67: Renal Glomerular Filtration

Question 1

The kidneys are partially protected by ….

Answer 1

Floating Ribs (False Ribs)

Question 2

The cortex of the kidney contains:

Answer 2

-Convoluted tubules
– more active processes
– more blood flow (100x medulla)

Question 3

The homeostatic functions of the kidney.

Answer 3

i. Filters and cleans the blood - eliminates waste products and water and urine production (1 – 1.5 L/day excreted) 
ii. Controls blood pH, electrolyte concentrations, and volume status

Question 4

The endocrine functions of the kidney:

Answer 4

i. Synthesizes erythropoietin to stimulate blood cell production
ii. Converts 25-OH vitamin D into its active form 1,25-dihydroxycholecalciferol by the 1-a-hydroxylase enzyme in the proximal tubule
iii. Secretes renin enzyme into circulation to start the renin-angiotensinaldosterone (RAA) axis to increase blood pressure

Question 5

What two components determine flux across the glomerulus?

Answer 5

Permeability and Glomerular filtration pressures

Question 6

Filterability Coefficient (Kf) describes…

Answer 6

Permeability of the renal corpuscle

Normal range: 10-15 mmHg

Question 7

Starling’s Law: 4 pressures in theory affect fluid movement

Answer 7

1. Hydrostatic pressure of capillary (PG)
2. Hydrostatic pressure of Bowman’s space (PBS)
3. Oncotic pressure of blood (plasma) (piG) 4. (Oncotic pressure of Bowman’s space (piBS))

Question 8

PGC decreases slightly from afferent to efferent due to ……. along the length of the capillary

Answer 8

Flow resistance

Question 9

pGC increases from afferent to efferent due to ……..of fluid

Answer 9

Filtration

Question 10

Rate at which the ultrafiltrate forms in Bowman’s space

Answer 10

Glomerular Filtration Rate (GFR)

Question 11

Formula of Glomerular Filtration Rate (GFR)

Answer 11

GFR = Kf x ΔP Normal values of GFR = 90 - 140 ml/min

Question 12

Effect of Constriction of Afferent Arterioles on (Renal plasma Flow) RPF and GFR:

Answer 12

Decreases RPF and GFR

Question 13

Effect of Constriction of Efferent Arterioles on (Renal plasma Flow) RPF and GFR:

Answer 13

Decreases RPF

Increases GFR

Question 14

Effect of Dilation of Afferent Arterioles on (Renal plasma Flow) RPF and GFR:

Answer 14

Increases RPF and GFR

Question 15

Effect of Dilation of Efferent Arterioles on (Renal plasma Flow) RPF and GFR:

Answer 15

Increase RPF

Decrease GFR

Question 16

How does Nephrotic Syndrome change Starling Forces?

Answer 16

Increased permeability of glomerular capillaries to plasma proteins
Results in Increased (piB)

Question 17

How does Urinary Tract Obstruction (Obstructive Uropathy)

change Starling Forces?

Answer 17

Backs up tubular flow

Results in Increased (PB)

Question 18

67% H20/solutes reabsorbed by proximal tubule – returned to bloodstream by ……….

Answer 18

Peritubular capillaries

Question 19

3 Starling forces that control H2O movement:

Answer 19

1. Plasma oncotic pressure in peritubular capillary (pPC) - driving force for reabsorption
2. Hydrostatic pressure in peritubular capillary (PPC) - force that prevents water from entering capillary
3. Hydrostatic pressure in interstitial space (Pi / Po) - H2O follows solutes – increase pressure – forces H2O into capillary

Question 20

If the GFR is too high:

Answer 20

Needed substances cannot be reabsorbed quickly enough and are lost in the urine

Question 21

If the GFR is too low:

Answer 21

Everything is reabsorbed, including wastes that are normally disposed.

Question 22

………. maintains a nearly constant GFR when mena arterial blood pressure is between 80-180 mmHG.

Answer 22

Autoregulation

Question 23

Effects of the myogenic response of autoregulation:

Answer 23

Increased arterial pressure stretches smooth muscle in blood vessel walls induces constriction of afferent arteriole;

Question 24

Effects of the Tubuloglomerular Feedback of autoregulation:

Answer 24

Involves macula densa and vasoactive substances (adenosine, kinins, PGs) to constrict/dilate afferent/efferent arteriole