Anatomy & Physiology Chapter 24 Lecture Outline PDF

Because learning changes everything. ® Chapter 24 Lecture Outline Anatomy & Physiology AN INTEGRATIVE APPROACH Fourth Edition Michael P. McKinley Valerie Dean O’Loughlin Theresa Stouter Bidle Copyrigh...

Because learning changes everything. ® Chapter 24 Lecture Outline Anatomy & Physiology AN INTEGRATIVE APPROACH Fourth Edition Michael P. McKinley Valerie Dean O’Loughlin Theresa Stouter Bidle Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 24.1 Introduction to the Urinary System 1 Components of the urinary system Kidneys, filter blood Remove waste products and convert filtrate into urine Ureters, transport urine From kidneys to urinary bladder Bladder, expandable muscular sac Stores as much as 1 L urine Urethra, eliminates urine from body Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 2  Urinary System: Anterior View (a) ©McGraw -Hill Education/Christine Eckel Figure 24.1a Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 3  Urinary System: Posterior View Figure 24.1b Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 4 24.1 Introduction to the Urinary System 2 Processes that occur as filtrate is converted to urine: Elimination of metabolic wastes Regulation of ion levels For example, Na+, K+, Ca2+ Regulation of acid-base balance Alters levels of H+ and HCO3− Regulation of blood pressure Elimination of biologically active molecules hormones, drugs Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 5 24.1 Introduction to the Urinary System 3 Other functions of kidney Formation of calcitriol Production and release of erythropoietin Secretes erythropoietin (EPO) in response to low blood oxygen Stimulates red bone marrow to increase erythrocyte production Potential to engage in gluconeogenesis During prolonged fasting or starvation Produces glucose from noncarbohydrate sources; maintain glucose levels Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 6 Section 24.1 What did you learn? 1. Which structure of the urinary system forms urine, and which structure stores urine? 2. What are the two means by which the kidney helps to regulate blood pressure? Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 7 24.2 Gross Anatomy of the Kidney Kidneys are two symmetrical, bean-shaped organs Size of hand to second knuckle Concave medial border, hilum Where vessels, nerves, ureter connect to kidney Lateral border convex Adrenal gland rests on superior aspect of kidney Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 8 24.2a Location and Support 1 Kidney location On posterior abdominal wall Lateral to vertebral column Left kidney between level of T12 and L3 vertebrae Right kidney 2 cm inferior to left kidney To accommodate liver Both only partially protected by rib cage Vulnerable to forceful blows to inferior region of back Kidneys positioned posterior to parietal peritoneum Retroperitoneal Only anterior surface covered with parietal peritoneum Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 9 24.2a Location and Support 2 Kidney supported by several tissue layers Fibrous capsule Directly adhered to external surface of kidney Dense irregular CT Maintains kidney’s shape Protects it from trauma Prevents pathogen penetration Perinephric fat Adipose CT external to fibrous capsule Cushions and supports kidney Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 10 24.2a Location and Support 3 Kidney supported by several tissue layers (continued) Renal fascia External to perinephric fat Dense irregular CT Anchors kidney to surrounding structures Paranephric fat Outermost layer surrounding kidney Adipose CT Cushions and supports kidney Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 11  Position and Stabilization of the Kidneys Figure 24.2 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 12 Clinical View: Renal Ptosis and Hydronephrosis Renal ptosis Inferior movement of kidney within abdominal cavity Due to loss of adipose in elderly or individuals with anorexia nervosa May kink ureter, which blocks urine flow to urinary bladder Urine backs up, results in swelling of kidney (hydronephrosis) Can lead to renal failure Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 13 Clinical View: Kidney Variations and Anomalies Renal agenesis Failure of a kidney to develop Often asymptomatic if unilateral; fatal if bilateral Pelvic kidney Developing kidney fails to migrate from pelvic cavity Horseshoe kidney Inferior parts of left and right kidneys fused Supernumerary kidney Extra kidney develops All 3 typically asymptomatic Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 14 24.2b Sectional Anatomy of the Kidney 1 Two regions of functional tissue Outer renal cortex and inner renal medulla Renal columns Extension of cortex projecting into the medulla Renal pyramids Portion of medulla divided by renal columns Wide base at external edge of medulla, meets cortex Corticomedullary junction Medial apex, renal papilla Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 15 24.2b Sectional Anatomy of the Kidney 2 Renal lobe components Renal pyramid and portions of adjacent renal columns Renal cortex external to base Renal sinus Medially located urine drainage area Organized into minor calyces, major calyces, renal pelvis Minor calyces Funnel-shaped structures of renal pyramids Merge to form major calyx Renal pelvis Formed from merged major calyces Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 16  Kidney ©McGraw -Hill Education/Rebecca Gray Figure 24.3 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 17 24.2c Innervation of Kidney Each kidney innervated by both divisions of autonomic nervous system Sympathetic nerves from T10–T12 Blood vessels of kidney and juxtaglomerular apparatus Decreases urine production Parasympathetic nerves from CN X Specific effects not known Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 18 Section 24.2 What did you learn? 3. What tissue composes the fibrous capsule that directly adheres to the kidney, and what are its functions? 4. What are the regions of the kidney that drain urine? 5. What three anatomic structures of the kidney are innervated by the sympathetic division of the autonomic nervous system? Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 19 24.3a Nephron 1 Functional anatomy of the kidney Nephrons, collecting tubules, collecting ducts (and associated structures) Nephron Microscopic functional filtration unit of kidney Consists of: renal corpuscle and renal tubule All of corpuscle and most of tubules reside in cortex Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 20 24.3a Nephron 2 Renal corpuscle Enlarged bulbous region of nephron within renal cortex Composed of two structures: glomerulus and glomerular capsule Glomerulus Tangle of capillary loops, glomerular capillaries Blood enters via afferent arteriole Blood exits via efferent arteriole Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 21 24.3a Nephron 3 Renal corpuscle (continued) Glomerular capsule Internal permeable visceral layer Directly overlies glomerular capillaries External impermeable parietal layer Simple squamous epithelium Capsular space between two layers Receives filtrate, modified to form urine Vascular pole, afferent and efferent arterioles attach to glomerulus Tubular pole, origin of renal tubule Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 22 24.3a Nephron 4 Renal tubule Consists of three continuous sections 1. Proximal convoluted tubule (PCT) 2. Nephron loop 3. Distal convoluted tubule (DCT) 1. Proximal convoluted tubule First region of renal tubule Originates at tubular pole of renal corpuscle Simple cuboidal epithelium Microvilli increase surface area and reabsorption capacity Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 23 24.3a Nephron 5 Renal tubule (continued) 2. Nephron loop Originates at sharp bend in PCT Descending limb Extends medially from PCT Ascending limb Returns to renal cortex and ends at DCT “Hairpin turn” within medulla Thin segments lined with simple squamous epithelium Thick segments lined with simple cuboidal epithelium Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 24 24.3a Nephron 6 Renal tubule (continued) 3. Distal convoluted tubule Originates in renal cortex at end of ascending limb Extends to collecting tubule Lined by simple cuboidal epithelium without microvilli Appears clear when viewed with a light microscope Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 25  Nephron Structure 1 Figure 24.4a Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 26  Nephron Structure 2 Figure 24.4b Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 27 24.3a Nephron 7 Two types of nephrons: cortical & juxtamedullary Classified based on two factors Relative position of renal corpuscle in the cortex Length of nephron loop 1. Cortical nephrons Oriented with renal corpuscles near peripheral cortex Short nephron loop barely penetrates medulla 85% of nephrons Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 28 24.3a Nephron 8 Two types of nephrons (continued) 2. Juxtamedullary nephrons Renal corpuscles adjacent to corticomedullary junction Long nephron loops extend deep into medulla Help establish salt concentration gradient in interstitial space Allows for regulation of urine concentration by ADH Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 29  Two Types of Nephrons Figure 24.5 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 30 24.3b Collecting Tubules and Collecting Ducts Nephrons drain into a collecting tubule Multiple collecting tubules empty into larger collecting ducts Numerous collecting ducts empty into papillary duct located within renal papilla Specialized epithelial cells (in CT, CD) Principal cells Responsive to hormones aldosterone and antidiuretic hormone (ADH) Intercalated cells (types A and B) Both specialized epithelial cells Help regulate urine pH and blood pH Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 31  Histology of Renal Cortex and Medulla (a, b) ©McGraw -Hill Education/Al Telser Figure 24.6 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 32 24.3c Juxtaglomerular Apparatus 1 Juxtaglomerular (JG) apparatus Helps regulate blood filtrate formation, systemic blood pressure JG apparatus components: Granular cells Modified smooth muscle cells of afferent arteriole Located near entrance to renal corpuscle Contract when stimulated by stretch or sympathetic stimulation Synthesize, store, and release renin Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 33 24.3c Juxtaglomerular Apparatus 2 JG apparatus components (continued) Macula densa Modified epithelial cells in wall of DCT Located on tubule side next to afferent arteriole Detect changes in NaCl concentration of fluid in lumen of DCT Signal granular cells to release renin through paracrine stimulation Extraglomerular mesangial cells Just outside glomerulus In gap between afferent arteriole and efferent arteriole Communicate with other cells of JG apparatus Function not well understood Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 34  Juxtaglomerular Apparatus Figure 24.7 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 35 Section 24.3 What did you learn? 6. Diagram and label the components of a nephron similar to the one pictured in figure 24.4b. 7. Describe both the location and anatomic structure of each of the components of a nephron. 8. Compare and contrast cortical and juxtamedullary nephrons? 9. Differentiate between the functions of principal cells and the intercalated cells within the kidney. 10. What are the two primary cellular components of the juxtaglomerular apparatus, how is each stimulated, and what substance is released in response to stimulation? Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 36 24.4a Blood Flow Through the Kidney 1 Arteries Blood delivered to each kidney by renal artery Arises from abdominal aorta Segmental arteries Branch from renal artery within renal sinus Interlobar arteries Branch from segmental arteries Travel through renal columns toward corticomedullary junction Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 37 24.4a Blood Flow Through the Kidney 2 Arteries (continued) Arcuate arteries Branch from interlobar arteries at corticomedullary junction Branch parallel to base of medullary pyramid Interlobular arteries Branch from arcuate arteries Project peripherally into cortex Afferent arterioles branching off Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 38 24.4a Blood Flow Through the Kidney 3 Arterioles and capillaries Afferent arteriole Enters renal corpuscle forming glomerulus Some blood plasma filtered here Efferent arteriole Blood exiting from glomerulus Branches into peritubular capillaries or vasa recta Peritubular capillaries Intertwined around PCT and DCT Primarily reside in cortex of kidney Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 39 24.4a Blood Flow Through the Kidney 4 Arterioles and capillaries (continued) Vasa recta Associated with nephron loop Primarily reside in medulla of kidney All blood moves through two capillary beds Filtered at glomerular capillaries Then passes through peritubular capillaries or vasa recta for gas exchange, nutrients, or waste Finally, drain into network of veins Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 40 24.4a Blood Flow Through the Kidney 5 Veins Interlobular veins Smallest veins, travel alongside interlobular arteries Arcuate veins Form from merged interlobular veins at base of medullary pyramids Interlobar veins Form from merged arcuate veins, extend through renal columns Travel through renal vein Drains into inferior vena cava Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 41  Blood Supply to the Kidneys Figure 24.8 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 42 24.4b Filtrate, Tubular Fluid, and Urine Flow 1 Filtrate Blood flows through glomerulus Both water and solutes filtered from blood plasma Moves across wall of glomerular capillaries and into capsular space Forms filtrate Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 43 24.4b Filtrate, Tubular Fluid, and Urine Flow 2 Tubular fluid New name for filtrate when enters PCT Flows through 1. PCT 2. Nephron loop 3. DCT 4. Enters collecting tubules 5. Empties into collecting ducts 6. Enters papillary duct within renal papilla; now called urine Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 44 24.4b Filtrate, Tubular Fluid, and Urine Flow 3 Urine Enters papillary duct located within renal papilla Flows within renal sinus of kidney Minor calyx → major calyx → renal pelvis Renal pelvis connects to ureter Ureter connects to urinary bladder Stores and excretes from body through urethra Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 45  Structures That Transport Fluids Through the Urinary System Figure 24.9 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 46 Section 24.4 What did you learn? 