Categorie: Tutti

da Mei Le Padellec mancano 2 anni

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TOPIC 9

The Loop of Henle plays a critical role in the kidney's ability to concentrate urine, with its descending and ascending limbs serving distinct functions. The descending limb is permeable to water, allowing it to move out and concentrate the fluid, whereas the ascending limb actively transports sodium and chloride out, resulting in a lower osmolarity.

TOPIC 9

TOPIC 9

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Aquaporin 2

Collecting Duct

RAAS and ADH Systems

ADH/Vasopressin

Regulation
Antidiuresis: low urine flow rate

U/P > 1

stimulated by high plasma osmolarity

high urine osmolarity

Diuresis: high urine flow rate (unable to retain water)

U/P < 1

stimulated by low plasma osmolarity

low urine osmolarity

Increase plasma osmolarity, increase plasma vasopressin
Comes from the blood stream
Helps us increase BP by increasing water reabsroption.
Stimulates aquaporin translocation into collecting duct of apical membranes

Loop of Henle

Descending vs Ascending
Ascending

Thick: NaKCl cotransporter 2 (NKCC2) absorbs NaCl. Gap junctions are leaky and allow Na+ to slip through

Thin: Na and Cl are transported actively out of tubule (movement of solutes out = lower osmolarity = hypoosmotic fluid)

Descending

Water moves out to concentrate fluid

Water permeable (moves out of tubules because of hyperosmotic medulla)

Thick medulla allows increased urine osmolarity
Thicker medulla --> longer loops --> more concentrated urine --> more reabsorption of water
Medulla osmotic gradient determines max urine osmolarity
Extension of the loop
The longer the papilla, the longer the loop

Aquatic species have the shortest papilla (don't need to conserve as much water because live in water)

Mesic species (land/terrestrial) have an "average" papilla (have regular access to water)

Arid species have the longest papilla (need to conserve as much as possible because little access to water)

Dips down into medulla (where peritubular capillaries/vasa recta are located)
Loops allow fluid to be edited by environment of kidney