Kidney Tubular Function Flashcards
Where does filtration take place in the kidney
Renal corpuscle
180 l/day
Glomerulus, bowmans capsule
Where does reabsorption and secretion take place
Renal tubule
What is included in the renal tubule
- proximal convoluted tubule
- loop of henle
- distal convoluted tubule
- collecting ducts
What is the primary site of reabsorption
Proximal convoluted tubule
What percentage is reabsorbed in the proximal convoluted tubule
65%
How much of filtrate is reabsorbed in the the loop of Henle
25% is reabsorbed
What percentage is reabsorbed in the distal conjugated tubule
8%
How much sodium is reabsorbed in the kidney
98% Na reabsorbed - 80% energy consumption used by kidney
What increases the surface area of the proximal convoluted tubule
Microvilli
What are all portions of the nephron closely associated with
Closely associated with peritubular capillaries vasa recta
What is filtered and reabsorbed in the kidney
- sodium
- chloride
- calcium
- phosphate
- potassium
- bicarbonate
- water
- glucose
- amino acids
- urea
What is not reabsorbed in the kidney
Creatinine
What can be measured to determine kidney health
Creatinine levels because it shouldn’t be reabsorbed into the kidney
How does the filtrate move into the interstital space
Through passive diffusion
What is passive diffusion
Movement of molecules from high to low concentration until equilibrium is reached
What percentage of filtrate is reabsorbed into the blood
50% filtrate re absorbed into the blood and 50% remains in the tubule
The proximal tube reabsorbs … of filtrate
The proximal tube reabsorbs 2/3 of filtrate
What follows sodium
- water follows Na+ wherever it goes - osmosis
- glucose and amino acids co-transported with Na+
- chloride and negative ions follow Na+
Where is the sodium potassium pump
The sodium potassium pump is on the basolateral membrane and it facilitates 65% of sodium reabsorption
How does the sodium potassium pump facilitate nutrient reabsorption
By co transport
Why does water follow sodium
Water follows sodium via osmosis
Na+ active transport facilitates -
- 100% nutrient reabsorption - glucose and amino acids by co transport
- 65% of water reabsorption - water follows Na+
- 65% negative ions follow the electrochemical gradient
- no effect on waste removal
How much urea is reabsorbed by passive diffusion
50%
What happens to the remaining filtrate after reabsorption in the proximal convoluted tubule
Remaining filtrate (60l) continues through the loop of henle
What is the function of the loop of henle
Counter-current multiplication for the juxtamedullary nephrons
What are the three parts of the loop of henle
- thin decending limb
- thin ascending limb
- thick ascending limb
What part of the loop of henle contains aquaporins
The thin descending limb
Describe the thin descending limb
- freely permeable to water, allows movement of water into the intestinal space
- does not contain active sodium pumps
Describe the thick ascending limb
The site of sodium reabsorption
What is the role of the thick ascending limb
Actively pumps sodium into the intestinal space and water cannot follow because there are no aquaporins
Sodium reabsorption is via…
Via NKCC2 on the apical membrane
How many molecules of chloride are co transported in the thick ascending limb
2 molecules of chloride
How many molecules of potassium are co transported in the thick ascending limb
1 molecule of potassium
What is the main target site for drugs in the thick ascending limb
The sodium potassium pump is NKCC2 is the main target site for drugs
What conditions are created in the medullas as sodium is actively reabsorbed from the filtrate
The medulla becomes salty
What happens to the water in the filtrate as it enters the loop of henle
The water flows out of the loop of henle by osmosis
What happens to the concentration of the filtrate as it ascends the thick ascending limb
The concentration decreases
The most concentrated urine will be found deep in the medulla
This is called counter current multiplication
What is the function of counter current multiplication
Without this process we would need to go to the toilet and drink water all of the time
It’s a way to maintain a balance
What is the vasa rectas role in counter current multiplication
The vasa recta maintains the concentration gradient of the medulla, this is due to the fact that the blood flow is so slow it does not wash away the gradient
Why does the loop of henle employ counter current multiplication
To reabsorb water and concentrate urine
Where is sodium actively reabsorbed in the loop of henle
The thick ascending limb
The loop of henle maintains…
Creates and maintains high osmotic pressure within the medulla
Function of the distal convoluted tubule
Fine tuning - site of fluid volume and electrolyte regulation
Explain the role of hormones in the distal convoluted tubule
Sodium and water reabsorption are hormonally regulated
What is the function of the anti-diuretic hormone (ADH)
Increases water reabsorption
What is the function of aldesterone in the distal consulted tubule
Increases Na+ reabsorption
What is the function of atrial natriuretic hormone (ANH) in the distal convoluted tubule
Promotes Na+ secretion
What would happen if there was no hormonal regulation of the DCT
In the absence of external hormonal regulation a large volume of dilute (hypotonic) urine is produced
What produces ADH
The pituitary gland
How does ADH increase water reabsorption
Acts on distal and collecting tubules by inserting aquaporins, this allows the water to be reabsorbed from the filtrate
Small amount of urine produced
How does aldosterone act on the DCT
Upregulates activity and insertion of Na+K+ pumps and channels
Describe when Atrial natriuretic hormone (ANH) would be produced and why
Will be released when there is an increase in blood pressure and there is too much fluid in the circulation
Promotes Na+ secretion
