URINARY TRACT – I The kidney Maria M. Picken MD, PhD mpicken@luc

1. URINARY TRACT – I The kidney Maria M. Picken MD, PhD mpicken@luc.edu Renes = Latin kidneys nephros = Greek kidney

2. Outline: I – the kidney development gross structure vasculature

3. Objectives: • General objectives: • - to identify the kidney’s structures, function and location • - to analyze the relationship between microscopic structure and function • Specific objectives: • 1. Identify elements of the gross and microscopic structure of the kidney and analyze the relationship between them • 2. Identify developmental stages of kidney and their position • 3. On gross kidney identify: cortex, medulla, papillae at apex of medullary minor calyces, major calyces, renal pelvis • 4. Describe the renal blood supply: renal artery, arcuate arteries, interlobular arteries, differences between cortical • and medullary blood supply, define arterioles (afferent and efferent), peritubular capillary plexus

4. Retroperitoneum, Thoracic vertebra12-Lumbar vertebra3 115-170 g (M>F) 11-12 x 5-7.5 x 2.5-3 cm • Kidneys – paired, bean shaped • Ureters – paired • urinary bladder • Urethra, male versus female Renes = Latin kidneys Nephros = Greek kidney (Nephrology) Function: • Filter blood & reabsorb nutrients • Control water, ion, and salt balance of the body • Maintain acid-base balance of the blood (pH) • Excrete metabolic wastes (urea and uric acid), toxins, drug components • Secrete hormones (renin, erythropoietin) • Produce calcitriol (active form of vitamin D – absorption of dietary calcium into the blood)

5. Kidney development through a series of successive phases: • the pronephros (most immature) • mesonephros • metanephros, persists as the definitive adult kidney http://www.meddean.luc.edu/lumen/MedEd/urology/nlrendev.htm

6. Kidney development - complex • 3 stages: pronephros,mesonephros, metanephros • cranial to caudal direction followed by “ascend” • mesonephric duct comes in contact with cloaca, grows cranially as ureteric bud • ureteric bud & metanephros reciprocally induce growth, forming kidney • the kidney “ascends” • takes new arterial supply from the aorta, new venous drainage into the vena cava • developmental abnormalities are relatively common • important in pediatric nephrology

7. Kidney structure: bean shaped - capsule - cortex (outer) - medulla (inner) - hilum (pelvis, ureter, renal artery, vein) Cortex, renal columns (septa) of Bertin (cortical tissue on either side of the medullary pyramids) Medulla divided into several conical pyramids Papillae at apex of medullary pyramid Papillae lead into minor calyces Minor calyces lead into 2-3 major calyces Major calyces lead to the expanded upper end of the ureter, renal pelvis (latin: pelvis=basin) Glossary: capsule - a structure enclosing an organ, usually composed of dense connective tissue cortex - the outer portion of an organ, distinguished from its inner, medullary portion septum/septa - a wall, dividing a cavity or structure into smaller ones calyx; plural noun: calyces - a cuplike cavity or structure minor – lesser, small, major - greater hilus or hilum - a depression or pit at that part of an organ where the vessels and nerves enter medulla - the inner portion of an organ, usually in the center See also: http://www.bu.edu/histology/m/glossary.htm

8. on either side of medullary pyramid Posterior division of renal artery Interlobular arteries Kidney blood supply: 0.5% of total body weight, 25% of the cardiac output • renal artery, anterior & posterior divisions, segmental arteries (do not anastomose, “end arteries”) • interlobar arteries on either side of medullary pyramid - arcuate artery (Latin = curved) between cortex and medulla, parallel to kidney surface), interlobular arteries

9. juxtamedullary glomerulus Posterior segment • interlobular arteries → afferent arteriole → glomerulus → efferent arterioles • efferent arterioles in the cortex form peritubular capillary plexus - efferent arterioles of juxtamedullary nephrons (juxta [Latin]close to) go into medulla and loop back “vasa recta” (straight vessels [Latin]) Afferent, from afferre [Latin] = to bring toward Efferent, from efferre [Latin] = to bring out Correlation with pathology: - cortex: 90% of blood supply - medulla is relatively a-vascular (10%, low oxygenation) • tubular capillary beds derived from the efferent arterioles • acute tubular necrosis (injury), papillary necrosis

10. vascular pole Bc * tubular pole Glomerulus in paraffin section: Bowman’s capsule (Bc) + glomerular tuft* Afferentarterioles arise from interlobular vessels and supply the glomeruli Efferent arterioles arise from glomerular capillaries

11. Questions? mpicken@luc.edu