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28 Cards in this Set
- Front
- Back
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60-75% of glomerular ultrafiltrate is reabsorbed where?
Most of this occurs where within the PT? |
In the PT
Most occurs in the early PT |
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For some filtered solute such as glucose and amino acids, where does almost all of their reabsorption occur?
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In the PCT
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What drives both water and solute transepithelial membrane transport?
(different for water and solutes) |
Water - oncotic and hydrostatic pressure gradients
Solutes - Transepithelial electrochemical gradients - Apical membrane-cell and cell-basolateral membrane electrochemical gradients |
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What are the 2 routes of of trans-epithelial transport?
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Paracellular - between cells, the "low resistance" path
Transcellular - across the basolateral membrane, the "high resistance" path |
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What are the 3 types of active transport?
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1. Primary - ATP drives single pump
2. Secondary - Another pump uses the gradient the ATP pump setup to drive another ion in/out of cell 3. Tertiary - another pump? |
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How does the PCT Na-K-ATPase levels compare to other parts of the nephron?
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Relatively high (only DCT is higher)
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In the early part of the PT, what is reabsorbed?
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Most Na dependent reabsorption of bicarb, AA's, glucose, and some Cl
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In the later PT, what reabsorption predominates?
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NaCl reabsoprtion
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Does the osmolarity of the tubule fluid change along PT lenghth?
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Nah brahoeminen rapsody
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What describes the PT wrt to its water permeability?
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It is "leaky" with high water permeability
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Water movement occurs across the PT as a result of what?
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As a result of solute (Na) reabsorption and hydrostatic and oncotic pressure differences across the epithelium.
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How does water move out of the PT?
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Through aquaporines - AQP1
The majority (60-80%) via transcellular route |
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Loss of plasma water from the blood during filtration does what to oncotic pressure in the capillaries?
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Increases it - helps to draw more water back into the capillary
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The PT transport is large linked to what?
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Na - driving force is low intracelular [Na]
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NaCl reabsorption in the PT occurs via what?
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Passive diffusion across the paracellular space and via active transport through the cells
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How does Na pass through the cell?
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Via low intracellular [Na] to get it into the cell
Then Na/K pump to get it out of the cell (this is coupled to many other ions) |
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nearly all of filtered glucose is reabsorbed where?
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PT
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How is glucose reabsorbed?
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Co-transport with Na via SGLT1/2 transporter to put Glucose into cell
Then Glut1/2 transporter to efflux glucose out of cell |
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Draw out the glucose handling profile
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see page 355
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Where is phosphate reabsorbed?
How? |
In PT
Via Na-Phosphate cotransporters int he luminal membrane |
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How much AA is absorbed in the PT?
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INTENSE reabsorption brah
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If AA are not reabsorbed properly, what can form?
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Crystals and stones
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What is the reabsorption properties of urate handling in the kidneys?
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99% reabsorbed --> 49% secreted --> 40% reabsorbed
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Failure to adequately excrete uric acid is associated with what?
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Elevated blood levels, gout, and chonic kidney disease
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What ion is very important for maintenance of normal acid-base homeostatis?
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Bicarbonate
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How is bicarb reabsorbed?
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H+ secreted --> Adds to HCO3 to make H2CO3 --> Forms H2O and CO2 --> CO2 transported into PT cell --> Forms HCO3 --> HCO3 exported along with Na+
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How does the PT handle Ca and Mg?
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Reabsorbed by passive paracellular diffusion
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How is K+ reabsorbed?
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Via paracellular pathways
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