The Urinary System: Part A

Transcription

1 PowerPoint Lecture Slides prepared by Mr. BEHS C H A P T E R 25 The Urinary System: Part A

2 INTRODUCTION

3 Introduction All organisms within Kingdom Animalia, including humans (homo sapiens), need to excrete waste products from foods consumed. The urinary system is one the ways that the human body is able to eliminate waste products.

4 Urinary System Organs Kidneys (2) Paired ureters transport urine from the kidneys to the bladder Urinary bladder provides a temporary storage reservoir for urine Urethra transports urine from the bladder out of the body Urinary System Organs Kidneys Ureters Urinary Bladder Urethra

5 Hepatic veins (cut) Esophagus (cut) Inferior vena cava Adrenal gland Aorta Iliac crest Renal artery Renal hilum Renal vein Kidney Ureter Rectum (cut) Uterus (part of female reproductive system) Urinary bladder Urethra Figure 25.1

6 Functions THE KIDNEY

7 Kidney Functions Removal of toxins, metabolic wastes, and excess ions from the blood Removal Toxins Metabolic Wastes Excess Ions Regulation of blood volume, chemical composition, and ph Kidney Functions Regulation Glucogenesis Blood volume Chemical composition ph Endocrine Functions Activation of Vitamin D Renin Erythroprotein

8 Kidney Functions Gluconeogenesis during prolonged fasting Endocrine functions Renin: regulation of blood pressure and kidney function Kidney Functions Removal Regulation Toxins Metabolic Wastes Excess Ions Blood volume Chemical composition Erythropoietin: regulation of RBC production Activation of vitamin D Glucogenesis Endocrine Functions Activation of Vitamin D ph Renin Erythroprotein

9 Anatomy THE KIDNEY

10 Kidney Anatomy I Retroperitoneal, in the superior lumbar region Right kidney is lower than the left Space for liver Convex lateral surface, concave medial surface Renal hilum leads to the renal sinus Ureters, renal blood vessels, lymphatics, and nerves enter and exit at the hilum

11 Peritoneum Renal vein Renal artery Body of vertebra L 2 Body wall (a) Anterior Peritoneal cavity (organs removed) Posterior Inferior vena cava Aorta Supportive tissue layers Renal fascia anterior posterior Perirenal fat capsule Fibrous capsule Figure 25.2a

12 Renal hilum Renal cortex Renal medulla Major calyx Papilla of pyramid Renal pelvis Minor calyx Ureter Renal pyramid in renal medulla Renal column Fibrous capsule (a) Photograph of right kidney, frontal section (b) Diagrammatic view Figure 25.3

13 Blood Flow THE KIDNEY

14 Aorta Renal artery Segmental artery Interlobar artery Arcuate artery Cortical radiate artery Afferent arteriole Inferior vena cava Renal vein Interlobar vein Arcuate vein Cortical radiate vein Peritubular capillaries and vasa recta Efferent arteriole Glomerulus (capillaries) Nephron-associated blood vessels (see Figure 25.7) (b) Path of blood flow through renal blood vessels Figure 25.4b

15 Anatomy Parts/Areas of the Kidney THE KIDNEY

16 Nephrons THE KIDNEY

17 Nephrons Structural and functional units that form urine ~1 million per kidney Two main parts 1. Glomerulus*: a tuft of capillaries 2. Renal tubule: begins as cupshaped glomerular (Bowman s) capsule surrounding the glomerulus Glomerulus Renal Corpuscle Glomerulus {Bowman s Capsule} Glomerulus* Uriniferous Tubule Nephron Renal Tubule Collecting Duct* Proximal Tubule Loop of Henle Distal Tubule

18 Renal hilum Renal cortex Renal medulla Major calyx Papilla of pyramid Renal pelvis Minor calyx Ureter Renal pyramid in renal medulla Renal column Fibrous capsule (a) Photograph of right kidney, frontal section (b) Diagrammatic view Figure 25.3

19 Figure 25.5

20 Renal Tubule I Glomerular (Bowman s capsule) Parietal layer: simple squamous epithelium Uriniferous Tubule Renal Tubule Nephron Visceral layer: branching epithelial podocytes ( foot cells) Extensions terminate in foot processes that cling to basement membrane Parietal Layer Renal Corpuscle Glomerular (Bowman s) Capsule Visceral Lauer Filtration slits allow filtrate to pass into the capsular space

