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THE URINARY SYSTEM. Kristina C. Erasmo , M.D. URINARY SYSTEM. Kidneys (paired) Ureters (paired) Urinary bladder Urethra. Functions of the Urinary System. Production of urine Elimination of metabolic waste products Fluid and electrolyte balance Production of hormones/enzymes Renin
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THE URINARY SYSTEM Kristina C. Erasmo, M.D.
URINARY SYSTEM • Kidneys (paired) • Ureters (paired) • Urinary bladder • Urethra
Functions of the Urinary System • Production of urine • Elimination of metabolic waste products • Fluid and electrolyte balance • Production of hormones/enzymes • Renin • Erythropoietin • Calcitriol
KIDNEYS • Bean-shaped, reddish-brown organ • 10-12 cm • Posterior abdominal wall • T12-L3
KIDNEYS • Hilus • Renal pelvis • Major calyx • Minor calyx
KIDNEYS • Cortex • Medulla • Medullary pyramids • Medullary rays • Renal columns • Renal lobe
Nephron • Functional unit of the kidney • Approx. 1.5 million
Nephron • Functional unit of the kidney • Approx. 1.5 million
Parts of a Nephron • Renal corpuscle • Renal tubule • Proximal convoluted tubule • Thin and thick limbs of Henle’s loop • Distal convoluted tubule • Collecting tubules and ducts
Renal Corpuscle • Located in the cortex (grainy appearance) • 200 um diameter • Consists of a tuft of capillaries (glomerulus) surrounded by a double-walled epithelial capsule called Bowman’s (glomerular) capsule
Renal Corpuscle • Vascular pole • Afferent arteriole enters, efferent arteriole leaves • Urinary pole • Where the renal tubule begins
Glomerulus • Results from the breakup of an afferent arteriole • Drain into a single efferent arteriole • Fenestrated capillaries
Glomerulus • Mesangial cells • Juxtaglomerular cells
Glomerulus • Mesangial cells • Stellate-shaped cells • Found in the CT surrounding the glomerular capillaries • Contractile cells, phagocytes
Glomerulus • Juxtaglomerular cells • Polyhedral cells • Found in tunica media of afferent arteriole before it enters the vascular pole • Contain secretory granules • Responsible for production of renin
Bowman’s Capsule • Visceral layer • Internal, envelops the capillaries of the glomerulus • Parietal layer • External, forms the outer limit of the renal corpuscle
Bowman’s Capsule • Visceral layer • Internal, envelops the capillaries of the glomerulus • Parietal layer • External, forms the outer limit of the renal corpuscle
Bowman’s Capsule • Urinary (Bowman’s) space • Between the two layers of Bowman's capsule • Receives the fluid filtered through the capillary wall and the visceral layer
Bowman’s Capsule • Visceral layer • Made up of podocytes (cell body + primary processes) • Primary processes give rise to secondary processes (pedicels) that embrace the capillaries of the glomerulus • Filtration slits – small spaces between adjacent processes
Bowman’s Capsule • Parietal layer • Simple squamous epithelium • Basal lamina • Thin layer of reticular fibers • Epithelium changes to simple cuboidal or low columnar at level of urinary pole
Filtration Barrier • Between the fenestrated endothelial cells of the glomerular capillaries and the podocytes that cover their external surfaces is a thick basement membrane
Filtration Barrier • Separates the urinary space and the blood in the capillaries • From fusion of basal laminae of capillary and podocyte