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Flashcards in Kidney and Liver Function Tests Deck (154)
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1

Functions of the urinary system

• excretion and elimination (removal of organic waste products from body fluids such as urea, creatinine and uric acid: terminal prods of metabolism)
• homeostatic regulation (water, electrolyte, acid-base balance)
• endocrine function (kidney hormone production)

2

What are some hormones produced by kidneys

• renin
• erythropoietin
• 1,25-dihydroxy vitamin D3
• Prostaglandins

3

Main function of kidney (multifunctional)

storage of liquids by concentration of urine

4

Urine excreted daily in adults is

about 1.5 L (kidney is only 1% of total body weight)

5

Renal blood flow accounts for what % of cardiac output

20%

(plasma renal flow: 600 ml/min/1.73 meter squared)

6

Two processes involved in renal blood flow

ultrafiltration (GFR): 180 L/day
Reabsorption (>99% of amount filtered gets reabsorbed)

7

functional units of kidney

nephrons
(600,000-1.5 million)
*decrease in functioning nephrons =impaired kidney function

8

number of nephrons an individual is born with which may determine that individual’s susceptibility to renal injury

nephron dose

9

Parts of the nephron

• Glomerulus
• Distal tubule
• Proximal tubule
• Collecting duct
• Loop of Henle

10

What is formed when collecting ducts ultimately combine? This is where urine collects before passing along the ureter and into the bladder

renal calyces

11

Where does transport of solutes and water occur?

across and between the epithelial cells that line the renal tubules

12

Kinds of transport observed in nephrons

active and passive

*many passive transport are dependent upon active ie sodium transport

13

mediator of filtration which is formed from a specialized capillary network (capillary endothelial cells are ~40 nm thick)

glomerulus

14

Purpose of circular fenestrations/pores with diameters of ~60 nmn in glomerulus endothelium

Permits virtually free access of plasma solutes to the basement membrane

15

What is the renal threshold for glucose?

180 mg/dL

16

What is renal threshold?

Blood concentration of a substance that when surpassed, is excreted in urine

17

[Renal threshold]
What is tubular maximum?

maximum capacity of the kidneys to absorb a particular substance
*Tm for Glucose = 350 mg/min

18

What is the pre-renal cause of kidney functional disorder?

pre-renal: decreased intravascular volume

19

What is the renal cause of kidney functional disorder?

acute tubular necrosis

20

What is the post-renal cause of kidney functional disorder?

ureteral obstruction

21

What are the terminal products of hemoglobin catabolism?

bilirubin
urobilin

22

Hormone metabolites excreted from bloodstream

cortisol
testosterone
*other substances: organic acid, drugs, food additives

23

Other mechanisms of excretory function of kidneys

• Regulation of blood pressure, circulating volume, and water balance by urine concentration
• Regulation of electrolytes by excretion and resorption
• Maintenance of blood pH in a physiological range by eliminating radical acids, reabsorbing and forming bases

24

[Homeostatic regulation]
What hormone regulates maintenance of water balance

antidiuretic hormone

25

[Homeostatic regulation] ADH in maintenance of water balance responds primarily to changes in?

osmolality and intravascular volume
(secreted from posterior pituitary)

26

[Homeostatic regulation] What happens when ADH increases permeability of DCT and collecting ducts of water?

Results in increased water reabsorption and excretion of more concentrated urine

27

[Homeostatic regulation] What do the renal tubules do in states of dehydration?

reabsorb water at their maximal rate resulting in production of a small amount of maximally concentrated urine

28

[Homeostatic regulation]
When do renal tubules reabsorb water at only a minimal rate?

in states of water excess resulting in excretion of large volume of extremely dilute urine

29

hormonal factors affecting regulation of electrolyte concentration

*together with neurogenic stimuli

ADH (through detection of osmotic and mechanical stimuli)
Aldosterone
Natriuretic peptides (sodium urinary removal requires h2o removal)

30

How does aldosterone affect electrolyte concentration?
*triggered by decreased blood flow or blood pressure in renal arteriole and decreased plasma sodium

sodium reabsorption and excretion of potassium and hydrogen