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The Urinary System: Part A
25 The Urinary System: Part A
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Regulating total water volume (blood pressure)
Kidney Functions Regulating total water volume (blood pressure) Removal of metabolic wastes, toxins, drugs © 2013 Pearson Education, Inc.
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Kidneys - major excretory organs
Urinary System Organs Kidneys - major excretory organs Ureters - transport urine from kidneys to urinary bladder Urinary bladder - temporary storage reservoir for urine Urethra transports urine out of body © 2013 Pearson Education, Inc.
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Figure 25.1 The urinary system.
Hepatic veins (cut) Esophagus (cut) Inferior vena cava Renal artery Adrenal gland Renal hilum Aorta Renal vein Kidney Iliac crest Ureter Rectum (cut) Uterus (part of female reproductive system) Urinary bladder Urethra © 2013 Pearson Education, Inc.
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Figure 25.2b Position of the kidneys against the posterior body wall.
12th rib © 2013 Pearson Education, Inc.
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Internal Anatomy Renal cortex Renal medulla
Granular-appearing superficial region Renal medulla Composed of cone-shaped medullary (renal) pyramids Pyramids separated by renal columns Inward extensions of cortical tissue © 2013 Pearson Education, Inc.
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Internal Anatomy Papilla Lobe Renal pelvis
Tip of pyramid; releases urine into minor calyx Lobe Medullary pyramid and its surrounding cortical tissue; ~ 8/kidney Renal pelvis Funnel-shaped tube continuous with ureter © 2013 Pearson Education, Inc.
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Figure 25.2a Position of the kidneys against the posterior body wall.
Anterior Inferior vena cava Aorta Peritoneum Peritoneal cavity (organs removed) Supportive tissue layers Renal vein • Renal fascia anterior posterior Renal artery • Perirenal fat capsule • Fibrous capsule Body of vertebra L2 Body wall Posterior © 2013 Pearson Education, Inc.
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Figure 25.3 Internal anatomy of the kidney.
Renal hilum Renal cortex Renal medulla Major calyx Papilla of pyramid Renal pelvis Minor calyx Ureter Renal pyramid in renal medulla Renal column Fibrous capsule Photograph of right kidney, frontal section Diagrammatic view © 2013 Pearson Education, Inc.
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Structural and functional units that form urine
Nephrons Structural and functional units that form urine > 1 million per kidney © 2013 Pearson Education, Inc.
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Two parts of renal corpuscle
Glomerulus Tuft of capillaries; allows filtrate formation Glomerular capsule (Bowman's capsule) Cup-shaped, hollow structure surrounding glomerulus © 2013 Pearson Education, Inc.
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Figure 25.5 Location and structure of nephrons.
Renal cortex Renal medulla Renal pelvis Glomerular capsule: parietal layer Basement membrane Ureter Podocyte Kidney Fenestrated endothelium of the glomerulus Renal corpuscle • Glomerular capsule Glomerular capsule: visceral layer • Glomerulus Distal convoluted tubule Apical microvilli Mitochondria Highly infolded basolateral membrane Proximal convoluted tubule Proximal convoluted tubule cells Cortex Apical side Medulla Basolateral side Thick segment Thin segment Distal convoluted tubule cells Nephron loop • Descending limb • Ascending limb Nephron loop (thin-segment) cells Collecting duct Principal cell Intercalated cell Collecting duct cells © 2013 Pearson Education, Inc.
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Renal Tubule Three parts Proximal convoluted tubule Nephron loop
Proximal closest to renal corpuscle Nephron loop Distal convoluted tubule Distal farthest from renal corpuscle © 2013 Pearson Education, Inc.
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Proximal convoluted tubule (PCT)
Renal Tubule Proximal convoluted tubule (PCT) Functions in reabsorption and secretion © 2013 Pearson Education, Inc.
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Distal convoluted tubule (DCT)
Renal Tubule Distal convoluted tubule (DCT) Cuboidal cells with very few microvilli Function more in secretion than reabsorption Confined to cortex © 2013 Pearson Education, Inc.
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Receive filtrate from many nephrons
Collecting Ducts Receive filtrate from many nephrons Run through medullary pyramids striped appearance Fuse together to deliver urine through papillae into minor calyces © 2013 Pearson Education, Inc.
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Figure 25.5 Location and structure of nephrons.
