14 Land animals manage water budgets by drinking and eating moist foods and using metabolic water Water balance in a kangaroo rat (2 mL/day) Water balance in a human (2,500 mL/day) Water gain Water loss Derived from metabolism (1.8 mL) Ingested in food (0.2 mL) Derived from metabolism (250 mL) Ingested in food (750 mL) Ingested in liquid (1,500 mL) Evaporation (900 mL) Feces (100 mL) Urine (1,500 mL) Evaporation (1.46 mL) Feces (0.09 mL) Urine (0.45 mL)
15 if water intake water loss affects water content in blood affects water potential of tissue fluid water enters or leaves cells by osmosis cells do not function properly or even die 1.1 Importance of regulating water content
16 control of the water content in the body osmoregulation ( 滲透調節 ) done by kidneys of urinary system ( 泌尿系統 ) 1.1 Importance of regulating water content
17 1 keeps the water potential of the tissue fluid and hence the water potential of the cells stable, so that cells can function properly to sustain life. Osmoregulation 1.1 Importance of regulating water content
18 2 The of the system are the major organs for osmoregulation. kidneys 1.1 Importance of regulating water content urinary
19 1.2 The human urinary system (dorsal aorta) female (posterior vena cava) (renal artery) (renal vein)
20 1.2 The human urinary system female kidneys ureters urinary bladder
21 1.2 The human urinary system female sphincter muscles control urination
22 1.2 The human urinary system female urethra male
23 1.2 The human urinary system male ureters urinary bladder (vas deferens) urethra (penis)
24 1.1 Examination of the mammalian urinary system Video 1.2 The human urinary system 1 Examine the urinary system of a dissected rat. 2 Identify the structures.
25 1.2 The human urinary system Structure of the kidney 3D model cortex ( 皮質 ) medulla ( 髓 ) pelvis ( 腎盂 ) renal vein renal artery ureter
26 1.2 The human urinary system Structure of the kidney
27 1.2 The human urinary system Structure of the kidney cortex medulla
28 1.2 The human urinary system Structure of the kidney branch from renal artery branch from renal vein
29 1.2 The human urinary system Structure of the kidney nephron ( 腎元 )
30 Filtration Reabsorption Secretion Excretion Excretory tubule Capillary Filtrate Urine Key functions of most excretory systems: Filtration: pressure- filtering of body fluids Reabsorption: reclaiming valuable solutes Secretion: adding toxins and other solutes from the body fluids to the filtrate
31 1.2 The human urinary system Structure of the kidney Bowman’s capsule proximal convoluted tubule collecting duct distal convoluted tubule loope of Henle kidney tubule
32 1.2 The human urinary system Structure of the kidney Bowman’s capsule proximal convoluted tubule collecting duct distal convoluted tubule flow of urine from another nephron loop of Henle
33 1.2 The human urinary system Structure of the kidney glomerulus Bowman’s capsule kidney tubule
34 Capillary Beds of the Nephron has two capillary bedsEvery nephron has two capillary beds –Glomerulus –Peritubular capillaries Each glomerulus is: –Fed by an afferent arteriole –Drained by an efferent arteriole
35 1.2 The human urinary system Blood supply of a nephron branch from renal artery afferent arteriole glomerulus efferent arteriole Peritubular capillary branch from renal vein
36 1.2 Examination of the mammalian kidney The human urinary system 1 Put a fresh pig’s kidney on a dissection tray. 2 Examine whether there are tubes coming from the kidney. Remove any fatty tissues and identify the tubes.
37 1.2 The human urinary system 3 Cut the kidney longitudinally.
38 1.2 The human urinary system 4 Identify various structures of the kidney. 5 Draw a labelled diagram of the longitudinal section of the kidney.
