Power Point Lecture Slides prepared by Vince Austin
Power. Point® Lecture Slides prepared by Vince Austin, University of Kentucky The Urinary System Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings 25
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
Functions 1. maintains osmotic balance (salts & water) 2. eliminates nitrogenous wastes (e. g. urea) 3. regulates composition and volume of blood 4. help regulate blood pressure (hormone - renin) Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Other Renal Functions § Production of rennin to help regulate blood pressure and erythropoietin to stimulate RBC production § Activation of vitamin D Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Urinary System Organs § Kidney - filters the blood and forms urine § 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. 1 a 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 § Ureters, renal blood vessels, lymphatics, and nerves enter and exit at the hilus Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Layers of Tissue Supporting the Kidney § Renal capsule – inner fibrous capsule that prevents kidney infection § Adipose capsule – fatty mass between renal capsule and renal fascia 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. 2 a
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 urinecollecting tubules § Renal columns are inward extensions of cortical tissue that separate the pyramids § The medullary pyramid and its surrounding capsule constitute a lobe § 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. 3 b 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. 3 c
The Nephron § Nephron - 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 § 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. 4 b 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 1. Proximal convoluted tubule (PCT) – composed of cuboidal cells with numerous microvilli and mitochondria § Reabsorbs water and solutes from filtrate and secretes substances into it 2. 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) Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Renal Tubule 3. Distal convoluted tubule (DCT) – cuboidal cells without microvilli that function more in secretion than reabsorption 4. Collecting ducts - Receive filtrate from the distal convoluted tubules and deliver it to the minor calyces Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Renal Tubule Figure 25. 4 b Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Nephrons Two distinct types of nephrons based on location: 1. Cortical nephrons – 85% of nephrons; located in the cortex of the kidney 2. 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. 5 b
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 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 25. 5 a
Filtration Membrane § Filter that lies between the blood and the interior of the glomerular capsule It is composed of three layers: § Fenestrated endothelium of the glomerular capillaries § Visceral membrane of the glomerular capsule (podocytes) § Basement membrane composed of fused basal laminae of the other layers Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Filtration Membrane Figure 25. 7 a Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
Filtration Membrane Figure 25. 7 c 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 - Ureters enter the base of the bladder through the posterior wall § This closes their distal ends as bladder pressure increases and prevents backflow of urine into the ureters Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
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 § It lies retroperitoneally on the pelvic floor posterior to the pubic symphysis § 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. 18 a, 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 1. 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 2. 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. 18 a. b Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings
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