21 Renal Tubule Nephron Renal Corpuscle Bowman s Capsule Bowman s Capsule Glomerular Capsule Parietal Layer Visceral Layer

22 Renal Tubule Nephron Proximal Tubule Proximal convoluted tubule (PCT) Functions in reabsorption and secretion

23 Renal Tubule Nephron Loop of Henle Loop of Henle with descending and ascending limbs Simple squamous epithelium Freely permeable to water

24 Renal Tubule Nephron Distal Tubule Distal convoluted tubule (DCT) Function more in secretion than reabsorption

25 Renal Tubule Collecting Ducts Receive filtrate from many nephrons Fuse together to deliver urine through papillae into minor calyces

26 Renal Tubule Collecting Ducts Cell types Intercalated cells Function in maintaining the acid-base balance of the body Principal cells Help maintain the body s water and salt balance

27 Renal cortex Renal medulla Renal pelvis Kidney Ureter Renal corpuscle Glomerular capsule Glomerulus Distal convoluted tubule Glomerular capsule: parietal layer Basement membrane Podocyte Fenestrated endothelium of the glomerulus Glomerular capsule: visceral layer Microvilli Mitochondria Proximal convoluted tubule Cortex Highly infolded plasma membrane Proximal convoluted tubule cells Medulla Thick segment Thin segment Loop of Henle Descending limb Ascending limb Collecting duct Distal convoluted tubule cells Loop of Henle (thin-segment) cells Principal cell Intercalated cell Collecting duct cells Figure 25.5

28 CLASSES OF NEPHRONS

29 Classes of Nephrons I The nephrons are all located in the cortical region of the kidneys but they are at three levels in the cortex. The outer cortical nephrons The mid-cortical nephrons The inner cortical nephrons termed the Juxtamedullary nephrons Each kidney has approximately million nephrons.

30 Classes of Nephrons II Nephron Positions Outer cortical Mid-cortical (not shown) Juxta-medullary Notice the length of the loops of Henle longest in the Juxta-medullary nephrons More concentrating of urine ability

31 Classes of Nephrons III Cortical nephrons 85% of nephrons; almost entirely in the cortex Juxtamedullary nephrons The juxtamedullary nephrons have the longest loops of Henle (associated with concentrating the urine). Long loops of Henle deeply invade the medulla Extensive thin segments Important in the production of concentrated urine

32 NEPHRON CAPILLARY BEDS

33 Nephron Capillary Beds Glomerulus Afferent arteriole glomerulus efferent arteriole The glomerulus is a tuft of fenestrated capillaries that allows a filtrate of the blood to enter Bowman s capsule Specialized for filtration Vasa recta Long vessels parallel to long loops of Henle Function in formation of concentrated urine

34 Cortical nephron Has short loop of Henle and glomerulus further from the corticomedullary junction Efferent arteriole supplies peritubular capillaries Renal corpuscle Kidney Efferent arteriole Glomerular capillaries (glomerulus) Glomerular (Bowman s) capsule Proximal convoluted tubule Peritubular capillaries Ascending or thick limb of the loop of Henle Cortex Medulla Renal pelvis Ureter Arcuate vein Arcuate artery Loop of Henle Descending or thin limb of loop of Henle Juxtamedullary nephron Has long loop of Henle and glomerulus closer to the corticomedullary junction Efferent arteriole supplies vasa recta Cortical radiate vein Cortical radiate artery Afferent arteriole Collecting duct Distal convoluted tubule Afferent arteriole Efferent arteriole Corticomedullary junction Vasa recta (a) Figure 25.7a

35 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

36 REGULATION OF BLOOD PRESSURE WITHIN KIDNEY

37 Juxtaglomerular Apparatus (JGA) The juxtaglomerular apparatus is a specialized structure which has the main function(s) of Regulating blood pressure of the glomerulus Regulating the filtration rate (filtrate formation) of the glomerulus. There is one juxtaglomerular apparatus per nephron. Within the juxtaglomerular apparatus, the distal convoluted tubule makes direct contact with the afferent arteriole.

38 Juxtaglomerular Apparatus (JGA) II The parts of the nephron that makes up the juxtaglomerular apparatus are Modified portions of the distal convoluted tubule Afferent arteriole Efferent arteriole Some occasions.