39 1.2 The human urinary system 1 Parts of urinary system Function Purify blood and form urine Carry urine from kidneys to urinary bladder Kidneys Ureters
40 1.2 The human urinary system 1 Parts of urinary system Function Stores urine temporarily Carries urine from urinary bladder to the outside Urinary bladder Urethra
41 a A nephron consists of the 2 Structure of a nephron: Bowman’s capsule 1.2 The human urinary system, the proximal convoluted tubule the, distal convoluted tubule and the. collecting duct
42 b The Bowman’s capsule encloses a network of capillaries called the 2 Structure of a nephron: glomerulus 1.2 The human urinary system. The kidney tubule is surrounded by another network of capillaries which is continuous with the glomerulus.
43 ultrafiltration ( 超濾 ) reabsorption ( 重吸收 ) 1.3 Functioning of a nephron urine is formed by mainly two processes:
44 Active secretion 1.3 Functioning of a nephron and: ultrafiltration reabsorption
45 Mechanism of Urine Formation Urine formation and adjustment of blood composition involve three major processes –Glomerular filtration –Tubular reabsorption –Active Secretion Figure 24.9
46 1 Ultrafiltration blood is under high hydrostatic pressure 1.3 Functioning of a nephron glomerulus forces small molecules through the thin walls Bowman’s capsule capillary wall is differentially permeable
47 1 Ultrafiltration 1.3 Functioning of a nephron glucose amino acids water salts urea
48 1 Ultrafiltration fluid filtered into the Bowman’s capsule: glomerular filtrate 1.3 Functioning of a nephron to proximal convoluted tubule
49 1 Ultrafiltration 1.3 Functioning of a nephron to proximal convoluted tubule water glucose amino acids salts urea plasma proteins composition similar to plasma
50 Net Filtration Pressure (NFP) The pressure responsible for filtrate formation NFP equals the glomerular hydrostatic pressure (HP g ) minus the osmotic pressure of glomerular blood (OP g ) combined with the capsular hydrostatic pressure (HP c ) NFP = HP g – (OP g + HP c )
52 2 Reabsorption absorption of useful substances and most of the water from the filtrate to the blood 1.3 Functioning of a nephron Your kidneys filter approximately 180L of plasma/day 99% of the filtrate gets reabsorbed, leaving 1.5-2 L of urine per day Your kidneys filter approximately 180L of plasma/day 99% of the filtrate gets reabsorbed, leaving 1.5-2 L of urine per day
53 2 Reabsorption 1.3 Functioning of a nephron from renal artery flow of urine to renal vein
54 Sodium Reabsorption: Primary Active Transport Tubule lumen with renal fluid
55 Glucose Reabsorption: Secondary Active Transport
56 Reabsorption: Both Primary and secondary Active Transport Sodium reabsorption is almost always by active transport –Na + enters the tubule cells from the lumen / filtrate –Na + is actively transported out of the tubules by a Na + - K + ATPase pump From there it moves to peritubular capillaries Na + reabsorption provides the energy and the means for reabsorbing most other solutes
60 2 Reabsorption 1.3 Functioning of a nephron proximal convoluted tubuleblood glucose amino acids water salts amino acids
61 2 Reabsorption 1.3 Functioning of a nephron Substance reabsorbed Process Region where reabsorption occurs Glucose (100%) Amino acids (100%) Water (99%) Salts (80%) Urea (50%) Diffusion, active transport Osmosis Diffusion, active transport Diffusion At proximal convoluted tubule, loop of Henle, distal convoluted tubule & collecting duct At proximal convoluted tubule only
63 2 Reabsorption 1.3 Functioning of a nephron kidney tubule is highly coiled to increase the surface area and the time for reabsorption
64 2 Reabsorption 1.3 Functioning of a nephron remaining glomerular filtrate in collecting duct is called urine mostly water with salts, urea and other metabolic waste
65 Essentially reabsorption in reverse, where substances move from peritubular capillaries or tubule cells into filtrate Tubular secretion is important for: –Eliminating undesirable substances such as urea and uric acid –Controlling blood pH 3. Secretion
66 1.3 Functioning of a nephron Proteins pass through the walls of the glomerulus and the Bowman’s capsule.
