Kidney Function and Glomerulus

The rate at which fluid is filtered in the glomerulus (ml/min) Determined by the net filtration pressure and flow rate through the glomerulus

define GFR what is it determined by?

• Small molecules & ions in almost exactly same concentration as plasma • No proteins or red blood cells • No large molecules e.g albumen • Greater restrictions on filtration for negatively charged molecules

describe the composition of ultrafiltrate

1. same concentration as plasma 2. no cells, only trace amounts of protein

describe the concentration of the following in the filtrate: 1. ions and small molecules s (e.g. glucose, amino acids) 2. cells and proteins

- oncotic pressure favours the movement of water into the capillaries via osmosis - higher hydrostatic pressure in the capillaries

describe the oncotic pressure and hydrostatic pressure of the glomerulus and capillaries

LONG TERM - damage to filtration barrier

effects of high blood pressre on GFR

kidney stones - blockage in ureter decreased filtration

effects of high hydrostatic pressure in bowman's capsule

- renal failure - no filtration

effects of low blood pressure on GFR

known as nephrotic syndrome - failure of filtration barrier increased oncotic pressure and increased filtration

effects of protein levels in bowman's capsule on GFR

below 0 would have back filtration

filtration pressures through glomerulus

net filtration pressure = forces out - forces in

glomerular filtration complete: net filtration pressure = ?

less

if the glomerulus is blocked there will be (more/less) filtration

more

if the glomerulus is damaged there will be (more/less) filtration

slit pores

pedicels

• Non cellular, continuous layer of collagen and glycoproteins. • Main function - barrier to filtration of large molecules.

second layer of glomerular filtraion basement membrane

cell body, trabeculae, pedicels Main functions: • Maintenance of basement membrane. • Slit pores between pedicels - lined with negatively charged molecules - leads to perm selectivity

third layer of glomerular filtration podocytes

spaces between slit pores

what are the pedicels of podocytes

the wavey projection thingies

what are the trabeculum of podocytes?

podocytes

what are these yellow cells in the glomerulus called?

juxta-glomerular apparatus

what is this called?

• Molecular weight <80000 Mr wont go through • Shape • Electrical charge (-ve charge less likely to be filtered as GBM is -ve and repels)

what three factors does the rate of glomerular filtration depend on?

both hydrostatic pressure and blood flow decrease reduced filtration

what will the effect be of constriction of the afferent arteriole on hydrostatic pressure and blood flow? what is the effect on filtration?

increased hydrostatic pressure and decreased blood flow little change in filtration

what will the effect be of constriction of the efferent arteriole on hydrostatic pressure and blood flow? what is the effect on filtration?

•Plasma vol. = 1.6 litres •GFR = 80 litres / day •Urine output = 0.5 litres 94% is reabsorbed

In a 20kg dog what is the GFR?

Starling's Forces Oncotic (pi) and Hydrostatic (P) pressures

What are the forces that determine GFR?

podocytes

what are the black dots in this micrograph?

Glomerular filtration is vital for normal kidney function. i.e. how well the kidneys are producing filtrate. GFR can be impaired in many conditions e.g. infections, parasites, congenital conditions......

why is GFR important clinically?

filtration of plasma - glomerular filtration 1. glomerulus 2. ultra filtrate in tubule (nephron)

1st process in the formation of urine 1. where does it occurs? 2. what does it result in?

1. Endothelial cell of capillary 2. Glomerular basement membrane 3. Visceral epithelial cell (podocyte) of Bowman's capsule

3 layers that fluid filtered from capillary to Bownman's capsule crosses

low protein decreased oncotic pressure, increased filtration

Effects of plasma protein levels on GFR

- flattened cells, think cytoplasm - fenestrations (60nm) - increase permeability - line with -ve glycoprotein

First layer of glomerular filtration epithelial cell wall

glomerular filtration rate

GFR

• The surface area available for filtration (the greater the surface area the more filtrate is produced) • Permeability of filtration barrier (The more permeable the filtration barrier is, the more filtrate will be produced)

GFR is also affected by...?