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What kind of epithelium does the PCT have?
Cuboidal leaky microvilli
What kind of epithelium does the DCT have?
Cuboidal tight
What kind of epithelium does the nephron loop for the thin descending limb have?
Squamous tight
What kind of epithelium does the nephron loop for the thick ascending limb have?
Cuboidal tight
What kind of epithelium does the collecting duct have?
Cuboidal tight
Only the … is squamous; it is the one part of the nephron that does not transport ions
thin limb
What is the percentage of filtrate that the Loop of Henle is responsible for reabsorption?
25%
What is the amount of water that the Loop of Henle is responsible for reabsorption?
45L per day
What is the percentage of filtrate that the DCT and collecting reabsorbs?
5-14%
What is the amount of water that the DCT and collecting reabsorbs?
9L per day
Is the water (and solute) absorption in the Loop of Henle obligatory or facultative?
Obligatory
Is the water (and solute) absorption in the DCT obligatory or facultative?
Facultative
Where does each Loop of Henle descend into?
Hyperosmotic renal medulla
What kind of nephron loop extends further into the medulla
Juxtamedullary nephron
In the medulla there is an osmolarity gradient: … in the medulla = … osmolarity
deeper, higher
Tubular fluid flows from the PCT to the … limb and on into the … limb
thin descending, thick ascending
Counter-current: exchange occurs between fluids (in the limbs of the loop) moving in … directions
opposite
Multiplication: exchange … as movement of fluid continues
increases
The 2 limbs have different … for water and solute movement, which enhances overall reabsorption
permeabilities
The blood vessels of the … also contribute to counter-current multiplication
vasa recta
What phenomenon does the arrangement of the Loop of Henle create?
Counter-current multiplication
The thin descending limb is … to water, but … to solutes
permeable, impermeable
What water channel does thin limb cells express on their membrane?
Aquaporin-1
Because the osmolarity of the ISF … as the limb goes deeper, the direction of tubular flow … water reabsorption
increases, enhances
The thick ascending limb can … out of the tubular fluid but is … to water
pump ions, impermeable
The thick limb can pump sodium and chloride out of the tubular lumen and into ISF due to expression of what transporter on the apical surface?
NKCC transporter
What does NKCC stand for?
1 Na+ : 1 K+ : 2 Cl-
Does osmolarity of tubular fluid increase or decrease in the thin descending limb?
Increase
Does osmolarity of tubular fluid increase or decrease in the thick ascending limb?
Decrease
What is the osmolarity gradient in the deep medulla partly maintained by?
Urea permeability
Where are urea transporters (and thus permeability) only present in?
Papillary duct
Where does the papillary duct run through?
Renal papilla
The distal convoluted tubule and collecting duct are sites for … water and solute reabsorption
facultative
Reabsorption will only occur in the DCT and collecting duct if stimulated by … signals
hormonal
The epithelia in the DCT and collecting duct have little to no … transport and are … to water ‘at rest’
paracellular, impermeable
Without hormone signalling: water would be … in the lumen of the DCT and CD even while passing through the high osmolarity in the deep medulla
retained
Which hormones bind to DCT and CD cells allowing them to promote the addition of aquaporins to their apical membranes?
ADH/vasopressin
Where is the anti-diurectic hormone (also called vasopressin or AVP) is secreted from?
Posterior pituitary
AVPR activation signals for insertion of what?
Aquaporin-2
What creates transmembrane permeability to water, allowing for osmotic reabsorption and concentration of urine?
Aquaporins
What are aquaporins?
Water channels that allow water to rapidly diffuse according to the local osmotic gradient
What are the body’s key effector for homeostatic regulation of body fluid osmolarity?
ADH levels
ADH neurons in the hypothalamus are intrinsically …., so when plasma osmolarity increases, they produce higher frequencies of APs
osmosensitive
What kind of feedback loop is the ADH regulation of plasma osmolarity?
Direct
What endocrine disorder does the loss of either ADH secretion or AVPR2 lead to?
Diabetes insipidus (DI)
Inherited diabetes insipidus can be caused by mutations in which genes?
AVP gene or AVPR2 gene
Physical damage to what can prevent ADH secretion?
Hypothalamus or infundibulum of the pituitary
… regulates … reabsorption and urine volume primarily through …
RAAS, ion, aldosterone
Reductions in blood volume trigger the RAAS, resulting in … secretion
aldosterone
What does aldosterone stimulate?
Sodium/potassium ion ATPase pump
Aldosterone stimulate sodium/potassium ATPase pump, enhancing potassium ion … and sodium ion …
excretion, retention
Which side of the membrane in the DCT does aldosterone stimulate sodium/potassium ion ATPase?
Basolateral
In the DCT: aldosterone stimulates the sodium/potassium ion ATPase in the basolateral membrane, amplifying the gradient for sodium ion reabsorption at the … membrane
apical
In the CD (principle cells): aldosterone causes addition of … channels (sodium leak channels) to the apical surface, enhancing sodium ion reabsorption
ENaC
In response to a loss of volume, what does aldosterone (and ADH) both contribute to?
Homeostasis of fluid
What is a diuretic?
Any drug that causes diuresis (increased production of urine)
Most diuretics are … for specific renal transporter proteins, and they are often prescribed to manage hypertension or oedema
inhibitors