67 1.3 Functioning of a nephron It is the amino acids that are filtered into the Bowman’s capsule and reabsorbed later.
68 1 In ultrafiltration, the high hydrostatic pressure 1.3 Functioning of a nephron glomerulus forces small molecules out of the blood into the Bowman’s capsule. inside the
69 The capillary wall of the glomerulus is 1 differentially permeable 1.3 Functioning of a nephron only allows small molecules to pass through. and
70 2 The composition of the glomerular filtrate is similar to that of plasma but it contains no. plasma proteins 1.3 Functioning of a nephron
71 1.3 Functioning of a nephron a All and 3 Reabsorption along the kidney tubule: glucose amino acids in the glomerular filtrate are reabsorbed into the blood by diffusion and active transport.
72 1.3 Functioning of a nephron b Most is reabsorbed by osmosis. 3 Reabsorption along the kidney tubule: water
73 1.3 Functioning of a nephron c Some are reabsorbed by diffusion and active transport. 3 Reabsorption along the kidney tubule: salts
74 1.3 Functioning of a nephron d Some is reabsorbed by diffusion and the rest is removed in the urine. 3 Reabsorption along the kidney tubule: urea
75 1.4 The role of the kidneys kidneys carry out osmoregulation by controlling the amount of water reabsorbed from the glomerular filtrate Osmoregulation
76 the amount of water reabsorbed is controlled by antidiuretic hormone (ADH) ( 抗利尿激素 ) 1.4 The role of the kidneys secretion of ADH is controlled by the hypothalamus ( 下丘腦 )
77 Diuresis Diuretics are a group of drugs given to help the body eliminate excess fluid through the kidneys. e.g. to treat hypertension, glaucoma, et Natural diuretic foods and drinks Melon Watercress Coffee Tea Coke (caffeinated soda)
78 1.4 The role of the kidneys hypothalamus has receptors to detect water content in blood controls secretion of ADH
79 1.4 The role of the kidneys pituitary gland secretes ADH ADH is transported by blood
80 under the action of ADH 1.4 The role of the kidneys permeability of the wall of the collecting duct to water increases a greater proportion of water is reabsorbed from the filtrate urine in different volumes and concentrations can be formed
81 Figure 20-4 Urine Concentration Osmolarity changes as filtrate flows through the nephron
82 Formation of Dilute Urine / hypotonic urine Filtrate is hypotonic after passing through the 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 Collecting ducts remain impermeable to water; no further water reabsorption occurs Diuresis – hypotonic urine (large volume of)
84 Figure 20-5a Water Reabsorption Water movement in the collecting duct in the presence of vasopressin (ADH)
85 Formation of Concentrated / hypertonic Urine Antidiuretic hormone (ADH) inhibits diuresis In the presence of ADH, 99% of the water in filtrate is reabsorbed ADH is the signal to produce concentrated urine The kidneys’ ability to respond depends upon the high medullary osmotic gradient
86 The kidneys’ ability to make hypertonic urine depends upon the high medullary osmotic gradient Click the diagram to see an animation
87 1.4 The role of the kidneys receptors in hypothalamus water content increases normal water content in blood wall of collecting duct pituitary gland less ADH detected by less permeable smaller proportion of water reabsorbed larger volume of dilute urine
88 receptors in hypothalamus water content decreases normal water content in blood wall of collecting duct pituitary gland more ADH detected by more permeable smaller volume of concentrated urine greater proportion of water reabsorbed 1.4 The role of the kidneys
89 Filtrate H 2 O Salts (NaCl and others) HCO 3 – ; H + (control pH) Urea Glucose; amino acids Some drugs Key Active transport Passive transport INNER MEDULLA OUTER MEDULLA NaCl H 2 O CORTEX Descending limb of loop of Henle Proximal tubule NaCl Nutrients HCO 3 – H + K + NH 3 H 2 O Distal tubule NaCl HCO 3 – H + K + H 2 O Thick segment of ascending limb NaCl Thin segment of ascending limb Collecting duct Urea H 2 O
90 Figure 20-6 Water Reabsorption (reference) The mechanism of vasopressin action Collecting duct lumen Filtrate 300 mOsm H2OH2O Exocytosis of vesicles Cross-section of kidney tubule Collecting duct cell Second messenger signal H2OH2O cAMP Storage vesicles Aquaporin-2 water pores 600 mOsM H2OH2O Medullary interstitial fluid Vasopressin receptor 600 mOsM Vasa recta H2OH2O 700 mOsM Vasopressin binds to mem- brane receptor. Receptor activates cAMP second messenger system. Cell inserts AQP2 water pores into apical membrane. Water is absorbed by osmosis into the blood. 123 4 1 2 3 4
