Tube histology Flashcards
Where is the largest amount of solute and water reabsorbed
The PCT, because of its large surface area d/t microvilli
How much glucose, AA’s, and vitamins are reabsorbed from the filtrate in the PCT
100%
True or false the PCT is a large contributor to urea recycling
True
50% of filtered urea is reabsorbed here
How is sodium transported in the PCT
via active transport, AA and Glucose are co-transported with it
Describe the events that occur when Na is reabsorbed in the PCT
- AA and Glucose are co-transported with it
- Na creates a positive charged enviroment (electrical gradient) in interstitium/peritubular capillaries/vasa recta so Cl passively flows to even out charges
- Now that NaCl has moved into capillaries/vasa recta an osmotic gradient has been set up so water flows passively from the filtrate to the interstitium/ capillaries/vasa recta
- Water then drags K and Ca with it, this is called solvent drag
When urea moves out of the PCT where does it go
moves passively out of the PCT and it can either be reabsorbed into peritubular capillaries/vasa recta or it can stay in the interstitium or it can go from the interstitium back into the tubule system
Where can urea be secreted from the interstitium to the tubule system
- Descending LOH and the thin ascending LOH always
- The distal portion of DCT and collecting ducts when ADH is present
What parts of the tubule system are impermeable to urea
The thick ascending LOH and proximal DCT
What region starts the urea recycling process
The distal portion of the DCT
What is the effect of parathyroid hormone on the PCT/DCT
- increase secretion of Phos into tubules
- stimulates synthesis of Calcitriol in PCT cells
- stimulates DCT cells to absorb more Ca
True or false solute and water reabsorption in the LOH are dependent on each other.
False. Solute and water reabsorption are independently regulated, unlike PCT
What portions of the LOH reabsorb water
water is only reabsorbed in the descending portion only
In regards to reabsorption and secretion what happens in the descending LOH
Water reabsorption and solute secretion
concentrates filtrate=considered the 1st concentration.
In regards to reabsorption and secretion what happens in the ascending LOH
Reabsorption of solutes
Dilutes filtrates
How does solute reabsorption in the ascending LOH help drive water reabsorption in the descending LOH
Solute reabsorption in the ascending limp creates an osmotic gradient (This part of the LOH is impermeable to H20 so water doesnt follow) in the interstitium between the two limps of the LOH and it pulls water from the descending limb from the tubule to the interstitium
True or false the ascending LOH is insoluble to water
True
What portions of the LOH participates reabsorption of water
water is only reabsorbed in the descending portion only
concentrates filtrate=considered the 1st concentration.
Where in the ascending LOH are solutes reabsorbed
the thick portion of the ascending LOH
What specialized cells are found in the thick portion of the ascending LOH and what is there fxn
Macula densa cells
Sense concentration of Na and CL in filtrate and release ATP and adenosine as part of juxtamedullary apparatus
What are the 2 types of specialized cells in the DCT and collecting ducts and what do they do
- Principle cells= respond to ADH (increases H20 absorption by increasing aquaporin 2 channels) and aldosterone to reabsorb Na and secret K
- Intercalated cells= regulate H ions and bicarb
Describe what happens to urea in the DCT/collecting ducts in the presence of ADH
more water is reabsorbed, so urea follows this keeps osmotic gradient moving. Once this urea is in the interstitial fluid it travels back to the descending LOH and gets secreted back into the tubule there.
What causes Aldosterone to be released
HyperK, Angiotensin II (low BP)
What are the 2 types of intercalated cells and what does each type do
- Type A=more acidic enviroment
- secretion of H,
- reabsorb bicarb
- reabsorb K - Type B=more basic enviroment
- reabsorption of H
- secretion of bicarb
What is the effect of ANP/BNP on the DCT/collecting duct
Inhibits reabsorption of sodium and water and inhibits RAAS
Where does the final dilution/concentration of the filtrate occur
the collecting duct
