Nephron, Renal Clearance, RBF, GFR Flashcards
Structural and Functional unit of Kidneys
Nephron
Cortical Nephron
75% of nephrons
located in the RENAL CORTEX
SHORTER loop of Henle
(+) PERITUBULAR CAPILLARIES
Juxtamedullary Nephron
25% of nephrons
located in the CORTICOMEDULLARY junction
LONGER loop of Henle
(+) VASA RECTA
2 major parts of Nephron
Renal or Malphigian Corpuscle
Renal Tubules
Renal or Malphigian Corpuscle
Afferent arterioles Glomerular capillaries Efferent arterioles Podocytes Mesangial cells JG cells Bowman's capsule and space
Renal Tubules
PCT
LH
DT
CD
From interstitial cells in peritubular capillary bed
Released in response to hypoxia –> (+) RBC proliferation in bone marrow
Erythropoietin (EPO)
PCT converts 25-OG vitamin D3 –> 1,25 vitamin D3 (calcitriol, active form?
1a - hydroxylase - mediates conversion (upregulated by PTH)
Calciferol (Vitamin D)
From PCT cells
Promotes NATRIURESIS
LOW dose - dilates interlobular arteries, afferent arterioles, efferent arterioles –> INC RBF
HIGH dose - vasoconstrictor
3 Charge and Filtration Barriers of the Glomerulus
Capillary Endothelium
Basement Membrane
Podocytes
Other cells in Renal Corpuscle
Mesangial cells
Juxtaglomerular cells
Macula densa
Modified smooth muscles in the mesangial cells capable of phagocytosis
Intraglomerular
Cells in the mesangial cells that may play a role in RENAL autoregulation and RAAS
Extraglomerular( Lacis cells)
At the walls of afferent arterioles
Secrete RENIN
Juxtaglomerular (JG) cells
In DT
Monitor Na concentration in the lumen of DT
Macula Densa
If substance has a HIGH clearance most will be found in
URINE
If substance has a LOW clearance most will be found in
Blood
Highest clearance
PAH - filtered and secreted not reabsorbed
used to estimate renal plasma flow and renal blood flow
Lowest clearance
protein, Na, glucose, AA, HCO3 and Cl
Clearance EQUAL to GFR
Inulin, Creatinine - filtered but not secreted not reabsorbed
*marker for kidney function (glomerular marker)
Renal Blood Flow
25 % of Cardiac Output
Vasodilation of Renal Arterioles - Increases RBF
PGE2 PGI2 Bradykinin NO Dopamine
Vasoconstriction of Renal Arterioles - Decreases RBF
Sympathetic NS
Angiotensin II
Estimated by PAH clearance
Renal Plasma Flow (RBF)
Renal Blood Flow (RBF)
RBF = RPF/ 1-Hematocrit
Normal value of GFR
125 mL/min or 180 L/day
Increase when GFR decreases
BUN and Creatinine
GFR and RBF would increase if we vasodilate
AFFERENT and EFFERENT arterioles
Vasoconstriction of Afferent Arteriole
decreased GFR
decreased RPF
no change on FF
Vasoconstriction of Efferent Arteriole
increased GFR
decreased RPF
increased FF
Increased Plasma Protein
decreased GFR
no change in RPF
decreased FD
Ureteral Stone
decreased GFR
no change RPF
decreased FF
Myogenic mechanism
Renal afferent arterioles reflexively responds to stretch by contracting in order to maintain constant renal blood flow and subsequently GFR
Causes of K Influx –> HYPOKALEMIA
Insulin
Beta adrenergic agonists
Alkalosis
Hypoosmolarity
Causes of K efflux –> Hyperkalemia
Insulin deficiency Exercise Beta adrenergic antagonists Acidosis Hyperoosmolarity (-) of NaKATPase pump like digitalis Cell lysis
Causes of Increased Distal K Secretion
High K diet Hyperaldosteronism Alkalosis Thiazide Diuretics Loop Diuretics Luminal Anions
Causes of Decreased Distal K Secretion
Low K diet
Hypoaldosteronism
Acidosis
K Sparing Diuretics
Major extracellular buffer
HCO3
Major intracellular buffer
Hemoglobin
