14Land animals manage water budgets by drinking and eating moist foods and using metabolic water balance in akangaroo rat(2 mL/day)balance ina human(2,500 mL/day)gainlossDerived frommetabolism (1.8 mL)Ingestedin food (0.2 mL)metabolism (250 mL)in food(750 mL)in liquid(1,500 mL)Evaporation (900 mL)Feces (100 mL)UrineEvaporation (1.46 mL)Feces (0.09 mL)(0.45 mL)
151.1 Importance of regulating water content 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
161.1 Importance of regulating water content control of the water content in the bodyosmoregulation (滲透調節)done by kidneys of urinary system (泌尿系統)
171.1Importance of regulating water contentkeeps 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
182 The of the system are the major organs for osmoregulation. 1.1Importance of regulating water content2 The of the system are the major organs for osmoregulation.kidneysurinary
191.2 The human urinary system (dorsal aorta)(posterior vena cava)(renal artery)(renal vein)female
201.2 The human urinary system kidneysuretersurinary bladderfemale
21control urination 1.2 The human urinary system sphincter muscles female
231.2 The human urinary system uretersurinary bladder(vas deferens)urethra(penis)male
24Examination of the mammalian urinary system 1.2The human urinary systemVideo1.1Examination of the mammalian urinary system1 Examine the urinary system of a dissected rat.2 Identify the structures.
25Structure of the kidney 1.2The human urinary systemStructure of the kidney3D modelcortex (皮質)medulla (髓)renal veinpelvis (腎盂)renal arteryureter
26Structure of the kidney 1.2The human urinary systemStructure of the kidney
27Structure of the kidney 1.2The human urinary systemStructure of the kidneycortexmedulla
28Structure of the kidney 1.2The human urinary systemStructure of the kidneybranch from renal arterybranch from renal vein
29Structure of the kidney 1.2The human urinary systemStructure of the kidneynephron (腎元)
30Key functions of most excretory systems: Filtration: pressure-filtering of body fluidsReabsorption: reclaiming valuable solutesSecretion: adding toxins and other solutes from the body fluids to the filtrateCapillaryExcretorytubuleFiltrationFiltrateReabsorptionSecretionUrineExcretion
31Structure of the kidney 1.2The human urinary systemStructure of the kidneyproximal convoluted tubuledistal convoluted tubuleBowman’s capsulekidney tubuleloope of Henlecollecting duct
32Structure of the kidney 1.2The human urinary systemStructure of the kidneyproximal convoluted tubuledistal convoluted tubuleflow of urineBowman’s capsulefrom another nephronloop of Henlecollecting duct
33Structure of the kidney 1.2The human urinary systemStructure of the kidneyglomerulusBowman’s capsulekidney tubule
34Capillary Beds of the Nephron Every nephron has two capillary bedsGlomerulusPeritubular capillariesEach glomerulus is:Fed by an afferent arterioleDrained by an efferent arteriole
35Blood supply of a nephron 1.2The human urinary systemBlood supply of a nephronefferent arterioleglomerulusafferent arteriolePeritubularcapillarybranch from renal arterybranch from renal vein
36Examination of the mammalian kidney 1.2The human urinary system1.2Examination of the mammalian kidney1 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.
373 Cut the kidney longitudinally. 1.2The human urinary system1.23 Cut the kidney longitudinally.
384 Identify various structures of the kidney. 1.2The human urinary system1.24 Identify various structures of the kidney.5 Draw a labelled diagram of the longitudinal section of the kidney.
39Parts of urinary system 1.2The human urinary system1Parts of urinary systemFunctionPurify blood and form urineCarry urine from kidneys to urinary bladderKidneysUreters
40Parts of urinary system 1.2The human urinary system1Parts of urinary systemFunctionStores urine temporarilyCarries urine from urinary bladder to the outsideUrinary bladderUrethra
41proximal convoluted tubule distal convoluted tubule 1.2The human urinary system2 Structure of a nephron:a A nephron consists of theBowman’s capsule, theproximal convoluted tubule,thedistal convoluted tubuleand thecollecting duct
422 Structure of a nephron: 1.2The human urinary system2 Structure of a nephron:b The Bowman’s capsule encloses a network of capillaries called theglomerulus. The kidney tubuleis surrounded by another network of capillaries which is continuous with the glomerulus.
