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Histology of Urinary System
Introduction
- Composed of:
- Bilateral kidneys and ureters
- Single midline bladder
- Single urethra
- Function:
- Kidneys filter waste, produce urine
- Ureters transport urine to bladder
- Bladder stores urine
- Urethra eliminates urine from body
Kidney Anatomy and Organization
- Kidney Layers
- Renal capsule
- Outer dense connective tissue
- Inner layer of myofibroblasts
- Perirenal fat
- Renal fascia (Gerota)
- Pararenal (paranephric) fat
- Kidney Regions
- Cortex
- Cortical Labyrinth
- Renal Corpuscles
- Proximal Convoluted Tubules
- Distal Convoluted Tubules
- Medullary Ray
- Straight tubules
- Cortical collecting ducts
- Medulla
- Renal pyramids
- Renal papilla
- Minor and major calyces
- Renal pelvis
- Renal Lobe
- Renal Lobule
Nephron and Collecting Ducts
- Nephron Types
- Cortical Nephrons (85%)
- Shorter, mostly in cortex
- Produce "standard" urine
- Juxtamedullary Nephrons (15%)
- Responsive to ADH, can concentrate urine
- Nephron Divisions
- Renal Corpuscle
- Glomerulus
- Tuft of capillary loops
- Fenestrated capillaries
- Bowman's Capsule
- Parietal layer
- Visceral layer (Podocytes)
- Mesangial Cells
- Provide structural support
- Phagocytosis
- Cytokine secretion
- Tubular Passageways
- Proximal Convoluted Tubule
- Cuboidal epithelium with brush border
- Basal striation
- Henle's Loop
- Thick & Thin segments
- Distal Convoluted Tubule
- Cuboidal epithelium, smaller diameter
- Macula densa cells
- Collecting Tubule and Ducts
- Cuboidal epithelium
- Principal and Intercalated cells
- Glomerular Filtration Barrier
- Endothelial capillaries
- Glomerular basement membrane
- Podocyte pedicels and slit diaphragms
Juxtaglomerular Apparatus
- Macula Densa
- Tall columnar cells in distal tubule
- Sensitive to Na+ concentration
- Juxtaglomerular (JG) Cells
- Specialized smooth muscle in afferent arteriole
- Secrete renin
- Extraglomerular Mesangial Cells (Lacis Cells)
- Flat, elongated cells
- Participate in tubuloglomerular feedback
Intrinsic Renal Vascular System
- Renal Artery
- Segmental, Interlobar, Arcuate, Interlobular arteries
- Afferent arterioles
- Glomerular capillaries
- Efferent arterioles
- Peritubular capillaries
- Vasa recta
- Renal Vein
- Segmental, Interlobar, Arcuate, Interlobular veins
Histology of Other Structures
- Ureters
- Mucosa
- Transitional epithelium (urothelium)
- Lamina propria
- Muscular Layer
- Inner longitudinal
- Outer circular
- Lower third has outer longitudinal
- Adventitia
- Urinary Bladder
- Tunica Mucosa
- Transitional epithelium
- Lamina propria
- Tunica Muscularis
- Inner longitudinal
- Middle circular
- Outer longitudinal
- Tunica Serosa/Adventitia
- Prostate Gland
- Glandular Parenchyma
- Fibromuscular Stroma
- Urethra
- Female
- Male