The urinary system part 4

The vascular supply to the kidney
The vascular supply to the kidney comes from the renal artery,
which enters the kidney at the hilum; segmental branches of the renal
artery give rise to the interlobar arteries. These pass through the renal
columns between the renal pyramids and give rise to arcuate arteries. The
arcuate arteries run along the junction between the cortex and the medulla
of the kidney and give rise to the interlobular arteries, which extend into
the medulla to supply the afferent arterioles of renal corpuscles. Each
afferent arteriole supplies a glomerulus of capillaries from which blood is
drained by an efferent arteriole at the vascular pole. The efferent
arterioles of corpuscles in the outer cortex feed into the peritubular
capillary network, which supplies the cortical tissue surrounding the
cortical tubules. These peritubular capillaries provide for gas and material
exchange and also receive renal interstitial fluid, which is reabsorbed out
of the tubules and goes back into the vascular bed. Venules carry blood to
the interlobular veins and to the arcuate veins in the renal
corticomedullary junction. The efferent arterioles of deeper
(juxtamedullary) corpuscles extend into the medulla where they give rise
to capillaries called vasa recta, which receive interstitial fluid (reabsorbed
from filtrate) in the medulla and send it back to the circulation. The vasa
rectae take a hairpin course in the medulla following the loop of Henle.
They return to the corticomedullary junction to join the interlobular veins
and then drain into the arcuate veins. The arcuate veins drain blood into
the interlobar veins, which then merge to form the branches of the
segmental renal veins, which in turn finally merge into the renal vein
(Fig.7).
Histology URINARY SYSTEM Dr. Hameda A.Gazi
2
(Figur-7): Vascular Supply of the Kidney
Ureters
The two ureters lie in the extraperitoneal connective tissue, laterally
positioned on each side of the vertebral column. The ureters are long,
relatively small tubules lined by transitional epithelium and surrounded
by a thin layer of smooth muscle and connective tissue. Superiorly, they
drain the funnel-shaped
renal pelvis, and inferiorly, they empty into the bladder by penetrating its
posterior wall. The ureters have a much thinner wall than the bladder.
Like most tubular organs, the wall of the ureter is composed of several
layers of tissues: mucosa, muscularis, and adventitia. It possesses a twolayer
muscularis (an inner longitudinal and outer circular layer of smooth
muscle) in its upper two-thirds. The lowest third possesses an additional
outer longitudinal layer of smooth muscle.