Excretory SystemExcretory System(sometimes called Urinary System)(sometimes called Urinary System)

Function and PartsFunction and Parts

http://www.youtube.com/watch?v=chhNaLi9P3E

Drinking & Drinking & eating eating provides waterprovides water

Kidney Kidney conserves conserves water so output water so output = intake= intake

Body Water BalanceBody Water Balance

Why is excretion necessary?Why is excretion necessary? In order for cells to stay alive, they must In order for cells to stay alive, they must

continually intake water and other continually intake water and other molecules.molecules.

The cells would continue to get bigger The cells would continue to get bigger and bigger if they only took in moleculesand bigger if they only took in molecules

They must also export moleculesThey must also export molecules These molecules may be important These molecules may be important

signaling molecules such as hormones, or signaling molecules such as hormones, or they may be molecules of glucose on their they may be molecules of glucose on their way to other cells, or they may be way to other cells, or they may be waste waste products of cellular metabolism that cells products of cellular metabolism that cells need to disposeneed to dispose..

Waste ProductsWaste Products Carbon dioxide – a waste product of Carbon dioxide – a waste product of

cellular respiration is dumped into cellular respiration is dumped into the blood stream and eventually the blood stream and eventually removed by the removed by the lungslungs

Ammonia (NHAmmonia (NH33)) is removed through is removed through waterwater This waste comes from the cell’s This waste comes from the cell’s

breakdown of old proteinsbreakdown of old proteins In these high physiological In these high physiological

concentrations, it is concentrations, it is poisonouspoisonous to to the cells and must be removedthe cells and must be removed

Removal of AmmoniaRemoval of Ammonia

Once Once excreted into the bloodexcreted into the blood stream by cells, it is stream by cells, it is carried to carried to the liverthe liver where it is where it is converted converted from ammonia into ureafrom ammonia into urea which is which is much less toxicmuch less toxic

It is then carried from the It is then carried from the liver to liver to the kidneysthe kidneys where it is removed where it is removed

The Job of the KidneysThe Job of the Kidneys They are responsible for cleaning They are responsible for cleaning

the blood by the blood by removing metabolic removing metabolic wastes, excess solutes, and excess wastes, excess solutes, and excess water and excreting them as urinewater and excreting them as urine

Besides removing urea, it also Besides removing urea, it also removes removes excess salts or glucose, the excess salts or glucose, the remnants of drugs (rationale for remnants of drugs (rationale for urine tests), and excess water.urine tests), and excess water.

Regulation of Water LevelsRegulation of Water Levels If the blood becomes too dilute or If the blood becomes too dilute or

too concentrated with solutes, then too concentrated with solutes, then it can interfere with normal cellular it can interfere with normal cellular activity.activity.

The kidneys are able to The kidneys are able to regulate regulate water concentration in the blood by water concentration in the blood by removing excess water if the blood removing excess water if the blood is too dilute, or conserving water in is too dilute, or conserving water in the blood if it is not dilute enoughthe blood if it is not dilute enough

Regulation of Water LevelsRegulation of Water Levels If the blood becomes too dilute or If the blood becomes too dilute or

too concentrated with solutes, then too concentrated with solutes, then it can interfere with normal cellular it can interfere with normal cellular activity.activity.

The kidneys are able to regulate The kidneys are able to regulate water concentration in the blood by water concentration in the blood by removing excess water if the blood removing excess water if the blood is too dilute, or conserving water in is too dilute, or conserving water in the blood if it is not dilute enoughthe blood if it is not dilute enough

Kidney FunctionsKidney Functions Filter 200 liters of blood daily, Filter 200 liters of blood daily,

allowing toxins, metabolic wastes, allowing toxins, metabolic wastes, and excess ions to leave the body in and excess ions to leave the body in urineurine

Regulate volume and chemical Regulate volume and chemical makeup of the bloodmakeup of the blood

Maintain the proper balance between Maintain the proper balance between water, electrolyte salts, and acids water, electrolyte salts, and acids and basesand bases

Other kidney functionsOther kidney functions Gluconeogenesis during Gluconeogenesis during

prolonged fastingprolonged fasting Production of rennin to help Production of rennin to help

regulate blood pressure and regulate blood pressure and erythropoietin to stimulate RBC erythropoietin to stimulate RBC productionproduction

Activation of vitamin DActivation of vitamin D

The Hard-working KidneysThe Hard-working Kidneys The two kidneys in the body The two kidneys in the body

receive between 180 – 220 liters of receive between 180 – 220 liters of blood per day – about the volume blood per day – about the volume of a car!of a car!

Because the body has only about Because the body has only about 5.6 liters of blood, your blood runs 5.6 liters of blood, your blood runs through the kidneys to be cleaned through the kidneys to be cleaned about once every four minutes.about once every four minutes.