11. List the pathway that blood follows as it enters via the renal artery and later leaves via the renal vein. 12. What are the three major types of capillaries associated with the nephron? Describe the location and general function of each. 13. List the pathway of fluid filtered by the kidney from the glomerulus to its eventual excretion. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 47 24.5a Overview of Urine Formation 1 Urine formed through three interrelated processes Filtration, reabsorption, and secretion Steps of urine formation: 1. Glomerular filtration In glomerular capillaries Separates some water and dissolved solutes from blood plasma Water and solutes enter capsular space of renal corpuscle Due to pressure differences across filtration membrane Separated fluid is called filtrate Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 48 24.5a Overview of Urine Formation 2 Steps of urine formation (continued) 2. Tubular reabsorption Movement of components within tubular fluid Move by diffusion, osmosis, or active transport Move from lumen of tubules and collecting ducts across walls Return to blood within peritubular capillaries and vasa recta All vital solutes and most water reabsorbed Excess solutes, waste products, some water remaining in tubular fluid Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 49 24.5a Overview of Urine Formation 3 Steps of urine formation (continued) 3. Tubular secretion Movement of solutes, usually by active transport Move out of blood within peritubular and vasa recta capillaries Move into tubular fluid Materials moved selectively into tubules to be excreted Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 50  Overview of the Processes of Urine Formation Figure 24.10 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 51 24.5b Filtration Membrane 1 Filtration membrane characteristics Porous, thin, negatively charged structure Formed by glomerulus and visceral layer of glomerular capsule Layers of filtration membrane (innermost to outermost): 1. Endothelium of glomerulus Fenestrated, allows plasma and dissolved substances to pass Restricts passage of large structures (for example, erythrocytes) 2. Basement membrane of glomerulus Glycoprotein and proteoglycan molecules Restricts passage of large plasma proteins Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 52 24.5b Filtration Membrane 2 Layers of filtration membrane (continued) 3. Visceral layer of glomerular capsule Outermost layer wrapping around glomerular capillaries Composed of specialized cells called podocytes Have long processes, pedicels Support capillary wall but don’t completely enclose it Separated by thin spaces, filtration slits Restrict passage of most small proteins Mesangial cells Specialized cells positioned between glomerular capillary loops Phagocytic, contractile, and signaling properties Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 53  Filtration Membrane Figure 24.11a Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 54  Substances Filtered by Filtration Membrane Figure 24.11b Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 55 24.5c Formation of Filtrate and Its Composition 1 Filtrate 180 L produced daily Filtered plasma with certain solutes and minimal amounts of protein Caught within capsular space and funneled into PCT Materials not filtered remain in blood, exit renal corpuscle through efferent arteriole Some filtered material trapped within basement membrane Phagocytized by mesangial cells Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 56 24.5c Formation of Filtrate and Its Composition 2 Three categories of substances in blood Freely filtered Small substances For example, water, glucose, amino acids, ions Pass easily through filtration membrane Not filtered Formed elements and large proteins Cannot pass through filtration membrane Limited filtration Proteins of intermediate size Usually blocked from filtration Due to size or due to negative charge Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 57 24.5d Pressures Associated with Glomerular Filtration 1 Glomerular hydrostatic (blood) pressure (HPg) Blood pressure in glomerulus “Pushes” water and some solutes out of glomerulus Pushed into capsular space of renal corpuscle Higher than blood pressure of other systemic capillaries Required for filtration to occur Larger diameter of afferent arteriole Smaller diameter of efferent arteriole Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 58 24.5d Pressures Associated with Glomerular Filtration 2 Pressures opposing HPg Blood colloid osmotic pressure (OPg) Osmotic pressure exerted by dissolved solutes For example, plasma proteins Opposes filtration Draws fluid back into glomerulus Capsular hydrostatic pressure (HPc) Pressure in glomerular capsule due to filtrate Impedes movement of additional fluid Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 59 24.5d Pressures Associated with Glomerular Filtration 3 Determining net filtration pressure If pressures promoting filtration are greater than pressures opposing Difference is net filtration pressure (NFP) HPg − (OPg + HPc) = NFP 60 mm Hg − (32 mm Hg + 18 mm Hg) = NFP 60 mm −50 mm Hg = 10 mm Hg Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 60  Pressures That Determine Net Filtration Pressure Figure 24.12 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 61 24.5d Pressures Associated with Glomerular Filtration 4 Variables influenced by net filtration pressure Glomerular filtration rate (GFR) Rate at which the volume of filtrate is formed Volume per unit of time (usually 1 min) Increased net filtration pressure Increases GFR Increases solutes and water remaining in tubular fluid Increases substances in urine Decreases filtrate reabsorption Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 62 24.5e Regulation of Glomerular Filtration Rate 1 Glomerular filtration rate (GFR) is tightly regulated Helps kidney control urine production based on physiologic conditions For example, hydration status GFR influenced by Changing luminal diameter of afferent arteriole Altering surface area of filtration membrane Processes