Page 732 - Atlas of Histology with Functional Correlations

Distal Convoluted Tubules

Shorter than proximal convoluted tubules, less frequent in cortex, and lack
brush border
Basolateral membrane shows infoldings and contains numerous mitochondria
Under the influence of aldosterone, sodium ions actively absorbed from the

filtrate
Peritubular capillaries return ions to systemic circulation to maintain vital
acid–base balance

Juxtaglomerular Apparatus

Located adjacent to renal corpuscle and distal convoluted tubule
Consists of juxtaglomerular cells, macula densa, and extraglomerular
mesangial cells

Juxtaglomerular cells are modified smooth muscle cells in afferent arteriole
before entering glomerular capsule
Main function is to maintain proper blood pressure for blood filtration in

renal corpuscles
Juxtaglomerular cells respond to stretching in the wall of afferent arterioles,
as baroreceptors
Macula densa is a group of modified distal convoluted tubule cells
Macula densa responds to changes in sodium chloride concentration in

glomerular filtrate
Decreased blood pressure and ionic content causes release of enzyme renin
by juxtaglomerular cells

Renin release eventually causes plasma proteins to convert to angiotensin II,
a powerful vasoconstrictor
Angiotensin II stimulates release of aldosterone, which acts mainly on cells
in collecting ducts
Collecting ducts absorb NaCl with water, increasing blood volume and

pressure
Collecting ducts also eliminates hydrogen and potassium to maintain acid–
base balance

Collecting Tubules, Collecting Ducts, and

Antidiuretic Hormone

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