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COORDINATION & RESPONSE PART 3 - HOMEOSTATIS - URINE FORMATION

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COORDINATION & RESPONSE PART 3 - HOMEOSTATIS - URINE FORMATION

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COORDINATION & RESPONSE PART 3 - HOMEOSTATIS - URINE FORMATION

  1. 1. BIOLOGY FORM 5 CHAPTER 3 COORDINATION & RESPONSE PART 3
  2. 2. LEARNING OBJECTIVES 3.4 Synthesising the concept of homeostasis in humans LEARNING OUTCOMES  explain the necessity to maintain an optimal physical and chemical condition in the internal environment  state the meaning of homeostasis,  design an experiment to study the effect of different quantities of water intake on urine output,  relate changes in blood osmotic pressure to urine output,  describe the formation of urine,  relate the formation of urine to excretion,  describe briefly the mechanism of osmoregulation,  predict the consequences of impaired kidney function,  describe the regulation of blood sugar level,  describe the regulation of body temperature,  conceptualise homeostasis.
  3. 3. What is Homeostasis? Body cells work best if they have the correct  Temperature  Water levels  Glucose concentration Your body has mechanisms to keep the cells in a constant environment.
  4. 4. Homeostasis:  Greek: ‘homoios’ = similar ‘stasis’ = standing still Homeostasis is the maintenance of a relatively stable internal environment The ‘internal’ environment is the:  tissue fluid [interstitial fluid]  plasma
  5. 5. fluid surrounding cells where organism lives
  6. 6. Are variables absolutely constant? STEADY STATE High Variable Low NO
  7. 7. Examples of Physiological conditions requiring homeostasis: O2 and CO2 levels in the body energy requirements glucose level in blood water / ion balance pH temperature
  8. 8. Living systems are seen to be open systems. What does this mean? Require a continuous exchange of matter between the environment and themselves Oxygen Carbon dioxide Heat Urea Food Water
  9. 9. We are a complex system of chemical processes these processes are:  self-regulating  tend to maintain a steady state even though the external environment changes
  10. 10. What is Homeostasis? The maintenance of a constant environment in the body is called Homeostasis
  11. 11. Why is homeostasis important? We function more efficiently if conditions are maintained within optimum conditions Fluctuations are caused by: Changes in:  external  internal Toprevent large fluctuations from the optimum environments
  12. 12. Internal conditions may be maintained constant within the body by: developing a variety of mechanisms: Structural Physiological Behavioural
  13. 13. Fat Fur Feathers Structural
  14. 14. Sweat Increase in heart rate Cardiac arrest in frozen frog Physiological
  15. 15. HOT: Seek shade HOT: Seek shade COLD: Bask in the sun Behavioural
  16. 16. LEARNING OBJECTIVES 3.4 Synthesising the concept of homeostasis in humans LEARNING OUTCOMES  explain the necessity to maintain an optimal physical and chemical condition in the internal environment  state the meaning of homeostasis,  design an experiment to study the effect of different quantities of water intake on urine output,  relate changes in blood osmotic pressure to urine output,  describe the formation of urine,  relate the formation of urine to excretion,  describe briefly the mechanism of osmoregulation,  predict the consequences of impaired kidney function,  describe the regulation of blood sugar level,  describe the regulation of body temperature,  conceptualise homeostasis.