within kidney itself (intrinsic controls) Processes external to kidney (extrinsic controls) Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 63 24.5e Regulation of Glomerular Filtration Rate 2 Renal autoregulation: intrinsic controls Intrinsic ability of kidney to maintain constant blood pressure and GFR Maintains in spite of changes in systemic arterial pressure Functions by two mechanisms 1. Myogenic response 2. Tubuloglomerular feedback mechanism Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 64 24.5e Regulation of Glomerular Filtration Rate 3 Myogenic response: Contraction or relaxation of smooth muscle of afferent arteriole in response to stretch For example, Decreased blood pressure = less stretch of smooth muscle in arteriole Causes smooth muscle cells to relax, vessels to dilate Allows more blood into glomerulus Compensates for lower system pressure GFR remains normal Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 65 24.5e Regulation of Glomerular Filtration Rate 4 Myogenic response (continued) With increased blood pressure, more stretch of smooth muscle in arteriole Causes smooth muscle cells to contract Vessels constrict Allows less blood into glomerulus Compensates for greater systemic pressure GFR remaining normal Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 66  Renal Autoregulation: Myogenic Response Figure 24.13a-c Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 67 24.5e Regulation of Glomerular Filtration Rate 5 Tubuloglomerular feedback mechanism “Backup” to myogenic mechanism response to increased blood pressure If glomerular blood pressure increased Amount of NaCl in tubular fluid also increased Detected by macula densa cells in juxtaglomerular apparatus Results in further vasoconstriction of afferent arteriole Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 68 24.5e Regulation of Glomerular Filtration Rate 6 Limitations to maintaining GFR Renal autoregulation Maintains normal glomerular pressure when BP is within certain range, 80 to 180 mm Hg Decrease in blood pressure below 80 mm Hg Arterioles at maximum dilation Decrease in glomerular blood pressure and GFR If extremely low, cessation of waste elimination in urine Increase in blood pressure above 180 mm Hg Arterioles at maximum constriction Increase in glomerular blood pressure and GFR Urine formation increasing Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 69  Renal Autoregulation Figure 24.13d Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 70 24.5e Regulation of Glomerular Filtration Rate 7 Neural and hormonal control: extrinsic controls Involve physiologic processes to change GFR, in contrast to renal autoregulation which attempts to maintain GFR Decreasing GFR through sympathetic stimulation During exercise or emergency Results in decrease in GFR through Vasoconstriction of afferent and efferent arterioles Granular cells of JG apparatus release renin, which results in angiotensin II production and contraction of mesangial cells Contraction of mesangial cells decreases surface area of glomerulus, decreasing GFR Body therefore conserves water under stressful conditions Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 71 24.5e Regulation of Glomerular Filtration Rate 8 Increasing GFR through atrial natriuretic peptide (ANP) Peptide hormone released from cardiac muscle cells in response to stretch of atria in heart Increases GFR through Relaxation of afferent arteriole Inhibits release of renin, ultimately causing relaxation of mesangial cells Relaxation of mesangial cells increases filtration membrane surface area, increasing GFR Net increase in GFR with increased urine volume decreases blood volume and blood pressure Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 72  Decreasing GFR Through Sympathetic Stimulation Figure 24.14a Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 73  Increasing GFR Through Atrial Natriuretic Peptide Figure 24.14b Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 74 Section 24.5 What did you learn? 1 14. How does tubular reabsorption differ from tubular secretion? 15. How are the components of the filtration membrane of the glomerulus arranged? 16. What is normally filtered across the glomerular membrane? What is not normally filtered? 17. Certain diseases, kidney trauma, heavy metals, and some bacterial toxins can damage the filtration membrane. What effect would this have on relative permeability of the membrane and the substances that are filtered? Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 75 Section 24.5 What did you learn? 2 18. What is the value of the NFP if the glomerular hydrostatic pressure (HPg) is 65 mm Hg, OPg is 30 mm Hg, and HPc is 20 mm Hg? 19. What happens to the value of the NFP in question 18 if the HPg increases from 65 mm Hg to 75 mm Hg? 20. If HPg increases, what is the effect on NFP? Is the relationship between HPg and NFP direct or inverse? Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 76 Section 24.5 What did you learn? 3 21. Does urine production increase, decrease, or stay the same in response to an increase in glomerular filtration rate? 22. What are the three factors that regulate glomerular filtration rate? Does each of these increase, decrease, or maintain GFR? 23. Renal autoregulation is effective with a MAP between 80 and 180 mm Hg. Would renal autoregulation be effective in an individual with a blood pressure of 300/150 mm Hg? A pressure of 70/55 mm Hg? Explain. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 77 24.6a Overview of Transport Processes 1 Overview of structures and conditions that influence reabsorption and secretion Simple epithelium of tubule wall = transport barrier Paracellular transport Movement of substances between epithelial cells Transcellular transport Movement of substances across epithelial cells Must cross luminal membrane in contact with fluid Must cross basolateral membrane on basement membrane Order depends on whether being reabsorbed or secreted Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 78 24.6a Overview of Transport Processes 2 Overview of structures and conditions that influence reabsorption and secretion (continued) Transport proteins embedded within luminal and basolateral membranes Control movement of various substances Peritubular capillaries Low hydrostatic pressure and high oncotic pressure Facilitate reabsorption of substances through bulk flow Most reabsorption in PCT Aided by microvilli increasing surface area Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 79  Convoluted Tubules and Peritubular Capillaries Figure 24.16 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 80 24.6b Transport Maximum and Renal Threshold Transport Maximum (Tm) Maximum rate of substance that can be reabsorbed (or secreted) across tubule epithelium per a certain time Depends on number of transport proteins in membrane If no more than 375 mg/min, glucose in tubule all reabsorbed If greater than 375 mg/min, excess glucose excreted in urine