Renal I- Physiology Review Flashcards
made from upperclassman lecture notes.
1
Q
General kidney info:
location
% of CO?
innervation of kidney?
Innervation of bladder and ureters?
A
- Located retroperitoneal at L2
- Receives 25% of CO
- very low O2 extration ratio
- Innervation of kidney:
- SNS via preganglionic fibers (T8-L1
- Pain (SNS) T10-L1
- PSNS CN X
- Innervation of bladder and ureters
- motor: PSNS S2-S4
- sensory: SNS T11-L2
2
Q
How does blood flow through the kidney?
A
- Renal artery ->Arcuate arteries-> interlobular arteries
- Afferent arterioles (leading to glomerular tuft)
- Glomerular capillaries and bowman’s capsule->
- efferent arteriole-> peritubular capillaries/vasa Recta ->
- venous system
3
Q
How do the arterioles affect GFR?
How do vasoconstricting medications affect the GFR?
A
- contraction of efferent arteriole = increased GFR
- contraction of afferent arteriole = decreased GFR
- Vasoconstricting medications:
- mild/moderate causes preferential constriction of efferent, causing increase in GFR
- very high causes afferent constriction (decreases GFR in shock situations)
4
Q
Cortex of the kidney:
What are the anatomical parts?
How much blood flow?
How is blood flow regulated through the cortex?
A
- Anatomical parts:
- glomerulus
- proximal tubule
- distal tubule
- portion of the collecting duct
- Receives 94% of the total blood flow (approx 5 ml/L/g
- Regulated by vasoactive compounds
- adenosine induces vasoconstriction (opposite of usual effect) by stimulating the adenosine A1 receptor
- stress-> SNS -> renal cortical constriction and potential tubular ischemia
- **Kidney has no B2 receptors! Epi=vasoconstrict
5
Q
What is the PO2 in the cortex?
What is the extraction ratio of the cortex?
A
- 50 mmHg with an 18% extraction ratio
6
Q
Medulla of the Kidney:
What is the functional part of the kidney in the medulla?
How much blood flow does it receive?
How is the blood flow regulated?
A
- Contains the loop of Henle
- Receives 6% of total blood flow (approx 0.03mL/min/g)
- Regulated by:
- Prostaglandins (PGs) and NO, promoting vasodilation
- PGs and NO + adenosine A1 in cortex work to shunt blood into the medulla
- NSAIDS disrupt this compensatory mechanism and can cause medullary ischemia by inhibiting PGs
7
Q
What is the PO2 in the madulla?
What is the extraction ratio?
A
- PO2 = 8 mmHg with an 80% extraction ratio
- Severe hypoxia can develop in the medulla despite relatively adequate RBF
- High extraction ratio b/c this area is highly metabolically actively
8
Q
What happens with medullary ischemia in hemodynamically-mediated renal injury?
A
- First response is to increase active NaCL absorption
- this increases metabolic activity and O2 demand, decreasing O2 delivery
- compensation attempted via cortical vasoconstriction and flow redistribution
- ultimately ATP becomes depleted and NaCl reqbsorption decreases
- causes increased NaCl in tubular fluid
- renin is released from macula densa and afferent arteriole is constricted
9
Q
What are the different types of nephrons?
A
- Cortical nephrons (recieve 85% of RBF and make up majority of the nephrons)
- found in outer/middle cortex
- short loop of henle
- efferent arterioles drain into peritubular capillaries
- Justamedullary nephrons (recieve 10% of RBF)
- found in inner renal cortex
- longer loop of henle to reach inner medulla
- efferent arterioles drain into specialized peritubular capillaries (vasa recta)
- countercurrent mechanism
10
Q
What is the glomerulus?
What are the 5 components?
A
- Glomerulus: capillary network that originates from an afferent arteriole and are surrounded by dilated blind end of the nephron (bowman’s capsule)
- 5 components:
- capillary endothelium- produces NO and endothelin-1 which vasodilate and constrict
- glomerular basement membrane, and visceral epithelium- make up the filtration barrier
- parietal epithelium (bowman’s capsule)
- mesangium (interstitial cells)- contract in response to angiotensin II and other vasoconstrictors to decreasesflow and GFR
11
Q
What happens in the proximal convoluted tubule?
(5 actions)
A
-
Reabsorption
- PCT is a direct continuation of bowman’s capsule
- the higher the peritubular pressure, the less reabsorption occurs
- PCT is a direct continuation of bowman’s capsule
- Actions:
- 65% of H20, Na, K, Cl reabsorpion (ATP req for Na)
- almst 100% reabsorption of glucose, lactate, AA
- glucose max is 375 mg/dL
- H+ exchanged for bicarb
- Ca reabsorbed under influence of PTH
- waste products actively excreted ( bile salts, urea, Cr, dopamine, drugs)
12
Q
What happens in the loops of Henle?
A
- Ultrafiltration- interstitial osm increases from 300 to 1500
- Continuation of PCT
- Descending loop of Henle:
- permeable to H20, thus it passively leaves the tubule
- Ascending loop of henle
- impermeable to H2O, but d/t highly concentrated ultrafiltrate, NaCl passively diffuses out into the interstitial
- Thick ascending loop of henle
- thickness caused by active transport channels in the epithelium layer
- high metabolic activity, susceptible to ischemia
- Na/K/2Cl cotransporter to increase osm of interstitial and dilute urine
13
Q
What is the vasa recta?
A
- network of capillaries surrounding the loop of henle that take up and/or release Na, Cl, and H2o passively along the gradient
14
Q
What is the Juxtaglomerular apparatus?
What is the function?
How is this achieved?
A
- made of of the distal convoluted tubule and the afferent arteriole.
- main function is to control BP and filtration rate
- mesangial (sm muscle) cells contract, decreasing surface area of glomerulus and decreasing GFR (in response to vasoconstrictors)
- granular cells secrete renin in response to:
- Beta 1 stimulation
- decreased RBF which leads to decreased GFR
15
Q
What happens in the distal convoluted tubule?
A
- electrolyte, H2O, and pH fine tuning
- High metabolic activity
- 10% of Na/H2O reabsorption, also Cl reabsorption d/t
- ADH mediated V2 receptors
- aldosterone
