Chapter 26; The Urinary System: Functional
Anatomy and Urine Formation by the
Kidneys
The important functions of the kidneys include excretion of metabolic
waste products, regulation of water and electrolyte balances, of the
arterial pressure, of acid-base balance, of erythrocyte production (via
secretion of erythropoietin), of vitamin D3 synthesis, and glucose
synthesis.
Blood supply of kidneys:
Renal artery > Interlobar arteries > Arcuate arteries > Interlobular
arteries > Afferent arterioles > Glomerular capillaries > Efferent arterioles
> Peritubular capillaries > Interlobular veins > Arcuate veins > Interlobar
veins > Renal vein.
The glomerular capillaries have a high capillary hydrostatic pressure of 60
mmHg in order to cause filtration whereas the peritubular capillaries have
a low hydrostatic pressure of 13 mmHg to cause reabsorption.
The descending limb and lower end of the ascending limb of the loop of
Henle are quite thin, whereas the remaining upper portion of the
ascending limb is quite thick. The macula densa is located at the end of
the thick ascending limb.
The cortical nephrons have short loops of Henle while the juxtamedullary
nephrons have long ones that go deep into the medulla. Another
difference is that the peritubular capillaries of the juxtamedullary
nephrons are specialized and known as vasa recta.
Anatomy and Urine Formation by the
Kidneys
The important functions of the kidneys include excretion of metabolic
waste products, regulation of water and electrolyte balances, of the
arterial pressure, of acid-base balance, of erythrocyte production (via
secretion of erythropoietin), of vitamin D3 synthesis, and glucose
synthesis.
Blood supply of kidneys:
Renal artery > Interlobar arteries > Arcuate arteries > Interlobular
arteries > Afferent arterioles > Glomerular capillaries > Efferent arterioles
> Peritubular capillaries > Interlobular veins > Arcuate veins > Interlobar
veins > Renal vein.
The glomerular capillaries have a high capillary hydrostatic pressure of 60
mmHg in order to cause filtration whereas the peritubular capillaries have
a low hydrostatic pressure of 13 mmHg to cause reabsorption.
The descending limb and lower end of the ascending limb of the loop of
Henle are quite thin, whereas the remaining upper portion of the
ascending limb is quite thick. The macula densa is located at the end of
the thick ascending limb.
The cortical nephrons have short loops of Henle while the juxtamedullary
nephrons have long ones that go deep into the medulla. Another
difference is that the peritubular capillaries of the juxtamedullary
nephrons are specialized and known as vasa recta.