Renal threshold Max plasma concentration of a substance that can be transported in the blood without appearing in the urine If Tm exceeded, substance excreted in urine Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 81 Clinical View: Glucosuria Excretion of glucose in urine Plasma glucose concentration above 300 mg/dL Glucose acts as an osmotic diuretic Pulls water into tubular fluid Causes loss of fluid in urine Classic symptom of diabetes, along with frequent urination and thirst Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 82 24.6c Substances Reabsorbed Completely 1 Nutrient reabsorption Normally reabsorbed completely Each nutrient has own specific transport protein For example, glucose transport Transported into tubule cell by Na+ /glucose symporter proteins Energy from Na+ moving down gradient Used to move glucose up gradient into tubule By secondary active transport Moved by uniporters out of tubule across basolateral membrane Glucose returned to blood in peritubular capillaries 100% reabsorbed in healthy individual Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 83  Glucose Reabsorption Figure 24.17 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 84 24.6c Substances Reabsorbed Completely 2 Reclaiming small amounts of filtered protein Most not freely filtered (due to size and charge) Some small and medium-sized may appear in filtrate Small amounts of large proteins Transported from tubular fluid in PCT back into blood Protein moves across the luminal membrane By pinocytosis By receptor-mediated endocytosis Digested by lysosomes or peptidases Amino acids move by facilitated diffusion back into blood Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 85 Reclaiming Filtered Protein Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 86 24.6d Substances with Regulated Reabsorption 1 Sodium reabsorption 98% to 100% of Na+ reabsorbed from tubular fluid Reabsorbed along the entire nephron tubule; majority in PCT Concentration relatively low inside tubule cell Relatively high within tubule lumen and interstitial fluid Na+ moves down gradient across luminal membrane into tubular cell Na+/K+ pumps embedded in basolateral membrane Keep Na+ relatively low within tubule cells Require substantial energy Reabsorption regulated by hormones near end of tubule Aldosterone and atrial natriuretic peptide Dietary intake of Na+ varies significantly Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 87 24.6d Substances with Regulated Reabsorption 2 Sodium reabsorption (continued) Aldosterone Steroid hormone produced by adrenal cortex Stimulates protein synthesis of Na+ channels and Na+/K+ pumps Embedded in plasma membranes of principal cells Increase in Na+ reabsorption Water follows by osmosis Atrial natriuretic peptide Inhibits reabsorption of Na+ in PCT and collecting tubules Inhibits release of aldosterone More Na+ and water excreted in urine Increases GFR Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 88  Sodium Reabsorption Overview Figure 24.19a Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 89  Sodium Transport in PCT Figure 24.19b Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 90  Sodium Transport in DCT, CT, or CD Figure 24.19c Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 91 24.6d Substances with Regulated Reabsorption 3 Water reabsorption Reabsorbed by Paracellular transport between cells Transcellular transport through water transporter proteins, aquaporins 180 L filtered daily; all but 1.5 L reabsorbed Tubule permeability varies along its length 65% reabsorbed in PCT Aquaporins constant number Water follows Na+ by osmosis, obligatory water reabsorption Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 92 24.6d Substances with Regulated Reabsorption 4 Water reabsorption (continued) Nephron loop 10% of filtered water reabsorbed DCT, collecting tubules, and ducts Water reabsorption controlled by aldosterone and antidiuretic hormone Aldosterone increases Na+/K+ pumps and Na+ channels, increasing both Na+ and water reabsorption Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 93 24.6d Substances with Regulated Reabsorption 5 Water reabsorption (continued) Antidiuretic hormone (ADH) binds to principal cells Increases migration of vesicles containing aquaporins to membrane Adds channels to increase water reabsorption Concentration gradient within interstitial fluid Water reabsorption regulated by ADH near end of tubule Independent of Na+ reabsorption Tubular reabsorption, facultative water reabsorption Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 94 24.6d Substances with Regulated Reabsorption 6 Water reabsorption (continued) Antidiuretic hormone (ADH) Increases water reabsorption from filtrate into blood Results in smaller volume of more concentrated urine Elevated levels during dehydration Urine noticeably darker color With decrease, urine less concentrated Urine range, 1200 mOsm to 50 mOsm Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 95  Water Transport Overview Figure 24.20a Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 96  Water Transport in CT and CD Figure 24.20b Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 97 24.6d Substances with Regulated Reabsorption 7 Reabsorption and secretion of potassium It is both reabsorbed and secreted 60% to 80% reabsorbed in tubular fluid Dependent on movement of Na+ Sodium reabsorbed across luminal membrane, water follows Increased concentration of remaining solutes in tubular fluid Creates gradient between tubular fluid and interstitial fluid K+ moves down gradient from tubular fluid by paracellular route Allows passive reabsorption of other solutes Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 98 24.6d Substances with Regulated Reabsorption 8 Reabsorption and secretion of potassium (continued) 10% to 20% reabsorbed in thick segment of nephron loop Net secretion or reabsorption in collecting tubule Intercalated cells reabsorb K+ continuously Principal cells secrete K+ at varying rates Based on aldosterone level Stimulates principal cells to secrete K+ Most powerful stimulant for aldosterone, elevated K+ level Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 99  Potassium Movement Figure 24.21 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 100 24.6d Substances with Regulated Reabsorption 9 Calcium and phosphate balance 60% in blood goes into filtrate Remainder bound to protein and prevented from filtration 90% to 95% filtered as blood passes through glomerular capillaries Parathyroid hormone (PTH) Regulates excretion of Ca2+ and PO43− Inhibits PO43- reabsorption in PCT Stimulates Ca2+ reabsorption in DCT Less phosphate available to form calcium phosphate Calcium deposition in bone decreased Ca 2+ blood levels increased Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 101  PTH Regulation of Calcium Ion and Phosphate Ion Reabsorption Figure 24.22 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 102 24.6d Substances with Regulated Reabsorption 10 Bicarbonate