Physiology-Renal I Flashcards
2major regions of kidney anatomy
Outer cortex
Inner medulla
Functions of kidney
Excretion of metabolic waste, foreign chemicals, drugs and hormone metabolites
Regulation of water and electrolyte balance
Regulation of arterial pressure
Regulation of acid-base balance
Regulation of erythrocyte production
Regulation of vitamin D production
Glucose synthesis
How many pyramids in kidney
6-15
Where does base of each pyramid sit
Corticomedullary junction
Where does pyramid apex extend into?
Hilium; forms papilla
Function of papilla
Delivers urine into minor calyces
Where does urine flow from minor calyces
–> major calyces–> renal pelvis–> ureter
Blood flow through kidney
Renal artery–> interlobular artery–> arcuate artery–> interlobular artery–> afferent arteriole–> glomerular capillaries–> efferent arteriole–> peritubular capillaries
Two types of nephrons
Cortical
Juxtamedullary
Cortical nephron
Glomeruli located in outer cortex
Sort loop of henle that penetrates only a short distance into medulla
Entire tubular system surrounded by network of peri tubular capillaries
Juxtamedullary nephrons
Glomeruli lie deep in renal cortex near medulla
Long loop of henle deep in medulla
Long efferent arterioles extend from glomeruli down into outer medulla, then divide into two specialized capillaries called vasa recta
Mesangial cells
- In glomerulus
- Have properties of smooth muscle cells
- In charge of constriction/dilation
- Synthesize prostaglandins and react to all
- Involved in immune-mediated glomerular diseases producing cytokines
- Participate in phagocytic functions to remove macromolecules that cannot pass thru basement membrane and remain in capillary wall
Juxtaglomerular apparatus made up of
Macula densa
Mensagial cells
Granular cells
Key function of glomerulus
Act as filtration barrier
-glomerular capillary wall restricts solute movement by using both size and charge selectivity
Ultrafiltration
Passive movement of an essentially protein free fluid from the glomerular capillaries into bowman’s space
Size selectivity maintained in glomerulus by
Basement membrane
Podocyte slit diaphragms
Charge selectivity in glomerulus maintained by
Electrostatic repulsion created by a ionic sites in basement membrane and endothelial cell fenestrae
3 basic processes of urine formation
Ultrafiltration of plasma by glomerulus
Reabsorption of water and salutes from ultrafiltrate
Secretion of solutes into tubular fluid
Function of epithelial cells in glomerulus
Secrete hormones that influence vasomotor tone in renal circulation (endotheilin, prostacyclin, nitric oxide)
3 major factors of autoregulation that modulate either afferent or efferent arteriolar tone
- Myogenic reflex (afferent arteriole)
- Tubuloglomerular feedback
- Angiotensin II mediated vasoconstriction (efferent arteriole)
Myogenic reflex
Myogenic stretch receptors in afferent arteriolar walls sense changes in arterial pressure
Increase in BP in afferent–> constriction of afferent arteriole
Decrease in BP of afferent–> dilation of afferent arteriole
First line of defense against fluctuation in renal blood flow
Myogenic reflex
Tubuloglomerular feedback
Links changes in NaCl concentration at macula densa with control of renal afferent arteriolar resistance
Increase in GFR–> increases NaCl concentration in loop of henle–> increase in NaCl sensed by macula densa–> macula densa signals to increase resistance of afferent arteriole (constriction)–> decreases glomerular filtration rate
Ultrafiltration
Passive movement of an essentially protein free fluid from the glomerular capillaries into bowman’s space
Angiotensin II mediated vasoconstriction of efferent arteriole
Decrease in renal blood flow causes JGA to release renin from granular cells
Renin–> catalyzes angiotensin–> angiotensin I–> angiotensin II–> vasoconstriction of afferent and efferent arterioles–> increased pressure in glomerular capsule, normalizing glomerular filtration rate
Which arteriole is more sensitive to vasoconstriction?
Efferent
What will a decrease in angiotensin II do to renal blood flow
Increase
What will an increase in angiotensin II do to renal blood flow
Decrease
Constriction of efferent arteriole will _____ glomerular hydrostatic pressure, and therefore______glomerular filtration rate
Increase; increase
Constriction (increases/decreases) resistance
Increases
Dilation (increases/decreases) resistance
Decreases
How sympathetic nerves affect RBF and GFR
Innervate afferent and efferent arterioles
Norepinephrine and epinephrine cause vasoconstriction, which decreases GFR and RBF
-sympathetic tone is minimal when ECF is normal
-dehydration or strong emotional stimuli can activate sympathetic nerves
How prostaglandins affect RBF and GFR
Increase RBF
- during certain conditions (hemorrhage, stress, dehydration) prostaglandins are released locally within kidneys–> increase RBF by dampening vasoconstrictor effects of sympathetic nerves and angiotensin II to prevent severe vasoconstriction/renal ischemia
- not much of an effect in healthy, resting subjects
How nitric oxide affects RBF and GFR
Important vasodilator under basal conditions
Creatinine
Byproduct of skeletal muscle creatine metabolism
Used to measure glomerular filtration
It is not secreted, reabsorbed, or metabolized by cells in nephron, so amount of creatinine excreted in urine = amount if creatinine filtered by glomerulus each minute
