Urinary system 2.1 Flashcards
- Most abundant organic waste
- by-product of amino acid breakdown
Urea
By-product of creatine phosphate breakdown in muscles
Creatinine
Formed during recycling of nitrogenous bases of RNA
Uric acid
- filtration
- Reabsorption
- Secretion
Three processes of urine formation
blood hydrostatic pressure forces
water and solutes across the membranes of the glomerular capillaries into the capsular space
Filtration
Filtration only occurs where
Glomerulus
Resulting fluid entering capsular space after filtration
glomerular filtrate
Filtration occurs through
filtration membrane
Blood cells and proteins too big to cross
Fenestrations of glomerular endothelial cells
Large negatively charged ions do not fit
Basement membrane
Water, glucose, vitamins, amino acids, plasma proteins, ammonia, urea and ions fit through
Filtration slits
- Fenestrated epithelial cells
- Basement membrane
- Filtration slit
Filtration membrane layers
= 55 mmhg
* blood pressure in glomerular capillaries
* pro filtration
Glomerular blood hydrostatic pressure
= 15 mmhg
* Anti filtration
* Hydrostatic pressure pushing against filtration membrane by fluid in capsular space
Capsular hydrostatic pressure
= 30mmhg
* Osmotic pressure of large proteins pulling water into capillaries
* Anti filtrataion
Blood colloid osmotic pressure
Dictates how much will move in which direction
Net filtration pressure
(GBHP) - (CHP) - (BCOP) =
Net Filtration pressure (NFP)
Filtration stops if GBHP drops below
44mmhg
Volume of plasma that moves through kidneys per unit time
Renal plasma flow
Fraction of renal plasma flow that becomes glomerular filtrate
Filtration fraction
Amount of filtrate formed per minute in all renal corpuscles in both kidneys
Glomerular filtration rate
Needed substances pass quickly through renal tubules and are lost in urine
GFR too high
Metabolic wastes will not get filtered from blood into renal tubules
GFR too low
- Renal autoregulation
- Neural regulation
- Hormonal regulation
3 mechanisms to maintain consisten GFR
- Lie b/w adjacent glomerular capillaries
- control capillary diameter and rate of flow
Mesengial cells
- Specialized structure where distal convoluted tubule meets afferent arteriole
- Regulate BP and filtration rate in glomerulus
Juxtaglomerular Apparatus
- myogenic mechanism
- Tubuloglomerular feedback
Renal autoregulation types
Stretch receptors in afferent arterioles respond to increased of decreased BP
Myogenic mechanism
Smooth muscle of afferent arteriole constricts or dilates to increase/decrease GFR
Myogenic mechanism
- Uses juxtaglomerular apparatus
- When BP increased GFR increase
- When BP decrease GFR decrease
Tubuglomerular feedback
Myogenic mechanism and tubularglomerular feedback. Which one faster?
Myogenic mechanisms
At rest, not much ANS stimulation so which mechanism for glormerular filtration prevails
Renal autoregulation
During fight or flight, ANS causes decrease in GFR, this is part of which mechanism
Neural regulation
If blood pressure low sympathetic nervous system activated. Part of which mechanism
Neural regulation
- part of RAA system
- Increased in response to renin
Angiotensin II
Secreted by heart cells when blood in atria stretch walls
ANP (Atrial Natriuetic peptide)
Angiotensin II and Atrial Natriutic peptide are part of which mechanism
Hormonal regulation
Movement of solutes and water from renal tubules into blood
Reabsorption
Reabsorption dominates and most reabsorption occurs here
Proximal convoluted tubule
Lots of reabsorption, very little to no secretion
Nephron loop
- 15% of filtered H2O
- in descending limb only
- ascending limb impermeable to water
Nephron loop
- Fluid travelling very slowly, as 80% water reabsorbed
- PTH acts here to reabsorb ca2+
Early distal convoluted tubule