96 Figure 20-8 Water Balance The effect of plasma osmolarity on vasopressin secretion by the posterior pituitary
97 smaller amount of salts and greater proportion of water reabsorbed higher concentration of salts in blood smaller volume of urine with a high salt concentration formed (hypertonic urine) taking in excess salts 1.4 The role of the kidneys
98 Regulation of Kidney Function The osmolarity of the urine is regulated by nervous and hormonal control of water and salt reabsorption in the kidneys Antidiuretic hormone (ADH) increases water reabsorption in the distal tubules and collecting ducts of the kidney
99 Osmoreceptors in hypothalamus Hypothalamus ADH Pituitary gland Increased permeability Distal tubule Thirst Drinking reduces blood osmolarity to set point Collecting duct H 2 O reab- sorption helps prevent further osmolarity increase Homeostasis: Blood osmolarity STIMULUS The release of ADH is triggered when osmo- receptor cells in the hypothalamus detect an increase in the osmolarity of the blood
100 What’s the effect of the following on urine output : 1. a lot of water 2. a lot of salty foods 3. a large volume of salty solution. E.g seawater Assignment Assignment: 1.Explain why we cannot survive on seawater as drinking water. 2. Write an essay on how one can survive without drinking water while drifting on a raft in the open ocean (>300 words)
101 by forming urine Excretion 1.4 The role of the kidneys to remove metabolic waste (e.g. urea)
102 by forming urine Excretion 1.4 The role of the kidneys to remove metabolic waste (e.g. urea) constantly produced high concentration is toxic
103 Diuretics (reference) Chemicals that enhance the urinary output include: –Any substance not reabsorbed –Substances that exceed the ability of the renal tubules to reabsorb it 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 – inhibits Na + -K + -2Cl symporters
104 Physical Characteristics of Urine (reference) Color and transparency –Clear, pale to deep yellow (due to urobilin) -from the breakdown of hemeheme –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
105 Concentrated urine has a deeper yellow color
106 Physical Characteristics of Urine Odor / smell –Fresh urine is slightly aromatic –Standing urine develops an ammonia odor –Some drugs and vegetables (asparagus) alter the usual odor
107 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 1.001 to 1.035 –Dependent on solute concentration
108 Chemical Characteristics of Urine Urine is 95% water and 5% solutes Nitrogenous wastes include 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 Disease states alter urine composition dramatically
109 Functions of the Kidneys Regulation of extracellular fluid volume and blood pressure Regulation of osmotic potential in blood Maintenance of ion balance Homeostatic regulation of pH Excretion of wastes
110 secretes less ADH pituitary gland 1.4 The role of the kidneys 1 Regulation of water content by negative feedback mechanism: normal water content in blood high water content in blood hypothalamus kidneys
111 1.4 The role of the kidneys In the kidneys: awall of collecting duct becomes permeable to water less ba proportion of water reabsorbed smaller ca volume of urine is formed larger dilute
112 secretes less ADH pituitary gland 1.4 The role of the kidneys 1 Regulation of water content by negative feedback mechanism: normal water content in blood high water content in blood hypothalamus kidneys water content in blood falls
113 secretes more ADH pituitary gland 1.4 The role of the kidneys 1 Regulation of water content by negative feedback mechanism: normal water content in blood low water content in blood hypothalamus kidneys
114 1.4 The role of the kidneys In the kidneys: awall of collecting duct becomes permeable to water more ba proportion of water reabsorbed greater ca volume of urine is formed smaller concentrated
115 secretes more ADH pituitary gland 1.4 The role of the kidneys 1 Regulation of water content by negative feedback mechanism: normal water content in blood low water content in blood hypothalamus kidneys water content in blood rises
116 2 After excess salts are taken into the body, the excess salts have to be excreted. A amount of salts and a proportion of water are reabsorbed. As a result, a smaller 1.4 The role of the kidneys greater small volume of urine with a high salt concentration is formed.
