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Flashcards in Renal Function Deck (57)
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1

Kidney Anatomy

2 bean shaped organs
cortex & medulla housed in fibrous capsule of connective tissue
nephrons

2

kidney function

eliminate NPN compounds
water & electrolyte balance maintained
acid-base balance
endocrine functions

3

Nephron

glomerulus - end of renal tubule, capillary tuft, sits in Bowman capsule
proximal convoluted tubule
loop of henle
distal convoluted tubule
collecting duct

4

Glomerular filtration

depends on blood pressure through glomerular capillaries & integrity of semi-permeable glomerular membrane
membrane is negatively charged so proteins & others are repelled

5

GFR

volume of blood filtered per minute
glomerular filtration rate

6

Proximal convoluted tubule

returns 75% of water, Na, Cl
100% of glucose, amino acids, vitamins, proteins, & varying amounts of urea, uric acid & ions like Mg, Ca, K, HCO3
water & cl are passive transport; everything else is active

7

Loop of Henle

opposing flows result in osmolality changes & hypo-osmole urine
COUNTER CURRENT MULTIPLIER

8

ascending limb of henle

Na & Cl are reabsorbed into medulla interstitial fluid along limb
impermeable to water -> hyperosmotic medulla
diluting limb (!)

9

descending limb of henle

highly permeable to water but does not reabsorb Na & Cl
water leaves for the medulla
fluid in loop is hypo-osmotic urine

10

Distal convoluted tubule

adjusts the electrolyte & acid-base homeostasis via ADH & aldosterone actions

11

aldosterone

acts on distal tubule stimulates Na reabsorption & excretion of K & H+

12

Urea

ammonia from amino acid degradation made into urea in liver
40-60% reabsorbed into medulla to maintain high osmolality

13

creatinine

waste from muscle
not reabsorbed by tubules

14

Uric acid

waste from purine metabolism
only 6-12% of original uric acid is excreted; can contribute to crystal in urine, gout & calculi

15

water balance

controlled by ADH, proximal, distal & collecting ducts

16

sodium balance

aldosterone system (RAS)
governs Na reabsorption

17

Potassium balance

excretion controlled by kidneys
actively reabsorbed through nephron; negatively effected by aldosterone

18

Chloride balance

maintenance of extracellular balance; passive reabsorption in proximal tubule

19

Phosphate, Mg, Ca balance

PTH controls proximal tubule reabsorption of phosphates
Mg filtered by tubule & reabsorbed via PTH action
calcium under PTH & calcitonin control so tubule reabsorption is not significant

20

Endocrine function

makes EPO, 1,25-dihydroxy vitamin D3, & prostaglandins

21

Kidney renin

made by juxtaglomerular cells of renal medulla; released when blood pressure decreases
activates renin-angiotensin system

22

EPO production

made by cells close to proximal tubule, production regulated by 02 levels in blood within 2 hour window

23

1,25-dihydroxy vitamin D3 production

made when kidney enzyme converts 25-hydroxy vit D to this form
adds a methyl group & becomes an active vitamin

24

Prostaglandins

made from arachidonic acid
increase blood flow, Na & water excretion & renin release
oppose renal vasoconstriction due to angiotensin II & norepinephrine

25

Creatinine clearance

creatinine clearance to assess glomerular filtration rate
males: 97-137 ml/min
females: 88-128 ml/min

26

Urea clearance

urea 40% reabsorbed by tubules- not used now

27

Cystatin C

low molecular weight protein from nucleated cells; freely filtered by glomerulus;
reabsorbed & catabolized by proximal tubule
constant rate unaffected by age, gender, race, muscle mass;
may be better early indicator of decreased GFR

28

Cystatin C vs Creatinine

creatinine - more stable w/in a person so fluctuations seen indicate renal function over time
cystatin C- doesn't change much between people but within a person there is bioflux; marker better at detecting minor renal impairment

29

Urine electrophoresis

normally excrete 50-150 mg/24 hrs
increases in protein indicate disease states
do electrophoresis to ID proteins & define disease type

30

Beta2-Microglobulin

small, non-glycosylated peptide found on surface of nucleated cells
shed at constant rate normally
elevated levels indicate myeloproliferative & lymphoproliferative disorders, inflammation or renal failure
filtered by kidney & then 99.9% reabsorbed