Kidney Anatomy and Function: Nephrons, Blood Supply, and Urine Pathways

Kidney

The primary organ responsible for filtering blood, removing waste, regulating electrolytes, and maintaining fluid balance.

Fibrous Capsule

A transparent, outer layer of collagen fibers that protects the kidney from trauma and infection.

Renal Hilum

The 'gateway' on the medial concave surface where the renal artery, renal vein, and ureter enter or exit the kidney.

Renal Cortex

The light-colored outer region where the majority of filtration occurs; it contains the bulk of the nephrons.

Medulla of Kidney

The inner region characterized by darker, cone-shaped tissue masses.

Renal Pyramid

Triangular structures within the medulla that contain parallel bundles of urine-collecting tubules.

Renal Papilla

The apex (tip) of the renal pyramid that empties urine into the minor calyces.

Renal Column

Inward extensions of the cortex that separate the renal pyramids and provide a pathway for blood vessels.

Minor Calyx

Cup-shaped drains that collect urine from the renal papillae.

Major Calyx

Formed by the convergence of several minor calyces; they channel urine toward the renal pelvis.

Renal Pelvis

A funnel-like dilated proximal part of the ureter that acts as a central collecting basin for urine.

Ureter

A muscular tube that carries urine from the renal pelvis to the urinary bladder via peristalsis.

Urinary Bladder

A hollow, muscular sac that serves as a temporary storage reservoir for urine.

Rugae

Internal mucosal folds in the bladder wall that allow it to expand as it fills.

Renal Artery

Delivers oxygenated, unfiltered blood from the abdominal aorta to the kidney.

Segmental Arteries

The first branches of the renal artery as it enters the hilum.

Interlobar Arteries

Travel through the renal columns to reach the cortex.

Arcuate Arteries

Arch over the bases of the renal pyramids at the cortical-medullary junction.

Cortical Radiate Arteries

Extend outward into the cortex to supply the nephrons.

Vasa Recta

Long, straight capillaries that run parallel to the Loops of Henle in juxtamedullary nephrons; essential for concentrating urine.

Peritubular Capillaries

Low-pressure, porous capillaries that surround the tubular parts of the nephron in the cortex; they reclaim (reabsorb) water and solutes.

Renal Vein

Carries filtered, deoxygenated blood from the kidney back to the inferior vena cava.

Nephron

The structural unit responsible for forming urine through filtration, reabsorption, and secretion.

Glomerulus

A tuft of high-pressure capillaries where the actual filtration of blood occurs.

Bowman's Capsule

A cup-shaped enclosure that catches the 'filtrate' (fluid squeezed out of the glomerulus).

Afferent Arteriole

Feeds blood into the glomerulus; it has a wider diameter to maintain high filtration pressure.

Efferent Arteriole

Drains blood out of the glomerulus.

PCT (Proximal Convoluted Tubule)

The primary site of reabsorption; it reclaims most of the water, glucose, and amino acids from the filtrate.

Loop of Henle

Consists of descending and ascending limbs; its primary role is to create a salt gradient in the medulla to conserve water.

DCT (Distal Convoluted Tubule)

Focuses on selective secretion of ions (like potassium and hydrogen) and reabsorption of water, regulated by hormones.

Collecting Duct

Receives filtrate from many nephrons and performs final adjustments to urine concentration before delivering it to the minor calyx.

Juxtaglomerular Complex

A specialized structure where the distal part of the ascending limb meets the afferent arteriole.

Macula Densa

A group of tall, closely packed cells in the ascending limb that monitor the sodium chloride (NaCl) concentration of the filtrate.

Granular Cells

Enlarged smooth muscle cells in the arteriole wall that act as mechanoreceptors and secrete renin when blood pressure drops.