Lecture 4: Glomerular Filtration Flashcards
What is the first step in forming urine?
Glomerular filtration
What is the initial first step of GFR?
Renal plasma flow
GFR is siphoned from
RPF
Ultrafiltrate contains
Water and small solutes
There should be absolutely no what in ultrafiltrate?
Proteins
Starling’s forces cause
Filtration
The ______ rate is much higher than in rest pf the capillaries
Filtration
What is the filtration rate much higher than in the rest of capillaries?
Because surface area in glomerulus is higher
What are the two types of cells in the glomerulus?
- Endothelial cells
- Mesangial cells
Which of the glomerulus cells have large pores and decrease GFR
Endothelial cells
Modified smooth muscle cells located between capillaries
Mesangial cells
Mesangial cells contract in response to what?
Angiotensin 2
Cells found in between afferent and efferent arterioles
Extraglomerular mesangial cells
Cells found inside glomerulus and in between capillaries
Intraglomerular mesangial cells
Jobs and properties of extraglomerular mesangial cells and intraglomerular mesangial cells
- Remove trapped residue/debris from basement membrane
- Contractile properties
Name the 3 layers of the glomerular capillary
- Endothelium
- Basement membrane
- Epithelium
Describe the endothelium
Relatively large pores in which fluid, dissolved solutes, and plasma proteins can easily enter
What does the endothelium not filter?
Red blood cells
Name the 3 layers of the basement membrane
Lamina rara interna
Lamina dena
Lamina rara externa
Name the two characteristics of the basement membrane
- No filtration of plasma proteins
- Significant barrier, keeps proteins out
Epithelium has what attached to the basement membrane of foot processes?
Podocytes
Small filtration slits between foot processes which add an additional barrier to larger substances. Which layer of the glomerular capillary?
Epithelium
Filtration depends on
Size and charge
What serves as a charge barrier on every layer of the glomerulus besides the lamina dena?
Negatively charged glycoproteins
What does the negative charge attract and repel?
- Repels large solutes w/ negative charges (proteins)
- Attracts solutes with positive charges
- Small solutes w/ negative charges can still filter
Locations of the two hydrostatic (fluid) pressures of glomerular capillary
- Capillary blood
- Interstitial space (Bowman’s space)
Locations of the two oncotic pressures of glomerular capillary
- Interstitial blood
- Bowman’s space (but should be zero)
Kf =
Water permeability of glomerular capillary wall
What makes up Kf
Total surface area of capillary + permeability per unit SA
Pgc =
Force favoring filtration
Relative to systemic capillaries, Pgc is
Very high
Pgc changes are produced by
Changes in resistance of afferent and efferent arterioles
Pbs =
Force opposing filtration
Pbs significance
Not very significant
πgc =
Force opposing filtration
What is πgc due to?
Blood protein
πgc changes throughout length of capillary
Increases due to fluid leaving
Filtration equilibrium
When net filtration out of capillary stops, driving force for reabsorption, filtration and force opposing filtration are equal
Net ultrafiltration pressure
Always favors filtration out of capillaries
