lecture 17- (T3) Urine Concentration and dilution Flashcards Preview

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Flashcards in lecture 17- (T3) Urine Concentration and dilution Deck (29):
1

what are the major functions of the kidneys

regulation of extracellular osmolality, including water loss and conservation

2

what happens when there is a large excess of water in the body

kidneys can excrete as much as 20 liters per day with a concentration as low as 50 mOsm/L

3

what is avidly reabsorbed in the ascending thick limb of henle

sodium. potassium and chloride

4

is the ascending thick limb of henle permeable to water?

NOOOOO

5

what is osmolarity at the early distal tubular segment of the ascending thick limb of henle

100 mOsm/L

6

is the ascending thick limb of henle affected by ADH

NOOO

7

what happens to urine output when ADH is present

it decreases

8

what are attributes of the late distal convoluted tubule

addition reabsorption of sodium chloride
impermeable to water in absence of ADH
osmolarity reaches 50 mOsm/L

9

what is the maximum urine concentration of the kidneys

1200 mOsm/L

10

what are the requirements for forming concentrated urine

presence of ADH
high osmolarity of renal medullary interstitial tubule (establishes osmotic gradient necessary for water reabsorption to occur)

11

what is the normal obligatory urine volume

0.5 L/Day

12

what is the tubular osmolarity of the proximal tubule

300 mOsm/L

13

where is about 65% of filtered electrolytes reabsorbed

proximal tubule

14

is the descending loop of henle permeable to water?

YESSS

15

what is the osmolarity of the descending loop of henle when ADH is high

1200

16

what does the thin ascending loop of henle reabsorb

sodium chloride
urea also diffuses into ascending limb (comes from urea absorbed into interstitial from collecting ducts)

17

what is the osmolarity in the thick ascending loop of henle

100 mOsm./L

18

what does the osmolarity of fluid in the late distal tubule and cortical collecting duct dependent on

ADH

19

what is the concentration gradient limited to in the countercurrent multiplier system

200 mOsm/L because of paracellular diffusion of ions back into tubule

20

what parts of the kidney are impermeable to urea

ascending loop of henle and distal cortical collecting tubule

21

what happens when ADH increases and cortical collection tubule

water is reabsorbed form cortical collecting tubule
urea is not very permeant here and becomes more concentrated in the tubule

22

what happens when ADH increases and medullary collecting duct

more water is reabsorbed from medullary collecting duct, resulting in higher concentration of urea
higher concentration of urine results in diffusion of urea out of duct into interstitial fluid
facilitated by UT-A1 and UT-A3 (ADH activated) transporters

23

how is the high concentration of urea in the tubular fluid and the urin maintained even though urea is being reabsorbed

simultaneous movement of water and urea out of the inner medullary collecting ducts

24

what does vasa recta do

prevents medullary hyperosmolarity from being dissipated

25

what is the role of osmoreceptor-ADH feedback mechanism

controls extracellular fluid sodium concentration and osmolarity

26

where are int magnocelular neurons that form ADH found

supraoptic and paraventricular nuclei

27

where are osmoreceptor cells found

vicinity of the AV3V region (anterior region of third ventricle)

28

define isotonic volume depletion

osmolarity remains the same but volume decreases

29

define isovolemic osmotic increase:

volume remains the same but osmolarity increases