruli?
Thick ascending tubule
What are the two mechanisms of regulating glomerulus pressure?
Myoenteric reflex
Macula densa sensing
How do you calculate the clearance of a substance?
([X]urine x Volume of urine) / Plasma conc of X
What mediator regulates water reabsorption in the collecting duct?
Vasopressin
Which drugs act at the distal tubule?
Thiazide diuretics
What are the two types of glomeruli?
Superficial corticol
Juxtamedullary
What do the arterioles of juxtamedullary glomeruli become?
Vasa recta
T/F the thick ascending limb is permeable to water
False, the tight junctions are not permeable
Across what range of MAP does autoregulation keep GFR constant?
80-180mmHg
What does the 3 mean in vitamin D3?
It has 3 hydroxy groups
How much plasma is reuptaken into pertubular capillaries?
178L per day
What happens with anions in the proximal tubule?
They follow the gradient created by Na transport
Where in the proximal tubule is more Cl reabsorbed?
In the late PT
What is ureamia?
Accumulation of waste products in the blood - not necessarily urea
Is bicarbonate transport in the proximal tubule transcellular or paracellular?
Transcellular
What does microalbuminurea indicate?
Damage to the lamina propria in advanced diabetes that is allowing albumin to filter through capillaries
What is side effect of frusemide use?
K loss
Sometime the most important consequence of renal failure isn’t loss of tubular secretion but rather …?
Loss of endocrine function
What is the mechanism of renin release at the macula densa?
Non-active contraction of the arteriole is sensed > Renin is released via an unknown mechanism
What happens to NaCl at the tip of the loop of Henle?
It is reabsorbed due to there being relatively less of it in the ECF
How does the water and Na reabsorption change throughout the nephron
70% in proximal tubule
20-25% in the Loop of Henle
5% in the distal tubule
3% in the collecting duct
What what plasma concentration does glucose begin to be excreted?
10+mmol/L
What is the urine output per day?
1-2L
What is the resistance of the glomerulo-capillary?
Negligible
How much penilicin is reabsorbed in the kidneys?
None - it is all filtrated or secreted out
Overall, what happens to the contents of the TAL?
Diluted
What are the 4 physiological processes that occur in the kidneys?
Filtration
Reabsorption
Secretion
Excretion
What is major substance that is reabsorbed in the thin descending limb of the loop of Henle?
Water
How does the collecting duct vary its water permeability?
Inserting or removing aquaporins
How is HCO3 exchange at the baso-lateral membrane different in the thick ascending limb to the proximal tubule?
In the TAL it is coupled with Cl whereas in the proximal tubule it is coupled with Na
What mediator regulates Na reabsorption in the collecting duct?
Aldosterone
What is the myoenteric reflex?
Swelling of the afferent arteriole is sensed mechanically and the it constricts in response
What transport occurs at the distal tubule?
Transcellular co-transport of Na with Cl
Describe Na transport in the proximal tubule
Na/K pumps on the baso-lateral membrane creates a Na gradient into the epithelials. Na is coupled with other solutes and co-transported across the apical membrane.
Some Na backleaks through the paracellular path back into the lumen
What is the filtration rate of plasma?
180L per day
What pressure is the glomerulus kept at ideally?
50mmHg
What is the major O2 consumer in the kidneys?
Na/K ATPase
What is the target of frusemide?
Na/K/Cl co-transporters in the thick ascending limb
What are the implications of the high flow of water out of the lumen in the proximal tubule?
It takes solutes that are disolved in it with it, like K, Ca and urea
What factors influence GFR in the glomerulus?
Hydrostatic pressure in the glomerulo-capillaries
Hydrostatic pressure in the bowmen’s capsule
Onsotic pressure in the glomerulo-capillaries
Oncotic pressure in bowmen’s capsule
Why does the filtration rate decrease along the glomerulo capillary?
Oncotic pressure increases in the capillary
What does the macula densa do?
Senses the Na+ in the thick ascending tubule annd produces mediators that control the tone of the afferent arteriole
What is the maximum and minimum concentration that urine can be excreted at?
1200 miliosmols
30 miliosmols
How is phosphate reabsorbed?
Co-transported with Na in the apical membrane of the proximal tubule
How is Na transported in the thick ascending loop of Henle?
Active transport
T/F Each nephron has it’s own collecting duct
False, multiple distal tubules drain into a single collecting duct
What do efferent arterioles become?
Peritubular capillaries
How are amino acids reabsorbed?
Co-transported with Na in the apical membrane of the proximal tubule. 7 different types of co-transporters
Is Cl transport in the proximal tubule transcellular or paracellular?
Paracellular
What happens to GFR when the afferent arteriole constricts?
It decreases
Which arteriole does angiotensin II constrict more?
The efferent
Describe the sequential segments of the nephron
Bowmen’s capsule
Proximal tubule
Thin descending loop of Henle
Thin ascending loop of Henle
Thick ascending loop of Henle
Distal tubule
Collecting duct
What are the 2 parts of the proximal tubule?
Proximal convoluted tubule
Pars recta
How is glucose reabsorbed?
Co-transported with Na in the apical membrane of the proximal tubule
How can renal failure cause anaemia?
Loss of EPO production
What endocrine signals does the kidney produce?
EPO, renin, Vitamin D3, PGI2 (aka prostacyclin)
What is the effect of renin release?
Increase blood volume
Na conservation
What happens to K in the collecting duct?
It’s secreted
Why can’t most plasma proteins filter through the capillaries?
They are negatively charged and so it the lamina propria
Why do the capillaries have fenestration?
Limits the size of what can be filtered through
Where in the proximal tubule is more HCO3 reabsorbed?
Early on in the PT
How much phosphate is excreted?
20%
What happens to GFR when efferent arteriole constricts?
It increases
At what rate is GFR problematic?
30-40L per day
What is the mediator of arteriole constriction released by the macula densa?
Adenosine
Thromboxane
What is the renal blood flow rate?
1L per minute (in a 70kg adult)
How Ca reabsorption regulated?
Parathyroid in the proximal tubule
Vitamin D3 in the distal tubule
How is urea reabsorbed?
Passive means
How does the ECF concentration vary across the kidney?
300mOsmol at the cortex
1200mOsmol towards the papilla
What percentage of K is excreted?
10%
What is the filtration fraction of the kidneys?
20%
What percentage of urea is excreted?
50%
What are the functions of the kidneys?
Water and Na homeostasis
Control of ECF ion concentration (K+, Cl-, Ca++, Mg++, HPO4-2)
Acid-base control
Excretion of waste products and xenobiotics
Endocrine functions
Formation or concentrated/diluted urine
Which type of glomeruli are there more of?
Superficial cortical glomeruli
What must happen to calciferol?
Have 2 hydroxy groups added
How is water reabsorbed in the proximal tubule?
Passive transport transcellularly and paracellularly, following the gradient created by Na transport
What normally happens to GFR when MAP increases from 90 to 110?
It doesn’t change