39 Juxtaglomerular Apparatus (JGA) III Cell Types I The afferent arteriole, efferent arteriole and the distal convoluted tubule, have cells surrounding (afferent arteriole & efferent arteriole) and within (distal convoluted tubule) that help carry out the function of the juxtaglomerular apparatus. JGA Juxtaglomerular Apparatus Granular Cells Macula Densa Lacis Cells

40 Juxtaglomerular Apparatus (JGA) IV Cell Types II Granular cells Also called (juxtaglomerular cells, or JG cells) Modified, enlarged, smooth muscle cells found on the surface (outside)of the afferent arterioles Granular cells act as mechanoreceptors that sense blood pressure JGA Juxtaglomerular Apparatus Granular Cells Macula Densa Lacis Cells These cells will produce and store renin within secretory granule.

41 Juxtaglomerular Apparatus (JGA) V Cell Types III Macula densa Tall, closely packed cells found within the distal convoluted tubule. Act as chemoreceptors Na + sensors Sense NaCl content of filtrate Sense changes in concentration of filtrate Sense changes in flow rate of filtrate.

42 Juxtaglomerular Apparatus (JGA) VI Cell Types IV Lacis Cells Also called juxtaglomerular mesangial cells Form connections via actin (protein fiber within muscle cells) and microtubules (refer back to cell) to allow for selective vasoconstriction/vasodil ation of afferent and efferent arterioles.

43 Efferent arteriole Glomerular capsule Glomerulus Afferent arteriole Efferent arteriole Parietal layer of glomerular capsule Capsular space Foot processes of podocytes Podocyte cell body (visceral layer) Red blood cell Proximal tubule cell Juxtaglomerular apparatus Macula densa cells of the ascending limb of loop of Henle Extraglomerular mesangial cells Granular cells Afferent arteriole Lumens of glomerular capillaries Endothelial cell of glomerular capillary Mesangial cells between capillaries Juxtaglomerular apparatus Renal corpuscle Figure 25.8

44 FILTRATION MECHANISM

45 Filtration Membrane Porous membrane between the blood and the capsular space Consists of 1. Fenestrated endothelium of the glomerular capillaries 2. Visceral membrane of the glomerular capsule (podocytes with foot processes and filtration slits) 3. Gel-like basement membrane (fused basal laminae of the two other layers)

46 Efferent arteriole Glomerular capsular space Afferent arteriole Glomerular capillary covered by podocytecontaining visceral layer of glomerular capsule (a) Glomerular capillaries and the visceral layer of the glomerular capsule Parietal layer of glomerular capsule Proximal convoluted tubule Podocyte cell body Fenestrations (pores) Cytoplasmic extensions of podocytes Filtration slits Glomerular capillary endothelium (podocyte covering and basement membrane removed) Foot processes of podocyte Figure 25.9a

47 Filtration Membrane Allows passage of water and solutes smaller than most plasma proteins Fenestrations prevent filtration of blood cells Negatively charged basement membrane repels large anions such as plasma proteins Slit diaphragms also help to repel macromolecules

48 Capillary Filtration membrane Capillary endothelium Basement membrane Foot processes of podocyte of glomerular capsule Filtration slit Fenestration (pore) Plasma Filtrate in capsular space Slit diaphragm Foot processes of podocyte (c) Three parts of the filtration membrane Figure 25.9c

49 Parts of Filtration Machine

50 URINE PRODUCTION

51 Kidney Physiology: Mechanisms of Urine Formation Keywords Filtrate Blood plasma minus proteins Urine <1% of total filtrate Contains metabolic wastes and unneeded substances

52 Mechanisms of Urine Formation 1. Glomerular Filtration removal of substances from the blood at the filter (renal corpuscle) 2. Tubular Reabsorption returning much of the filtrate (minus most of the waste) back into the blood reason too much has been filtered Returns all glucose and amino acids, 99% of water, salt, and other components to the blood 3. Tubular Secretion active transport of substances absolutely needed to filtered into the kidneys in areas after the filter Reverse of reabsorption: selective addition to urine Filtration Glomerulus Reabsorption PCT Loop of Henle DCT Collecting Ducts* Secretion PCT Loop of Henle DCT Collecting Ducts*

53 Afferent arteriole Glomerular capillaries Cortical radiate artery Efferent arteriole Glomerular capsule Rest of renal tubule containing filtrate Three major renal processes: Glomerular filtration Tubular reabsorption Tubular secretion Peritubular capillary To cortical radiate vein Urine Figure 25.10

