Interlobular Arteries

1. Overview

Interlobular arteries, also known as cortical radiate arteries, are small arteries in the kidney that branch off from arcuate arteries and extend into the renal cortex. Their primary function is to supply blood to the glomeruli and cortical tissues of the nephron. These arteries are crucial for maintaining renal perfusion and enabling efficient glomerular filtration across the kidney’s cortical region.

2. Location

Interlobular arteries are located within the renal cortex. They arise perpendicularly from the arcuate arteries, which run along the corticomedullary junction at the base of the renal pyramids. Once they enter the cortex, interlobular arteries radiate outward toward the renal capsule, traveling between cortical lobules. Along their course, they give rise to:

• Afferent arterioles that supply the glomeruli

• Peritubular capillaries that support cortical tubules

3. Structure

Interlobular arteries are small-caliber muscular arteries composed of three primary layers:

• Tunica intima: Endothelial lining with a thin subendothelial connective tissue layer.

• Tunica media: Composed of smooth muscle cells, allowing for regulation of vascular resistance.

• Tunica adventitia: A connective tissue sheath containing nerves and vasa vasorum (in larger vessels).

These arteries are arranged in a radial pattern in the cortex, giving them the alternate name "cortical radiate arteries."

4. Function

Interlobular arteries perform several key functions in renal blood supply:

• Deliver oxygenated blood: Supply the outer cortex and nephrons, particularly the glomeruli.

• Branch into afferent arterioles: Which then feed individual glomerular capillary beds.

• Support cortical microcirculation: By forming the peritubular capillary networks essential for tubular reabsorption and secretion.

5. Physiological Role(s)

The interlobular arteries are vital to kidney physiology and homeostasis:

• Filtration initiation: They supply blood to the glomeruli where filtration begins.

• Oxygen delivery: Ensure adequate oxygenation of metabolically active cortical structures such as the proximal and distal convoluted tubules.

• Blood pressure regulation: Influence renal vascular resistance and GFR by affecting afferent arteriole tone.

• Hormonal interaction: Serve as entry points for hormones (e.g., angiotensin II, aldosterone) to exert effects on renal perfusion.

6. Clinical Significance

Acute Cortical Necrosis

Severe ischemia affecting interlobular arteries may lead to patchy or diffuse cortical necrosis, often seen in:

• Sepsis

• Shock

• Obstetric complications

This condition results in rapid and often irreversible kidney failure.

Glomerular Disease

Since interlobular arteries give rise to afferent arterioles, they are upstream of glomerular filtration. Diseases that impair their flow may contribute to:

• Reduced GFR

• Hypoxia-induced glomerular injury

• Progressive renal dysfunction

Renal Artery Stenosis

In advanced cases of renal artery or segmental artery stenosis, the downstream interlobular arteries may be underperfused, resulting in:

• Reduced glomerular pressure

• Increased renin secretion from JG cells

• Secondary hypertension

Atheroembolic Renal Disease

Microemboli from cholesterol plaques may lodge in small arteries like interlobular branches, leading to:

• Ischemic glomerular damage

• Patchy cortical infarctions

• Progressive renal insufficiency

Histological Relevance

In kidney biopsies, interlobular arteries are often used as landmarks. Pathologists evaluate:

• Wall thickening (arteriolosclerosis)

• Hyaline deposits (in diabetes or hypertension)

• Vasculitic changes

Transplant and Surgical Relevance

Preservation of interlobular arterial perfusion is crucial for renal graft function. Any damage to these vessels during surgery can lead to focal infarction or reduced nephron viability.