Histology of Urinary System Lecture Notes PDF

College of Applied Medical sciences Department of Medical Laboratory technology. Histology of urinary system The Urinary System Paired kidneys & ureters Urinary bladder Urethra Functions of Urinary system 1- Maintain homeostasis by a complex process involves filtration, active absorpti...

College of Applied Medical sciences Department of Medical Laboratory technology. Histology of urinary system The Urinary System Paired kidneys & ureters Urinary bladder Urethra Functions of Urinary system 1- Maintain homeostasis by a complex process involves filtration, active absorption, passive absorption & secretion 2- Urine formation into which metabolic wastes are eliminated 3- Hormonal secretion which includes erythropoietin and renin.  The Kidney The kidney is a bean-shaped retroperitoneal organ The Kidney is formed of: I- Stroma: - Capsule: dense CT surrounded by adipose CT (peri-renal pad) - Renal interstitium defined as the intertubular, extraglomerular, extravascular space of the kidney minimal CT between parenchymal elements II- Parenchyma (the functional tissue of an organ as distinguished from the connective tissue) - Outer Cortex - Inner Medulla  The Uriniferous tubule The structural unit of the kidney Consist of nephron & a collecting tubule. The nephron produces urine The collecting tubules concentrates urine & conveys it to the calyces. The Nephron The basic functional unit of the kidney Each kidney contains 1-4 million nephrons Components : Renal (Malpighian) corpuscle Proximal convoluted tubule Loop of Henle Distal convoluted tubule Nephron KIDNEY H&E CORTEX: CORTICAL LABYRINTH Bowman’s capsule 1- RENAL CORPUSCLES 2- PROXIMAL CONVOLUTED 3- DISTAL CONVOLUTED TUBULES TUBULES glomerulus RENAL CORPUSCLE DC T PCT Renal corpuscle Glomerulus: Vascular ball (200 µm d) covered by Bowman’s capsule Bowman’s capsule: Double wall epithelial cup-shaped capsule that has: Visceral layer: modified S. Sq. epith.(Podocytes) Parietal layer: Lined by S. Sq. epithelium Filtration Barrier Definition: It is the barrier that separates blood inside glomerular capillaries from urinary space of Bowman’s capsule Components: Fenestrated endothelial capillaries Thick continuous basement membrane(the principle barrier) Filtration slits covered with diaphragms. Mesangial Cells Small stellate shaped cells present among glomerular capillaries. Functions Structural support Phagocytic function  Juxtaglomerular Apparatus (JGA) Located at the vascular pole of renal corpuscle Parts: 1-Macula Densa 2-Juxtaglomerular cells 3-Lacis cells 1-Macula Densa Part of DCT facing the glomerulus Function: Osmoreceptors (sensitive to concentration of Na+) 2-Juxta-glomerular cells (Rennin-producing cells) ❖Modified smooth muscle cells in media of afferent arteriole ❖Rounded nuclei , with granules in cytoplasm Function: Renin secretion to maintain blood pressure within normal limits. 3-Lacis Cells (Extraglomerular mesangial cells) Small pale cells with pale nuclei  Proximal Convoluted Tubule (PCT) - Lined by simple cuboidal epithelium - Tubule cells have microvilli on their luminal surfaces (typical brush border). Function of PCT: Active reabsorption of glucose & amino acids Reabsorption of Na+, Cl-, K+ & H2O  Distal Convoluted Tubule (DCT) Wide lumen, Lined with cubical cells No brush border Function of DCT: I- Reabsorption of Na+, K+ & water under the effect of aldosterone & ADH 2-Excretion of H2O & NH3 Urinary Passages Calyces Pelvis Ureter Bladder Urethra Layers of urinary passage 1-Mucosa: transitional epithelium (urothelium). 2-Muscular layer: Smooth muscle fibers (Detrusor muscle) 3-Adventitia: loose CT  References Basic histology Functional histology High- yield histology