Structure and Function of
unit is the nephron
Regulation of extracellular fluid by urine formation
Blood volume/blood pressure
Concentration of wastes
Concentration of Na+, K+, HCO3-
pH of plasma
2 kidneys below diaphragm
of a fist
renal pyramids, separated by renal columns
join to form renal pelvis
is 4 cm in women, 20 cm in men
sphincters: upper internal urethral sphincter
lower external urethral sphincter.
center at 2,3,4 sacral levels of spinal cord. Internal relaxes, urgency and
external relaxation is under voluntary control. Ability develops at 2-3 years of
Microscopic Structure of
kidney has 1 million nephrons
Renal Blood Vessels
blood, renal artery, interlobar arteries, Arcuate arteries, interlobar arteries,
afferent arterioles, glomeruli efferent arteriole, peritubular capillaries,
interlobar veins, arcuate veins, interlobar veins, renal vein, inferior vena
capsule: in cortex, Bowman's Capsule
Convoluted tubule: in cortex, Cubodial
cells with lots of microvilli
of Henle: in medulla
Convoluted Tubule: cortex
nephrons: Originate in inner 1/3 of cortex. Longer loops.
nephrons: originate in outer 2/3 of cortex
Kidney disease: develops in middle age, autosomal dominant trait. Cysts on renal
collects in collecting duct, minor calyx, renal pervis-ureter.
capillaries have pores (fenestral)
WBC, platelets can't be filtered.
layer of glomerular capsule are cells called podocytes (shaped like octopus)
which form a web like clasped hands, which wrap the capillaries forming slits as
passageway for filtered molecules.
don't usually go into filtrate.
filtration pressure is 10 mmHg
to large surface area of glomerular capillaries a lot of filtrate is produced
filtration rate(GFR) Volume/minute of both kidneys.
women, 125ml/min in men.
blood filtered every 40 minutes, 180L/day…water is reabsorbed.
or vasodilation of afferent arterioles
regulation mechanism: renal autoregulation
Sympathetic Nerve Effects
of afferent arterioles.
may change but GFR does not.
changes direct constriction or dilation of afferent arterioles.
in filtrate volume sensed at ascending limb. Increase in fitrate=constriction.
Reabsorption of Salt and
follows salt by osmosis
salt and water reabsorbed at proximal tubule
water reabsorbed at collecting duct.
L of filtrate produces 1-2 Liters of urine in 24 hours.
of filtrate is excreted.
urine/day is minimum
the filtrate solute concentration is the same as plasma solute concentration
(300mOsm) solutes need to be reabsorbed to blood.
lots of microvilli and mitochondria
and Passive Transport
and lateral sides of cells have Na/K pumps that keep Na concentration low in the
diffuses into apical side of cell. Cl- passively follows.
returns to blood.
% of salt and water in filtrate is returned at proximal tubule.
% returned at Descending limb, no hormonal control, 6 % of energy expense.
returned later and hormone are involved.
renal medulla is 4 x as saltly as the filtrate due to juxtamedullary nephron
Limb: extrudes salt
and CL- moves by secondary active transport.
actively transported to interstial fluid.
permeable to water.
Descending Limb(20 % of salt
and water returned to blood here)
permeable to salt
leaves via diffusion.
you move from cortex to medulla, it gets more and more salty. This is a feature
of the descending(water leaves) and ascending loop moving in opposite
directions, and the active extrusion of salt from the Ascending
Vasa Recta: capillary-like
the salt concentration by removing the water that comes out of filtrate, but
leaving the salt in the medulla.
exchange: attracts water but extrudes urea and salt out at ascending limb.
from thin segment of loop of henle and collecting duct.
Collecting Duct: ADH
duct impermeable to salt but is permeable to water. Urine is hypotonic compared
to interstitial fluid in this region.
returned to circulation.
rate of water reabsorption at this region determined by water permeability of
depends on the number of aquaporins.
ADH binds to receptor proteins on
cAMP is activated.
Exocytosis of vesicles from golgi
that have aquaporins.
No ADH the aquaporins are removed
in hypothalamus trigger ADH release from Posterior Pituitary.
insipidus is when not enough ADH secreted.
