Renal Anatomy

General Renal Architecture

in perirenal fat in retroperitoneal space of posterior abdominal cavity (anterior to T and L vertebrae)

125 grams each, surrounded by a fibrous layer (Glisson's capsule)

blood, ureters, lymph enter through hilum, which communicates with the flattened space of renal sinus

within the sinus, renal pelvis communicates to 2-4 major calyces; each branches to 6-18 minor calyces

Lobes: 6-18 sections, develop separately during fetal life and fuse; clefts rarely persist into adulthood

Lobules: demarcated by arcuate and interlobular arteries; exocrine (drained by duct, the collecting tubule)

Cortex: outer section that contains all glomeruli and receives 90-95% of blood flow

renal columns – projections toward hilus; arise from base of medullary pyramid, defines lobule center

medullary rays – radial striations which comprise collecting tubules and ducts

Medulla: inner section, receives 5-10% renal blood flow; cortex surrounds pyramids like acorn cap

outer zone called corticomedullary junction, subdivided into inner and outer stripe; inner zone near hilus
8-12 striated pyramids with collecting ducts and loops of Henle; base next to cortex, apex in renal sinus
apex of each medullary pyramid (medullary papilla) projects to minor calyx

Nephron: one million tubes per kidney (lined with simple epithelium); begin blindly, terminate in drainage duct

renal corpuscle (glomerulus) – set of capillaries in modified squamous epith. (Bowman's Capsule)
to proximal convoluted tubule – plunges to medulla only if corpuscle is mid-cortical or juxtamedullary
to descending and ascending limbs of Loop of Henle – returns to cortex
to distal convoluted tubule – attached to renal corpuscle (where it all began)
to arched collecting tubules, which converge into straight collecting tubules – run through medullary ray
papillary duct (of Bellini) – opening through papilla of pyramid into urinary space of calyx

Vasculature of the Kidney

renal arteries

arise from the aorta at the level of the superior mesenteric artery

right is longer than the left; gives rise to the right gonadal artery (left gonadal comes directly from aorta)

renal Þ segmental Þ interlobar arteries – in renal columns between medullary pyramids

Þ arcuate arteries – run parallel to the surface along medulla/cortex border

Þ interlobular arteries – radially through cortex; no anastomosis between lobules

Þ afferent arterioles (in medullary rays) Þ glomerular capillaries Þ efferent arterioles

outer or middle cortex: cortical peritubular networks – reabsorbtion/secretion (adjacent tubule)

lower (juxtamullary) cortex: vasa rectae – straight hairpin capillaries along loop of Henle in medulla

arteriolae rectae spuriae Þ arteriolae rectae Þ venae rectae Þ interlobular OR arcurate vein

renal veins

interlobular veins Þ arcuate veins Þ interlobar veins Þ main renal vein Þ inferior vena cava

unlike arteries, left is longer than right, and left gonadal vein empties into it (right gonadal direct to IVC)

nerves – sympathetics innervate all nephron segments; stimulation decreases cortical flow, diverts blood to medulla

lymphatics – two major networks