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26 Cards in this Set
- Front
- Back
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Chronic kidney disease (CKD) in US pop.
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- Mostly caused by diabetes and high BP
- Affects about 11% of population - 100,000 new patients with end-stage renal failure each year - dialysis support, etc. |
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4 Primary renal functions
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- Elimination of metabolic waste
- Fluid and electrolyte homeostasis - Regulate osmotic pressure of body fluids - Na+, K+, Ca2+, Mg2+, Cl-, HCO3-, PO3-, SO42- - BP control - Hormonal regulation - Erythropoetin - Vitamin D activation - Renin (Renin-Angiotensin assist with BP control) |
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5 important substances made by kidney
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1) Erythropoietin (EPO)
2) 1,25-(OH)2 Vitamin D3 3) Renin 4) Kallikrein 5) Prostaglandin and Thromboxane |
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EPO feedback loop
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- Hypoxic conditions -> Release of EPO from renal cortex -> Marrow -> increased production, maturation of RBC -> increased O2 carrying capacity
- Increase in RBC's = negative feedback loop - inhibits EPO release - Many CKD patients have anemia from reduced EPO release! - Patients originally given transfusions... - Synthetic EPO is waaayyyy better! |
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Risk of synthetic EPO use
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- Applicable to athletes and patients
- Higher hematocrit = more viscous blood - Greater risk of heart attack or stroke |
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Vitamin D3 (calcitriol) activation
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1-α-hydroxylase in proximal tubule of kidney
- D3 undergoes hydroxylations in liver, etc. - 25-oH-D3 (via 1-α-hydroxylase) -> 1,25-OH-D3 (calcitriol) - Critical step for activation - Leads to Ca2+ uptake in small intestine - CKD patients also have Ca2+ homeostasis issues - Bones thin, vascular calcification, hyperparathyroidism |
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Renin-angiotensin system mechanism
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- Angiotensinogen produced in liver
- Renin cleaves Angiotensinogen -> Angiotensin I - Angiotensin I -> Angiotensin II via ACE in lungs - Angiotensin II - increases Na+, H2O reabsorption, vasoconstriction -> Overall increase in BP! |
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Renal vasculature overview
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- One way in, two ways out
- Everything comes in via renal artery - Leaves either by renal vein or ureter *** Kidney gets lion share of CO because of key functionality! |
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Kidney arterial vasculature levels
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- Renal artery -> Arcuate artery -> Afferent arteriole -> Glomerulus (capillary bed) -> efferent arteriole -> peritubular capillary bed
- Only instance in body where blood flows from arteriole to capillary bed back to arteriole and on to another bed - Normally straight from first bed to venous system |
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Two types of glomerulus
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- Both are types of capillary bed
- Superficial cortical glomerulus = located at outer portion of cortex - Have peritubular capillaries that circulate around the cortex - Juxtamedullary glomerulus = located at border of cortex and outer medulla - Send out vasa recta into the outer/inner medullae - Deep vasa recta = Critically important for getting concentrated urine |
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Nephron
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- Most basic funtional unit of the kidney
- About a million nephrons/kidney - 85% = cortical, 15% = juxtamedullar |
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Nephron arrangement/components
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- Renal corpuscles contain glomeruli and Bowman's capsules
- Bowman's capsule gets fluid from glomerulus vessels - Bowman's -> proximal convoluted tubule -> proximal straight tubule -> Thin descending limb -> Thin ascending limb -> Thick ascending limb -> meets parent glomerulus (juxtamedullar apparatus) -> Distal convoluted tubule -> Connecting tubule -> collecting ducts *** Collecting ducts don't technically belong to single nephron! |
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2 gradients in kidney
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- Osmotic and oxygen
- Osmotic gradient - roughly iso-osmotic at superficial cortex -> 1200 mOSM/L deep in the medulla - Function = concentrating effect - Oxygen gradient - shunt between descending and ascending limbs - O2 doesn't make it very deep into loops - High cortex PO2, Low medulla PO2 - Inner medulla = always in danger of hypoxic damage |
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Urine excretion formula
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Excretion = filtration (Bowman's) + secretion - reabsorption
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Px definition
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- Concentration of any compound X in the plasma
- Thus, have PNa, PK, PCa, PCl, Purea, etc. - Plasma values tend to be relatively constant... |
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Ux definition
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- Concentration of x in Urine
- Can vary dramatically with metabolism and intake |
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V definition
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- Volume of urine flow per unit time
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Excretion rate equation
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- Gives mass of substance excreted over time
- Excretion rate = Ux * V - mL/min * mg/mL = mg/min |
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Glomerular filtration rate (GFR)
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- Amount of plasma filtered into Bowman's space in a given time
- typically 125 mL/min |
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Renal plasma flow (RPF)
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- Amount of plasma that flows through kidney in a given time
- typically 600 mL/min |
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Filtration fraction (FF)
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- % of plasma filtered into Bowman's capsule
FF = GFR/RPF - Typically around 21% |
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GFR calculation
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- Often calculated from RPF and FF
GFR = RPF * FF - Changes in either RPF or FF alter the GFR |
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Tubular load calculation
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- Amount of substance being filtered and entering tubule
TL = GFR * Px |
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Comparison of Tubular load (TL) vs. Urinary excretion (Ux * V)
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- Basically 3 different scenarios
- GFR * Px > UxV = amount excreted is less than the filtered load - GFR * Px < UxV = amount excreted is greater than filtered load - GFR * Px = UxV = amount excreted is equalt to the filtered load *** Basically indicates whether compounds are being reabsorbed or secreted, etc. |
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Clearance (Cx)
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Theoretical amount of plasma that is completely cleared of a substance in a given time
- Expressed as a rate - varies by compound - Related to Excretion, but not the same! - Ex. - for 100 mL/min -> in 1 min., 100mL were cleared of substance - Alternately, could be said that it takes 100mL of plasma to get certain amount of substance |
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Excretion vs. Clearance
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- Excretion gives mass of substance excreted over time (mg/min)
- Clearance is the rate at which plasma is freed of a compound (mL/min) |