Renal Plasma Clearance
is removed from blood.
is the active process of eliminating wastes/toxins by passing them to urine.
tubule has receptors that will select a variety of products to be eliminated.
drugs block secretion of antibiotics and increase effectiveness of these drugs.
a polymer of fructose is used to measure GFR. It is not reabsorbed or secreted.
excreted per minute mg/min=V ml/min x Umg/ml
filtered per minute mg/min=GFR ml/min x Pmg/ml
x P = V x U
V X U/P
120 ml/min clearance
used to check GFR in practice.
Plasma Clearance is volume of plasma from which substance totally removed in one
minute by kidney.
Plasma Clearance = V xU/P
urea is reabsorbed
of renal blood flow
is possible for all of a substance to be cleared in a single pass even though
not all blood is filtered. This occurs by secretion. PAH is a substance that can
be cleared. 625 ml/min.
into account that RBC take up space in blood. Calculate volume and divide by
plasma volume to get the total real blood flow.
and amino acids are reabsorbed at proximal tubule.
mediated transport can become saturated.
only 125 mg/min of glucose in tubules.
mg/min is transport maximum.
glucose is 180 mg per 100ml glucose gets into urine.
renal plasma threshold for glucose.
glucose is 1mg/ml.
mellitus is when there is not enough secretion of insulin
of urine to help get glucose out.
Electrolyte and Acid-Base
for regulation of blood volume and pressure
for regulation of cardiac and skeletal muscles.
% of Na and K reabsorbed before distal tubule.
collecting duct and distal tubule reabsorb varying amounts depending on need.
g Na secreted in urine per day, unless aldosterone involved.
aldosterone secreted, then NO NA in urine!
occurs at cortical collecting duct.
K in blood stimulates Aldosterone secretion
in Na reabsorption and secretion of K increases.
increase Na secretion at distal tubule. This increases K secretion and loss.
amount of K leads to heart problems.
of Na and K changes aldosterone secretions.
arteriole comes in contact with ascending limb of loop.
in this region secrete renin.
converted to angiotensin 1 by renin.
1 converted to angiotensin 2 by ACE.
2 stimulates adrenal cortex to secrete aldosterone.
enough salt in diet leads to a fall in blood volume.
blood volume causes increased renin secretion.
cells are baroreceptors.
nervous system can stimulate this when it detects decrease in blood volume.
example of negative feedback (retain more Na, blood volume rises).
in ascending limb called macula densa can inhibit renin secretin when blood Na
Atrial Natriurectic Peptide
in blood volume stretches atria and increases ANP.
promotes the excretion of Na and water in urine
Sodium, potassium, and H+
concentration and H + concentration are related
H+ concentration goes up, and H+ moves in to cell
then moves out.
Distal tubule and cortical collecting duct, K+ and H+ secreted to urine when Na+
acid blood, then more H+ secreted, but not as much K+ leading to too much K+ in
K+ secreted not enough H+ is secreted.
enough K+ it can be reabsorbed by collecting duct.
disease is not enough aldosterone (which would promote secretion of K+ and H+)
leads to acidosis and hyperkalemia.
H+ and reabsorb bicarbonate.
goes in filtrate, is secreted at proximal tubule(antiport with Na+).
filtrate bicarbonate turned to CO2 which diffuses into apical cells and turns
back to bicarbonate.
elevation: Low Pco2, alkalosis
renal carbonic anhydrase,
reabsorbtion of bicarbonate
Acute Mountain Sickness
in urine buffered by HPO4 2-(H2PO4) , and NH3(ammonium)
blood volume with diuretics
congestive heart failure, edema
diuretics: most powerful, stop Na+ movement out of loop,
stop salt and water reabsorption at distal convoluted tuble.
anhydrase inhibitors: stop bicarbonate reabsorption and water that goes with it.
diuretics: extra solutes in filtrate
diuretics: Aldosterone agonist, or blocks Na+ reabsorption and K+ secretion
you don't have enough K+ you have heart problems and neurological problems.
Supplement diuretics with K+ supplement and low salt diet.
Renal Function Tests and
plasma clearance of PAH
of GFR via inulin clearance
concentration in plasma
albumin levels--hypertension and diabetes can damage the kidney.
Acute Renal Failure
loss of ability to excrete waste, regulate blood volume, pH and electrolyte
can cause this as can reduced blood flow, inflammation, atheriosclerosis.
leak into urine.
in patients abdomen