ERU: Urinary Flashcards
(34 cards)
Osmolarity of ECF
~290 mOsmol/L
What type of osmolarity urine does vertebraes produce? What about birds and mammals?
Vertebraes produce hypotonic or isotonic urine. Birds and mammals produce hypertonic (able to conserve water)
Juxtamedullary nephrons
- 20%
- Long proximal tubule + LOH
- Concentrating urine
Cortical/ Sub-capsular nephrons
- 80%
- Short proximal tubule + LOH
Glomerular filtration product
Results in ultra filtrate (small molecules and ions. No proteins and no RBCs).
What are the 2 factors controlling renal blood flow?
Myogenic (muscles of afferent and efferent arterioles).
Tubulo-glomerular feedback (distal tubule fluid- juxtaglomerular apparatus (arteriole constriction))
What are the 3 layers of glomerular filtration (capillary to Bowman’s capsule)
- Capillary endothelial cells (flattened, thin epithelium w/fenestrations)
- Basement membranes (non-cellular collagen, glycoproteins, barrier to large molecules)
- Podocytes (made of cell body, trabeculae + pedicels, interdigitate to repel negative molecules)
How is GFR calculated?
Net filtration= Hydrostatic of capillary - (capillary oncotic + hydrostatic of BC)
What happens to filtration rate when afferent arteriole is constricted?
Reduced hydrostatic, blood flow and filtration
What happens to filtration when efferent arteriole is constricted?
High hydrostatic, lower blood flow, little change in filtration
What happens in the proximal tubule?
2/3 of filtrate reabsorbed and secretory (organic acids and bases)
What makes PT good at reabsorption?
- Located next to glomerulus
- Convuluted
- High oncotic blood pressure
- Apical/ tubule cells
Features of apical/ tubule cells in proximal tubule
- Brush border
- Infoldings of basal membrane
- Lots of mitochondria
- Tight junctions to reduce paracellular reabsorption
Secondary active transport
Relies on Na gradient from Na/k ATP pump
Symport transport
Co-transport (ex. Na + Glucose ->)
Antiport transport
Counter-transport (ex. Na<->H+)
How much glucose is reabsorbed?
100% (If not, it’s called glucosurea)
How much water is reabsorbed?
60-70%
- From high oncotic in capillaries
- Osmolarity of tubular fluid doesn’t change in P.T
How much urea is reabsorbed? Where is the highest concentration found?
- 50% in P.T
- Concentration high in LOH
Secretions of PT
Organic anions (acids) and cations (bases)
What happens in the distal tubule?
Low permeability to water. Na reabsorption through naCl symporter in apical membrane
Does the osmolarity in plasma change?
Stays constant. Kidneys remove/ retain required water
Vasa recta
Blood supply to medulla. Counter current which prevents loss of salt gradients
What happens in the Collecting duct?
- Parallel to LOH, opposite direction. - - Water out by osmosis due to hyperosmotic medulla.
- Impermeable to water, urea nad NaCl if no ADH