ions, hydrogen ions, and pH Bicarbonate ions Move freely across filtration membrane If filtered HCO3− not reabsorbed, blood too acidic 80% to 90% reclaimed from tubular fluid Remaining 10% to 20% taken up from thick segment of ascending limb Filtered HCO3 − “replaced” not reabsorbed Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 103 24.6d Substances with Regulated Reabsorption 11 Bicarbonate ions, hydrogen ions, and pH (continued) pH of urine and blood regulated in collecting tubules If acidic blood, then Synthesized HCO3− reabsorbed into blood H+ excreted within filtrate by type A intercalated cells Increase blood pH and decrease urine pH If alkaline blood, then Type B intercalated cells active Secrete HCO3– and reabsorb H+ Lower blood pH and increase urine pH Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 104  Bicarbonate Ion and Hydrogen Ion Movement Figure 24.23a Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 105  Movement of Bicarbonate Along the PCT and Nephron Loop Figure 24.23b Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 106  Movement of Bicarbonate Through Type A Intercalated Cells of CT and CD Figure 24.23c Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 107 24.6e Substances Eliminated as Waste Products 1 Elimination of nitrogenous waste Nitrogenous waste: metabolic waste containing nitrogen Main nitrogenous waste products Urea, molecule produced from protein breakdown Both reabsorbed and secreted 50% excreted in the urine Helps establish concentration gradient in the interstitial fluid Uric acid, produced from nucleic acid breakdown in liver Both reabsorbed and secreted Creatinine, produced from creatinine metabolism in muscle Only secreted Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 108 24.6e Substances Eliminated as Waste Products 2 Elimination of drugs and bioactive substances Most secretion occurring in PCT Certain drugs For example, penicillin, sulfonamides, aspirin Other metabolic wastes For example, urobilin, hormone metabolites Some hormones For example, human chorionic gonadotropin, epinephrine Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 109 24.6f Establishing the Concentration Gradient 1 Concentration gradient Present in interstitial fluid surrounding nephron Established by various solutes For example, Na+ and Cl− Progressively increase in concentration from cortex into medulla Exerts osmotic pull to move water into interstitial fluid When is ADH present Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 110 24.6f Establishing the Concentration Gradient 2 The nephron loop Positive feedback mechanism called the countercurrent multiplier involves nephron loop and helps establish gradient Juxtamedullary nephrons are primarily involved Descending limb permeable to water, impermeable to salts Water moves from tubular fluid to interstitial fluid Salts retained in tubular fluid; becomes concentrated Ascending limb impermeable to water; salts pumped out More concentrated the salts, the more is pumped out (For example beginning of ascending limb) Less concentrated the salts, the less is pumped out (For example end of ascending limb) Get salt gradient in interstitial fluid Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 111 24.6f Establishing the Concentration Gradient 3 Vasa recta Blood in vasa recta Travels in opposite direction to tubular fluid of adjacent nephron loop Countercurrent exchange Helps maintain concentration gradient Water diffuses out of vasa recta capillaries by osmosis Salt in interstitial fluid enters vasa recta by diffusion Increases concentration of salt in vasa recta Vasa recta next runs along descending limb of nephron Gradients reversed, with salt diffusing out and water in Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 112  Interstitial Fluid Concentration Gradient Figure 24.24 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 113 24.6f Establishing the Concentration Gradient 4 Urea recycling Help concentrating process in interstitial fluid Recycled urea ½ of solutes of interstitial fluid gradient Urea removed from tubular fluid in collecting duct by uniporters Diffuses back into tubular fluid in thin segment of ascending limb Remains within tubular fluid until it reaches collecting duct Urea “cycled” between collecting tubule and nephron loop Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 114 24.6f Establishing the Concentration Gradient 5 Summary of reabsorption and secretion After filtration Majority or most other substances reabsorbed or secreted Nephron loop, vasa recta, and urea recycling Responsible for establishing concentration gradient of interstitial fluid Necessary for normal function of ADH Regulation of specific substances Controlled mainly by principal cells and intercalated cells Urine Composed of water, dissolved substances, waste products Drained into renal sinus of kidney Excreted by urinary tract Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 115 Section 24.6 What did you learn? 1 24. What are the significant anatomic and physiologic factors that influence tubular reabsorption and tubular secretion? 25. What is the transport maximum of a substance? How is it different from the renal threshold of the substance? 26. Diagram how glucose is reabsorbed across the two membranes of the tubule cells. 27. Why are proteins said to be transported rather than simply reabsorbed in the proximal convoluted tubule? Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 116 Section 24.6 What did you learn? 2 28. How does Na+ reabsorption occur? Which two hormones are involved? 29. What is the effect of parathyroid hormone on the reabsorption of both PO43− and Ca2+? 30. How is the movement of H+ and HCO3− regulated by type A and type B intercalated cells? 31. What are some examples of drugs and bioactive substances eliminated in the urine? Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 117 Section 24.6 What did you learn? 3 32. How is the concentration gradient that is essential for normal function of ADH in water reabsorption established and maintained? 33. Which substances are reabsorbed in tubular processing in the different regions of the nephron? Which are secreted? What are the general processes that occur in the different regions of the tubules: (a) PCT, (b) nephron loop, and (c) DCT, CT, and CD? Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 118 24.7a Measuring Glomerular Filtration Rate Glomerular filtration rate (GFR) The rate filtrate is formed per unit of time Can be measured with inulin injection Freely filtered polysaccharide, not reabsorbed or secreted Urine collected and measured for volume and concentration Plasma concentration of inulin measured at given time intervals GFR = UV/P U = concentration of inulin in urine V = volume of urine produced per minute P = concentration inulin in plasma Normal GFR 125 mL/min Less than this indicating decrease in kidney function Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 119 24.7b Measuring Renal Plasma Clearance 1 Renal plasma clearance test Another means of assessing kidney function Measures volume of plasma cleared of substance in given time If substance neither reabsorbed nor filtered Clearance equal to GFR If substance reabsorbed Clearance lower than GFR Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 120 24.7b Measuring Renal Plasma Clearance 2 Renal plasma clearance test (continued) If substance filtered and secreted Clearance higher than GFR Drug clearance Affects appropriate dosage level Creatinine clearance Clearance only slightly higher than GFR Can be used to approximate glomerular filtration rate Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 121 Clinical View: Renal Failure, Dialysis, and Kidney Transplant Renal failure Greatly diminished or absent renal functions Often from chronic disease affecting glomerulus or small blood vessels From autoimmune disease, high blood pressure, diabetes Once destroyed will not function again Two main treatments: dialysis or kidney transplantation Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 122 Section 24.7 What did you learn? 34. What is the purpose of measuring the glomerular filtration rate? 35. What information is gained by measuring the renal plasma clearance for a specific substance (for example, medication)? Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 123 24.8a Characteristics of Urine 1 Urine Product of filtered and processed blood plasma Sterile unless contaminated with microbes in kidney or urinary tract Characteristics: composition, volume, pH, specific gravity, color and turbidity, smell Composition 95% water, 5% solutes Salts, nitrogenous wastes, some hormones drugs, ketone bodies See Table 24.4 for abnormal constituents Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 124 24.8a Characteristics of Urine 2 Urine (continued) Volume Average 1 to 2 L per day Variations due to fluid intake, blood pressure, temperature, diuretics, diabetes, other fluid excretion Minimum of 0.5 L to eliminate wastes from body Below 0.40, wastes will accumulate in blood pH Normally between 4.5 and 8.0 More acidic with larger amounts protein or wheat in diet Less acidic with diet high in fruits and vegetables Influenced by metabolism, infection Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 125 24.8a Characteristics of Urine 3 Urine (continued) Specific gravity Density of a substance compared to density of water Specific gravity slightly higher than water due to solutes Color Ranges from almost clear to dark yellow Depends on concentration of urobilin With increased volume of urine, lighter color Smell Urinoid, normal smell of fresh urine May develop ammonia smell if allowed to stand Fruity smell in diabetes Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 126 24.8b Urinary Tract (Ureters, Urinary Bladder, Urethra) 1 Urinary tract: ureters, urinary bladder, urethra Ureters Long epithelial-lined fibromuscular tubes Conduct urine from kidneys to urinary bladder Retroperitoneal Originate from renal pelvis as it exits hilum of kidney Enter posterolateral wall of base of urinary bladder Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 127 24.8b Urinary Tract (Ureters, Urinary Bladder, Urethra) 2 Wall of ureter is composed of three tunics Mucosa Formed by transitional epithelium and external lamina propria Distensible and impermeable to urine Folds to fill lumen when no urine present Muscularis Inner longitudinal and outer circular layer of smooth muscle cells Contract rhythmically with presence of urine Propel urine through ureters into bladder Adventitia External layer of ureter wall Collagen and elastic fibers within areolar CT Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 128 24.8b Urinary Tract (Ureters, Urinary Bladder, Urethra) 3 Ureters project through bladder wall obliquely Compressed as bladder distends Decreases likelihood of urine backflowing while emptying Ureters are innervated by autonomic nervous system Sympathetic axons from T11–L2 Pain referred to these dermatomes in “loin-to-groin” region Parasympathetic axons from vagus and pelvic splanchnic nerves Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 129  Ureters (b) ©McGraw -Hill Education/Alvin Telser Figure 24.26 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 130 Clinical View: Intravenous Pyelogram Intravenous pyelogram: X-ray of kidneys, ureters, urinary bladder Inject radiopaque dye into vein Dye passes through kidneys and into urine Sequential x-rays provide “time lapse” view of urinary flow Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 131 24.8b Urinary Tract (Ureters, Urinary Bladder, Urethra) 4 Urinary bladder Expandable, muscular container Reservoir for urine Positioned immediately posterior to pubic symphysis Anteroinferior to uterus in females Anterior to rectum and superior to prostate gland in males Retroperitoneal Superior surface covered with parietal peritoneum Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 132 24.8b Urinary Tract (Ureters, Urinary Bladder, Urethra) 5 Urinary bladder (continued) Inverted pyramidal shape when empty Oval shape when full Trigone Posteroinferior triangular area of bladder wall Formed by imaginary lines connecting ureter openings and urethra Remains immobile as bladder fills and empties Funnel to direct urine into urethra during contraction Infections common in this area Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 133 24.8b Urinary Tract (Ureters, Urinary Bladder, Urethra) 6 Urinary bladder (continued) Four tunics forming wall of bladder Mucosa, submucosa, muscularis, adventitia Mucosa Innermost layer lining bladder lumen Formed by transitional epithelium Accommodates shape changes with distension Lamina propria supporting mucosa Mucosal folds allowing for greater distension Submucosa Lies immediately external to the mucosa Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 134 24.8b Urinary Tract (Ureters, Urinary Bladder, Urethra) 7 Urinary bladder (continued) Muscularis Three layers of smooth muscle Collectively termed detrusor muscle Involuntary internal urethral sphincter Formed by smooth muscle encircling urethral opening Adventitia Outer layer of areolar CT Forms serosa in superior region Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 135  Urinary Bladder, Anterior View Figure 24.27a Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 136  Histology of the Urinary Bladder (b) ©Garry DeLong/Getty Images Figure 24.27b Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 137 24.8b Urinary Tract (Ureters, Urinary Bladder, Urethra) 8 Urethra Epithelial-lined fibromuscular tube Exits urinary bladder through urethral opening Conducts urine to exterior of body Two sphincters restrict release of urine until bladder pressure is high enough Internal and external urethral sphincters Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 138 24.8b Urinary Tract (Ureters, Urinary Bladder, Urethra) 9 Urethra (continued) Internal urethral sphincter Involuntary, superior