54 The Process of Urine Production Filtration Reabsorption Secretion Glomerulus PCT Loop of Henle DCT Collecting Ducts* PCT Loop of Henle DCT Collecting Ducts*

55 Glomerular Filtration Passive mechanical process driven by hydrostatic pressure The glomerulus is a very efficient filter because 1. Its filtration membrane is very permeable and it has a large surface area 2. Glomerular blood pressure is higher (55 mm Hg) than other capillaries Molecules >5 nm are not filtered (e.g., plasma proteins) and function to maintain colloid osmotic pressure of the blood

56 Net Filtration Pressure (NFP) The pressure responsible for filtrate formation (10 mm Hg)

57 Net Filtration Pressure (NFP) Determined by Glomerular hydrostatic pressure (HP g ) the chief force Two opposing forces: Colloid osmotic pressure of glomerular blood (OP g ) Capsular hydrostatic pressure (HP c ) NFP = HP g (OP g + HP c )

58

59 Glomerular capsule Afferent arteriole 10 mm Hg Net filtration pressure Glomerular (blood) hydrostatic pressure (HP g = 55 mm Hg) Blood colloid osmotic pressure (Op g = 30 mm Hg) Capsular hydrostatic pressure (HP c = 15 mm Hg) Figure 25.11

60 SYSTEMIC BLOOD PRESSURE ( ) Blood pressure in afferent arterioles; GFR GFR Granular cells of juxtaglomerular apparatus of kidney Baroreceptors in blood vessels of systemic circulation Stretch of smooth muscle in walls of afferent arterioles Vasodilation of afferent arterioles Filtrate flow and NaCl in ascending limb of Henle s loop Targets (+) Renin Catalyzes cascade resulting in conversion Angiotensinogen Release Angiotensin II (+) (+) Sympathetic nervous system Macula densa cells of JG apparatus of kidney (+) Adrenal cortex Releases (+) Systemic arterioles (+) Release of vasoactive chemical inhibited Aldosterone Targets Vasoconstriction; peripheral resistance GFR Vasodilation of afferent arterioles Kidney tubules Na + reabsorption; water follows Blood volume (+) Stimulates ( ) Inhibits Increase Decrease Systemic blood pressure Myogenic mechanism of autoregulation Tubuloglomerular mechanism of autoregulation Hormonal (renin-angiotensin) mechanism Neural controls Intrinsic mechanisms directly regulate GFR despite moderate changes in blood pressure (between 80 and 180 mm Hg mean arterial pressure). Extrinsic mechanisms indirectly regulate GFR by maintaining systemic blood pressure, which drives filtration in the kidneys. Figure 25.12

61 PowerPoint Lecture Slides prepared by Mr. BEHS C H A P T E R 25 The Urinary System: Part B

62 Important Note: -The online animations DO NOT illustrate the movement of ALL ions/molecules via absorption/secretion. The remainder are mentioned in the packet. REABSORPTION

63 Reminder The Process of Urine Production Filtration Reabsorption Secretion Glomerulus PCT Loop of Henle DCT Collecting Ducts* PCT Loop of Henle DCT Collecting Ducts*

64 Sodium Reabsorption Na + (most abundant cation in filtrate) Primary active transport out of the tubule cell by Na + -K + ATPase Sodium-Potassium Pump

65 Methods of Reabsorption of Materials Into Bloodstream Methods of Reabsorption Diffusion Facilitated Diffusion Primary Active Transport Secondary Active Transport Co-Transport Osmosis Sodium

66 Sodium Reabsorption Low hydrostatic pressure and high osmotic pressure in the peritubular capillaries Promotes bulk flow of water and solutes (including Na + )

67 Reabsorption of Nutrients, Water, and Ions Na+ reabsorption provides the energy and the means for reabsorbing most other substances Organic nutrients are reabsorbed by secondary active transport

68 Methods of Reabsorption of Materials Into Bloodstream Methods of Reabsorption Diffusion Facilitated Diffusion Primary Active Transport Secondary Active Transport Co-Transport Osmosis Sodium Other Organic Molecules

69 Reabsorption of Nutrients, Water, and Ions Water is reabsorbed by osmosis (obligatory water reabsorption), Cations and fat-soluble substances follow by diffusion

70 Methods of Reabsorption of Materials Into Bloodstream Methods of Reabsorption Diffusion Facilitated Diffusion Primary Active Transport Secondary Active Transport Co-Transport Osmosis Cations Sodium Other Organic Molecules Water Fat-soluble substances

