Overview of Renal Structure and Function - Wall Flashcards
What is the major extracellular cation?
Sodium
What does total body Na determine?
Size of total body water
What is the major intracellular cation?
Potassium
What are the major extracellular anions?
Chloride
Bicarbonate
What is bicarbonate’s role in ECF?
Major ECFV buffer
Key factor in acid-base balance
What are the kidney’s endocrine functions?
Erythropoietin
1-alpha hydroxylase produce calcitriol
Renin
What are the kidney’s paracrine/autocrine functions?
Bradykinin (vasodilatory, natriuretic)
Prostaglandin (mostly vasodilatory)
Nitric oxide (vasodilatory)
Endothelin (potent vasoconstrictor)
What does angiotensin II do?
Vasoconstrict
What does aldosterone do?
Promote Na reabsorption
Name two accessory functions of the kidney.
Small peptide catabolism (ie insulin)
Gluconeogenesis during fasting (25-33%)
Define neutral, positive, and negative balance.
Neutral - Intake + Production = Excretion
Positive - Intake + Production > Excretion
Negative - Intake + Production < Excretion
What is the best index of kidney function?
GFR
What vertebral segments do the kidneys span?
T12 to L3
What percent of total blood flow to the kidney does the cortex receive?
90%
What does the hilum contain?
Renal artery, vein, nerves, pelvis, ureter, and lymphatics
What does the medulla contain?
Loops of Henle
Collecting ducts
Vasa recta
What are sites of potential obstruction within the ureter?
Pelvic ureteral junction
Crossover of pelvic brim
Urinary trigone
What is the most common spot for urethral obstruction in males?
Prostatic urethra
Which type of nephrons have a higher pressure in the glomerular capillaries?
Juxtamedullary > Cortical
Are nephrons working at full capacity under normal conditions?
Cortical - No (basis for reserve capacity)
Juxtamedullary - Yes
What layers are between the mesangium and circulation?
Endothelial cells (with large fenestrations)
Is urine volume a good index of kidney function?
No (urine flow rate / volume is not autoregulated)
What does clearance represent?
Volume of plasma cleared of the substance
What is the equation for clearance?
Cx = U * V / P
What is the equation for clearance ratio?
Cx / GFR
What does a clearance ratio 1 imply?
< 1 - filtered and reabsorbed
= 1 - filtered
> 1 - filtered and secreted
What is the clearance of PAH equivalent to?
Renal Plasma Flow
What is a normal filtration fraction?
~20% of RPF becomes glomerular filtrate
What does decreased cardiac output or volume depletion result in?
RAS - increased FF
What can the autoregulatory response in a hypovolemic state be disturbed by?
Decreased AT II production
ACE-inhibitors, AT receptor blockers, renin inhibitors
Prevent production of vasodilatory prostaglandins (NSAIDS)
Describe the proximal and distal tubule in terms of resistance and capacity.
Proximal tubule - High capacity, Low resistance
Distal tubule - Low capacity, high resistance
What is the major difference between carriers and channels?
Channels are not saturable
What is the tonicity of the bulk reabsorption in the PCT?
Isotonically
How much of the filtered load is reabsorbed by the PCT?
50-55%
What is the tonicity of fluid that enters the LOH?
Isotonic
What is reabsorbed in the thin descending limb?
Passive water and urea
What is reabsorbed in the thin ascending limb?
Passive sodium / chloride
What is reabsorbed in the thick ascending limb?
Active NaCl
Ca, Mg
What is reabsorbed in the DCT?
NaCl
Calcium
