To make pee, there are 3 steps...
1. Filtration
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@ Bowman's Capsule
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the cells form a selectively permeable membrane
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​water, NaCl, glucose, amino acids, H+, urea and uric acid are cool enough to go thru
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B/c they're too big, plasma, proteins, Red Blood Cells and platelets cant come in :(
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Glomerus does the filtering and it's hard core as it's 1.5 x the normal cappilary pressure
2. Reabsortion
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Important solutes and water go back to blood​
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Ion pumps transport k+, Na+ + Cl- in tubules which have mircovilli extentsions to increases surface area to reabsorb more
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Water movement is controlled by aquaporins water channels
Reabsorption happens by active + passive transport:
NaCl Active Transport
Na+ is the leader as it is pumped from tubules into kidney cells so then Cl- follows by diffusion and water follows by osmosis
Water Passive Transport
1. Efferent arteriole blood is high in [plasma protein] and low in [water] so water leaves tubules into blood
2. Solutes leave tubules which makes an osmostic gradient: this makes the [ ] increase in the surrounding cells so water moves into them
When water reabsorbs, nephron's solutes are more concentrated
Urea is left to make pee
Material left in nephron = filtrate
3. Secretion
- Waste movement from blood to nephron
-release toxins that aren't filtred
-maintain electrolyte balance
*HCO3- is not secreted b/c it's a buffer to maintain blood pH
(Pearson, 2014)