Glomerular Filtration Flashcards
What is the healthy rate of glomerular filtration?
125mL per min
What is the glomerular filter made up of?
Fenestrated endothelium
Podocyte foot processes
Connective tissue layer
What constructs the podocyte foot processes?
Nephrin Podocin Zonula occludens 1 Cadherins Cytoskeletal proteins
What connective tissues are located in the glomerular filter?
Collagen IV
Laminin
What affects the likelihood of a substance being freely filtered
Size and charge
Up to what size are molecules freely filtered regardless of charge?
17kDa
What may cause leaky filtration?
Defective proteins in the filter
What are the driving forces of filtration?
Capillary hydrostatic pressure
Bowman’s oncotic pressure
What are the opposing forces of filtration?
Capillary oncotic pressure
Bowman’s hydrostatic pressure
In which capillaries is filtration favoured?
Glomerular capillaries
In which capillaries is absorption favoured/
Peritubular capillaries
What is the effect of afferent arteriolar constriction on GFR?
Renal blood flow is decreased so GFR is decreased
What is the effect of efferent arteriolar constriction on GFR?
Capillary hydrostatic pressure increases so GFR is increased
What is the effect of afferent arteriolar dilation on GFR?
Capillary hydrostatic pressure increases so GFR is increased
What is the effect of efferent arteriolar dilation on GFR?
Capillary hydrostatic pressure decreases so GFR is decreased
What is the effect of angiotensin II on GFR?
Causes vasoconstriction of both arterioles, but affects efferent more. This reduced renal blood flow and decreases GFR
Describe the myogenic response
The arterial smooth muscle is stretched, causing contraction and increasing resistance
Both arterioles are constricted by the afferent will constrict more, reducing GFR
Describe tubuloglomerular feedback
The nephron monitors GFR using the macula densa cells
If fluid in the DCT is increased, increase chloride transport from DCT to macula densa occurs
Chloride stimulates ATP and ADP release from macula densa cells
ATP and ADP cause calcium influx into juxtaglomerular cells
Juxtaglomerular cells contract causing afferent constriction, decreasing GFR
Describe neural feedback on GFR
The juxtaglomerular cells and afferent arteriolar muscle cells receive direct sympathetic innervation which causes vasoconstriction to decrease GFR
