Ganong's Review of Medical Physiology, 23rd Edition

642
SECTION VIII
Renal Physiology

mitochondria. They are concerned with acid secretion and
HCO
3

• transport. The total length of the nephrons, including
  the collecting ducts, ranges from 45 to 65 mm.
  Cells in the kidneys that appear to have a secretory function
  include not only the juxtaglomerular cells but also some of the
  cells in the interstitial tissue of the medulla. These cells are
  called
  type I medullary interstitial cells.
  They contain lipid
  droplets and probably secrete prostaglandins, predominantly
  PGE
  2
  . PGE
  2
  is also secreted by the cells in the collecting
  ducts; prostacyclin (PGI
  2
  ) and other prostaglandins are
  secreted by the arterioles and glomeruli.

BLOOD VESSELS

The renal circulation is diagrammed in Figure 38–3. The
af-
ferent arterioles
are short, straight branches of the interlobu-

lar arteries. Each divides into multiple capillary branches to

form the tuft of vessels in the glomerulus. The capillaries coa-

lesce to form the

efferent arteriole,

which in turn breaks up

into capillaries that supply the tubules

(peritubular capillar-

ies)

before draining into the interlobular veins. The arterial

segments between glomeruli and tubules are thus technically a

portal system, and the glomerular capillaries are the only cap-

illaries in the body that drain into arterioles. However, there is

relatively little smooth muscle in the efferent arterioles.

The capillaries draining the tubules of the cortical nephrons

form a peritubular network, whereas the efferent arterioles

from the juxtamedullary glomeruli drain not only into a peri-

tubular network, but also into vessels that form hairpin loops

(the

vasa recta

). These loops dip into the medullary pyramids

alongside the loops of Henle (Figure 38–3). The descending

vasa recta have a nonfenestrated endothelium that contains a

FIGURE 38–3
Renal circulation.
Interlobar arteries divide into arcuate arteries, which give off interlobular arteries in the cortex. The inter-
lobular arteries provide an afferent arteriole to each glomerulus. The efferent arteriole from each glomerulus breaks up into capillaries that supply
blood to the renal tubules. Venous blood enters interlobular veins, which in turn flow via arcuate veins to the interlobar veins.
(Modified from Boron
WF, Boulpaep EL:
Medical Physiology.
Saunders, 2003.)

Renal cortex

Superficial

glomeruli

Interlobular vein

Peritubular

capillary bed

Arcuate

vein

Arcuate

artery

Ascending

vasa recta

Descending

vasa recta

Loop of Henle

Interlobar

vein

Interlobar

artery

Renal medulla

(pyramid)

Efferent

arteriole

Afferent

arteriole

Interlobular

artery

Juxtamedullary

glomerulus