Presentation is loading. Please wait.

Presentation is loading. Please wait.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology SEVENTH EDITION Elaine N. Marieb Katja Hoehn PowerPoint.

Similar presentations


Presentation on theme: "Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology SEVENTH EDITION Elaine N. Marieb Katja Hoehn PowerPoint."— Presentation transcript:

1 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology SEVENTH EDITION Elaine N. Marieb Katja Hoehn PowerPoint ® Lecture Slides prepared by Vince Austin, Bluegrass Technical and Community College C H A P T E R 25 The Urinary System P A R T A

2 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Kidney Functions-water and salt balance Next six slides are for renal physiology lab.

3 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Kidney Functions  Filter 200 liters of blood daily, allowing toxins, metabolic wastes, and excess ions to leave the body in urine  Regulate volume and chemical makeup of the blood  Maintain the proper balance between water and salts, and acids and bases

4 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Na + Reabsorption  90% filtered Na + reabsorbed in PCT.  In the absence of aldosterone, 80% of the remaining Na + is reabsorbed in DCT.  Final [Na + ] controlled in CD by aldosterone.  When aldosterone is secreted in maximal amounts, all Na + in DCT is reabsorbed. Insert fig

5 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Physical Characteristics of Urine  Color and transparency  Clear, pale to deep yellow (due to urochrome)  Concentrated urine has a deeper yellow color  Drugs, vitamin supplements, and diet can change the color of urine  Cloudy urine may indicate infection of the urinary tract

6 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Physical Characteristics of Urine  Odor  Fresh urine is slightly aromatic  Standing urine develops an ammonia odor  Some drugs and vegetables (asparagus) alter the usual odor

7 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Physical Characteristics of Urine  pH  Slightly acidic (pH 6) with a range of 4.5 to 8.0  Diet can alter pH  Specific gravity  Ranges from to  Is dependent on solute concentration

8 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Composition of Urine  Urine is 95% water and 5% solutes  Nitrogenous wastes: urea, uric acid, and creatinine  Other normal solutes include:  Sodium, potassium, phosphate, and sulfate ions  Calcium, magnesium, and bicarbonate ions  Abnormally high concentrations of any urinary constituents may indicate pathology

9 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Kidney Functions  Filter 200 liters of blood daily, allowing toxins, metabolic wastes, and excess ions to leave the body in urine  Regulate volume and chemical makeup of the blood  Maintain the proper balance between water and salts, and acids and bases

10 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Other Renal Functions  Gluconeogenesis during prolonged fasting  Production of rennin to help regulate blood pressure and erythropoietin to stimulate RBC production  Activation of vitamin D

11 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Urinary System Organs Figure 25.1a

12 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Internal Anatomy Figure 25.3b

13 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Blood and Nerve Supply  Approximately one-fourth (1200 ml) of systemic cardiac output flows through the kidneys each minute  Arterial flow into and venous flow out of the kidneys follow similar paths  The nerve supply is via the renal plexus PLAY InterActive Physiology ®: Anatomy Review, page 5

14 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Nephron Anatomy Figure 25.5a

15 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Renal Tubule Figure 25.4b

16 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Nephrons  Cortical nephrons – 85% of nephrons; located in the cortex  Juxtamedullary nephrons:  Are located at the cortex-medulla junction  Have loops of Henle that deeply invade the medulla  Have extensive thin segments  Are involved in the production of concentrated urine

17 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Vascular Resistance in Microcirculation  Afferent and efferent arterioles offer high resistance to blood flow  Blood pressure declines from 95mm Hg in renal arteries to 8 mm Hg in renal veins

18 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Vascular Resistance in Microcirculation  Resistance in afferent arterioles:  Protects glomeruli from fluctuations in systemic blood pressure  Resistance in efferent arterioles:  Reinforces high glomerular pressure  Reduces hydrostatic pressure in peritubular capillaries

19 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Juxtaglomerular Apparatus (JGA) Figure 25.6

