L2: Renal Circulation Flashcards
Peritubular Capillaries
Electrolyte reabsorption and secretion and delivery of substances
Vasa Recta
Important for osmotic gradient - linked to H2O reabsorption
many nephrons share..
a collecting duct
Renal blood flow is denoted as
RBF or QR
Assume the total RBF __% of C.O. of _L so _ to each kindey
25%, 5L so 12.5% to each kidney
25% of 5L is
1250mL/min
What is RBF?
Flow of blood through both kidneys
20-25% of C.O. (1/4) delivered from the abdominal aorta to renal arteries
Kidney cortex receives 90% and medulla 10%
Blood flow to the kidney 3
Allows for filtration of plasma
Indirectly determines GFR
Delivers O2 and nutrients to tubules for reabsorption and secretion
Blood flow to the kidney cont 3
Returns HCO3-, electrolytes and H2O to the bloodstream
Delivers substances to the tubule for urinary excretion
Delivers drugs to tubular sites of action
Where fo the two major pressure changes occur?
afferent and efferent arterioles
Describe the vascular pressure changes along the kidney
Sharp decreases in the afferent and efferent to maintain high hydrostatic pressure aling the glomerular capillary
What is the equation for QR
QR=P/R
How can we reduce the hydrostatic pressure coming into the glomerular capillaries?
constrict the afferent
How can we increase the pressure?
constrict the efferent
Assume that renal vein pressure is
2-3mmHg
Renal plasma flow eq
RPF = [1-Hct] x RBF (Hct is the RBC conc.)
Filtration fraction
FF=GFR/RPF
What is the average FF
125ml/min
Autoregulation occurs where ______ remains constant despite..
organ blood flow remains constant despite fluctuations in arterial pressure
Autoregulation of RBF occurs above
80mmHG
Renal autoregulation refers to the regulation of both
RBF and GFR
RBF is controlled by:
Renal sympathetic nerves
Vasoconstrictors (angiotensin II, endothelin-1)
Vasodilators (nitric oxide, prostaglandins)
Nerve plexus
branching of network of intersecting nerves composed of afferent and efferent fibres
Renin-angiotensin pathway
Angiotensinogen
Renin
Angiotensin I
ACE
Angiotension II
AT1Rs/AT2Rs (receptors)
Why does NO need to be created locally?
It is a gas and thus, only effective for a short period of time
Synthesis of NO
L-arginine to L-citrulline
Endothelin (ET-1)
Like snake venom - extreme vasoconstrictor
Low levels normally
Buffered by NO
Endothelial-derived
Increase in ET-1 in hypertension, coronary arter disease
Prostaglandins (PGs)
Low levels normally
Increase in PGI2 and E2 in dehydration and stress (buffers AngII)
Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit PGs (ibuprofen,aleve,aspirin)
NSAIDs contraindicated if RBF is low - will shut kidney down if NSAIDs are administered when RBF is low
Endothelial cells produce local factors that cause vasodilation.cons in adjeacent
smooth muscle cells