43ultrafiltration reabsorption 1.3 Functioning of a nephronurine is formed by mainly two processes:ultrafiltration(超濾)reabsorption(重吸收)
44ultrafiltration reabsorption Active secretion 1.3 Functioning of a nephronand:ultrafiltrationreabsorptionActive secretion
45Mechanism of Urine Formation Urine formation and adjustment of blood composition involve three major processesGlomerular filtrationTubular reabsorptionActiveSecretionFigure 24.9
461 Ultrafiltration blood is under high hydrostatic pressure 1.3Functioning of a nephron1 UltrafiltrationBowman’s capsuleblood is under high hydrostatic pressurecapillary wall is differentially permeableforces small molecules through the thin wallsglomerulus
471 Ultrafiltration urea salts glucose water amino acids 1.3 Functioning of a nephron1 Ultrafiltrationureasaltsglucosewateramino acids
481.3Functioning of a nephron1 Ultrafiltrationfluid filtered into the Bowman’s capsule: glomerular filtrateto proximal convoluted tubule
49 1 Ultrafiltration composition similar to plasma water 1.3Functioning of a nephron1 Ultrafiltrationcomposition similar to plasmawaterplasma proteinsglucoseamino acidssaltsureato proximal convoluted tubule
50Net Filtration Pressure (NFP) The pressure responsible for filtrate formationNFP equals the glomerular hydrostatic pressure (HPg) minus the osmotic pressure of glomerular blood (OPg) combined with the capsular hydrostatic pressure (HPc)NFP = HPg – (OPg + HPc)
521.3Functioning of a nephron2 Reabsorptionabsorption of useful substances and most of the water from the filtrate to the bloodYour kidneys filter approximately 180L of plasma/day99% of the filtrate gets reabsorbed, leaving L of urine per day
532 Reabsorption to renal vein flow of urine from renal artery 1.3 Functioning of a nephron2 Reabsorptionto renal veinflow of urinefrom renal artery
54Sodium Reabsorption: Primary Active Transport Tubule lumen with renal fluid
55Glucose Reabsorption: Secondary Active Transport
56Reabsorption: Both Primary and secondary Active Transport Sodium reabsorption is almost always by active transportNa+ enters the tubule cells from the lumen / filtrateNa+ is actively transported out of the tubules by a Na+-K+ ATPase pumpFrom there it moves to peritubular capillariesNa+ reabsorption provides the energy and the means for reabsorbing most other solutes
631.3Functioning of a nephron2 Reabsorptionkidney tubule is highly coiled to increase the surface area and the time for reabsorption
64mostly water with salts, urea and other metabolic waste 1.3Functioning of a nephron2 Reabsorptionremaining glomerular filtrate in collecting duct is called urinemostly water with salts, urea and other metabolic waste
653. SecretionEssentially reabsorption in reverse, where substances move from peritubular capillaries or tubule cells into filtrateTubular secretion is important for:Eliminating undesirable substances such as urea and uric acidControlling blood pH
661.3Functioning of a nephronProteins pass through the walls of the glomerulus and the Bowman’s capsule.
671.3Functioning of a nephronIt is the amino acids that are filtered into the Bowman’s capsule and reabsorbed later.
681 In ultrafiltration, the high 1.3Functioning of a nephron1 In ultrafiltration, the highhydrostatic pressureinside theglomerulus forces small molecules out of the blood into the Bowman’s capsule.
69differentially permeable 1.3Functioning of a nephron1The capillary wall of the glomerulus isdifferentially permeableandonly allows small molecules to pass through.
701.3Functioning of a nephron2 The composition of the glomerular filtrate is similar to that of plasma but it contains noplasma proteins
713 Reabsorption along the kidney tubule: 1.3Functioning of a nephron3 Reabsorption along the kidney tubule:a All andglucoseamino acidsin the glomerular filtrate are reabsorbed into the blood by diffusion and active transport.