20 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Juxtaglomerular Apparatus (JGA)  Where the distal tubule lies against the afferent (sometimes efferent) arteriole  Arteriole walls have juxtaglomerular (JG) cells  Enlarged, smooth muscle cells  Have secretory granules containing renin  Act as mechanoreceptors

21 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Juxtaglomerular Apparatus (JGA)  Macula densa  Tall, closely packed distal tubule cells  Lie adjacent to JG cells  Function as chemoreceptors or osmoreceptors  Mesanglial cells:  Have phagocytic and contractile properties  Influence capillary filtration PLAY InterActive Physiology ®: Anatomy Review: page 16

22 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Filtration Membrane  Filter that lies between the blood and the interior of the glomerular capsule  It is composed of three layers  Fenestrated endothelium of the glomerular capillaries  Visceral membrane of the glomerular capsule (podocytes)  Basement membrane composed of fused basal laminae of the other layers

23 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Filtration Membrane Figure 25.7a

24 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Filtration Membrane PLAY InterActive Physiology ®: Anatomy Review, page 11 Figure 25.7c

25 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mechanisms of Urine Formation  The kidneys filter the body’s entire plasma volume 60 times each day  The filtrate:  Contains all plasma components except protein  Loses water, nutrients, and essential ions to become urine  The urine contains metabolic wastes and unneeded substances

26 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mechanisms of Urine Formation  Urine formation and adjustment of blood composition involves three major processes  Glomerular filtration  Tubular reabsorption  Secretion Figure 25.8

27 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Glomerular Filtration  Principles of fluid dynamics that account for tissue fluid in all capillary beds apply to the glomerulus as well  The glomerulus is more efficient than other capillary beds because:  Its filtration membrane is more permeable  Glomerular blood pressure is higher  It has a higher net filtration pressure  Plasma proteins are not filtered and are used to maintain oncotic pressure of the blood

28 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Net Filtration Pressure (NFP)  The pressure responsible for filtrate formation  NFP equals the glomerular hydrostatic pressure (HP g ) minus the oncotic pressure of glomerular blood (OP g ) combined with the capsular hydrostatic pressure (HP c ) NFP = HP g – (OP g + HP c )

29 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Glomerular Filtration Rate (GFR)  The total amount of filtrate formed per minute by the kidneys  Factors governing filtration rate at the capillary bed are:  Total surface area available for filtration  Filtration membrane permeability  Net filtration pressure

30 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Glomerular Filtration Rate (GFR)  GFR is directly proportional to the NFP  Changes in GFR normally result from changes in glomerular blood pressure

31 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Glomerular Filtration Rate (GFR) Figure 25.9

32 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Regulation of Glomerular Filtration  If the GFR is too high:  Needed substances cannot be reabsorbed quickly enough and are lost in the urine  If the GFR is too low:  Everything is reabsorbed, including wastes that are normally disposed of

33 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Regulation of Glomerular Filtration  Three mechanisms control the GFR  Renal autoregulation (intrinsic system)  Neural controls  Hormonal mechanism (the renin-angiotensin system)

34 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Intrinsic Controls  Under normal conditions, renal autoregulation maintains a nearly constant glomerular filtration rate  Autoregulation entails two types of control  Myogenic – responds to changes in pressure in the renal blood vessels  Flow-dependent tubuloglomerular feedback – senses changes in the juxtaglomerular apparatus

35 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Extrinsic Controls  When the sympathetic nervous system is at rest:  Renal blood vessels are maximally dilated  Autoregulation mechanisms prevail

36 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Sympathetic Regulation of GFR  Stimulates vasoconstriction of afferent arterioles.  Preserves blood volume to muscles and heart.  Cardiovascular shock:  Decreases glomerular capillary hydrostatic pressure.  Decreases urine output (UO). Insert fig

37 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Extrinsic Controls  Under stress:  Norepinephrine is released by the sympathetic nervous system  Epinephrine is released by the adrenal medulla  Afferent arterioles constrict and filtration is inhibited  The sympathetic nervous system also stimulates the renin-angiotensin mechanism PLAY InterActive Physiology ®: Glomerular Filtration, pages 3–14

