What is the functional unit of a kidney?
A Nephron
(Each kidney has about 1 million)
What are the 3 specific processes to urinary formation?
Filtration, re-absorbtion, secretion
Where is filtration (for urine formation)
It occurs in where the glomerulus meets the Bowman’s capsule
What occurs during filtration? (For urine formation)
High pressures force fluid and small molecules out of the blood and into the capsule.
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(Blood cells & large proteins stay in the blood. They are too large to pass through the filter.)
What type of components get filtered into the Bowman’s capsule? (5)
Water, glucose, amino acids, urea, ions
What occurs during Reabsorption? Where?
It makes useful substances from the filtrate back into the blood.
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-The Proximal Convoluted Tubule (active & passive transport)
- Loop of henle(ascending & descending limb)
What happens in the Proximal Convoluted Tubule?
Active Transport: where Mitochondria provide energy to pump glucose, amino acids & Na back into interstitial fluid
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Passive Transport: Where water follows the solutes via osmosis
What happens in the loop of henle? (Permeability)
Descending Limb: Permeable to water, but not salts, so water exits via aquaporins since medulla is salty.
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Ascending Limb: Permeable to salts but not water, so Na & Cl are transported out, making medulla salty.
What occurs during secretion? Where?
Wastes are actively removed from the blood to the nephron
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- In the Proximal Convoluted Tubule, Distal Convoluted Tubule & Collecting Duct
What are some substances that are secreted into the nephron? (3)
- H ions
- Potassium
- Drugs/Toxins
Where do the collecting ducts descend into?
Salty renal medulla
What are collecting ducts permeable to?
To water but NOT salt
What happens as urine descends through the collecting ducts into the salty medulla?
Water from the urine is drawn out by osmosis into the (salty) medulla. This concentrates the urine.
Why does urea leak out of the bottom of the collecting duct, into the medulla?
To help maintain high salt concentration of the medulla
Why is it important that the medulla is salty?
It is essential for the descending limb’s function