117 3 Excretion is necessary because metabolic waste is constantly produced and a high concentration of this waste is to the body. The kidneys form to remove metabolic waste (e.g. urea) from the blood. 1.4 The role of the kidneys toxic urine
118 1.5 The dialysis machine kidney machine Animation helps remove metabolic waste by haemodialysis ( 血液透析 )
119 1.5 The dialysis machine 1 blood with metabolic waste pump dialysis tubing fresh dialysis fluid
120 1.5 The dialysis machine dialysis tubing fresh dialysis fluid same concentration of solutes as normal plasma but has no metabolic waste
121 1.5 The dialysis machine dialysis tubing fresh dialysis fluid constant temperature bath dialysis fluid
122 1.5 The dialysis machine differentially permeable membrane of dialysis tubing
123 1.5 The dialysis machine 2 urea diffuses through the pores to the dialysis fluid
124 1.5 The dialysis machine 3 glucose is retained in blood (no net movement from blood to dialysis fluid
125 1.5 The dialysis machine 4 plasma proteins and blood cells are too large to pass through the pores
126 1.5 The dialysis machine 5 ‘cleaned’ blood used dialysis fluid (with urea)
127 1.5 The dialysis machine each treatment lasts for 4-6 hours three times a week costly
128 Peritoneal dialysis Peritoneal dialysis (PD) is a treatment for patients with severe chronic kidney disease. The process uses the patient's peritoneum in the abdomen as a membrane across which fluids and dissolved substances are exchanged from the blood.dialysiskidney diseaseperitoneumabdomenblood
130 1 A dialysis machine removes metabolic waste patient’s blood. from the 1.5 The dialysis machine
131 2 The dialysis fluid has the same concentration of solutes as normal plasma 1.5 The dialysis machine This allows metabolic waste to diffuse from the patient’s blood to the dialysis fluid while but no metabolic waste. glucose and other useful substances are retained in the blood.
132 Why may a person die quickly if the kidneys fail to function? 1 When the kidneys fail to function, the body cannot keep the water content in blood stable for cells to function properly.
133 Why may a person die quickly if the kidneys fail to function? 1 Besides, metabolic waste builds up in blood which can cause death.
134 How does a kidney machine treat kidney failure? 2 A kidney machine removes metabolic waste from the patient’s blood by haemodialysis.
135 Why can’t people with kidney failure take in too much fluid and high-protein food? 3 Excess proteins in the body are converted to urea by the liver.
136 3 The failed kidney cannot remove excess fluid and urea from the body. Why can’t people with kidney failure take in too much fluid and high-protein food?
137 3 Therefore, excessive intake of fluid and high-protein food must be avoided. Why can’t people with kidney failure take in too much fluid and high-protein food?
138 detected by is the maintenance of a stable Osmoregulation water content in blood hypothalamus urinary system done by kidneys main parts include
139 hypothalamus kidneys controls secretion of antidiuretic hormone functional units nephrons controls concentration and volume of form urine
140 by ultrafiltration kidneysurine reabsorption helps body remove fail to function can be treated by metabolic waste contains dialysis machine