71 Reabsorptive Capabilities of Renal Tubules and Collecting Ducts PCT Site of most reabsorption 65% of Na + and water All nutrients Ions Small proteins

72 Location of Reabsorption of Materials Within Renal Tubule Reabsorption of Materials From Filtrate to Bloodstream PCT Loop of Henle DCT Collecting Duct(s) Na + Descending Water Ascending Glucose Ions Small Proteins HCO 2 - Urea Lipid soluble solutes

73 Reabsorptive Capabilities of Renal Tubules and Collecting Ducts Loop of Henle Descending limb: H 2 O Ascending limb: Na +, K +, Cl

74 Location of Reabsorption of Materials Within Renal Tubule Reabsorption of Materials DCT From Filtrate to Bloodstream Collecting Duct(s) PCT Loop of Henle Na + Descending Ascending Water H 2 O Na + Glucose Na + Ca + Ions Cl - Mg 2+ Small Proteins K + K + HCO 2 - Cl - Urea Lipid soluble solutes

75 Reabsorptive Capabilities of Renal Tubules and Collecting Ducts DCT and collecting duct Reabsorption is hormonally regulated Ca 2+ (PTH) Water (ADH) Na + (aldosterone and ANP)

76 Summary of 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

77 Location of Reabsorption of Materials Within Renal Tubule Reabsorption of Materials From Filtrate to Bloodstream PCT Loop of Henle DCT Collecting Duct(s) Na + Descending Ascending Water H 2 O Na + Glucose Na + Ca + Ions Cl - Mg 2+ Small Proteins K + K + HCO 2 - Cl - Urea Lipid soluble solutes

78 Summary of 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

79 Location of Reabsorption of Materials Within Renal Tubule Reabsorption of Materials From Filtrate to Bloodstream PCT Loop of Henle DCT Collecting Duct(s) Na + Descending Ascending Ca 2+ Water Water H 2 O Na + Na + Urea Glucose Na + Ca + H + Ions Cl - Mg 2+ K + Small Proteins K + K + H 2 O HCO 2 - Cl - HCO 3 - Urea Cl - Lipid soluble solutes

80 Connection Methods of Reabsorption of Materials Into Bloodstream* Methods of Reabsorption Diffusion Facilitated Diffusion Primary Active Transport Secondary Active Transport Co-Transport Osmosis Cations Fat-soluble substances Cations Na + Other Organic Molecules Glucose Water H + H + H + Na + K + Ca 2+

81 Reabsorption

82 Reminder The Process of Urine Production Filtration Reabsorption Secretion Glomerulus PCT Loop of Henle DCT Collecting Ducts* PCT Loop of Henle DCT Collecting Ducts*

83 Special Note! Please view Packet #15 to view the role of hormones in the reabsorption of sodium, water and calcium.

84 Important Note: -The online animations DO NOT illustrate the movement of ALL ions/molecules via absorption/secretion. The remainder are mentioned in the packet. SECRETION

85 Reminder AGAIN The Process of Urine Production Filtration Reabsorption Secretion Glomerulus PCT Loop of Henle DCT Collecting Ducts* PCT Loop of Henle DCT Collecting Ducts*

86 Secretion Introduction Bloodstream Filtrate Secretion is ALSO the REMOVAL of wastes from the blood into the filtrate (urine). Secretion is the OPPOSITE of reabsorption. Rather than moving materials from the filtrate to the blood, materials are moved from the blood into the filtrate. Process occurs outside of renal corpuscle. Glomerulus Bowman s Capsule

87 Tubular Secretion I Bloodstream Filtrate 1. Reabsorption in reverse K +, H +, NH 4+, creatinine [kree-at-n-een, -in], and organic acids move from peritubular capillaries or tubule cells INTO FILTRATE 2. Disposes of substances that are bound to plasma proteins Disposes substances Sub. Bound to proteins Reabsorption in Reverse Eliminate Undesirable Substances Tubular Secretion Rids of excess K+ Controls Blood ph Alter H+ or HCO3-

88 Tubular Secretion II Bloodstream Filtrate 3. Eliminates undesirable substances that have been passively reabsorbed (e.g., urea and uric acid) 4. Rids the body of excess K + 5. Controls blood ph by altering amounts of H + or HCO 3 in urine

