Organogenesis 2 Flashcards
Give a brief overview of nephron development
- MM cells condense around UB
- transform into small cysts with epithelial characteristics (renal vesicles)
- differentiation and morphogenesis. fuses with UB
- blood vessel progenitors invade and make glomerular capillaries
- nephron differentiation
What does the signal from UB to MM do?
- indices mesenchymal to epithelial transition (MET)
What signal causes the MM to undergo MET?
- Wnt9B (paracrine)
Where is Wnt9B expressed in kidney development?
in the UB
How is renal vesicle size measured?
- Wnt9B indices Wnt4 expression in the MM
- Wnt4 is autocrine and propagates mesenchymal aggregation
- Renal vesicle will grow until Wnt4 reached threshold
- at this threshold RV will then differentiate
What are the characteristics of the epithelial cells formed by MET?
- tubular shape and forms a lumen
- adhesion junctions to stick together - tight junctions and desmosomes
- established apico-basal polarity
- tubes are not leaky because of tight junctions
explain the proximal-distal axis in the nephron
- proximal - glomerulus
- other side of loop of henle
give 3 examples of differentiated cell types in the nephron
- proximal tubes - recovery of salt, water and metabolites
- loop of henle - produces hypertonic urine
- distal tubes - K+, Na+, Ca+ regulation
Describe the pattern formation in the renal vesicle
- renal vesicle - patterning is established into 3 by a morphogen secreted at the distal end
- comma-shaped - proximal end sticks out
- s-shaped
What is Bartter syndrome?
- low potassium levels
- excessive urinary losses of Na+, Cl-, K+
- dysfunction in Na-K-Cl transporter in loop of henle
Explain the structure of the mature glomerulus
- Bowmans capsule around the outside
- podocytes ontop of capillaries
- capillaries inside Bowmans capsule
Explain the development of the glomerular capillaries
- migrating epithelial cells move into the developing glomerulus when it is s-shaped
- migrates by a chemoattractant secreted by podocyte precursors
- chemoattractant is vascular endothelial growth factor (VEGF)
what is a chemoattractant?
cells move towards signal up concentration gradient
What is a chemorepellent?
cells move away from a signal down the concentration gradient
What is VEGF?
- vascular endothelial growth factor
- chemoattractant ssecreted my podocyte precursor cells to attract endothelial cells
Why is it important that the podocyte precursor cells and the endothelial cells communicate with each other?
- ensures that blood delivery and filtration is matched
- there is enough podocytes for each capillary
What is the role of the glomerular capillaries?
- bring blood to the kidneys
What is the role of the podocytes?
- filter blood in the kidney
What is polycystic kidney disease?
- genetic
- autosomal dominant or recessive
- progressive formation of fluid filled sacks
- increase in tubular diameter, nephron loss, kidney failure
What are two ways to shape an organ?
- oriented cell division - cells only divide along one axis ect
- cell inter calculation - cells slot in-between each other
Explain the orientation of cell division in renal tubes
- tubes increase in length but not diameter
- orientation of cells along long axis
What does defects in the orientation of cell division result in?
- abnormal tubule shape
- formation of cysts
Explain cell rearrangement in renal tubules
- diameter decreases from ~11 or 12 cells to ~3 or 4
- highly ordered cell inter calculation takes place
- convergent extension
What is convergent extension?
- converging on one axis
- extending on another
