Lecture 34: Concentrating Mechanisms

Question 1

ADH requirements to make conc urine

Answer 1

REQS an osmotic gradient of solutes in ISF of RENAL MEDULLA

three major ones

Question 2

3 major solutes for high osmolarirty gradient in ISF of renal medulla

Answer 2

Na+
Cl-
urea

Question 3

urea

Answer 3

formed when knock an NH3 of proteins

NH3 TOXIC so we make it urea

Question 4

factors affecting osmotic gradeint gradient

Answer 4

1. Peremeability differences

2. Countercurrent flow

Question 5

Peremeability differences

Answer 5

in different section of LH and CD

Question 6

Countercurrent flow

Answer 6

in opp directions through tube shaped structures arranged closely and parallely in medulla

ex LHs can exchange matreials this way

Question 7

Countercurrent Multiplication definition

Answer 7

progressively INC osmotic gradeint forms in ISF of renal medulla DUE TO countercurrent flow

Question 8

Countercurrnet Exchange

Answer 8

process where solutes and water exchanged BETWEEN blood of vasa recta and ISF of renal medulla

Vasa recta: descending and ascending loops PARALLEL to each other AND to loops of Henle

Question 9

Countercurrent flow

Answer 9

through limbs=schange of soultes and water BETWEEN VASA RECTA BLOOD AND ISF OF MEDULLA

Question 10

vasa recta…

Answer 10

is a countercurrent exchanger

Question 11

what does vasa recta provide

Answer 11

oxygen and nutrients to renal medulla W/O washing out osmtic gradient

Question 12

Long loop of Henlee AND vasa recta together…

Answer 12

LLH ESTABLISHES osmotic gradient in renal medulla

VR: MAINTAINS gradient by countercurrent exchange

Question 13

Slides to ADD

Answer 13

20

Question 14

countercurrent multiplication involves…

Answer 14

involves long LHs of Juxtamedullary nephrons

Question 15

who is the countercurrent multiplier?

Answer 15

Long loop f henlee

Question 16

countercurrent multiplication: 4 steps overview

Answer 16

1. symporters in thick ALH=buildup Na Cl in medulla
2. countercurrent flow in DLH and ALH=osmotic gradient in medulla
3. cells in CD reabs more water AND urea
4. urea recycling= buildup of urea in medulla

Question 17

descending and ascending loops location

Answer 17

they are close and can exchange things!!! THis is why COUNTERCURRENT FLOW

Question 18

what is urea recycling?

Answer 18

constant movement of urea between tubule and ISF outside

Question 19

Countercurrent multiplication step ONE

Answer 19

WATER NOT REABSORBED (Talh walls impermeable)

So Na and Cl ions buildup in ISF

(def symporters in ascending=buildup ions in medulla)

Question 20

Countercurrent multiplication step TWO

Answer 20

desceding loop PERMEABLE to WATER NOT SOULTES

IS permeable to UREA

(establishment of osmotic gradient)

Question 21

Countercurrent multiplication step TWO: Osmolarity

Answer 21

osmolarity of ISF OUTSIDE DLH is HIGHER than tubular fluid inside

so water moves out of DLH into ISF (osmosis)

Question 22

Countercurrent multiplication step TWO: Ascending loop

Answer 22

ALH impermeable water, SYMPORTERS of cells reabs Na and Cl from tubular fluid INTO ISF

Question 23

Countercurrent multiplication step THREE: ADH

Answer 23

ADH inc water permeablilty of P cells

Water quick to go out of CD to ISF to VASA RECTA (more blood vol!)

Question 24

Countercurrent multiplication step THREE: loss of tubular water=

Answer 24

very conc UREA

BUT duct cells urea permeable, so urea diffuse into ISF of medulla

Question 25

Countercurrent multiplication step FOUR

Answer 25

urea accumulation (ISF), some diffuses to tubular fluid in LH (thin and descending) (urea permeable)

Question 26

What part of LH is UREA PERMABLE? (4)

Answer 26

thin ascending

descending

Question 27

what part of tubule NOT permeable to urea (4)

Answer 27

THICK ascending
DCT
cortical part of CD

Question 28

so what happens to urea imperable?` (4)

Answer 28

Urea stays in the tubule fluid in these parts

Question 29

4: tubule fluid in CD

Answer 29

ADH present
water reabs (osmosis)

Question 30

4: water reabs=

Answer 30

MORE UREA CONC in TUBULAR fluid

more urea diffuses into ISF of inner medulla

repeat cycle

Question 31

What moves around the most?

Answer 31

UREA!

moves a lot, then restart cycle (some we do get rid of)

Question 32

4: urea recycling def

Answer 32

constant transfer of urea between segments of renal tubule and ISF

Question 33

flow chart of urea recycling

Answer 33

water reabs from tubular fluid->
urea builup in ISF->
promote water reabs

Question 34

so what happens overall? (step four)

Answer 34

SOLUTES left in lumen become CONCENTRATED

small vol of urine excreted

Question 35

can vasa recta exchange with loops of Henle?

Answer 35

yes

Question 36

what all can excahnge

Answer 36

ascneding and descending LH with eachother

vasa recta with other vasa recta

flow of both systems moves OPPOSITE

Question 37

what is the countercurrent exchanger

Answer 37

VASA RECTA

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