Urinary System Histology Lecture Notes PDF

URINARY SYSTEM HISTOLOGY  URINARY SYSTEM  Two kidneys  Two ureters  Urinary bladder  Urethra  Primary role: ensure optimal properties of the blood, which the kidneys continuously monitor  KIDNEYS  large, bean-shaped...

URINARY SYSTEM HISTOLOGY  URINARY SYSTEM  Two kidneys  Two ureters  Urinary bladder  Urethra  Primary role: ensure optimal properties of the blood, which the kidneys continuously monitor  KIDNEYS  large, bean-shaped organs located retroperitoneally  adrenal gland - superior to each kidney  FUNCTIONS: Excretion - elimination of water-soluble metabolic wastes and foreign substances as urine Regulation - maintain an appropriate fluid volume and concentrations of various electrolytes in the body fluids, maintain normal blood pressure, and maintain the pH of blood Endocrine - secretion of hormones Renin , Erythropoietin, Vitamin D  KIDNEYS  HILUM  concave, medial border  contains three structures:  renal artery  renal vein  renal pelvis  major calyces  minor calyces  leaves each kidney through the hilum, narrows to become a muscular ureter  RENAL PARENCHYMA  CORTEX  outer, darker stained region  containsthe renal corpuscle, proximal, and distal convoluted tubules, cortical collecting duct  MEDULLA  inner lighter stained region  consistsmostly of aligned linear tubules and ducts (loops of Henle and medullary collecting duct)  RENAL PYRAMIDS  separated from each other by extensions of the cortex called RENAL COLUMNS OF BERTIN  extends downward to form the domelike RENAL PAPILLA  NEPHRON  structural and functional unit of each kidney  Cortical nephrons -located in the cortex of kidney  Juxtamedullary nephrons-are situated near the junction of the cortex and medulla of the kidney  Two compartments:  RENAL CORPUSCLE  Glomerulus  Bowman’s capsule  RENAL TUBULES  Proximal tubule  Loop of Henle  Distal tubule  RENAL CORPUSCLE  initial segment of each nephron responsible for the filtration of plasma  consists of:  GLOMERULUS  Tuft of capillaries  Mesangial cells – Possess contractile properties  GLOMERULAR (BOWMAN CAPSULE)  Visceral (inner) layer- consists of specialized branching epithelial cells called podocytes  Parietal (outer) layer- simple squamous RENAL CORPUSCLE  has:  Vascular Pole  afferent arteriole enters and efferent arteriole leaves  Urinary Pole  proximal convoluted tubule begins  RENAL TUBULES PROXIMAL CONVOLUTED TUBULE  long convoluted/tortuous part, located entirely in the cortex, with a shorter straight part that enters the medulla  simple cuboidal epithelium  specialized for both reabsorption and secretion  presence of long and closely spaced microvilli (brush border) greatly increases the surface area and facilitates absorption of the filtered material  RENAL TUBULES LOOP OF HENLE  U-shaped structure with a thin descending limb and a thin ascending limb, both composed of simple squamous epithelia.  thin ascending limb of the loop becomes the thick ascending limb (TAL), with simple cuboidal epithelium and many mitochondria  THIN LIMBS: permeable to water; impermeable to most solutes  THICK ASCENDING LIMB: actively transport sodium and chloride ions out of the tubule; impermeable to water  RENAL TUBULES DISTAL CONVOLUTED TUBULE  shorter, less convoluted than the proximal tubules, and less frequently observed in the cortex and near the renal corpuscles  simple cuboidal cells differ from those of the proximal tubules in being smaller and having no brush border and more empty lumens  fewer mitochondria than cells of proximal tubules, making them less acidophilic  actively reabsorb sodium ions  controlled by the hormone aldosterone secreted by the adrenal cortex  RENAL TUBULES DISTAL CONVOLUTED TUBULE  Cells become more columnar as it contacts the vascular pole of the renal corpuscle – MACULA DENSA  Monitors NaCl concentration in tubular fluid  Juxtaglomerular cells are modified smooth muscle cells of afferent arteriole  More rounded nuclei, granular cytoplasm (renin)  Lacis cells = Extraglomerular mesangial cells  Similar fxn to glomerular mesangial cells (supportive, contractile and defensive)  Macula densa + JG cells + Lacis cells = Juxtaglomerular Apparatus (Tubuloglomerular feedback)  RENAL TUBULES COLLECTING TUBULE AND DUCT  not part of the nephron  all DCTs drain into collecting tubule at the cortex, passing down to the medulla, to the calyces and renal pelvis  progressively increase in diameter towards medulla -> cuboidal to columnar cells  Principal cells - pale-staining, water reabsorption and Na and K transport; rich in aquaporins sequestered in cytoplasmic vesicles  Intercalated cells - darker with more abundant mitochondria and microvilli, high carbonic anhydrase activity, with an important role in acid-base balance  URETER MUCOSA  consists of transitional epithelium (urothelium) and a wide lamina propria  transitional epithelium has several cell layers:  outermost layer characterized by large cuboidal cells (UMBRELLA CELLS)  intermediate cells are polyhedral in shape  basalcells are low columnar or cuboidal  NO SUBMUCOSA  MUSCULARIS  Upper two-thirds of ureter  consists of two muscle layers, an inner longitudinal smooth muscle layer and a outer circular smooth muscle layer  Lower third of ureter  additional third outer longitudinal layer of smooth muscle is found near the bladder ADVENTITIA  loose connective tissue with blood vessels, nerves and adipose cells  URINARY BLADDER MUCOSA  EPITHELIUM-exhibits mucosal folds that disappear during bladder distensions, TRANSITIONAL(UROTHELIUM)  RELAXED: 5-7 layers thick; STRETCHED: 2-3 layers thick  Apical layer  singlelayer of umbrella-shaped cells (umbrella cells) that are frequently binucleated; form an impermeable barrier  Intermediate layer - formed from two to three layers of polygonal cells  Basallayer - formed from two to three layers of small cuboidal cells MUCOSA  LAMINA PROPRIA  separating the urothelium and underlying muscularis propria (detrusor muscle) NO SUBMUCOSA MUSCULAR PROPRIA  consists of three poorly delineated layers, collectively called the detrusor muscle  seen most distinctly at the bladder neck: a. inner longitudinal – circular at prostatic urethra & entire urethra of females (involuntary urethral sphincter) b. middle circular layer c. outer longitudinal- continue up to prostate in males & meatus in females  ADVENTITIA/SEROSA THANK YOU! ☺