  17. 17. Principles of Homeostasis Stimulus Receptors Self-corrective Mechanism Negative Feedback Change in internal environment Detect the change Regulation of blood glucose concentration Examples To rectify the change Regulation of blood water potential Regulation of body temperature The reverse effect of the change HOMEOSTASIS The maintenance of a constant internal environment
  18. 18. Three basic components of a control system: 1. Detector / Receptor / Sensor 2. Regulator / Control centre / Co-ordinator / Integrating centre 3. Effector
  19. 19. Integrating Centre in mammals is: An endocrine gland Brain or spinal cord
  20. 20. What is Feedback? Feedback refers to responses made after a change has been detected
  21. 21. Positive feedback Two forms of feedback: Equilibrium Time Divergence Time Negative feedback
  22. 22. Negative Feedback: refers to the mechanism by which a system responds to a fluctuation in the opposite direction
  23. 23. Body temperature: RISES Corrective mechanism: DECREASES body temperature Body temperature: DECREASES Corrective mechanism: INCREASES body temperature
  24. 24. Negative feedback also applies to the regulation of a population size: Death rate increasesBirth rate increases
  25. 25. Why is negative feedback very common in the body? increases the stability of systems
  26. 26. Examples of Negative Feedback Control: O2 and CO2 levels in the body hormone levels, e.g. thyroxine sex hormones metabolic levels e.g. glucose water balance the regulation of pH body temperature
  27. 27. Control of thyroxine release as an example of negative feedback
  28. 28. Positive feedback:  a disturbance leads to events which increase the disturbance even further  rare in biological systems WHY rare? lead to:  an unstable situation  extreme states Time Divergence
  29. 29. Examples of Positive Feedback Control: 1. Blood clotting Activated platelet releases chemicals More platelets are activated A blood clot forms
  30. 30. Examples of Positive Feedback Control: 2. Child birth Oxytocin stimulates muscular contractions of the uterus More oxytocin is released
  31. 31. Does the disturbance ever stop?  once the purpose of the feedback loop is completed Oxytocin level drops once baby is born
  32. 32. LEARNING OBJECTIVES 3.4 Synthesising the concept of homeostasis in humans LEARNING OUTCOMES  explain the necessity to maintain an optimal physical and chemical condition in the internal environment  state the meaning of homeostasis,  design an experiment to study the effect of different quantities of water intake on urine output,  relate changes in blood osmotic pressure to urine output,  describe the formation of urine,  relate the formation of urine to excretion,  describe briefly the mechanism of osmoregulation,  predict the consequences of impaired kidney function,  describe the regulation of blood sugar level,  describe the regulation of body temperature,  conceptualise homeostasis.
  33. 33. LEARNING OBJECTIVES 3.4 Synthesising the concept of homeostasis in humans LEARNING OUTCOMES  explain the necessity to maintain an optimal physical and chemical condition in the internal environment  state the meaning of homeostasis,  design an experiment to study the effect of different quantities of water intake on urine output,  relate changes in blood osmotic pressure to urine output,  describe the formation of urine,  relate the formation of urine to excretion,  describe briefly the mechanism of osmoregulation,  predict the consequences of impaired kidney function,  describe the regulation of blood sugar level,  describe the regulation of body temperature,  conceptualise homeostasis.
  34. 34. Formation of Urine
  35. 35. The kidneys contribute to homeostasis Let us see how:
  36. 36. Urine Production • Regulation of water and salts in the body - osmoregulation • Rids body of waste – excretion • Maintaining blood pH • Regulating blood volume & pressure
  37. 37. Human Urinary System
  38. 38. The organs of the urinary system: a)Kidneys b)Ureters c)Bladder d)Urethra
  39. 39. Urinary system
  40. 40. The kidney Organ of excretion & osmoregulation
  41. 41. The Job of the Kidneys • cleans the blood • by removing metabolic wastes, • excess solutes (eg. salts or glucose) • excess water • and excreting them as urine • maintain homeostasis in blood solute concentration.
  42. 42. The Hard-working Kidneys • The two kidneys in the body receive between 1100 – 2000 liters (1160 – 2100 quarts or 500 gallons) of blood per day – about the volume of a car! • Because the body has only about 5.6 liters of blood, your blood runs through the kidneys to be cleaned about once every four minutes.
  43. 43. Position and structure of kidneys
  44. 44. External structure of a Pig Kidney
  45. 45. Kidneys are surrounded by a fibrous capsule:
  46. 46. Kidneys are surrounded by a fibrous capsule:
  47. 47. (b) Kidney structure Ureter Section of kidney from a rat Renal medulla Renal cortex Renal pelvis Figure 44.13b • Kidney has 2 internal layers renal cortex - outer light red region renal medulla – inner darker red-brown region
  48. 48. LS through human kidney medulla cortex
  49. 49. LS through human kidney
  50. 50. The renal artery branches inside kidney Renal artery Ureter Renal vein Each capillary supplies blood to hundreds of thousands of tiny filtration units called nephrons Detail of a nephron
  51. 51. Nephron • functional unit of the kidney • About a million in each kidney. • Consists of 3 major parts : a) the glomerulus • b) Bowman’s capsule • c) Renal tubule
  52. 52. Bowman’s Capsule glomerulus afferent arteriole efferent arteriole proximal convoluted tubule capsular space
  53. 53. Nephron Structure
  54. 54. The nephron 1.5 million per kidney collecting duct Bowman’s capsule distal tubule loop of Henle proximal tubule
  55. 55. The nephron blood supply peritubular capillaries Vasa Recta glomerulus branch of renal artery afferent arterioles efferent arterioles branch of renal vein The glomerular capillaries drain into efferent arterioles not venules. ‘Portal System’
  56. 56. CORTEXMEDULLA The nephron
  57. 57. Nephron Structure (Draw)
  58. 58. vasa recta Slow blood flow: important to produce a concentrated urine
  59. 59. Three key process in urine formation: Ultrafiltration
  60. 60. Ultrafiltration • takes place in the glomerulus & Bowman’s capsule • is filtration under pressure • pressure comes from blood pressure (hydrostatic pressure)
  61. 61. Glomerulus & Bowman’s capsule
  62. 62. Hydrostatic pressure caused by: Efferent arteriole Afferent arteriole Filtration pressure GFR maintained • Diameter of the afferent arterioles bigger than the efferent arteriole •  blood enters glomerulus under high hydrostatic presssure • Pushes/filters small particles from the blood into the capsular space.
