Renal Physl 5 Flashcards
What is the initial step in the formation of urine?
Filtration
What percent of plasma is filtered out of glomerular capillaries at anytime?
20%. The rest returns into systemic circulation
What is the Filtration Fraction?
The proportion of plasma volume that filters into the tubule
What are the three filtration barriers in the renal corpuscle?
- Glomerular capillary endothelium
- Basal Lamina (basement membrane)
- Epithelium of bowman’s capsule
What does it mean that Glomerular capillaries are fenestrated?
They have large gaps between endothelial cells
What do the large gaps between the glomerular capillary endothelial cells do?
They help to facilitate filtration by allowing solutes to pass through but not plasma proteins or blood cells
What helps to repel plasma proteins in the glomerular endothelium?
The surface being comprised of negatively charged proteins that repel plasma proteins
What is the Glomerular Basement Membrane (basal lamina)?
A layer of extracellular matrix that is acellular
What does the GBM (basal lamina) separate?
It layer separates the glomerular capillary endothelium from the epithelium of the bowman’s capsule
What is the GBM (basal lamina) composed of?
Negatively charged glycoproteins and collagen
What epithelium is closest to the glomerular capillaries?
The bowman’s capsule epithelium
What is the Bowman’s capsule epithelium composed of?
Podocytes
Why are they called Podocytes?
Because they feature long foot like processes
What can pass through the slits of podocytes?
Filtrate can pass through
What cells are in between and around glomerular capillaries?
Mesangial cells
What can Mesangial cells do and why?
They are capable of contracting which can alter capillary blood flow and the amount of filtrate entering the tubule
What forces are found in the glomerular capillaries?
- Capillary hydrostatic pressure
- Capillary colloid osmotic pressure
- Bowman’s capsule hydrostatic pressure
What kind of pressure does blood in glomerular capillaries exert?
Glomerular capillary hydrostatic pressure
What is Glomerular capillary hydrostatic pressure?
The pressure the blood in the glomerular capillaries exerts on the capillary wall
What does Glomerular Capillary Hydrostatic Pressure Favor?
Fluid filtration out of the capillary and into bowman’s capsule
Why does Glomerular capillary hydrostatic pressure favor filtration?
Because Bowman’s capsule hydrostatic pressure is normally lower
What opposes filtration?
Protein remaining the capillaries
What pressures oppose filtration?
- Bowman’s capsule hydrostatic pressure
* Capillary colloid osmotic pressure
What is the Glomerular filtration rate?
The volume of fluid entering Bowman’s capsule/unit time
What two things is GFR influenced by?
- Net filtration pressure
* Filtration Coefficient (Kf)
What is net filtration pressure based on the balance of?
The three forces
What can net filtration pressure be altered by?
Renal blood flow and blood pressure
What can raise glomerular hydrostatic pressure and drive further filtration and increasing GFR?
Increasing renal blood flow and blood pressure
What are the two main components of the filtration coefficient?
- Total surface area for filtration
* Permeability of barrier between capillaries & Bowman’s capsule
What happens if functional nephrons and glomerular capillaries are lost?
The filtration coefficient and GFR are reduced