723 Reabsorption along the kidney tubule: 1.3Functioning of a nephron3 Reabsorption along the kidney tubule:b Most is reabsorbed by osmosis.water
733 Reabsorption along the kidney tubule: 1.3Functioning of a nephron3 Reabsorption along the kidney tubule:c Some are reabsorbed by diffusion and active transport.salts
743 Reabsorption along the kidney tubule: 1.3Functioning of a nephron3 Reabsorption along the kidney tubule:d Some is reabsorbed by diffusion and the rest is removed in the urine.urea
751.4 The role of the kidneysOsmoregulationkidneys carry out osmoregulation by controlling the amount of water reabsorbed from the glomerular filtrate
76secretion of ADH is controlled by the hypothalamus (下丘腦) 1.4The role of the kidneysthe amount of water reabsorbed is controlled by antidiuretic hormone (ADH) (抗利尿激素)secretion of ADH is controlled by the hypothalamus (下丘腦)
77DiuresisDiuretics are a group of drugs given to help the body eliminate excess fluid through the kidneys. e.g. to treat hypertension, glaucoma, etNatural diuretic foods and drinksMelonWatercressCoffeeTeaCoke (caffeinated soda)
78has receptors to detect water content in blood 1.4The role of the kidneyshypothalamushas receptors to detect water content in bloodcontrols secretion of ADH
79ADH is transported by blood 1.4The role of the kidneyspituitary glandsecretes ADHADH is transported by blood
80 permeability of the wall of the collecting duct to water increases 1.4The role of the kidneysunder the action of ADH permeability of the wall of the collecting duct to water increases a greater proportion of water is reabsorbed from the filtrateurine in different volumes and concentrations can be formed
81Urine ConcentrationOsmolarity changes as filtrate flows through the nephronFigure 20-481
82Formation of Dilute Urine / hypotonic urine Filtrate is hypotonic after passing through the loop of HenleDilute urine is created by allowing this filtrate to continue into the renal pelvisThis will happen as long as antidiuretic hormone (ADH) is not being secretedCollecting ducts remain impermeable to water; no further water reabsorption occursDiuresis – hypotonic urine (large volume of)
84Water ReabsorptionWater movement in the collecting duct in the presence of vasopressin (ADH)Figure 20-5a84
85Formation of Concentrated / hypertonic Urine Antidiuretic hormone (ADH) inhibits diuresisIn the presence of ADH, 99% of the water in filtrate is reabsorbedADH is the signal to produce concentrated urineThe kidneys’ ability to respond depends upon the high medullary osmotic gradient
86Click the diagram to see an animation The kidneys’ ability to make hypertonic urine depends upon the high medullary osmotic gradientClick the diagram to see an animation
87receptors in hypothalamus pituitary gland less ADH detected by 1.4The role of the kidneysreceptors in hypothalamuspituitary glandless ADHdetected bywall of collecting ductwater content increasesless permeablesmaller proportion of water reabsorbednormal water content in bloodlarger volume of dilute urine
88smaller volume of concentrated urine normal water content in blood 1.4The role of the kidneyssmaller volume of concentrated urinenormal water content in bloodgreater proportion of water reabsorbedwater content decreasesmore permeablewall of collecting ductdetected byreceptors in hypothalamusmore ADHpituitary gland
96Water BalanceThe effect of plasma osmolarity on vasopressin secretion by the posterior pituitaryFigure 20-896
97higher concentration of salts in blood 1.4The role of the kidneystaking in excess saltshigher concentration of salts in bloodsmaller amount of salts and greater proportion of water reabsorbedsmaller volume of urine with a high salt concentration formed (hypertonic urine)
98Regulation of Kidney Function The osmolarity of the urine is regulated by nervous and hormonal control of water and salt reabsorption in the kidneysAntidiuretic hormone (ADH) increases water reabsorption in the distal tubules and collecting ducts of the kidney
99hypothalamus detect an increase in the osmolarity of the blood Osmoreceptorsin hypothalamusThirstHypothalamusDrinking reducesblood osmolarityto set pointADHIncreasedpermeabilityPituitaryglandDistaltubuleCollecting ductH2O reab-sorption helpsprevent furtherosmolarityincreaseSTIMULUSThe release of ADH istriggered when osmo-receptor cells in thehypothalamus detect anincrease in the osmolarity of the bloodHomeostasis:Blood osmolarity
100What’s the effect of the following on urine output : 1. a lot of water2. a lot of salty foods3. a large volume of salty solution. E.g seawaterAssignment: 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)
101Excretion by forming urine to remove metabolic waste (e.g. urea) 1.4 The role of the kidneysExcretionby forming urine to remove metabolic waste (e.g. urea)
102Excretion by forming urine to remove metabolic waste (e.g. urea) 1.4The role of the kidneysExcretionby forming urine to remove metabolic waste (e.g. urea)constantly producedhigh concentration is toxic
103Diuretics (reference) Chemicals that enhance the urinary output include:Any substance not reabsorbedSubstances that exceed the ability of the renal tubules to reabsorb itOsmotic diuretics include:High glucose levels – carries water out with the glucoseAlcohol – inhibits the release of ADHCaffeine and most diuretic drugs – inhibit sodium ion reabsorptionLasix – inhibits Na+-K+-2Cl symporters
104Physical Characteristics of Urine (reference) Color and transparencyClear, pale to deep yellow (due to urobilin) -from the breakdown of hemeConcentrated urine has a deeper yellow colorDrugs, vitamin supplements, and diet can change the color of urineCloudy urine may indicate infection of the urinary tract