  63. 63. Glomerular Filtrate (GF): is the filtered fluid  chemical composition is similar to blood plasma, containing:- Glucose Amino acids Vitamins Ions Nitrogenous waste Some hormones Water Glomerular filtrate
  64. 64. Explain why proteins & RBC are not found in urine. Too large to be filtered.
  65. 65. But can blood ever be detected in urine? YES. But, this shows that something is wrong .
  66. 66. Ultrafiltration takes place through three layers: 1) Endothelium of the blood capillary 2) Basement membrane of the blood capillaries 3) Epithelium of the Bowman' capsule
  67. 67. Filtrate passes through 3 layers
  68. 68. Cells lining the Bowman’s capsule: Podocyte Squamous epithelium Podocytes are highly modified for filtration
  69. 69. Basement membrane Fenestrated capillaries (capillaries with windows)Permeable to substances < 100 nm endothelial cell fenestration nucleus Filtration Barrier
  70. 70. mesangial cells podocyte slit pore
  71. 71. glucoseamino acids (basement membrane) podocyte slit pore Na+ -- - - - --- - - - - - - - - - - - - - - - - -- - - - Limited permeability to molecules between 7000 > mwt > 70000 Da 4 nm > diameter > 8 nm Freely permeable to small molecules mwt < 7000 Da diameter < 4 nm Not permeable to large molecules mwt > 70000 Da diameter > 8 nm Water Permeablealbumin 60000 Da completely excluded… because of –ve charge endothelial cell fenestration
  72. 72. Bowman’s Capsule Bowman’s Space Proximal Tubule petesmif@liv.ac.uk
  73. 73. Hydrostatic Pressure
  74. 74. GLOMERULAR FILTRATE
  75. 75. Glomerular Filtrate Molecule or ion Approx. concentrations / g dm-3 Plasma Filtrate water protein glucose amino acids urea inorganic ions 900.0 80.0 1.0 0.5 0.3 7.2 900.0 0.0 1.0 0.5 0.3 7.2
  76. 76. Where does the glomerular filtrate go to after being formed?
  77. 77. Recap: What is ultrafiltration? Ultrafiltration begins in the Bowman's Capsule. a) Blood arrives in the kidney in the Afferent arteriole (with a wide blood vessel) at high pressure. b) Blood passes through the Glomerulus and passes out the Efferent arteriole (with a narrow blood vessel). c) Blood pressure increases in the Glomerulus. d) High hydrostatic pressure forces the plasma (liquid in blood - water, salts, amino acids, glucose and urea) out of the blood vessel into the inside of the Bowman's Capsule - This is called "Glomerular Filtrate."
