The Urinary System PDF

PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky The Urinary System Part A 25 Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb Copyright © 2004 Pear...

PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky The Urinary System Part A 25 Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Kidney Functions ▪ Filter 200 liters of blood daily, allowing toxins, metabolic wastes, and excess ions to leave the body in urine ▪ Regulate volume and chemical makeup of the blood ▪ Maintain the proper balance between water and salts, and acids and bases Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Other Urinary System Organs ▪ Urinary bladder – provides a temporary storage reservoir for urine ▪ Paired ureters – transport urine from the kidneys to the bladder ▪ Urethra – transports urine from the bladder out of the body Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Urinary System Organs Figure 25.1a Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Kidney Location and External Anatomy ▪ The bean-shaped kidneys lie in a retroperitoneal position in the superior lumbar region and extend from the twelfth thoracic to the third lumbar vertebrae ▪ The right kidney is lower than the left because it is crowded by the liver ▪ The lateral surface is convex and the medial surface is concave, with a vertical cleft called the renal hilus leading to the renal sinus Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Layers of Tissue Supporting the Kidney ▪ Renal capsule – fibrous capsule that prevents kidney infection ▪ Adipose capsule – fatty mass that cushions the kidney and helps attach it to the body wall ▪ Renal fascia – outer layer of dense fibrous connective tissue that anchors the kidney Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Kidney Location and External Anatomy Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 25.2a  Internal Anatomy ▪ A frontal section shows three distinct regions ▪ Cortex – the light colored, granular superficial region ▪ Medulla – exhibits cone-shaped medullary (renal) pyramids ▪ Pyramids are made up of parallel bundles of urine-collecting tubules ▪ Renal columns are inward extensions of cortical tissue that separate the pyramids ▪ The medullary pyramid and its surrounding capsule constitute a lobe Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Internal Anatomy ▪ Renal pelvis – flat, funnel-shaped tube lateral to the hilus within the renal sinus Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Internal Anatomy ▪ Major calyces – large branches of the renal pelvis ▪ Collect urine draining from papillae ▪ Empty urine into the pelvis ▪ Urine flows through the pelvis and ureters to the bladder Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Internal Anatomy Figure 25.3b Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Blood and Nerve Supply ▪ Approximately one-fourth (1200 ml) of systemic cardiac output flows through the kidneys each minute ▪ Arterial flow into and venous flow out of the kidneys follow similar paths ▪ The nerve supply is via the renal plexus Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 25.3c  The Nephron ▪ Nephrons are the structural and functional units that form urine, consisting of: ▪ Glomerulus – a tuft of capillaries associated with a renal tubule ▪ Glomerular (Bowman’s) capsule – blind, cup-shaped end of a renal tubule that completely surrounds the glomerulus Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The Nephron ▪ Renal corpuscle – the glomerulus and its Bowman’s capsule ▪ Glomerular endothelium – fenestrated epithelium that allows solute-rich, virtually protein-free filtrate to pass from the blood into the glomerular capsule Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The Nephron Figure 25.4b Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Anatomy of the Glomerular Capsule ▪ The external parietal layer is a structural layer ▪ The visceral layer consists of modified, branching epithelial podocytes ▪ Extensions of the octopus-like podocytes terminate in foot processes ▪ Filtration slits – openings between the foot processes that allow filtrate to pass into the capsular space Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Renal Tubule ▪ Proximal convoluted tubule (PCT) – composed of cuboidal cells with numerous microvilli and mitochondria ▪ Reabsorbs water and solutes from filtrate and secretes substances into it Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Renal Tubule ▪ Loop of Henle – a hairpin-shaped loop of the renal tubule ▪ Proximal part is similar to the proximal convoluted tubule ▪ Proximal part is followed by the thin segment (simple squamous cells) and the thick segment (cuboidal to columnar cells) ▪ Distal convoluted tubule (DCT) – cuboidal cells without microvilli that function more in secretion than reabsorption Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Renal Tubule Figure 25.4b Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Connecting Tubules ▪ The distal portion of the distal convoluted tubule (DCT) nearer to the collecting ducts Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Nephrons ▪ Cortical nephrons – 85% of nephrons; located in the cortex ▪ Juxtamedullary nephrons: ▪ Are located at the cortex-medulla junction ▪ Have loops of Henle that deeply invade the medulla ▪ Have extensive thin segments ▪ Are involved in the production of concentrated urine Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Nephrons Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 25.5b  Capillary Beds of the Nephron ▪ Every nephron has two capillary beds ▪ Glomerulus ▪ Peritubular capillaries ▪ Each glomerulus is: ▪ Fed by an afferent arteriole ▪ Drained by an efferent arteriole Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Capillary Beds of the Nephron ▪ Blood pressure in the glomerulus is high because: ▪ Arterioles are high-resistance vessels ▪ Afferent arterioles have larger diameters than efferent arterioles ▪ Fluids and solutes are forced out of the blood throughout the entire length of the glomerulus Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Capillary Beds ▪ Peritubular beds are low-pressure, porous capillaries adapted for absorption that: ▪ Arise from efferent arterioles ▪ Empty into the renal venous system ▪ Vasa recta – long, straight efferent arterioles of juxtamedullary nephrons Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Capillary Beds Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 25.5a  Filtration Membrane Figure 25.7a Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Filtration Membrane Figure 25.7c Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Mechanisms of Urine Formation ▪ Urine formation and adjustment of blood composition involves three major processes ▪ Glomerular filtration ▪ Tubular reabsorption ▪ Secretion Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 25.8  Ureters ▪ Slender tubes that convey urine from the kidneys to the bladder Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Ureters ▪ Ureters have a trilayered wall ▪ Transitional epithelial mucosa ▪ Smooth muscle muscularis ▪ Fibrous connective tissue adventitia ▪ Ureters actively propel urine to the bladder via response to smooth muscle stretch Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Urinary Bladder ▪ Smooth, collapsible, muscular sac that temporarily stores urine ▪ Trigone – triangular area outlined by the openings for the ureters and the urethra ▪ Clinically important because infections tend to persist in this region Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Urinary Bladder ▪ The bladder wall has three layers ▪ Transitional epithelial mucosa ▪ A thick muscular layer ▪ A fibrous adventitia ▪ The bladder is distensible and collapses when empty Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Urinary Bladder Figure 25.18a, b Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Urethra ▪ Muscular tube that: ▪ Drains urine from the bladder ▪ Conveys it out of the body Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Urethra ▪ Sphincters keep the urethra closed when urine is not being passed ▪ Internal urethral sphincter – involuntary sphincter at the bladder-urethra junction ▪ External urethral sphincter – voluntary sphincter surrounding the urethra as it passes through the urogenital diaphragm Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Urethra ▪ The female urethra is tightly bound to the anterior vaginal wall ▪ Its external opening lies anterior to the vaginal opening and posterior to the clitoris ▪ The male urethra has three named regions ▪ Prostatic urethra – runs within the prostate gland ▪ Membranous urethra – runs through the urogenital diaphragm ▪ Spongy (penile) urethra – passes through the penis and opens via the external urethral orifice Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Urethra Figure 25.18a. b Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings