L118: Kidney 1/2 Recap Flashcards
What is the function of the kidneys?
- Filter blood;
- Produce urine as a by-product.
What is the functional unit of the kidneys?
Nephron
In the kidneys, where does filtration of blood occur?
The renal corpuscle
What are the major components of the renal corpuscle?
- Glomerulus;
- Bowman’s capsule.
What are the major components of the filtration barrier?
- Fenestrated glomerular endothelium;
- Basement membrane;
- Pedicels of podocytes.
What is GFR?
Glomerular Filtration Rate
What is GFR equal to?
Kidney function (measured by the blood concentration of creatinine)
How much filtrate do the kidneys filter in one day and how much is reabsorbed?
180L/day, 99% is reabsorbed
In the kidneys, where does reabsorption and secretion occur?
The renal tubule
What are the major components of the renal tubule?
- PCT;
- L of H;
- DCT;
- Collecting duct.
Why is the PCT much longer than the DCT?
To ensure maximal reabsorption of nutrients
What kind of epithelium surrounds the Bowman’s capsule (parietal layer)?
Simple, squamous
What part of the L of H is freely permeable to water?
Thin, descending limb
What part of the L of H is impermeable to water?
Thick, ascending limb
What part of the L of H actively pumps ions (Na+, Cl- and K+) into the interstitium?
Thick, ascending limb
What is the purpose of the thick, ascending limb generating a ‘salty’ interstitium?
To generate an osmotic gradient which facilitates water reabsorption from the thin, ascending limb
In the kidneys, where does fine-tuning of filtrate occur?
DCT
What is fine-tuning?
Site of fluid volume and electrolyte regulation
How is sodium and water reabsorption regulated?
Hormones
Give an example of a hormone that increases water reabsorption:
Anti-diuretic hormone (ADH)
Give an example of a hormone that increases sodium reabsorption:
Aldosterone
Give an example of a hormone that promotes sodium excretion:
Atrial natriuretic hormone (ANH)
How does aldosterone promote sodium reabsorption?
Acts on distal and collecting duct to allow Na+ to be reabsorbed
How does aldosterone promote sodium reabsorption?
- Acts on distal and collecting duct to allow Na+ to be reabsorbed;
- Works (distally) with ADH to reabsorb water;
- Collecting duct becomes permeable to water.
Aldosterone acts to increase sodium reabsorption, how does this effect water regulation?
- Increases the concentration of sodium;
- Creates an osmotic gradient;
- Water follows and is reabsorbed.
(K+ concentrated urine)