  78. 78. After ultrafiltration 2 more processes 2) Reabsorbtion 3)Secretion
  79. 79. Function of the nephron is to : actively secrete waste substances from the blood capillaries to the tubules selectively reabsorb substances useful to the body
  80. 80. The Proximal Convoluted Tubule  longest (14 mm) and widest (60 m) part of the nephron carries filtrate from Bowman’s capsule to loop of Henle CORTEX MEDULLA
  81. 81. b) Reabsorption • Selective reabsorption takes place when substances move across the walls of the renal tubule into the capillary network. • It mostly occurs in the proximal convoluted tubule
  82. 82. Why Reabsorbtion? Molecule or ion Approx. concentrations / g dm-3 Plasma Filtrate water protein glucose amino acids urea inorganic ions 900.0 80.0 1.0 0.5 0.3 7.2 900.0 0.0 1.0 0.5 0.3 7.2
  83. 83. Selective reabsorption in the proximal convoluted tubule In humans: Glomerular filtrate production: 125 cm3 min-1 Urine production: 1 cm3 min-1 24 cm3 100 cm3 Urine 1 cm3 125 cm3
  84. 84. Proximal convoluted tubule • 65% water reabsorbed by osmosis into blood capillaries • All glucose, AA, vitamins & some salts reabsorbed by active transport • Urea not reabsorbed • GF – now only water, some salts & urea
  85. 85. Proximal Convoluted Tubule is composed of: a single layer of cuboidal epithelial cells with extensive microvilli forming a ‘brush border’ on the inside surface of the tubule Figure 44.9
  86. 86. Proximal Convoluted Tubule is adapted for reabsorption in three ways: 1.large surface area for absorption due to: Figure 44.9 Microvilli Basal channels BLOOD FILTRATE Tight junction Epithelial cell
  87. 87. Proximal Convoluted Tubule is adapted for reabsorption: Figure 44.9 2. numerous mitochondria (M) to provide ATP for active transport.
  88. 88. Proximal Convoluted Tubule is adapted for reabsorption: Figure 44.9 3.closeness of blood capillaries blood capillary Glomerular filtrate Microvilli Cuboidal epithelium
  89. 89. Over 80% of filtrate is reabsorbed in the proximal tubule REABSORBED  all the glucose, amino acids, vitamins, hormones  about 80% water  about 80% sodium  about 80% chloride  about 80% potassium  about 40-50% urea MECHANISM  diffusion + active transport  osmosis  diffusion + active transport  diffusion
  90. 90. Selective reabsorption of sodium and glucose in the proximal convoluted tubule Figure 44.9 Secondary Active Transport
  91. 91. Na+ glucoseNa+ ATP ADP Blood Urine Proximal tubule epithelial cell petesmif@liv.ac.uk
  92. 92. Question: Briefly describe the following processes in the context of urine formation in humans. a) Ultrafiltration. (2) Filtration of blood occurs under high pressure. Small molecules which can cross the glomerular lining, end up as glomerular filtrate inside the Bowman’s capsule. b) Selective reabsorption of glucose. (3) Occurs in the proximal convoluted tubule. All glucose is reabsorbed in a normal person but appears in urine in a diabetic one. Active transport is involved in the reabsorption of glucose.
  93. 93. THE LOOP OF HENLE Function: to conserve water the concentration of urine produced is directly related to the: length of the loop of Henle  thickness of the medulla relative to the cortex
  94. 94. The longer the loop of Henle, the more concentrated the urine that can be produced BEAVER (abundant water) RABBIT (moderate water) SAND RAT (scarce water)
  95. 95. Birds & Mammals are the only vertebrates: which can produce a urine which is more concentrated than the blood [hypertonic] with loops of Henle Loop of Henle
  96. 96. Three distinct regions in the loop of Henle Thin ascending limb Descending limb Thick ascending limb Thin walls Thick walls
  97. 97. Loop of Henle • 20% of water & some salts reabsorbed
  98. 98. REABSORPTION IN LOOP OF HENLE
  99. 99. Permeability of the loop of Henle to water: Highly permeable Descending limb Almost totally impermeable to waterThin ascending limb Thick ascending limb
  100. 100. Permeability of the loop of Henle to Na+ & Cl-ions: Not very permeable Descending limb Thin ascending limb Thick ascending limb Permeable Active secretion
  101. 101. What happens to the concentration of the fluid in the ascending limb as it reaches the distal convoluted tubule? The fluid becomes very dilute Distal convoluted tubule Reason: IONS are lost
  102. 102. WHY it is vital for ions to move out of the tubule? ions
  103. 103. To create an Osmotic Gradient From Cortex to Medulla PelvisMedulla Cortex The outer layer of the kidney is isotonic with the blood: ~300 milliosmoles/liter The innermost layer (medulla) is very hypertonic: ~1200 milliosmoles/liter
  104. 104. The concentration gradient allows: water to move out by osmosis from the descending loop of Henle
  105. 105. Osmotic gradient is produced by a:  countercurrent mechanism located in the loop of Henle What is a ‘countercurrent mechanism’?
  106. 106. Countercurrents exist when : fluids flow in opposite directions in parallel and adjacent tubes
  107. 107. Three Countercurrents: 1. the two limbs of the Henle's loop
  108. 108. Three Countercurrents: 1. the two limbs of the Henle's loop 2. the two limbs of the vasa recta
  109. 109. Three Countercurrents: 1. the two limbs of the Henle's loop 2. the two limbs of the vasa recta 3. the descending limb of Henle with the ascending limb of the vasa recta; the ascending limb of Henle and the descending vasa recta
  110. 110. Cortex Water leaves - ion concentra tion in filtrate increases Filtrate reaches maximum concentration Chloride ions out (sodium follows) - ion concentrat ion in filtrate decreases Medulla
  111. 111. To ureter Collecting duct •Several nephrons empty into one collecting duct. •The collecting duct passes through the progressively more concentrated medulla, losing water by osmosis. This water is reabsorbed by the capillaries. •This water is conserved, and a highly concentrated urine is produced. Water reabsorbed into vasa recta, urine becomes more concentrated Cortex Medulla
  112. 112. Question: [SEP, 2009] Briefly describe the role of each of the following in osmoregulation in humans: i) The descending limb of the Loop of Henle; (2) Is permeable to water. Functions towards water conservation. ii) The ascending limb of the Loop of Henle; (2) Is relatively impermeable to water but permeable to salts. The tissue fluid inside the medulla becomes concentrated as salts move out of the ascending limb. This causes water to be drawn out of the descending limb.
  113. 113. Question: The diagram below shows the simplified structure of a human nephron.the loop of Henle Substance Quantity passing through P Quantity passing through Q % reabsorbed Water 180 dm3 1.5 dm3 99.17% Glucose 180 g 0 g 100% Urea 53 g 25 g 52.8% The table below represents the quantities of water, glucose and urea passing through P and Q over a period of time, while the last column shows the percentage reabsorption during the same period of time.
  114. 114. Question: a) Relate the role of structure R to the filtrate composition as it passes through Q. (5) Structure Q is permeable to water. Water is reabsorbed by the vasa recta as fluid passes through Q. This is possible because the ascending limb creates the ideal concentration gradient within the medulla by losing ions. The thin ascending limb of Structure R is permeable to ions but impermeable to water. The thick ascending limb of Structure R allows ions to move actively out of it and is also impermeable to water. Loss of ions from the whole ascending limb, creates an ever increasing salt concentration on moving deeper into the medulla.
  115. 115. Question: Substance Quantity passing through P Quantity passing through Q % reabsorbed Water 180 dm3 1.5 dm3 99.17% Glucose 180 g 0 g 100% Urea 53 g 25 g 52.8% b) Explain the biological significance of the percentage reabsorption of water and urea. (3) Most of the water is reabsorbed to avoid dehydration. Only half of the urea is reabsorbed so that it contributes to the concentration of solutes in the medulla. A high solute concentration is needed to ensure reabsorption of water from the loop of Henle.
  116. 116. Distal convoluted tubule Reabsorption & Secretion occur • More H2O reabsorbed  osmosis • Na+ and Cl- , HCO3 - ions are reabsorbed  active transport • Secretion of NH4 -, H+, some drugs & poisons  active transport
  117. 117. COLLECTING DUCT • More water leaves the tube by osmosis, since the tube is surrounded by salty tissue. • Some urea leaves by diffusion, and may be cycled through the system. • More Na+ and Cl- reabsorbed by active transport
  118. 118. Summary: REABSORPTION 1. Proximal tubule • Glucose, amino acid, Na+ and Cl- (active transport) • Water, HCO3 - (passive transport) 2. Loop of Henle • Na+ and Cl- (active transport) • Water (passive transport) 3. Distal tubule • Na+ and Cl- , HCO3- (active transport) • Water (passive transport) 4. Collecting duct • Na+ and Cl- (active transport) • Water, urea (passive transport)
  119. 119. 3. Secretion • By active transport • Occurs only in the PROXIMAL TUBULE & DISTAL TUBULE • Proximal tubule – NH4-, H+, some drugs & poisons • Distal tubule – K+, H+ • Substances not filtered in the glomerulus are secreted into the renal tubule to be excreted. • Reason: 1. To get rid of certain substances 2. To regulate blood pH
  120. 120. 1. Urine from collecting duct drips into pelvis 2. passes via the ureter to the bladder 3. Stored in bladder 4. Once ~200 cm3 urine collected, stretch receptor stimulated desire to urinate
  121. 121. OSMOREGULATION, ADH & URINE FORMATION
  122. 122. In this topic we mention TWO hormones that affect the kidneys: Urine ADH (antidiuretic hormone) Posterior pituitary Adrenal cortex Aldosterone
  123. 123. ADH : 1. increases the permeability of the distal convoluted tubule and collecting duct to water More ADH, more water is reabsorbed.
