Module A

Urinary System

Martin ŠpačekHistology and Embryology

• Pictures from:• Junqueira et al.: Basic histology• Rarey, Romrell: Clinical human embryology• Sadler: Langman’s medical embryology• Young, Heath: Wheather’s functional histology

UrinarySystem

• Kidney• Ureter• Urinary

bladder• Urethra

Development of the Urinary System

• Development of the kidney– Pronephros– Mesonephros– Metanephros

• Development of excretory passages

Pronephros• Intermediate mesoderm of the cranial 12-13 somites• Rudimentary, nonfunctional

Mesonephros

• At the end of the 4th week• Functional for a short time• Renal corpuscle

– glomerulus– Bowman’s capsule

• Tubules enter collecting duct –mesonephric or Wolffian duct

Mesonephros

Metanephros• Permanent kidney• Development begins in the 5th week• Ureteric bud (an outgrowth of the mesonefric duct)

• Metanephric blastema

Metanephros• Ureteric bud → collecting tubules,

calyces, renal pelvis, ureter• Metanephric blastema → nephrons

Position of the Kidney• Ascent of the kidney

– initially located in the pelvic region– later more cranial position in the abdomen

Horseshoe kidney

Urogenital SinusUrorectal septum divides cloaca into:

anorectal canalurogenital sinus

Urinary BladderDevelops from the upper and largest part of the urogenital sinusContinuous with the allantois, but the lumen obliterates → urachus (median umbilical ligament)

Kidney

• Nephrons• Collecting tubules

& ducts• Juxtaglomerular

apparatus• Blood supply• Intersticium

Nephron

• Renal corpuscle– Glomerulus– Bowman’s capsule

• Proximal tubule• Henle’s loope• Distal tubule

Renal Corpuscle• Glomerulus

– fenestrated capillaries (no diaphragms)

Renal Corpuscle• Bowman’s capsule

– parietal layer (simple squamous epitelium)– visceral layer (podocytes with pedicels)

Renal Corpuscle• Filtration barrier

– basement membrane (collagen type IV and heparansulfate)

glomerular capillary – lumen urinary space

direction of flow of the plasma ultrafiltrate

Renal Corpuscle• Mesangial cells

– synthesize the extracellular matrix and collagen– macrophages (?)

Proximal Tubule

• Simple cuboidalepithelium– brush border– basolateral labyrinth– abundant

mitochondria• Reabsorption of NaCl

and water (80-95%)

Henle’s loope

• Squamous simple epithelium– ascending limb is

impermeable to water• Juxtamedullary

nephrons have long HL

Distal Tubule• Simple cuboidal

epithelium– cells are smaller than

those of the proximal tubule

– no brush border– basolateral labyrinth

• Absorption of sodium, secretion of potassium

• Macula densa – modified segment– chemoreceptors

Collecting Tubules & Ducts• Collecting tubules

– simple cuboidalepithelium

• Papillary ducts– simple columnar

epithelium• ADH-dependent

water reabsorption

Juxtaglomerular Apparatus

• Macula densa of the distal tubule– sensitive to changes in NaCl concentration

• Extraglomerular mesangial cells (laciscells)

• Juxtaglomerular cells of the afferent arteriole– produce renin

Blood supply

• renal artery• interlobar arteries• arcuate arteries• interlobular arteries• afferent arterioles• efferent arterioles• peritubular capillary

network or vasa recta

Renal Intersticium

• Intersticial cells in the spaces between tubules and vessels

• Non-cellular elements• proteoglycans, glycoproteins, interstitial fluid

Kidney HE (U1)Kidney HE (U1)

Kidney HE (U1)Kidney HE (U1)

Kidney Van Kidney Van GiesonGieson (U2)(U2)

Excretory Passages

• Calyces and renal pelvis

• Ureters• Urinary bladder• Urethra

Excretory passages

• Mucosa (tunica mucosa)– transitional epithelium– lamina propria mucosae (connective

tissue)• Smooth muscle (tunica muscularis)• Adventitia (tunica adventitia)

Ureter

• Folded mucosa• Smooth muscle

– inner layer longitudinal

– outer layer circular

UreterUreter HE (U3)HE (U3)

UreterUreter HE (U3)HE (U3)

Urinary bladder

• Mucosa folded• Smooth muscle layer

– mixture of randomly arranged fibers (m. detrusor)

– at the neck the fibers form a three layer sphincter (inner longitudinal, middle circular, outer longitudinal)

Urinary bladder HE (U4)

Urinary bladder HE (U4)

Urinary bladder Van Urinary bladder Van GiesonGieson (U5)(U5)