106Physical Characteristics of Urine Odor / smellFresh urine is slightly aromaticStanding urine develops an ammonia odorSome drugs and vegetables (asparagus) alter the usual odor
107Physical Characteristics of Urine Slightly acidic (pH 6) with a range of 4.5 to 8.0Diet can alter pHSpecific gravityRanges from to 1.035Dependent on solute concentration
108Chemical Characteristics of Urine Urine is 95% water and 5% solutesNitrogenous wastes include urea, uric acid, and creatinineOther normal solutes include:Sodium, potassium, phosphate, and sulfate ionsCalcium, magnesium, and bicarbonate ionsAbnormally high concentrations of any urinary constituents may indicate pathologyDisease states alter urine composition dramatically
109Functions of the Kidneys Regulation of extracellular fluid volume and blood pressureRegulation of osmotic potential in bloodMaintenance of ion balanceHomeostatic regulation of pHExcretion of wastes109
110normal water content in blood 1.4The role of the kidneys1 Regulation of water content by negative feedback mechanism:pituitary glandsecretes less ADHkidneyshypothalamushigh water content in bloodnormal water content in blood
111less smaller larger dilute 1.4The role of the kidneysIn the kidneys:a wall of collecting duct becomeslesspermeable to waterb a proportion of water reabsorbedsmallerc a volume of urine is formedlargerdilute
112normal water content in blood 1.4The role of the kidneys1 Regulation of water content by negative feedback mechanism:pituitary glandsecretes less ADHkidneyshypothalamuswater content in blood fallshigh water content in bloodnormal water content in blood
113normal water content in blood 1.4The role of the kidneys1 Regulation of water content by negative feedback mechanism:normal water content in bloodlow water content in bloodsecretes more ADHkidneyshypothalamuspituitary gland
114more greater smaller concentrated 1.4The role of the kidneysIn the kidneys:a wall of collecting duct becomesmorepermeable to waterb a proportion of water reabsorbedgreaterc a volume of urine is formedsmallerconcentrated
115normal water content in blood 1.4The role of the kidneys1 Regulation of water content by negative feedback mechanism:normal water content in bloodwater content in blood riseslow water content in bloodsecretes more ADHkidneyshypothalamuspituitary gland
1161.4The role of the kidneys2 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, asmallergreatersmallvolume of urine with ahighsalt concentration is formed.
1171.4The role of the kidneys3 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.toxicurine
118helps remove metabolic waste by haemodialysis (血液透析) Animation1.5 The dialysis machinekidney machinehelps remove metabolic waste by haemodialysis (血液透析)
1191 blood with metabolic waste 1.5The dialysis machinepumpdialysis tubing1 blood with metabolic wastefresh dialysis fluid
1201.5The dialysis machinedialysis tubingsame concentration of solutes as normal plasma but has no metabolic wastefresh dialysis fluid
121constant temperature bath 1.5The dialysis machinedialysis tubingdialysis fluidfresh dialysis fluidconstant temperature bath
122differentially permeable membrane of dialysis tubing 1.5The dialysis machinedifferentially permeable membrane of dialysis tubing
1232 urea diffuses through the pores to the dialysis fluid 1.5The dialysis machine2 urea diffuses through the pores to the dialysis fluid
1241.5The dialysis machine3 glucose is retained in blood (no net movement from blood to dialysis fluid
1251.5The dialysis machine4 plasma proteins and blood cells are too large to pass through the pores
127each treatment lasts for 4-6 hours three times a week costly 1.5The dialysis machineeach treatment lasts for 4-6 hoursthree times a weekcostly
128Peritoneal dialysisPeritoneal 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.
1301 A dialysis machine removes 1.5The dialysis machine1 A dialysis machine removesmetabolic wastefrom thepatient’s blood.
1312 The dialysis fluid has the same concentration of solutes as normal 1.5The dialysis machine2 The dialysis fluid has the same concentration of solutes as normalplasmabut no metabolic waste.This allows metabolic waste to diffuse from the patient’s blood to the dialysis fluid whileglucoseand other useful substances are retained in the blood.
1321 Why may a person die quickly if the kidneys fail to function? When the kidneys fail to function, the body cannot keep the water content in blood stable for cells to function properly.
1331 Why may a person die quickly if the kidneys fail to function? Besides, metabolic waste builds up in blood which can cause death.
1342 How does a kidney machine treat kidney failure? A kidney machine removes metabolic waste from the patient’s blood by haemodialysis.
1353 Why can’t people with kidney failure take in too much fluid and high-protein food?Excess proteins in the body are converted to urea by the liver.
1363 Why can’t people with kidney failure take in too much fluid and high-protein food?The failed kidney cannot remove excess fluid and urea from the body.
1373 Why can’t people with kidney failure take in too much fluid and high-protein food?Therefore, excessive intake of fluid and high-protein food must be avoided.
138Osmoregulation urinary system water content in blood kidneys is the maintenance of a stabledone byurinary systemwater content in bloodmain parts includekidneysdetected byhypothalamus