38 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Renin-Angiotensin Mechanism  Is triggered when the JG cells release renin  Renin acts on angiotensinogen to release angiotensin I  Angiotensin I is converted to angiotensin II  Angiotensin II:  Causes mean arterial pressure to rise  Stimulates the adrenal cortex to release aldosterone  As a result, both systemic and glomerular hydrostatic pressure rise

39 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Renin Release  Renin release is triggered by:  Reduced stretch of the granular JG cells  Stimulation of the JG cells by activated macula densa cells  Direct stimulation of the JG cells via  1 -adrenergic receptors by renal nerves  Angiotensin II

40 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Other Factors Affecting Glomerular Filtration  Prostaglandins (PGE 2 and PGI 2 )  Vasodilators produced in response to sympathetic stimulation and angiotensin II  Are thought to prevent renal damage when peripheral resistance is increased  Nitric oxide – vasodilator produced by the vascular endothelium  Adenosine – vasoconstrictor of renal vasculature  Endothelin – a powerful vasoconstrictor secreted by tubule cells

41 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Tubular Reabsorption  A transepithelial process whereby most tubule contents are returned to the blood  Transported substances move through three membranes  Luminal and basolateral membranes of tubule cells  Endothelium of peritubular capillaries  Only Ca 2+, Mg 2+, K +, and some Na + are reabsorbed via paracellular pathways

42 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Tubular Reabsorption  All organic nutrients are reabsorbed  Water and ion reabsorption is hormonally controlled  Reabsorption may be an active (requiring ATP) or passive process

43 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Sodium Reabsorption: Primary Active Transport  Sodium reabsorption is almost always by active transport  Na + enters the tubule cells at the luminal membrane  Is actively transported out of the tubules by a Na + -K + ATPase pump

44 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Sodium Reabsorption: Primary Active Transport  From there it moves to peritubular capillaries due to:  Low hydrostatic pressure  High osmotic pressure of the blood  Na + reabsorption provides the energy and the means for reabsorbing most other solutes

45 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Routes of Water and Solute Reabsorption Figure 25.11

46 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Reabsorption by PCT Cells  Active pumping of Na + drives reabsorption of:  Water by osmosis, aided by water-filled pores called aquaporins  Cations and fat-soluble substances by diffusion  Organic nutrients and selected cations by secondary active transport

47 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Reabsorption by PCT Cells PLAY InterActive Physiology ®: Early Filtrate Processing, pages 3–15 Figure 25.12

48 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Nonreabsorbed Substances  A transport maximum (T m ):  Reflects the number of carriers in the renal tubules available  Exists for nearly every substance that is actively reabsorbed  When the carriers are saturated, excess of that substance is excreted

49 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Nonreabsorbed Substances  Substances are not reabsorbed if they:  Lack carriers  Are not lipid soluble  Are too large to pass through membrane pores  Urea, creatinine, and uric acid are the most important nonreabsorbed substances

50 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Absorptive Capabilities of Renal Tubules and Collecting Ducts  Substances reabsorbed in PCT include:  Sodium, all nutrients, cations, anions, and water  Urea and lipid-soluble solutes  Small proteins  Loop of Henle reabsorbs:  H 2 O, Na +, Cl , K + in the descending limb  Ca 2+, Mg 2+, and Na + in the ascending limb

51 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Absorptive Capabilities of Renal Tubules and Collecting Ducts  DCT absorbs:  Ca 2+, Na +, H +, K +, and water  HCO 3  and Cl   Collecting duct absorbs:  Water and urea

52 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Na + Entry into Tubule Cells  Passive entry: Na + -K + ATPase pump  In the PCT: facilitated diffusion using symport and antiport carriers  In the ascending loop of Henle: facilitated diffusion via Na + -K + -2Cl  symport system  In the DCT: Na + -Cl – symporter  In collecting tubules: diffusion through membrane pores

