Renal System Flashcards
What are the functions of the kidney?
Homeostatic regulation of H2O + ion content in blood
Excretion of metabolic waste products
Production of hormones
What is the overall structure of the kidney?
Cortex (outer) Medulla (inner) Nephrons Cortical nephrons = cortex Juxtamedullary nephrons = medulla
Describe nephron structure
Bowman's capsule Proximal tubule Loop of Henle Distal tubule Collecting duct
What is the bowman’s capsule surrounded by?
Glomerulus
What happens at the bowman’s capsule?
Ultrafiltration
Describe blood flow around bowman’s capsule
Blood flows from afferent arteriole into glomerulus + leaves through efferent arteriole
What surrounds the arterioles?
Peritubular capillaries
What are the role of the renal capillaries?
Form venules = conduct blood out of the kidney
What is the function of renal portal system?
Filter blood + into lumen of nephron
Where are fluid reabsorbed?
From tubule back into blood at peritubular capillaries
What processes happen at the nephron?
Filtration
Excretion
Reabsorption
Secretion
What is filtration?
Movement of fluid from blood into lumen
What is excretion?
Anything filtered from renal capsule
What is reabsorption?
Movement of filtrate from lumen of tubule back into blood through peritubular capillaries
What is secretion?
Removes selected molecules from blood + adds them to filtrate in tubule lumen
How do you calculate the amount of urine?
(amount filtered) - (amount reabsorbed) + (amount secreted)
What are the two mechanisms in autoregulation of GFR?
Myogenic mechanism of regulation
Tubuloglomerular feedback
Describe myogenic mechanism of regulation
Afferent + efferent have smooth muscles
Contraction = blood pressure + = smooth muscle contracts = reduce diameter = oppose flow
Relaxation = bp - = relaxes = + diameter = facilitate flow
Describe tubuloglomerular feedback
GFR + Flow through tubule + Paracrine factors released Afferent constricts Resistance + Hydrostatic pressure in glomerulus - GFR -
What is clearance?
Vol of plasma from which a substance has been removed + excreted into urine per unit time
What is the equation for clearance?
Plasma Conc
What is clearance used as an index for?
Kidney function
Describe the structure of glomerulus
Capillary endothelium has pores
Basal lamina
Podocytes with long cytoplasmic extensions
What is the significance of capillary endothelium in glomerulus?
Pore surface negatively charged = negatively charged proteins = repulse negatively charged proteins
What is the significance of basal lamina in glomerulus?
Layer of extracellular matric that separates capillary + endothelium of Bowman’s capsule
Negatively charged = exclude plasma proteins from filtration
What is the significance of podocytes in glomerulus?
Form narrow filtration slits
Describe what happens in glomerulus
Proteins excluded from filtration based on charge + molecular weight
H2O, Na+, K+, Ca2+, glucose + urate = YES
Blood plasma = NO
What happens in proximal tubule?
Glucose + amino acid reabsorption
= co-transport
What is the descending limb?
H2O permeable
What is the ascending limb?
H2O impermeable
What happens in the descending limb?
Impermeable to NaCl = no active transport
= osmolarity + = reach max at loop
What happens in ascending limb?
Reabsorbed NaCl passively
= active transport by NaK
= osmolarity - = min at top
Describe what happens overall in Loop of Henle
Isosmotic fluid leave proximal tubule
= more concentrated as descends limb
Removal of solute in ascending limb
= hypoosmotic fluid
Permeability of H2O + solutes in DT + CD regulated by hormones
Final urine osmolarity depends on reabsorption in CD
Describe the transport of solutes out of Loop of Henle
Transport out of ascending limb dilutes filtrate + helps concentrate interstitial fluid in medulla
BUT H2O leaving descending limb DOESNT do this
Describe the transport of solutes into Loop of Henle
Solute reabsorbed by ascending limb moves into descending limb of vasa recta
= + blood osmolarity
H2O reabsorbed by descending limb moves into ascending limb of vasa recta
= - blood osmolarity
Describe what happens in the initial segment of DT
NaCl reabsorbed by Na+/Cl- co-transporter
H2O impermeable
Osmolarity falls further
Describe what happens in last segment of DT + CD
Principle cells recover more than Na+ + H2O via channels
α- intercalated cells reabsorb K+ + secrete H+
Through K+/H+ transporter
Reabsorbs HCO3-
= regulate pH
β- intercalated cells = secrete HCO3- + reabsorb Cl-
Through Cl-/HCO3-
What is the last segment of DT + CD composed of?
Principle cells + intercalated cells
What are the processes that form urine?
Filtration
Reabsorption
Secretion
What does Na+ balance + blood pressure do?
Increase osmolarity
What is vasopressin?
Anti-diuretic hormone (ADH)
What does vasopressin do?
Stimulate H2O recovery via aquaporin at CD
= concentrates urine
What does aldosterone do?
Control Na+ balance
How does aldosterone control Na+ balance?
Physiological modulation
Physiological modulation = + extracellular K+ + - BP = stimulates aldosterone secretion by adrenal cortex
How does aldosterone control Na+ balance?
Pathological modulation
+ in ECF osmolarity = inhibit aldosterone release from adrenal cortex = abnormal - in Na+ = stimulate aldosterone secretion
What happens when there is an increase in Na+?
+ BP = Na+ retention increases osmolarity = + thirst
= drinking + ECF, blood vol + = BP +
What happens aldosterone acts on principle cells in DT + CD?
More Na+ reabsorbed due to insertion of more ENaC on membrane
= urine dilutes
Why does a decrease in blood pressure increase H2O retention?
ANG II activates release of aldosterone
= BUT high osmolarity = blood aldosterone = - reabsorption of Na+
= BUT high osmolarity = release vasopressin = + reabsorption of H2O
= + BP + H2O retention = - osmolarity
What are diuretic drugs used for?
High blood pressure
What do loop acting diuretics do?
Inhibit transport system in ascending limb
What do thiazide diuretics do?
Inhibit transport system in DT
What do K+ sparing diuretics do?
Inhibit ENaC in CD
Block effects of aldosterone on channels
