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The Urinary System: Part A
25 The Urinary System: Part A
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Regulating total water volume and total solute concentration in water
Kidney Functions Regulating total water volume and total solute concentration in water Ensuring long-term acid-base balance Removal of metabolic wastes, toxins, drugs © 2013 Pearson Education, Inc.
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Activation of vitamin D
Kidney Functions Endocrine functions Renin - regulation of blood pressure Erythropoietin - regulation of RBC production Activation of vitamin D © 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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Location: in the superior lumbar region; ~ T12 to L5
Kidney Anatomy Location: in the superior lumbar region; ~ T12 to L5 Right kidney crowded by liver lower than left Adrenal (suprarenal) gland atop each kidney Convex lateral surface, concave medial surface; vertical renal hilum leads to renal sinus Ureters, renal blood vessels, lymphatics, and nerves enter and exit at hilum © 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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Layers of surrounding supportive tissue
Kidney Anatomy Layers of surrounding supportive tissue Renal fascia Anchoring outer layer of dense fibrous connective tissue Perirenal fat capsule Fatty cushion Fibrous capsule Prevents spread of infection to kidney © 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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Internal Anatomy Minor calyces Major calyces Urine flow
Drain pyramids at papillae Major calyces Collect urine from minor calyces Empty urine into renal pelvis Urine flow Renal pyramid minor calyx major calyx renal pelvis ureter © 2013 Pearson Education, Inc.
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Homeostatic Imbalance
Pyelitis Infection of renal pelvis and calyces Pyelonephritis Infection/inflammation of entire kidney Normally - successfully treated with antibiotics © 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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Kidneys cleanse blood; adjust its composition rich blood supply
Blood and Nerve Supply Kidneys cleanse blood; adjust its composition rich blood supply Renal arteries deliver ~ ¼ (1200 ml) of cardiac output to kidneys each minute Arterial flow into and venous flow out of kidneys follow similar paths Nerve supply via sympathetic fibers from renal plexus © 2013 Pearson Education, Inc.
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Figure 25.4a Blood vessels of the kidney.
Cortical radiate vein Cortical radiate artery Arcuate vein Arcuate artery Interlobar vein Interlobar artery Segmental arteries Renal vein Renal artery Renal pelvis Ureter Renal medulla Renal cortex Frontal section illustrating major blood vessels © 2013 Pearson Education, Inc.
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Figure 25.4b Blood vessels of the kidney.
Aorta Inferior vena cava Renal artery Renal vein Segmental artery Interlobar vein Interlobar artery Arcuate vein Arcuate artery Cortical radiate vein Peritubular capillaries or vasa recta Cortical radiate artery Afferent arteriole Efferent arteriole Glomerulus (capillaries) Nephron-associated blood vessels (see Figure 25.7) (b) Path of blood flow through renal blood vessels © 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 Two main parts Renal corpuscle Renal tubule © 2013 Pearson Education, Inc.
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Two parts of renal corpuscle
Glomerulus Tuft of capillaries; fenestrated endothelium highly porous 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 Glomerular capsule
Parietal layer - simple squamous epithelium Visceral layer - branching epithelial podocytes Extensions terminate in foot processes that cling to basement membrane Filtration slits between foot processes allow filtrate to pass into capsular space © 2013 Pearson Education, Inc.
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Figure 25.5 Location and structure of nephrons. (2 of 7)
Glomerular capsule: parietal layer © 2013 Pearson Education, Inc.
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Figure 25.5 Location and structure of nephrons. (3 of 7)
Basement membrane Podocyte Fenestrated endothelium of the glomerulus Glomerular capsule: visceral layer © 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) Cuboidal cells with dense microvilli (brush border surface area); large mitochondria Functions in reabsorption and secretion Confined to cortex © 2013 Pearson Education, Inc.
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Figure 25.5 Location and structure of nephrons. (4 of 7)
Apical microvilli Mitochondria Highly infolded basolateral membrane Proximal convoluted tubule cells © 2013 Pearson Education, Inc.
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Renal Tubule Nephron loop Descending and ascending limbs
Proximal descending limb continuous with proximal tubule Distal descending limb = descending thin limb; simple squamous epithelium Thick ascending limb Cuboidal to columnar cells; thin in some nephrons © 2013 Pearson Education, Inc.
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Figure 25.5 Location and structure of nephrons. (6 of 7)
Nephron loop (thin-segment) cells © 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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Figure 25.5 Location and structure of nephrons. (5 of 7)
Apical side Basolateral side Distal convoluted tubule cells © 2013 Pearson Education, Inc.
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Collecting Ducts Two cell types Principal cells Intercalated cells
Sparse, short microvilli Maintain water and Na+ balance Intercalated cells Cuboidal cells; abundant microvilli; two types A and B; both help maintain acid-base balance of blood © 2013 Pearson Education, Inc.
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Figure 25.5 Location and structure of nephrons. (7 of 7)
Principal cell Intercalated cell Collecting duct cells © 2013 Pearson Education, Inc.
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Receive filtrate from many nephrons
Collecting Duct 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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Nephron Capillary Beds
Glomerulus - specialized for filtration Different from other capillary beds – fed and drained by arteriole Afferent arteriole glomerulus efferent arteriole Blood pressure in glomerulus high because Afferent arterioles larger in diameter than efferent arterioles Arterioles are high-resistance vessels © 2013 Pearson Education, Inc.
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Kidney Physiology: Mechanisms of Urine Formation
180 L fluid processed daily; only 1.5 L urine 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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The Filtration Membrane
Porous membrane between blood and interior of glomerular capsule Water, solutes smaller than plasma proteins pass; normally no cells pass Three layers Fenestrated endothelium of glomerular capillaries Basement membrane (fused basal laminae of two other layers) Foot processes of podocytes with filtration slits; slit diaphragms repel macromolecules © 2013 Pearson Education, Inc.
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Figure 25.10a The filtration membrane.
Glomerular capsular space Efferent arteriole Cytoplasmic extensions of podocytes Filtration slits Podocyte cell body Afferent arteriole Proximal convoluted tubule Glomerular capillary covered by podocytes that form the visceral layer of glomerular capsule Parietal layer of glomerular capsule Fenestrations (pores) Glomerular capillaries and the visceral layer of the glomerular capsule Glomerular capillary endothelium (podocyte covering and basement membrane removed) Foot processes of podocyte © 2013 Pearson Education, Inc.
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Figure 25.10b The filtration membrane.
Filtration slits Podocyte cell body Foot processes Filtration slits between the podocyte foot processes © 2013 Pearson Education, Inc.
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Figure 25.10c The filtration membrane.
• Capillary endothelium Capillary • Basement membrane • Foot processes of podocyte of glomerular capsule Filtration slit Slit diaphragm Plasma Filtrate in capsular space Foot processes of podocyte Fenestration (pore) Three layers of the filtration membrane © 2013 Pearson Education, Inc.
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The Filtration Membrane
Macromolecules "stuck" in filtration membrane engulfed by glomerular mesangial cells Allows molecules smaller than 3 nm to pass Water, glucose, amino acids, nitrogenous wastes Plasma proteins remain in blood maintains colloid osmotic pressure prevents loss of all water to capsular space Proteins in filtrate indicate membrane problem © 2013 Pearson Education, Inc.
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