P30 - Urinary System

Question 1

3 major processes of the nephron

Answer 1

• glomerular filtration (passive
• tubular resorption (passive and active)
• tubular secretion (passive and active)

Question 2

what passes through glomerular filtration

Answer 2

• water

- solutes (small proteins - smaller than albumin)

Question 3

what does not pass through glomerular filtration and stays in the blood

Answer 3

• cells

- most plasma proteins

Question 4

decrease glomerular filtration rate effects (2)

Answer 4

• substances cleared slower -> stay in plasma longer

- substances stay longer -> concentrations usually increase

Question 5

what part of blood does the glomerulus filter

Answer 5

• plasma

Question 6

factors that affect GFR

Answer 6

• cardiac output
• number of functional glomeruli
• constriction/dilation of afferent/efferent arterioles
• capsular hydrostatic pressure

Question 7

most H2O in glomerular ultrafiltrate is resorbed by what

Answer 7

• tubules

Question 8

in a healthy person how much H2O enters tubules each day and how much is excreted each day

Answer 8

• 180 L

- 1-2 L

Question 9

concentrating ability of cats

Answer 9

• can really concentrate their urine

Question 10

proximal CT effect on concentrating urine

Answer 10

• removes volume
• no change in concentration
• osmolality of tubular fluid is same as plasma

Question 11

descending loop of Henle effect on concentrating urine

Answer 11

• removes H2O
• increases solute concentration
• urine becomes more concentrated

Question 12

ascending loop of Henle effect on concentrating urine

Answer 12

• removes solutes

- dilutes (decreases concentration)

Question 13

distal nephron effect on concentrating urine if removes H2O

Answer 13

• increases concentration

Question 14

distal nephron effect on concentrating urine if does not remove H2O

Answer 14

• stays dilute

Question 15

azotemia

Answer 15

• increase nonprotein nitrogen compounds

- increase [urea] &/or increase [creatinine] in serum/plasma

Question 16

if azotemic 3 areas to try and define the problem

Answer 16

• prerenal
• renal
• postrenal

Question 17

uremia is a clinical sign indicating what

Answer 17

• renal failure

Question 18

major criteria for CRF diagnosis

Answer 18

• decrease GFR -> azotemia

- decrease concentrating ability -> USG (1.007-1.013)

Question 19

progressive renal disease urine production

Answer 19

• polyuria -> oliguria -> anuria

Question 20

acute renal insufficiency/failure (3)

Answer 20

• reversible or irreversible
• frequently oliguria or anuria
• acid-base problems

Question 21

where is urea produced

Answer 21

• in hepatocytes from ammonia

Question 22

urea excreted into intestine is important in what animals

Answer 22

• large animals

Question 23

what is a better measurement of renal failure in large animals

Answer 23

• creatinine

Question 24

where is creatinine produced

Answer 24

• from degradation of creatine or creatine-PO4 from muscle

Question 25

T/F: creatinine is reabsorbed by tubules

Answer 25

- false

Question 26

T/F: urea is reabsorbed by tubules

Answer 26

- true

Question 27

what can cause prerenal azotemia

Answer 27

- decrease renal blood flow (dehydration, shock) | - increase urea production

Question 28

pathophysiology of prerenal azotemia due to dehydration (decrease blood volume) (3 main things)

Answer 28

- release renin -> increase angiotensin II -> constrict glom. arterioles -> decrease blood flow -> decrease urea & Crt clearance - decrease amount of fluid into proximal tubules -> decrease flow rate -> increase time for urea resorption - increase increase release of ADH -> increase resorption of urea in distal nephron

Question 29

pathophysiology of prerenal azotemia due to protein degradation

Answer 29

- increase formation of NH4 -> increase formation of urea -> increase [UN] (if production > clearance) - no decrease in GFR

Question 30

pathophysiology of renal azotemia due to glomerular &/or tubular disease

Answer 30

- loss of functional nephrons -> decrease renal blood flow -> decrease GFR -> decrease clearance of urea and creatinine from plasma -> increase [UN] and [Crt]

Question 31

pathophysiology of post renal azotemia due to partial or complete urinary tract obstruction

Answer 31

- release of vasoactive substances -> constriction of glomerular arterioles -> decrease renal blood flow -> decrease GFR -> decrease clearance of urea and creatinine from plasma -> increase [UN] & [Crt]

Question 32

pathophysiology of post renal azotemia due to urine leakage

Answer 32

- fluid with increase [urea] and [creatinine] in extravascular fluid -> urea and creatinine diffuse into plasma -> increase [UN] and [Crt]

Question 33

decreased [UN] in serum or plasma can be due to (3)

Answer 33

- disorders that cause decreased urea synthesis (hepatic insufficiency) - disorders that cause increased renal excretion of urea - disorders that cause impaired proximal tubular resorption of urea

Question 34

is decreased [UN] or [Crt] considered not clinically relevant

Answer 34

- [Crt]

Question 35

what is a better indicator of decrease GFR in horses

Answer 35

- [Crt]

Question 36

how does central diabetes insipidus create decreased [UN] in the serum or plasma

Answer 36

- decrease ADH release -> increase excretion

Question 37

how does renal diabetes insipidus create decreased [UN] in the serum or plasma

Answer 37

- decrease tubular response to ADH