Renal Basics (Muster) - W1 Flashcards
List the 9 functions of the kidney:
- filtration (urine production)
- Blood pressure
- Sodium (Na) homeostasis
- Potassium (K+) homeostasis
- Bone and mineral
- RBC production (via EPO)
- Gluconeogenesis
- Acid base status
- water homeostasis
- How much of the cardiac output goes through the kidney on the first pass?
- How much of the cardiac output is plasma?
- 20% of cardiac output goes through kidney on first pass
- 60% of this is plasma = renal plasma flow
How does the glomerulus restrict filtration based on size?
-
capillary endothelium - pores, clefts, fenestrations
- no cells or proteins pass
-
basement membrane - anionic heparin sulfate, proteoglycan, type IV collagen network, laminin
- acts like sponge
- Podocytes: exterior, form small negatively charged slits - lay out foot proceses
What are the glomerulus size limitations?
- <7,000 Da = FREELY FILTERED
- INCLUDES: sodium, potassium, chloride, and urea from the PLASM
- >70,000 is completely excluded in normal state
- albumin is 66,000
Do anions or cations filter better?
- anions filter better because GMB and slit diaphragms are negatively charged
what is defined as the movement of fluid and solute across from the capillary lumen into Bowman’s space across ALL glomeruli in both kidneys
Glomerular Filtration rate
What are the primary forces in the afferent arterial?
(Pgc + Obs) - (Pbs + Ogc) = net ultrafiltration pressure
- Favors Filtration
- Pgc = 50 mmHG
- Ogc = 18
- Pgc = 15
- Obs = 0
What are the primary forces on the efferent arteriole?
- see INCREASE in oncotic glomerular capillary.
- favors EQUILIBRATION
- Pgc=50 + Obs = 0
- Pbs = 15 + Ocg=33
What is a normal GFR - how much is filtered per day and per minute?
- 180 L/day
-
125 mL/min
- although 1000mL delivered to kidney, this much isn’t filtered. 20% of flow is filtered of 60% (plasma portion).
What happens to filtration & GFR if you change renal plasma flow?
- Decreased renal plasma flow
- Decreased GFR
- Increased renal plasma flow
- increased GFR - up to 20% (20% is filtered)
What happens if you increase the hydrostatic pressure at each capillary end?
-
Afferent End
- Increased filtration
-
Efferent end
- Increased filtraiton (normally at equilibrium)
What happens if you increase the oncotic pressure of glomerular capillary at each end?
- Afferent end
- Increase in oncotic = decrease in GFR
- Efferent end
- Increase in oncotic = decrease in GFR - could end up favoring reabsorption.
What happens if you increase the oncotic pressure of bowmans space?
- Increased filtration –> increased GFR
What is the filtration fraction?
- the amount we filter per day
- 60% of blood is filterable plasma
- 20% is actually filtered
What is the excretion rate?
- the amout the kidney gets rid of
- must get rid of excess sodium and what we eat
- = urine flow rate x solute in urine
- what keeps us in BALANCE
