Reabsorption/secretion In The Proximal Tubule

Front 1

While excreting wastes, the essential components of glomerular filtrate need to be saved. How is this achieved?
Where is mass reabsorption?

Back 1

Tubular reabsorption.

Mass reabsorption of glomerular filtrate (2/3) in the proximal tubule.

Front 2

What is the primary role of the proximal tubule?

Back 2

Reabsorb most of the filtered water and solutes (important for regulation of ECF volume)

Front 3

What is the equation for the rate of flow in the proximal tubule?

Back 3

GFR- reabsorption [+secretion] = rate of flow in LOH

Front 4

What are the major solutes that contribute to isotonic reabsorption in the proximal tubule?

What is the effect of distance from glomerulus on inulin concentration ratio (TF/P)

Back 4

Sodium, chloride, and bicarbonate

Front 5

How does sodium reabsorption occur?

Back 5

Occurs throughout the length of the nephron (active transport mechanism = consumes energy, MAJORITY OF O2 consumed by kidney)

Na-K ATPase pumps out 3Na+ into interstitium and brings in 2 K+ ions (1 molecule ATP) --> decrease in intracellular Na+ concentration and membrane potential brings in a sodium ion through the luminal Na+ membrane channel.

Front 6

What is this passive diffusion of sodium into the luminal channel also provide the energy for?

Back 6

Reabsorption of other solutes from lumen of proximal tubule (bicarbonate, glucose, AA, organic acids)

Front 7

True or false.
Na+ is the only quantitatively important substance whose transport is directly coupled to metabolic energy in proximal tubule.

What two types of channels is the import of sodium tied to?

Back 7

True.

Antiport and cotransport

Front 8

What is sodium reabsorption accompanied by? Why?

What would a leaky epithelium cause?
What is absorbed in the STRAIGHT tubule?

Back 8

Front 9

What is the pathway of water reabsorption and how it affects the osmotic gradient?

Back 9

Front 10

What accounts of the maintenance of isosmotic reabsorption of filtrate? Where are they located (3)?

Back 10

Front 11

What forces are involved in capillary uptake of fluid from interstitial fluid?

What are the three forces? What does each favor?
Another name for these forces?

Back 11

Front 12

True or false.
Reabsorption from proximal tubule is iso-osmotic, but it is selective. What does this mean?

Back 12

True
All solutes are not absorbed to the same extent.

Front 13

What is the absorption of each?
Na, K, Cl, Bicarbonate, nutrients, inulin, PAH

Back 13

Front 14

What is HCO3 preferred over an what is its reabsorption driven by?
What three components all secrete H+ into lumen?
What is proton secretion mediated by in the PT?
How is HCO3 pumped out to ISF?
What does HCO3 react with to form carbonic acid?

Back 14

Front 15

What is the transporter for glucose reabsorption?
What is it coupled to? Does it have a threshold?

What are some causes of glucosuria? Symptoms?

Back 15

Front 16

What is AA reabsorption coupled to? Is it almost completely reabsorbed?

How are organic acids reabsorbed?
How are proteins and peptides reabsorbed?
When is protein excretion high?

Back 16

Front 17

How is phosphate reabsorbed?
Does it have a low threshold? Is it partially excreted continuously in urine? What controls threshold? What regulates Tm?

Back 17

Front 18

Cl- is passively reabsorbed due to what two things?
How much is reabsorbed due to active transport of HCO3-?

Back 18

1. Concentration gradient created by water reabsorption.
2. Electrochemical potential gradient created by Na+ reabsorption.

Front 19

How is potassium reabsorbed?

How is urea reabsorbed? What increased urea clearance?

Back 19

Front 20

Substances that are freely filtered, but not reabsorbed, can increase what?
What is the clinical significance of this?

Back 20

Osmolarity and diuresis (excessive water excretion)

Reduction of intracranial and intraocular pressure, promote excretion of toxins, edema.

Front 21

What is a substance that can reduce water reabsorption and increase excretion? How (pathway)?

Back 21

Front 22

What substances are secreted in PT? How? What transporters?

Back 22