Kidney Structure and Function Flashcards
Challenges to maintenance of ECF homeostasis
Food and fluid intake - increase interstitial (food)and plasma (fluid) water
Cell metabolites - move cellular water to ECF
Fluid losses - lose ECF
Role of kidneys in ECF homeostasis
Output=input=homeo
ECF filtered into nephrons
Most of filtered fluid and solutes are reabsorbed and returned to ECF
Excess fluid and solutes excreted as urine
Major zones and pyramids
Urine path
Human kidney
Outer - cortex
Medulla - inner
Pyramids - base origniates at cortico-medullary border…apexx terminates in a papilla…pyramids are surrounded by calyx…these converge to form renal pelvis…this is holding chamber for urine from kidneys
Produced by neprhons in the cortico-medullary tissue…collected in pelvic space…to bladder
HUmany kidney is mmultipapillate
Nephron structure
Sub-segements
Each nephron is ONE epithelial cell thick
Proximal tubule - loop of henle - distal tubule - collecting tubule
How to tell histo of proximal vs. distal
Proximal - brush border membrane in luminal surface…increases SA
Cortical and juxtamedullary neprhons
Cortical - glumeruls located close to surface of the kidney…short-loooped nephrons with no thin ascending limb…very short loops of Henle
JM - glomeulus close to border between cortex and medulla…long-looped nephrons essential for urine concentration
80% cortical
More JM, means greater ability to concentrate
Renal vasculature
Renal artery divides into segmental arteries…each segmental supplies blood to a specific area of renal tissue
Affarent arteriole—glomerular capillaries—efferent arteriole—peritbular capillaries
Allows resistance upstream AND downstream of the glomeruluar capillaries to be regulated…critical for filtration
Vasa recta
Subset of periptubular capillaries
Derived from efferent arterioels of JM nephrons
Hairpin-loop orientation vasa recta parallel loops of Henle
Play a crticial role in maintaining the
hypertonicity of the renal medulla
Cardiac output
Receive about 25%
Compared to other organs, the renal a-v O2 concentration difference is relatively low, suggesting that renal O2 consumption is low…BUT this is not the case, renal O2 consumption is actually very high
Blood flow to the kidneys is HIGH…only relatively low extraction % is required to provide O2 needs
O2 consumption=a-v diff*blood flow rate
Glomerular filtration
Plasma filtered from glomerulate cpaillaries into Bowman’s space
Only 20% of plasma entering glomerular caps is filtered (filtration fraction)
Filtration fraction = GFR/RPF (renal plasma flow rate)
ONE directional movement from the capillaries into Bowman’s space
Bowman’s capsule
Glomerular capillaries contained in proximal tubule extension
Tubular reabsorption
Movement of substances from the lumen into the peritubular capillary
PRINCIPAL mech for modifying compositon of the filtered fluid
FROM the lumen INTO the peritubular capillary
Tubular secretion
Movement FROM The peritubular capillary INTO the lumen
Secretion mostly restricted to solutes poorly filtered due to size, charge, or protein binding
Daily renal turnover of water and solutes
AMount excreted=amount filtered(+amount secreted)-amount reabsorbed
Percent of filtered load that is reabsorbed can be altered accordng to hemostatic demands
Location of tubular secretion
Across the proximal tubule
