Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
22 Cards in this Set
- Front
- Back
How many neprons are in a kidney? |
Each human kidney has 1 million nephrons. Kidney size is dependent on numbe rof nephrons.
|
|
AV nicking |
Symptom of hypertension - pinching between arterial and venous side in eye. |
|
Basic functions of proximal tubule |
Workhouse of nephron Reabsorbs 66% of glomerular filtrate Also reabsorbs HCO3-, glucose, amino acids Secretes H+, organic acids |
|
Early proximal tubule |
Apical Na+ driven, secondary active transporters
Basolateral Na/K ATPase moves Na+ across basal X transporters |
|
Reabsorption of solutes over distance of proximal tubule |
As substance reabsorbed, concentration decreases. By halfway through proximal tubule, almost all of nutrients have been absorbed. |
|
Reabsorption of HCO3- in early proximal tubule |
1. Filtered bicarbonate combines with secreted proton outside cell - H+ + HCO3- -> H2CO3 -CA-> CO2 + H2O 2. CO2 gas diffuses into cell. CA catalyzes CO + H2O to create H+ and HCO3- 3- HCO3- moves out of basolateral membrane via HCO3-/Na+ transporter. For every H+ filtered through glomerulus, one HCO3- is reabsorbed. 85% of bicarbonate filtered load reabsorbed (1/3 kg per day) |
|
Filtered Load |
GFR * P(bicarbonate) |
|
Late proximal tubule - transcellular absorption |
2/3 of NaCl absorption in late proximal tubule. NaCl absorption coupled by nonionic diffusion. Secreted H+ combines with secretes organic acid to form HA - nonionic species that diffuses into cell. HA dissociates in cell and H+ and A- are recycled to maintain Na+ and Cl- absorption. Na+ passed through basolateral membrane via Na/K ATPase. Cl- moves through basolateral membrane through selective channel or K+/Cl- cotransporter |
|
Late proximal tubule - paracellular absorption |
For every HCO3- absorbed in PT, we leave behind a Cl- so Cl- increases along tubule. Transepithelial potential is lumen negative in early proximal tubule because reabsorbing Na+ and leaving behind Cl-. As Cl- builds up in lumen, transepithelial potential becomes positive because Cl- is paracellularly reabsorbed down concentration gradient. Positive transepithelial potential causes Na+ to be reabsorbed paracellularly via electral gradient. |
|
Isoomotic Water Reabsorption |
PT is very leaky - generates little to no detectable osmotic gradient. 140L of water reabsorbed by proximal tubule each day. Cell volume turns over once per minute. |
|
Change in sodium osmolarity over course of PT |
Does not change - reabsorbed isotonically with water. |
|
Inulation osmolarity over course of PT |
Inulin is not reabsorbed so change is index of water being absorbed. [Inulin] increases linearly through length of PT as water is reabsorbed, leaving inulin behind. |
|
Absorption in thin limb |
Passive, driven by gradients created in thick limb |
|
NaCl absorption in ascending thick limb |
Reabsorbs 20-25% of filtered NaCl transcellularly. Apical Na/2Cl/K brings Cl- into cell. Cl- diffuses passively through basolateral channel. Na+ is pumped out by Na/K pump. K+ is needed for Cl- import. Must be recycled by apical K+ channel to keep transporter going. |
|
Na absorption in ascending thick limb |
Na/HCO3- pathway - same as in proximal tubule |
|
Paracellular transport in ascending thick limb |
K channel is only electrogenic transporter on apical side. Creates positive transepithelial potential which repels Na+, K, Ca2+, and Mg2+ to be reabsorbed paracellularly. |
|
Water transport in thick ascending limb |
Thick ascending limb is water impermeable. Absorbs salt and leaves water behind Luminal fluid becomes more dilute - thick ascending limb is also called diluting segment. |
|
Early distal convoluted tubule |
Reabsorbs 5-7% of filtered load of Na+ Water impermeable - tubular fluid diluted as salt reabsorbed. |
|
Late distal convoluted tubule and CCD - Principal cell |
Majority cell type. Exchanges Na+ with K+. Uses apical Na+ channel ENaC. Na+ moves down EC gradient into cell and pumped out via Na/K ATPase. K+ recycled out via apical or basal K+ channels. ENaC creates negative transepithelial potential so apical K+ channel is more active. Negative transepithelial potential also causes Cl- reabsorption paracellularly. |
|
Influence of ADH on principal cells (late distal tubule) |
Principal cell is impermeable to water ADH/vasopressin induces water channels to be incorporated into membrane so water can be reabsorbed. Regulated. |
|
Intercalated cell of late distal tubule |
Responsible for acid base transport Alpha-intercalated cell secretes protons into lumen. Beta-intercalated cell secretes base/HCO3- into lumen. Balance of alpha and beta intercalated cell regulates acid-base balance |
|
Medullary collecting duct |
Populated by principal-like cells except no apical K+ channel, no K secretion. Carries out final salt reabsorption. ADH controls both water and urea transport in this segment. |