What’s the glomerulus?
network of capillaries located at the beginning of the nephron
where does the glomerulus receive its blood supply from?
an afferent arteriole that came from renal artery
where do glomerular capillaries exit into?
efferent arterioles
glomerular filtration rate (GFR)
the rate blood is filtered through all the glomeruli
- the measure of overall renal function
what must happen in order for blood to be filtered through glomerulus
must pass through 3 layers that make up the glomerular membrane
what are the three layers of the glomerular membrane?
Innermost- glomerular capillary wall
middle- basement membrane
outermost- inner layer of bowmans capsule
glomerular capillary wall
- single layer of endothelial cells
- has many large pores (100x more permeable to fluids and solutes than regular capillaries)
- large plasma proteins cannot pass through but smaller ones (albumin) can
basement membrane of glomerulus
- has no cells
- composed of collagen
- provides structural strength
- has glycoproteins to discourage the filtration of small plasma proteins
- neg charge of glycoproteins helps repel other proteins that get thorough capillary walls
- only ~1% of albumin passes into bowmans
what is the charge of glycoproteins in the basement membrane of glomerulus?
negative
inner layer of bowmans capsule
- composed of podocytes
- podocytes form narrow filtration slits between them allowing fluid to pass into bowmans
podocytes
cells that wrap around the capillaries of the glomerulus
what are the forces that regulate glomerular filtration? and what are they similar to?
they are similar to bulk flow
forces:
- glomerular capillary BP
- plasma-colloid oncotic pressure
- bowman’s capsule hydrostatic pressure
what is glomerular capillary BP?
- the pressure exerted by the blood in the glomerular capillaries
- abt 55mmHg pressure in these capillaries (18mmHg in normal)
- a smaller diameter in the efferent arterioles will increase resistance to blood leaving glomerular capillaries
– also prevents pressure from decreasing along the length, favouring filtration
does afferent or efferent arterioles have larger diameter?
afferent
Plasma-colloid oncotic pressure
presence of large proteins in plasma that can’t be filtered creates oncotic force
- resists movement of water into bowmans capsule
- Plasma-colloid oncotic pressure is abt 30 mmHg
bowmans capsule hydristatic pressure
the pressure of fluid in the bowmans capsule
- resists movement of water out of glomerular capillaries
- on avg. it is 15mmHg
mathematical representation of glomerular filtration rate
filtration coefficient (Kf) x filtration pressure = GFR
what is GFR also determined by
surface area available and permeability of membrane
avg male and female GFR
male= 125 ml/min
female= 115ml/min
net filtration equation
glomerular cappilary BP - (plasma colloid oncotic pressure + bowmans capsule hydrostatic pressure) = net filtration pressure
what is the relationship between GFR and glomerular capillary BP
directly proportional
what is auto regulatory (or intrinsic) mechanisms in place for?
to prevent sudden swings of GFR
how does autoregulation prevent swings in GFR?
regulating diameter of afferent arterioles
– constrict to decrease glomerular BP
– dilate to increase glomerular BP
wha tare two intrarenal mechanisms to allow constriction and dilation of arterioles?
- myogenic activity
- tubuloglomerular feedback (TFG)
-
Module 4: Section 136
-
Module 4: Section 228
-
Module 4: Section 330
-
Module 4: Section 454
-
Module 4: Section 516
-
Module 4: Section 637
-
Module 5: Section 115
-
Module 5: Section 223
-
Module 5: Section 321
-
Module 5: Section 427
-
Module 6: Section 146
-
Module 6: Section 229
-
Module 6: Section 351
-
Module 6: Section 450
-
Module 6: Section 534
-
Module 6: Section 629