89 Secretion Movement of Materials From Bloodstream Into Filtrate (Renal Tubule) Secretion Bloodstream Into Filtrate PCT Loop of Henle DCT Collecting Duct(s)* H + Descending Ascending K + N/A NH 3 N/A* N/A* H + Creatinine

90 Secretion III

91 Altogether Reabsorption & Secretion The Nephron & Collecting Duct Reabsorption & Secretion PCT Loop of Henle DCT Collecting Duct Reabsorption Into Bloodstream Secretion Into Tubule Reabsorption Into Bloodstream Secretion Into Tubule Reabsorption Into Bloodstream Secretion into Filtrate Reabsorption into Bloodstream Secretion Into Filtrate Na + H + Descending Ascending N/A* Na + K + H 2 O N/A* Water NH 3 H 2 O Na + H 2 O H + Urea Glucose Creatinine Na + Ca + Ca 2+ NaCl Ions Cl - Mg 2+ NaCl Small Proteins K + K + HCO 3 HCO 2 - Cl - Urea Lipid soluble solutes

92 Reminder The Process of Urine Production Filtration Reabsorption Secretion Glomerulus PCT Loop of Henle DCT Collecting Ducts* PCT Loop of Henle DCT Collecting Ducts*

93 Important Note: -Please view Packet #14 for hormonal regulation of urine concentration & volume. Important Note: -Please view Packet #10A for information on diffusion and osmosis. REGULATION OF URINE CONCENTRATION & VOLUME

94 Regulation of Urine Concentration and Volume Osmolality Number of solute particles in 1 kg of H 2 O Reflects ability to cause osmosis Osmolality of body fluids Expressed in (mosm) The kidneys maintain osmolality of plasma at ~300 mosm, using countercurrent mechanisms

95 GFR Calculation GFR is calculated using renal clearance RC = UV/P RC = renal clearance rate U = concentration (mg/ml) of the substance in urine V = flow rate of urine formation (ml/min) P = concentration of the same substance in plasma

96 COUNTERCURRENT MECHANISM

97 Countercurrent Mechanism I The countercurrent mechanism system is a mechanism in place that is used to create a concentration gradient, osmotic gradient, that allows one to reabsorb water from the filtrate (tubular fluid). Observed at the loop of Henle & the vasa recta.

98 Countercurrent Mechanism II The establishment of the osmotic gradient, allows the kidney to vary the concentration of one s urine and is also why one is not drinking water every second of the day.

99 Countercurrent Mechanism III Occurs when fluid flows in opposite directions in two adjacent segments of the same tube The filtrate in the loop of Henle flows in one direction while the blood in the vasa recta flows in the opposite direction. Filtrate flow in the loop of Henle (countercurrent multiplier) Blood flow in the vasa recta (countercurrent exchanger)

100 Countercurrent Mechanism IV Further details to come at the university level!

101 URETERS

102 Ureters Function Carry urine from the kidneys to the urinary bladder Oblique entry into bladder prevents backflow of urine Histology of ureter Histology of Ureter Mucosa Transitional epithelium Mucosa Muscularis Adventitia Muscularis two layers Inner longitudinal layer Transitional Epithelium Two Layers Connective Tissue Outer circular layer Adventitia [ad ven ti tia] [ad-ventish-ee-uh] Typical connective tissue

103 Microscopic Structure of the Ureter Figure 23.12

104 BLADDER

105 Urinary Bladder I A collapsible muscular sac Stores and expels urine Full bladder Spherical Expands into the abdominal cavity Empty bladder Lies entirely within the pelvis Figure 23.13

106 Urinary Bladder II Urachus Closed remnant of the allantois Prostate gland In males Lies directly inferior to the bladder Surrounds the urethra Figure 23.14

107 Urinary Bladder III Wall of bladder Mucosa Transitional epithelium Wall of Bladder Muscular layer Mucosa Muscular layer Adventitia Detrus or muscle Adventitia [ad ven ti tia] [ad-ven-tish-ee-uh] Transitional Epithelium Detrus/Muscle

108 Histology of the Urinary Bladder Figure 23.15a, b

109 Structure of the Urinary Bladder and Urethra {Males} Figure 23.16a

110 Structure of the Urinary Bladder and Urethra {Females} Figure 23.16b

111 URETHRA

112 The Urethra I Extends from the urinary bladder to the exterior of the body Passes through urogenital diaphragm (external urinary sphincter) Differs in length and function in males and females Internal urethral sphincter - involuntary smooth muscle External urethral sphincter - voluntarily inhibits urination, relaxes when one urinates

