Lecture 2 Flashcards
Functions of the Kidneys?
-Remove wastes
-Regulate volume and composition of ECF
-Acid-Base Balance
-Blood Pressure Regulation
-Removal of Foreign Substances
-RBC Production
-Vitamin D Activity
Blood Supply to the Kidneys?
3 Capillary Beds
-Glomerular capillaries
-Peritubular capillaries
-Vasa recta
Afferent Arteriole?
Enter
Efferent Arteriole?
Exit
Peritubular Capillaries?
Wraps around tubule to allow diffusion between capillary and tubule
Vasa Recta?
-Branch of Efferent Arteriole
-Ascending limb is next to descending limb of another nephron
-ONLY in medullary nephron and no exchange of nutrients for away from tubules
Cortical Nephron located in?
Cortex of Kidney
Juxtamedullary Nephron located in?
Medulla of Kidney
Innervation of Kidneys?
Sympathetic
-Afferent and Efferent Arterioles
-Juxtaglomerular Cells
-Tubule
(Innervation of Kidneys)
Afferent and Efferent Arterioles?
Vascular Resistance
(Innervation of Kidneys)
Juxtaglomerular Cells?
Secretes renin to increase blood pressure
(Innervation of Kidneys)
Tubule?
Increase reabsorption
Histology of Nephron?
Form follows function:
-Proximal tubule has brush border for large surface area
-Thin ascending limb has few mitochondria, little active transport
-Other segments have many mitochondria and other organelles
(Histology of Nephron)
Proximal tubule has brush border for large surface area?
-Increase mitochondria because need ATP for ATP-ase
-Increase absorption
(Histology of Nephron)
Thin ascending limb has few mitochondria, little active transport?
Because moving H2O
Functional Unit of Kidney?
Nephron
Glomerular Filtration?
Production of a protein - free filtrate of plasma
(Glomerular Filtration)
Driving Force?
Diameter differences between capillaries for osmotic pressure differences
(Glomerular Filtration)
Reabsorption?
Tubular lumen into peritubular capillaries
(Glomerular Filtration)
Secretion?
Outflow from capillary to lumen
(Glomerular Filtration)
Excretion?
Urine
Glomerular Membrane (3 Sieves in Series)?
-Capillary Endothelium
-Basement Membrane
-Bowman’s Capsule Epithelium (podocytes)
(Glomerular Membrane)
Capillary Endothelium?
Allows for filtration
(Glomerular Membrane)
Basement Membrane?
Mainly lamnin in ECM
(Glomerular Membrane)
Bowman’s Capsule Epithelium (podocytes)?
Keeps proteins out of urine
(podocytes are finger-like projections)
Damage of podocytes causes?
Increase protein in urine and cannot be regenerated (ex. hypertensive patients)
GFR = ?
GFR = Kf [(Pgc - Pbc) - pi gc]
(GFR Equation)
Kf?
Filtration Coefficient
(GFR Equation)
PGC?
Glomerular Capillary
(GFR Equation)
PBC?
Bowman’s Capsules
(GFR Equation)
PiGC?
Oncotic Pressure in Capillaries
(GFR Equation)
Changes in Kf?
(Permeability or Surface Area)
-Mesangial Cell Contraction or Relaxation
-+ ANP, NO (cGMP = vasodilation)
– A pi, Endothelin, Norepinephrine, Epi, ADH (contract mesangial cell = vasoconstriction)
(GFR Equation)
Relaxation?
-Increase Surface Area
-Increase Kf
(GFR Equation)
Contraction?
-Decrease Surface Area
-Decrease Kf
Filtration Coefficient (Kf) or Hydraulic Conductance?
-Permeability
-Surface Area
What would promote an increase in GFR?
Decrease Renal Sympathetics
Clearance?
Volume of plasma from which a substance is completely removed by kidneys per unit time
Clearance Equation?
Cx= (UF * Ux)/(Px) = Volume/Time
(Clearance Equation)
UF?
Urine Flow
(Clearance Equation)
Ux?
Urine Concentration of X
(Clearance Equation)
Px?
Plasma Concentration of X
Inulin can be used to measure?
GFR
What are the 6 criteria needed by a substance to achieve GFR?
1) Freely Filtered
2) Not Reabsorbed
3) Not Secreted
4) Not Metabolized
5) Does Not Change in GFR
6) Not Produced
GFR and Inulin Equation?
GFR = ((UF * Uin)/(Pin)) = Cin
Daily Production of Creatinine is always equal to?
Daily excretion of Creatinine
Daily Creatinine Excretion?
-Varies based on weight and gender
-Equals creatinine production
-May be normal even in chronic renal failure
GFR for Creatinine Equation?
GFR = (UF * Ucreatinine)/ (Pcreatinine)
(Renal Blood Flow (RBF))
Normal?
1200-1300 mL/min (both kidneys)
20-25% of Cardiac Output
(Renal Blood Flow (RBF))
Renal Plasma Flow (RPF)?
( RPF = RBF (1 - hematocrit))
600-700 mL/min (both kidneys)
(Renal Blood Flow (RBF))
Filtration Fraction (FF)?
How much plasma is being filtered out
(FF = (GFR)/(RPF))
125 mL/min/650 mL/min
20%
Most Distribution of Blood Flow?
Cortex (1000 mL/min) (75%)
Least Distribution of Blood Flow?
Inner Medulla (60 mL/min) (5%)
Distribution of Blood Flow?
-Cortex (1000 mL/min (75%))
-Outer Medulla (240 mL/min (20%))
-Inner Medulla (60 mL/min (5%))
(Measurement of Renal Plasma Flow (RPF))
Fick Method?
Infuse a substance in a patient to achieve a steady plasma concentration
(Xartery/min) = (Xvein/min) + (XUreter/min)
ERPF(CPAH)/0.9 = ?
RPF
Autoregulation of Renal Blood Flow?
-GFR and RBF are auto-regulated in parallel because need steady blood flow for filtration
-Autoregulation fails as arterial blood pressure falls below 80 mmHg
Autoregulation fails as?
Arterial Blood Pressure falls below 80 mmHg
Changes in Vascular Resistance determine both?
Renal Blood Flow (RBF) and GRF
Mechanisms of RBF Autoregulation?
1) Tubuloglomerular (endothelial cells) feedback (TGF) which is a flow-sensitive mechanism
2) Myogenic response, which is a pressure-sensitive mechanisms intrinsic to vascular smooth muscle (directly to cells without brain function)
Tubuloglomerular Feedback (TGF)?
-Increased filtering with increased GFR
-Increased flow sensed by increased NaCl
-Increased contraction leads to constrict afferent arteriole and decreased GFR and decreased RBF
Control of Renal Blood Flow?
-Blood Pressure
-Intrinsic
-Extrinsic
(Control of Renal Blood Flow)
Blood Pressure?
Autoregulation
(Control of Renal Blood Flow)
Intrinsic?
Autoregulation
1) Myogenic (macula densa)
2) Tubuloglomerular feedback prostaglandins (increased pressure, increased prostaglandins; vasodilation to increased blood flow to kidney)
(Control of Renal Blood Flow)
Extrinsic?
-Nerves: sympathetic
-Hormones: angiotensin II (strongest)