sphincter Composed of smooth muscle Surrounds neck of bladder Controlled by autonomic nervous system External urethral sphincter Inferior to internal urethral sphincter Formed by skeletal muscle fibers of pelvic diaphragm Voluntary sphincter controlled by somatic nervous system Learn control of muscle during “toilet training” Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 139 24.8b Urinary Tract (Ureters, Urinary Bladder, Urethra) 10 Urethra (continued) Female urethra Single function: to transport urine from urinary bladder to exterior Lumen lined with transitional epithelium near junction with bladder, then nonkeratinized stratified squamous along most of its length Opens at external urethral orifice in female perineum Male urethra Passageway for urine and semen Three segments: prostatic urethra, membranous urethra, spongy urethra Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 140 24.8b Urinary Tract (Ureters, Urinary Bladder, Urethra) 11 Male urethra (continued) Prostatic urethra Extends through prostate gland inferior to male bladder Most dilatable portion Multiple small prostatic ducts enter Lined by transitional epithelium Two smooth muscle bundles surrounding mucosa Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 141 24.8b Urinary Tract (Ureters, Urinary Bladder, Urethra) 12 Male urethra (continued) Membranous urethra Shortest and least dilatable portion Extends from inferior prostate gland Surrounded by skeletal muscle fibers forming external urethral sphincter Spongy urethra Longest part of male urethra Encased in cylinder of erectile tissue in penis, corpus spongiosum Extends to external urethral orifice Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 142  Female Urethra Figure 24.28a Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 143  Male Urethra Figure 24.28b Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 144 Clinical View: Renal Calculi Also know as kidney stones Formed from crystalline minerals building up in kidney Risk factors Inadequate fluid intake, reduced urinary flow Frequent urinary tract infections Abnormal chemical or mineral levels in urine Small stones asymptomatic Larger stones obstructed in kidney, renal pelvis, ureter Severe pain along “loin-to-groin” region Most pass on their own if less than 4 mm diameter May require lithotripsy or ureteroscopy Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 145 24.8c Micturition 1 Micturition Expulsion of urine from the bladder Associated with two reflexes Storage reflex and micturition reflex Regulated by sympathetic and parasympathetic divisions of the autonomic nervous system, respectively Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 146 24.8c Micturition 2 Innervation of the urinary bladder and urethral sphincters Urinary bladder Has sympathetic, parasympathetic, somatic innervation Sympathetic axons Extend from T11 to L2 Cause contraction of internal urethral sphincter Inhibits contraction of detrusor muscle and micturition Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 147 24.8c Micturition 3 Innervation of the urinary bladder and urethral sphincters (continued) Parasympathetic division From micturition center in pons Extends from S2–S4 in pelvic splanchnic nerves Contraction of detrusor, relaxation of internal urethral sphincter Stimulates micturition Pudendal nerve of somatic nervous system Innervates external urethral sphincter; contracts to prevent urination Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 148 24.8c Micturition 4 Storage reflex Continuous sympathetic stimulation Causes relaxation of detrusor to accommodate urine Stimulates contraction of internal urethral sphincter So urine retained in bladder External urethral sphincter Continuously stimulated by pudendal nerve to remain contracted Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 149  Storage Reflex Figure 24.29a Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 150 24.8c Micturition 5 Micturition reflex 1) Volume of urine in bladder between 200 to 300 mL Bladder distended and baroreceptors activated in bladder wall activated 2) Visceral sensory neurons signaled by baroreceptors Stimulate micturition center in pons 3) Micturition center Alters nerve signals down spinal cord through pelvic splanchnic nerves 4) Parasympathetic stimulation Causes detrusor muscles to contract Causes internal urethral sphincter to relax Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 151  Micturition Reflex Figure 24.29b Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 152 24.8c Micturition 6 Conscious control of urination Initiated from cerebral cortex through pudendal nerve Causes relaxation of external urethral sphincter Facilitated by voluntary contraction of abdominal and expiratory muscles After emptying Detrusor muscle relaxed Neurons of micturition reflex inactivated Neurons of storage reflex activated Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 153 24.8c Micturition 7 Conscious control of urination (continued) If urination not activated at time of first reflex Relaxation of detrusor muscle due to stress-relaxation response Micturition reflex activated again after another 200 to 300 mL added Urination occurs involuntarily between 500 mL and 600 mL Can empty bladder prior to micturition reflex Contract abdominal muscles and compress bladder Initiates micturition reflex by stimulating stretch receptors Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 154 Clinical View: Urinary Tract Infections UTI occurs when bacteria or fungi multiply within urinary tract Women more prone due to short urethra close to anus Often first develops in urethra, urethritis If spreads to bladder, cystitis May spread up into kidneys, pyelonephritis Symptoms Painful urination, dysuria Frequent urination Pressure in pubic region Pyelonephritis causing flank pain, back pain, nausea Diagnosed through urinalysis Treated with antibiotics Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 155 Clinical View: Impaired Urination Incontinence Inability to voluntarily control urination May occur due to childbirth, strong detrusor muscle contractions, secondary result of medications, fear response Retention Failure to eliminate urine normally Side effects from general anesthesia, enlarged prostate May require insertion of catheter to allow urine to flow out Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 156 Section 24.8 What did you learn? 36. What characteristics are used to describe urine? What conditions cause variation in pH of urine? 37. What are the major components of the urinary tract? What tunics are found in each of these? 38. How do the urethras of a male and female differ? 39. What steps lead to micturition? At what point does the micturition reflex overcome conscious control? Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC. 157  Because learning changes everything. ® www.mheducation.com Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution w ithout the prior w ritten consent of McGraw Hill LLC.