Renal cortex Renal medulla Renal pelvis Glomerular capsule: parietal layer Basement membrane Ureter Podocyte Kidney Fenestrated endothelium of the glomerulus Renal corpuscle • Glomerular capsule Glomerular capsule: visceral layer • Glomerulus Distal convoluted tubule Apical microvilli Mitochondria Highly infolded basolateral membrane Proximal convoluted tubule Proximal convoluted tubule cells Cortex Apical side Medulla Basolateral side Thick segment Thin segment Distal convoluted tubule cells Nephron loop • Descending limb • Ascending limb Nephron loop (thin-segment) cells Collecting duct Principal cell Intercalated cell Collecting duct cells © 2013 Pearson Education, Inc.
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Figure 25.7a Blood vessels of cortical and juxtamedullary nephrons.
Cortical nephron Juxtamedullary nephron • Short nephron loop • Glomerulus further from the cortex-medulla junction • Efferent arteriole supplies peritubular capillaries • Long nephron loop • Glomerulus closer to the cortex-medulla junction • Efferent arteriole supplies vasa recta Renal corpuscle Glomerulus (capillaries) Efferent arteriole Cortical radiate vein Cortical radiate artery Glomerular capsule Afferent arteriole Collecting duct Proximal convoluted tubule Distal convoluted tubule Afferent arteriole Efferent arteriole Peritubular capillaries Ascending limb of nephron loop Cortex-medulla junction Arcuate vein Kidney Arcuate artery Vasa recta Nephron loop Descending limb of nephron loop © 2013 Pearson Education, Inc.
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Figure 25.8 Juxtaglomerular complex (JGC) of a nephron.
capsule Glomerulus Foot processes of podocytes Efferent arteriole Parietal layer of glomerular capsule Podocyte cell body (visceral layer) Capsular space Afferent arteriole Red blood cell Efferent arteriole Proximal tubule cell Juxtaglomerular complex • Macula densa cells of the ascending limb of nephron loop Lumens of glomerular capillaries • Extraglomerular mesangial cells • Granular cells Endothelial cell of glomerular capillary Afferent arteriole Glomerular mesangial cells Juxtaglomerular complex Renal corpuscle © 2013 Pearson Education, Inc.
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Kidney Physiology: Mechanisms of Urine Formation
Three processes in urine formation and adjustment of blood composition Glomerular filtration Tubular reabsorption Tubular secretion © 2013 Pearson Education, Inc.
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Kidney Physiology: Mechanisms of Urine Formation
Glomerular filtration – produces cell- and protein-free filtrate Tubular reabsorption Selectively returns 99% of substances from filtrate to blood in renal tubules and collecting ducts Tubular secretion Selectively moves substances from blood to filtrate in renal tubules and collecting ducts © 2013 Pearson Education, Inc.
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Kidney Physiology: Mechanisms of Urine Formation
Kidneys filter body's entire plasma volume 60 times each day; consume 20-25% oxygen used by body at rest; produce urine from filtrate Filtrate (produced by glomerular filtration) Blood plasma minus proteins Urine <1% of original filtrate Contains metabolic wastes and unneeded substances © 2013 Pearson Education, Inc.
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To cortical radiate vein Glomerular filtration
Figure A schematic, uncoiled nephron showing the three major renal processes that adjust plasma composition. Afferent arteriole Glomerular capillaries Efferent arteriole Cortical radiate artery Glomerular capsule 1 Renal tubule and collecting duct containing filtrate Peritubular capillary 2 3 To cortical radiate vein Three major renal processes: Urine 1 Glomerular filtration 2 Tubular reabsorption 3 Tubular secretion © 2013 Pearson Education, Inc.
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Glomerular Filtration
Passive process No metabolic energy required Hydrostatic pressure forces fluids and solutes through filtration membrane No reabsorption into capillaries of glomerulus © 2013 Pearson Education, Inc.
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Figure 25.11 Forces determining net filtration pressure (NFP).
Glomerular capsule Efferent arteriole HPgc = 55 mm Hg OPgc = 30 mm Hg Afferent arteriole HPcs = 15 mm Hg NFP = Net filtration pressure = outward pressures – inward pressures = (HPgc) – (HPcs + OPgc) = (55) – ( ) = 10 mm Hg © 2013 Pearson Education, Inc.
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