  124. 124. 2. increases the permeability of the collecting duct to urea 1. Urea moves into medulla 2. Medulla becomes concentrated RESULT: 3. Water moves out of descending limb
  125. 125. ADH is released when osmoreceptors: detect a low level of water in blood kidney
  126. 126. Water Salts Fig. 21 The effect of ADH on the permeability of the distal convoluted tubule and collecting duct to water Blood too concentrated ADH level high Blood too dilute ADH level low Dilute urine Urine concentrated Water Salts
  127. 127. Reabsorbing water If you have too little water in your blood, you will produce very concentrated urine. (very little water in it) If you have too much water in your blood, you will produce very dilute urine. (lots of water in it)
  128. 128. Water level regulation by negative feedback control
  129. 129. Water content of the blood normal Water content of the blood HIGH Water content of the blood LOW Too much water drunk Too much salt or sweating Brain produces More ADH Urine output LOW Brain produces Less ADH Urine output HIGH High volume of water reabsorbed by kidney Low volume of water reabsorbed by kidney (small volume of Concentrated urine) (large volume of dilute urine)
  130. 130. Release of ADH from the posterior pituitary is inhibited by drinking alcohol & caffeine. How would this affect urination? Increases ADH
  131. 131. Failure to release sufficient ADH leads to a condition: DIABETES INSIPIDUS large quantities of dilute urine are produced could lead to dehydration  death
  132. 132. ALDOSTERONE:  is secreted by the adrenal cortex  stimulates sodium reabsorption in the nephron  stimulates excretion of potassium ions Control of Blood Sodium Level: Aldosterone is a: Steroid hormone
  133. 133. Aldosterone causes: 2. K+ to move into lumen & ends in urine 1. Na+ ions to be pumped from distal tubule into the blood capillaries TS distal tubule K+ Na+ RESULT OF more Na+ in blood is…. More aldosterone secreted, more Na+ ions reabsorbed from distal tubule into the blood capillaries
  134. 134. A decrease in blood Na leads to a decrease in blood volume. WHY? Because less water enters the blood by osmosis. Less water = reduction in blood pressure
  135. 135. b) Complete the table below by filling in the empty spaces with the appropriate answers: (3) Hormone Site of production Effect Antidiuretic hormone Hypothalamus Stimulates distal convoluted tubule and collecting duct to reabsorb water Aldosterone Adrenal cortex Stimulates excretion of potassium ions and reabsorption of sodium ions in the nephron
  136. 136. Factors that affect kidney function • Antidiuretic hormone (ADH) – prevents excess water loss from kidneys • Alcohol – inhibits secretion of ADH = more urine volume • Aldosterone – prevents excess loss of sodium and water from kidneys • Caffeine – increases rate of salt and water loss from kidneys • Increased blood pressure – increase rate of water loss from kidneys.
  137. 137. IIMPAIRED KIDNEY FUNCTION
  138. 138. Kidney transplant
  139. 139. HAEMODIALYSIS
  140. 140. HAEMODIALYSIS
  141. 141. HAEMODIALYSIS VIDEO
  142. 142. KIDNEY STONES
  143. 143. KIDNEY STONES
  144. 144. Cause of kidney stones • Exact cause of kidney stones cannot always be found, although they are usually formed following a build-up of a substance such as calcium. • The leading cause of kidney stones is a lack of water. • A kidney stone is formed when a small speck of mineral settles out of the urine into the kidney or the ureter, a tube that links the kidney to the bladder.
  145. 145. Control of Blood pH
  146. 146. Longer-term adjustments in the ion balance of the blood : are made in the distal convoluted tubule If the pH falls below 7.4: distal tubule cells secrete H+ into the urine If the pH rises: Distal tubule cells secrete OH- & HCO3 - into the urine H+ HCO3 - OH-
  147. 147. Manneken Piss [Brussels, Belgium]
  148. 148. THE END OF URINARY SYSTEM

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