Acute Kidney Injury Flashcards
functions of kidney
- maintain fluid and electrolyte balance
- remove metabolic waste products
- maintain acid-base balance
- maintain endocrine function (BP, helps w/ RBC prod., activates vitamin D)
location of kidneys on body
bilaterally below diaphragm
cortex
outer area, highly vascular, houses nephrons, blood vessels, secretes EPO, produces urine
flow pattern
cortex -> pyramid -> renal papilla -> minor calyx -> major calyx -> renal pelvis -> hilium -> ureter -> bladder -> urethra
what is important to note about urea?
urea can diffuse back into blood or be actively transported into filtrate
what is important to note about creatinine?
filtered by glomerulus, should never be reabsorbed
what does ADH work on?
collecting duct and distal convoluted tubule
aldosterone affects the reabsorption of ____ at the ____
sodium, distal convoluted tubule
glomerulus function
filters fluids and solutes from blood
proximal tubule
- resorbs Na, K, Cl, HCO3, urea, glucose, and amino acids
- filtrate leaves isosmotic
loop of henle function
- resorbs Na, K, Cl
- blocks resorption of H2O from ascending limb
- countercurrent mechanism dilutes or concentrates urine
- filtrate leaves hypoosmotic
distal tubule function
- Na, K, Ca, Phosph selectively resorbed
- H2O resorbed in the presence of ADH
- Na resorbed in the presence of aldosterone
- filtrate leaves hypoosmotic
collecting duct function
- resorption similar to that in distal tubule
- H2O resorbed in presence of ADH
- HCO3 and H resorbed or secreted to acidify urine
- filtrate leaves hyperosmotic or hypoosmotic depending on body needs
urine is produce through
filtration, secretion, reabsorption
passive transport
gradient high to low (diffusion), no ATP
active transport
- uses ATP, against concentration gradient
- rate of movement depends on availability and saturation of carriers and ATP availability
renal BP regulation
maintains renal blood flow, GFR and BP
intrinsic renal BP regulation
– internal kidney compensation mechanisms
1) Arteriole Myogenic mechanism
2) Tubuloglomerular feedback mechanism:
- Juxtaglomerular Apparatus = Juxtaglomerular cells, Macula Densa cells and Extraglomerular Mesangial cells
- Adjust blood flow into glomerulus and stimulates RAAS/SNS
- Responsible for hormonal regulation of body’s BP, kidney’s blood flow and GFR
extrinsic BP regulation
- global compensation mechanisms (affect GFR but primary role is to increase BP)
- SNS
- RAAS
flow of blood
afferent to efferent
juxtaglomerular cells location and function
location: smooth muscle cells of the afferent arteriole
function: act as baroreceptors that detect changes of pressure in the afferent arteriole.
- they produce, store, and secrete renin, which is released in low BP states
- play critical role in RAAS
- autoregulation of renal blood flow
- Low BP → JG cells sense this → stimulate renin release → RAAS
macula densa
location: in the wall of the distal tubule where it comes into contact with the glomerulus
function: Detect changes in NaCl levels in DCT
Low BP → low GFR → increased NaCl
reabsorption time in PCT → less NaCl gets to DCT → Macula densa senses low NaCl and releases Prostaglandins → PG stimulates JG cells to release renin ( for RAAS), and stimulates afferent arteriole to vasodilate → increases GFR
High BP → high GFR → increased NaCl in tubules b/c too fast to absorb it in PCT –> increase in NaCl at DCT → macula densa senses high NaCl → stimulates afferent arteriole to vasoconstrict → decrease GFR
AKI
- refers to anything from mild impairment to acute renal failure
- characterized by a sharp increase in Cr and a decline in urine output
- more than 50% of critical care patients will develop an AKI
- AKI increases mortality by 10-50%
pre-renal AKI
- arises from inadequate blood flow to the kidney
- due to prolonged hypoTN (sepsis, vasodilation), prolonged low CO (heart failure, cardiogenic shock), prolonged volume depletion (dehydration, hemorrhage), renal vasculature thrombo-emboli
- reversible if treated early