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Kidney Location and External Anatomy

The KidneyThe Kidney

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The The KidneyKidney

The KidneyThe Kidney

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Proximalconvolutedtubule

Ascending thin limb of loop of Henlé

Ascending thick limb of loop of Henlé

Collecting duct

Distal convolutedtubule

The nephronThe nephron is the functional unit of the kidneyEach region is composed of cells suited to perform specific transport functions

The KidneyThe Kidney

Proximalconvoluted

tubule

Capsulespace

Efferent arteriole

Pedicel

PodocyteEndothelium of glomerulus

Afferent arteriole

Juxtaglomerularcell

Parietal layer of glomerular capsule

Structure of the Bowman’s (glomerular) capsule

http://www.youtube.com/watch?v=_XL_uxFseYQ&feature=related

Formation of UrineFormation of Urine The kidneys filter the body’s entire The kidneys filter the body’s entire

plasma volume 60 times each dayplasma volume 60 times each day The filtrate:The filtrate:

Contains all plasma components Contains all plasma components except proteinexcept protein

Loses water, nutrients, and Loses water, nutrients, and essential ions to become urineessential ions to become urine

The urine contains metabolic wastes The urine contains metabolic wastes and unneeded substancesand unneeded substances

Formation of UrineFormation of Urine If there is too much water in the blood, If there is too much water in the blood,

then it is removed and put in urine.then it is removed and put in urine. If there is not enough water in the If there is not enough water in the

blood, the kidneys will not remove any.blood, the kidneys will not remove any. If there is too much urea or other If there is too much urea or other

solutes in the blood, the kidneys will solutes in the blood, the kidneys will remove these excess solutes.remove these excess solutes.

By regulating solute numbers and water By regulating solute numbers and water volume, the kidneys normally maintain volume, the kidneys normally maintain homeostasis in blood solute homeostasis in blood solute concentration.concentration.

Mechanisms of Urine FormationMechanisms of Urine Formation

Urine formation Urine formation and adjustment and adjustment of blood of blood composition composition involves three involves three major major processes processes Glomerular Glomerular

filtrationfiltration Tubular Tubular

reabsorptionreabsorption SecretionSecretion

Nephron Recycling: OverviewNephron Recycling: Overview

Countercurrent Countercurrent multiplier exchange multiplier exchange

Medullary osmotic Medullary osmotic gradientgradient

HH22OOECFECFvasa vasa recta vesselsrecta vessels

Water Reabsorption in Water Reabsorption in Descending Loop of HenleDescending Loop of Henle

Factors that affect kidney functionFactors that affect kidney function Antidiuretic hormone (ADH) – prevents Antidiuretic hormone (ADH) – prevents

excess water loss from kidneysexcess water loss from kidneys Alcohol – inhibits secretion of ADH = Alcohol – inhibits secretion of ADH =

more urine volume, leading to more urine volume, leading to dehydrationdehydration

Aldosterone – prevents excess loss of Aldosterone – prevents excess loss of sodium and water from kidneyssodium and water from kidneys

Caffeine – increases rate of salt and Caffeine – increases rate of salt and water loss from kidneyswater loss from kidneys

Increased blood pressure – increase Increased blood pressure – increase rate of water loss from kidneys.rate of water loss from kidneys.

Normal kidneys Kidneys beyond help!Normal kidneys Kidneys beyond help!

End-stage kidneys

Chronic kidney disease

2525

The Urinary SystemThe Urinary SystemPart BPart B

Tubular ReabsorptionTubular Reabsorption All organic nutrients are reabsorbedAll organic nutrients are reabsorbed Water and ion reabsorption is Water and ion reabsorption is

hormonally controlledhormonally controlled Reabsorption may be an active Reabsorption may be an active

(requiring ATP) or passive process(requiring ATP) or passive process

Sodium reabsorption is almost Sodium reabsorption is almost always by active transportalways by active transport NaNa++ enters the tubule cells at the enters the tubule cells at the

luminal membraneluminal membrane Is actively transported out of the tubules Is actively transported out of the tubules

by a by a NaNa++-K-K++ ATPase pump ATPase pump

Sodium Reabsorption: Sodium Reabsorption: Primary Active TransportPrimary Active Transport

From there it moves to peritubular From there it moves to peritubular capillaries due to:capillaries due to: Low hydrostatic pressureLow hydrostatic pressure High osmotic pressure of the bloodHigh osmotic pressure of the blood

NaNa++ reabsorption provides the energy reabsorption provides the energy and the means for reabsorbing most and the means for reabsorbing most other solutesother solutes

Sodium Reabsorption: Sodium Reabsorption: Primary Active TransportPrimary Active Transport