53 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Atrial Natriuretic Peptide Activity  ANP reduces blood Na + which:  Decreases blood volume  Lowers blood pressure  ANP lowers blood Na + by:  Acting directly on medullary ducts to inhibit Na + reabsorption  Counteracting the effects of angiotensin II  Indirectly stimulating an increase in GFR reducing water reabsorption

54 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Tubular Secretion  Essentially reabsorption in reverse, where substances move from peritubular capillaries or tubule cells into filtrate  Tubular secretion is important for:  Disposing of substances not already in the filtrate  Eliminating undesirable substances such as urea and uric acid  Ridding the body of excess potassium ions  Controlling blood pH

55 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Regulation of Urine Concentration and Volume  Osmolality  The number of solute particles dissolved in 1L of water  Reflects the solution’s ability to cause osmosis  Body fluids are measured in milliosmols (mOsm)  The kidneys keep the solute load of body fluids constant at about 300 mOsm  This is accomplished by the countercurrent mechanism

56 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Countercurrent Mechanism  Interaction between the flow of filtrate through the loop of Henle (countercurrent multiplier) and the flow of blood through the vasa recta blood vessels (countercurrent exchanger)  The solute concentration in the loop of Henle ranges from 300 mOsm to 1200 mOsm  Dissipation of the medullary osmotic gradient is prevented because the blood in the vasa recta equilibrates with the interstitial fluid

57 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Loop of Henle: Countercurrent Mechanism Figure 25.14

58 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Osmotic Gradient in the Renal Medulla Figure 25.13

59 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Loop of Henle: Countercurrent Multiplier  The descending loop of Henle:  Is relatively impermeable to solutes  Is permeable to water  The ascending loop of Henle:  Is permeable to solutes  Is impermeable to water  Collecting ducts in the deep medullary regions are permeable to urea

60 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Loop of Henle: Countercurrent Exchanger  The vasa recta is a countercurrent exchanger that:  Maintains the osmotic gradient  Delivers blood to the cells in the area PLAY InterActive Physiology ®: Early Filtrate Processing, pages 16–21

61 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Loop of Henle: Countercurrent Mechanism Figure 25.14

62 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Formation of Dilute Urine  Filtrate is diluted in the ascending loop of Henle  Dilute urine is created by allowing this filtrate to continue into the renal pelvis  This will happen as long as antidiuretic hormone (ADH) is not being secreted

63 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Formation of Dilute Urine  Collecting ducts remain impermeable to water; no further water reabsorption occurs  Sodium and selected ions can be removed by active and passive mechanisms  Urine osmolality can be as low as 50 mOsm (one- sixth that of plasma)

64 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Formation of Concentrated Urine  Antidiuretic hormone (ADH) inhibits diuresis  This equalizes the osmolality of the filtrate and the interstitial fluid  In the presence of ADH, 99% of the water in filtrate is reabsorbed

65 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings PLAY InterActive Physiology ®: Late Filtrate Processing, pages 3–12 Formation of Concentrated Urine  ADH-dependent water reabsorption is called facultative water reabsorption  ADH is the signal to produce concentrated urine  The kidneys’ ability to respond depends upon the high medullary osmotic gradient

66 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Formation of Dilute and Concentrated Urine Figure 25.15a, b

67 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Summary of Nephron Function Figure 25.16

68 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Diuretics  Chemicals that enhance the urinary output include:  Any substance not reabsorbed  Substances that exceed the ability of the renal tubules to reabsorb it  Substances that inhibit Na + reabsorption

69 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Diuretics  Osmotic diuretics include:  High glucose levels – carries water out with the glucose  Alcohol – inhibits the release of ADH  Caffeine and most diuretic drugs – inhibit sodium ion reabsorption  Lasix and Diuril – inhibit Na + -associated symporters


Download ppt "Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology SEVENTH EDITION Elaine N. Marieb Katja Hoehn PowerPoint."

Similar presentations


Ads by Google