Pathology

of the

Urinary System

(Kidney, Urinary Tract, Bladder)

Plan:

Lecture 1: Recap of anatomy and physiology, clinical aspects of renal disease, pathogenesis of glomerulonephritis

Lecture 2:Morphologic expressions of glomerular injury, primary glomerular diseases

Lecture 3:Primary glomerular disease

Introduction.

• Weight 150 g

• Cortex (1.5 cm) and

medulla

• Renal pelvis - 2 to 3

major calyces - each

3-4 minor calyces.

Filters about 1700 L of blood

to prepare 1 L of urine

Anatomical structure of parenchyma ..

Lobe

Lobule

Cortex

Medulla

Anatomical structure of parenchyma .

Lobules

Cortex

o Columns of

Bertin

Medulla (O , I)

o Pyramid

o Papilla

The Cortex

Labyrinth

Medullary rays

Vasculature

Renal artery

- anterior and posterior br ---- interlobar ---- arcuate ---

interlobular ---- afferent arteriole ---- glomerulus ---- efferent

arteriole ---- peritubular capillaries ---- vasa recta ---- venous

vasa recta ---- renal vein

Vascular structure of parenchyma

Renal vasculature

• Arteries are end arteries• Glomerular diseases can compromise

vascular supply to other components• Medulla is relatively avascular and

vulnerable to ischemia• Cortex is more vulnerable to hypertensive

changes

The Nephron

(Pathology) Compartments

• Glomeruli

• Tubules

• Interstitium

• Blood vessels

Glomerulus

• Formation• Components• Structure

Glomerulus

• Formation• Components• Structure

• Bowmans capsule• Parietal epithelial cells• Visceral epithelial cells• Basement membrane• Endothelial cells• Mesangial cells• Mesangial matrix

Glomerulus

• Formation• Components• Structure

Bowmans capsuleParietal epithelial cellsVisceral epithelial cellsBasement membraneEndothelial cellsMesangial cellsMesangial matrix

Glomerulus

• Formation• Components• Structure

Filtration membrane

• fenestrated endothelial cells (70-100

nm);

• glomerular Basement Membrane

• visceral epithelial cells -podocytes

(20-30 nm)

Glomerulus

• Formation• Components• Structure

• Glomerular basement membrane: - Thick inner lamina densa - Lamina rara externa and interna.

Collagen IV, laminin, polyanionic proteoglycans, intermediate filaments, other glycoproteins.

Filtration is governed by size and charge.

The Glomerulus

The Glomerulus

Basement Membrane: (LM)

Identified better using special

stains such as

PAS (Per-iodic acid Schiff)

Silver impregation methods

Invests capillaries incompletely,

and is continuous with capsular

BM

Juxta-glomerular apparatus

• JG cells of afferent arteriole,

• macula densa of DCT,

• Lacis cells of mesangium

Principal source of renin

Tubules and interstitium

• Proximal tubules: Rich in mitochondria, microvilli, canaliculi

and interdigitations - Major site for re-absorption of water,

glucose, sodium, potassium, phosphate, proteins, amino acids.

Vulnerable to vascular and toxic injury.

.

.

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Histology of PCT

Proximal tubules:

Abundant granular cytoplasm

Distal tubules:

Cuboidal cells

Loops of

Henle,

and

Collecting

Ducts

Interstitium:

Scanty in the cortex and outer medulla

More abundant in inner medulla