Blood supply and innervations of kidney in animals

Blood supply and innervations of kidney in animals

Blood supply to kidney

Blood flow to the kidneys is normally 22% of the cardiac output. The renal artery enters the kidney and branches to form the interlobar arteries, arcuate arteries, interlobular arteries and afferent arterioles which lead to the glomerular capillaries, where large amount of fluid and solutes (except plasma proteins) are filtered to begin urine formation. The distal ends of the capillaries of each glomerular coalesce to form the efferent arteriole which leads to a second capillary network, the peritubular capillaries surrounding the renal tubules

• Renal circulation is unique, in that it has two capillary beds-
  1. Glomerular capillaries and
  2. Peri-tubular capillaries, separated by efferent arterioles which help to regulate the hydrostatic pressure.

The glomerulus has a high pressure of 60 mm Hg and peritubular capillaries have a low pressure of 13 mm Hg which helps in rapid fluid filtration.

The peritubular capillaries empty into vessels of the venous system which run parallel to the arteriolar vessels and progressively form the interlobular vein, arcuate vein, interlobar vein and renal vein.

Vasa recta

The peritubular capillaries branches to form the vasa recta into the medulla and lie side by side with the loops of Henle. Like the loops of Henle, the vasa recta return toward the cortex and empty into the cortical veins. Vasa recta are associated with long looped nephrons. They play an essential role in the formation of concentrated urine.

Innervations of Kidney

Innervation to the kidney is provided by fibres from the sympathetic division of the autonomic nervous system which assists in the regulation of renal blood flow (RBF), glomerular filtration rate (GFR), salt and water reabsorption by the nephron.

RBF and GFR is brought about by vasoconstriction initiated by reflexes through the vasomotor centre in the medulla and pons. Increased sympathetic tone elicits renin secretion from granular cells and enhances sodium reabsorption from nephron segments.