Nephron workshop Flashcards
What are the possible causes of reduced nephron numbers?
Normal ageing
Renal injury
Renal injury
Describe juxtamedullary nephrons
Long
Adapted to resorb lots of water back into blood
Ideal for animals that need to retain water e.g., desert animals
Ability to make concentrated urine is associated with higher percentage of juxtamedullary nephrons
Describe the renal corpuscle
ball of capillaries (glomerulus) where blood flows and is filtered towards a double walled capsule (Bowman’s capsule)
Describe the glomerulus
Acts as a sieve to filter blood and create a filtrate
Formed by an afferent arteriole that divides into looping capillaries
Intraglomerular mesangial cells and matrix occupy spaces between capillary loops
Afferent arterioles enter at vascular pole
Ultrafiltrate is created and enters Bowman’s capsule at the urinary pole
Describe the Bowman’s capsule
Cup shaped
2 layers separated by the urinary space (where the filtrate is collected)
Inner layer (visceral layer) is made up of podocytes that play a role in filtration
Describe the function of the cells of the Bowman’s capsule
Podocytes have foot-like processes that interdigitate with other podocytes to make a layer that spreads out to cover glomerular endothelial cells and intraglomerular mesangial cells with a glomerular basement membrane inbetween
Mesangial cells keep the glomerular basement membrane ‘clean’ for filtration by having cytoplasmic projections that extend between the endothelial cells and GBM for phagocytosis of debris
Label the histology of the renal filter
How does the glomerulus act as a filter?
Endothelial cells have large fenestrations (pores) which allow passage of small molecules
There is also a charge-barrier as the material that makes up the pores is -ve
Blood cells and most proteins are too large
What 3 layers does blood in the glomerular capillary get filtered through?
Endothelial cells of glomerulus
Glomerular basement membrane
Podocytes of visceral layer of Bowman’s capsule
Describe the podocytes of the visceral layer of the Bowman’s capsule
Podocytes don’t completely cover the glomerular basement membrane - some gaps
Spaces between foot projections (filtration slits) which block small molecules due to -ve membrane within slit
What is the juxtaglomerular apparatus (JGA)
Region at the vascular pole of the glomerulus made of 3 cell types:
- juxtaglomerular cells
- macula densa cells
- extraglomerular mesangial cells
Describe the juxtaglomerular cells
Modified smooth muscle cells in wall of the afferent arteriole which contain renin granules
Describe the macula densa cells
Specialised epithelial cells in wall of ascending limb of LoH and distal tubule
Sits close to afferent and efferent arterioles
Detect changes luminal NaCl conc
Signal changes in arteriolar resistance to affect blood flow to glomerulus
Signals release of renin
Describe extraglomerular mesangial cells
bridge the afferent and efferent arterioles and the macula densa cells to help coordinate messages and effects of juxtaglomerular apparatus
Describe the anatomy of the proximal convoluted tubule
Coiled
Cuboidal epithelial cells
Apical intercellular tight junctions (stop molecule leakage, allows passage of water and small ions)
Microvilli increase SA
Lots of mitochondria