Routes of Water and Solute Routes of Water and Solute ReabsorptionReabsorption

Figure 25.11

Osmotic Gradient in the Renal Osmotic Gradient in the Renal MedullaMedulla

Loop of Henle: Countercurrent Loop of Henle: Countercurrent MultiplierMultiplier

The descending loop of Henle:The descending loop of Henle: Is relatively impermeable to solutesIs relatively impermeable to solutes Is permeable to waterIs permeable to water

The ascending loop of Henle:The ascending loop of Henle: Is permeable to solutesIs permeable to solutes Is impermeable to water Is impermeable to water

Collecting ducts in the deep medullary Collecting ducts in the deep medullary regions are permeable to urearegions are permeable to urea

Loop of Henle: Countercurrent Loop of Henle: Countercurrent ExchangerExchanger

The vasa recta is a countercurrent The vasa recta is a countercurrent exchanger that:exchanger that: Maintains the osmotic gradientMaintains the osmotic gradient Delivers blood to the cells in the areaDelivers blood to the cells in the area

Loop of Henle: Countercurrent Loop of Henle: Countercurrent MechanismMechanism

Figure 25.14

Formation of Dilute and Formation of Dilute and Concentrated UrineConcentrated Urine

Figure 25.15a, b

DiureticsDiuretics

Chemicals that enhance the urinary Chemicals that enhance the urinary output include:output include: Any substance not reabsorbedAny substance not reabsorbed Substances that exceed the ability of Substances that exceed the ability of

the renal tubules to reabsorb itthe renal tubules to reabsorb it Substances that inhibit NaSubstances that inhibit Na++ reabsorption reabsorption

DiureticsDiuretics

Osmotic diuretics include:Osmotic diuretics include: High glucose levels – carries water out High glucose levels – carries water out

with the glucose with the glucose Alcohol – inhibits the release of ADHAlcohol – inhibits the release of ADH Caffeine and most diuretic drugs – Caffeine and most diuretic drugs –

inhibit sodium ion reabsorptioninhibit sodium ion reabsorption Lasix and Diuril – inhibit NaLasix and Diuril – inhibit Na++-associated -associated

symporterssymporters

Renal ClearanceRenal Clearance

The volume of plasma that is cleared The volume of plasma that is cleared of a particular substance in a given of a particular substance in a given timetime

Renal clearance tests are used to:Renal clearance tests are used to: Determine the GFRDetermine the GFR Detect glomerular damageDetect glomerular damage Follow the progress of diagnosed renal Follow the progress of diagnosed renal

diseasedisease

Renal ClearanceRenal Clearance

RC = UV/PRC = UV/P

RC = renal clearance rateRC = renal clearance rateU = concentration (mg/ml) of the U = concentration (mg/ml) of the

substance in urinesubstance in urineV = flow rate of urine formation (ml/min)V = flow rate of urine formation (ml/min)P = concentration of the same P = concentration of the same

substance in plasmasubstance in plasma

Chemical Composition of UrineChemical Composition of Urine

Urine is 95% water and 5% solutesUrine is 95% water and 5% solutes Nitrogenous wastes include urea, uric Nitrogenous wastes include urea, uric

acid, and creatinineacid, and creatinine Other normal solutes include:Other normal solutes include:

Sodium, potassium, phosphate, and sulfate Sodium, potassium, phosphate, and sulfate ionsions

Calcium, magnesium, and bicarbonate ions Calcium, magnesium, and bicarbonate ions Abnormally high concentrations of any Abnormally high concentrations of any

urinary constituents may indicate urinary constituents may indicate pathologypathology

Micturition (Voiding or Urination)Micturition (Voiding or Urination)

The act of emptying the bladderThe act of emptying the bladder Distension of bladder walls initiates spinal Distension of bladder walls initiates spinal

reflexes that:reflexes that: Stimulate contraction of the external urethral Stimulate contraction of the external urethral

sphinctersphincter Inhibit the detrusor muscle and internal Inhibit the detrusor muscle and internal

sphincter (temporarily)sphincter (temporarily) Voiding reflexes:Voiding reflexes:

Stimulate the detrusor muscle to contractStimulate the detrusor muscle to contract Inhibit the internal and external sphinctersInhibit the internal and external sphincters

Kidney dissectionKidney dissection http://www.youtube.com/watch?v=JBhttp://www.youtube.com/watch?v=JB

sUUYZKAlU&feature=relatedsUUYZKAlU&feature=related http://www.youtube.com/watch?v=Yhttp://www.youtube.com/watch?v=Y

nU6REgJU74&feature=relatednU6REgJU74&feature=related http://www.youtube.com/watch?v=Ahttp://www.youtube.com/watch?v=A

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