113 Urinary Bladder and Urethra - Male Males 20 cm in length Three named regions 1. Prostatic urethra - passes through the prostate gland 2. Membranous urethra - through the urogenital diaphragm 3. Spongy (penile) urethra passes through the length of the penis Figure 23.16a

114 Urinary Bladder and Urethra - Female In females - length of 3 4 cm The smooth triangular region of the base is is called the trigone - many bladder infections persist in this region

115 Urethral Opening Female

116 Urethra II Epithelium of urethra Transitional epithelium At the proximal end (near the bladder) Stratified and pseudostratified columnar mid urethra (in males) Transitional Epithelium Epithelium of Urethra Stratified & Psuedostratified Columnar Stratified Squamous Stratified squamous epithelium At the distal end (near the urethral opening)

117 Urethra III Internal urethral sphincter [sphinc ter] [ Involuntary smooth muscle External urethral sphincter Voluntarily inhibits urination Relaxes when one urinates

118 DETAILS ON URINE

119 Formation of Dilute Urine Filtrate is diluted in the ascending loop of Henle In the absence of ADH, dilute filtrate continues into the renal pelvis as dilute urine See Packet #14 Na + and other ions may be selectively removed in the DCT and collecting duct, decreasing osmolality to as low as 50 mosm

120 Active transport Passive transport Collecting duct Descending limb of loop of Henle DCT Cortex NaCI H 2 O Outer medulla NaCI NaCI H 2 O Inner medulla Urea (a) Absence of ADH Large volume of dilute urine Figure 25.17a

121 Formation of Concentrated Urine Depends on the medullary osmotic gradient and ADH ADH triggers reabsorption of H 2 O in the collecting ducts Facultative water reabsorption occurs in the presence of ADH so that 99% of H 2 O in filtrate is reabsorbed

122 Renal Clearance Definition Volume of plasma cleared of a particular substance in a given time Renal clearance tests are used to 1. Determine GFR 2. Detect glomerular damage 3. Follow the progress of renal disease

123 Urination MICTURITION [MIK-CHUH-RISH-UH N]

124 Micturition Urination or voiding Three simultaneous events 1. Contraction of detrusor muscle by ANS 2. Opening of internal urethral sphincter by ANS 3. Opening of external urethral sphincter by somatic nervous system

125 DISORDERS OF URINARY SYSTEM

126 Disorders of the Urinary System Urinary tract infections More common in females Burning sensation during micturition Renal calculi Kidney stones Bladder cancer 3% of cancers more common in men Kidney cancer Arises from epithelial cells of uriniferous tubules

127 CHARACTERISTICS OF URINE

128 Physical Characteristics of Urine I Color & Transparency Clear, pale to deep yellow (due to urochrome) Concentrated urine has a deeper yellow color Drugs, vitamin supplements {Vitamin B}, and diet can change the color of urine Cloudy urine may indicate infection of the urinary tract.

129 Physical Characteristics of Urine II Odor Fresh urine is slightly aromatic Standing urine develops an ammonia odor Some drugs (amoxicillin) and vegetables (asparagus) alter the usual odor.

130 Physical Characteristics of Urine III ph Slightly acidic (ph 6) with a range of 4.5 to 8.0 Diet can alter urine ph Specific Gravity Is dependent on solute concentration

131 Chemical Composition of Urine I Urine is 95% water and 5% solutes Nitrogenous wastes: urea, uric acid and creatinine (byproduct from muscle) 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.

132 URINARY SYSTEM & DEVELOPMENT

133 The Urinary System Throughout Life Embryo develops three pairs of kidneys Pronephros Mesonephros Metanephros Only metanephros persists to become the adult kidneys Metanephric kidney produces urine by fetal month three Contributes to the volume of amniotic fluid Three Pairs Embryo & Kidneys Pronephros Mesonephros Metanephros

134 Development of the Urinary Organs Figure 23.18a,b

135 Development of the Urinary Organs Figure 23.18c, d

136 The Urinary System Throughout Life Kidney and bladder function declines with advancing age Nephrons decrease in size and number Tubules less efficient at secretion and reabsorption Filtration declines Recognition of desire to urinate is delayed Loss of muscle tone in the bladder

137 REVIEW