Osmoregulation and Disposal of Metabolic Wastes

Osmoregulation and Disposal Osmoregulation and Disposal of Metabolic Wastesof Metabolic Wastes

Chapter 47Chapter 47

Learning Objective 1Learning Objective 1

• How do the processes of How do the processes of osmoregulationosmoregulation and and excretionexcretion contribute to fluid and contribute to fluid and electrolyte homeostasis?electrolyte homeostasis?

Fluid-Electrolyte HomeostasisFluid-Electrolyte Homeostasis

• OsmoregulationOsmoregulation• active regulation of osmotic pressure of body active regulation of osmotic pressure of body

fluids fluids • maintains fluid and electrolyte homeostasis maintains fluid and electrolyte homeostasis

• ExcretionExcretion • process of ridding body of metabolic wastesprocess of ridding body of metabolic wastes


• Contrast the benefits and costs of Contrast the benefits and costs of excreting excreting ammoniaammonia, , uric aciduric acid, or , or ureaurea

Nitrogenous WastesNitrogenous Wastes

• AmmoniaAmmonia (toxic) (toxic)• excreted mainly by aquatic animalsexcreted mainly by aquatic animals

• UreaUrea (less toxic) (less toxic)• synthesis requires energy synthesis requires energy • excretion requires water excretion requires water

• Uric acid Uric acid (less toxic)(less toxic)• excreted as semisolid paste (conserves water) excreted as semisolid paste (conserves water)

Nitrogenous Nitrogenous WastesWastes

Fig. 47-1, p. 1013

Amino acids Nucleic acids

Deamination

Ammonia Keto acids Purines

Urea cycle 15 steps

Ammonia Urea Uric acid

More energy needed to produce

More water needed to excrete

Stepped Art

Fig. 47-1, p. 1013

Amino acids

Deamination

Ammonia Keto acids

Nucleic acids

Purines

Urea cycle 15 steps

Ammonia Urea Uric acid

More energy needed to produce

More water needed to excrete


• Compare Compare osmoconformersosmoconformers and and osmoregulatorsosmoregulators

OsmoconformersOsmoconformers

• Most marine invertebrates Most marine invertebrates

• Salt concentration of body fluids varies Salt concentration of body fluids varies with changes in sea water with changes in sea water

OsmoregulatorsOsmoregulators

• Some marine invertebratesSome marine invertebrates• especially in coastal habitats especially in coastal habitats

• Maintain optimal salt concentration despite Maintain optimal salt concentration despite changes in salinity of surroundingschanges in salinity of surroundings

KEY CONCEPTSKEY CONCEPTS

• Osmoregulation is the process by which Osmoregulation is the process by which organisms control the concentration of organisms control the concentration of water and salt in the body so that their water and salt in the body so that their body fluids do not become too dilute or too body fluids do not become too dilute or too concentratedconcentrated


• Describe Describe protonephridiaprotonephridia, , metanephridiametanephridia, , and and Malpighian tubulesMalpighian tubules

• Compare their functionsCompare their functions

Nephridial OrgansNephridial Organs

• Help maintain homeostasisHelp maintain homeostasis• by regulating concentration of body fluidsby regulating concentration of body fluids• osmoregulation osmoregulation • excretion of metabolic wastes excretion of metabolic wastes

ProtonephridiaProtonephridia

• Tubules with no internal openingsTubules with no internal openings• in flatworms and nemerteans in flatworms and nemerteans

• Interstitial fluid enters blind endsInterstitial fluid enters blind ends• flame cellsflame cells (cells with brushes of cilia) (cells with brushes of cilia)•

• Cilia propel fluid through tubulesCilia propel fluid through tubules

• Excess fluid exits through nephridioporesExcess fluid exits through nephridiopores

ProtonephridiaProtonephridia

Fig. 47-2ab, p. 1014

Flame cells

Protonephridial network

Nephridiopores

Excretory tubule

Flatworm

Fig. 47-2c, p. 1014

Nucleus

Cytoplasm

Cilia (“flame”)

Movement of interstitial fluid

Excretory tubule

MetanephridiaMetanephridia

• Tubules open at both endsTubules open at both ends• in most annelids and mollusks in most annelids and mollusks

• Fluid from coelom moves through tubuleFluid from coelom moves through tubule• needed materials reabsorbed by capillaries needed materials reabsorbed by capillaries

• Urine exits body through nephridioporesUrine exits body through nephridiopores• contains wastescontains wastes

MetanephridiaMetanephridia

Fig. 47-3, p. 1014

Tubule

AnteriorPosterior

Gut

Funnel

Septum Nephridiopore Capillary network

Malpighian Tubules 1Malpighian Tubules 1

• Extensions of insect gut wallExtensions of insect gut wall• blind ends lie in hemocoel blind ends lie in hemocoel

• Tubule cells actively transport uric acid Tubule cells actively transport uric acid from hemolymph into tubulefrom hemolymph into tubule

• water follows by diffusion water follows by diffusion

• Contents of tubule pass into gut Contents of tubule pass into gut

Malpighian Tubules 2Malpighian Tubules 2

• Water and some solutes reabsorbed in Water and some solutes reabsorbed in rectum rectum

• Malpighian tubules effectively conserve Malpighian tubules effectively conserve water water

• contribute to success of insects as terrestrial contribute to success of insects as terrestrial animalsanimals

Malpighian TubulesMalpighian Tubules

Fig. 47-4, p. 1014

Gut Malpighian tubules

Waste

HindgutRectum

Midgut

Water and needed ions


• Excretory systems have evolved that Excretory systems have evolved that function in both osmoregulation and in function in both osmoregulation and in disposal of metabolic wastesdisposal of metabolic wastes


• Relate the function of the vertebrate Relate the function of the vertebrate kidneykidney to the success of vertebrates in a to the success of vertebrates in a wide variety of habitatswide variety of habitats

The VertebrateThe Vertebrate KidneyKidney

• Excretes nitrogenous wastesExcretes nitrogenous wastes

• Helps maintain fluid balance by adjusting Helps maintain fluid balance by adjusting salt and water content of urine salt and water content of urine

Adaptation to HabitatsAdaptation to Habitats

• Freshwater, marine, terrestrial habitatsFreshwater, marine, terrestrial habitats• different problems for maintaining internal different problems for maintaining internal

fluid balance, excretion of nitrogenous wastes fluid balance, excretion of nitrogenous wastes

• Structure and function of vertebrate kidneyStructure and function of vertebrate kidney• adapted to various osmotic challenges of adapted to various osmotic challenges of

different habitatsdifferent habitats


• The vertebrate kidney maintains water and The vertebrate kidney maintains water and electrolyte balance and excretes metabolic electrolyte balance and excretes metabolic wasteswastes


• Compare adaptations for Compare adaptations for osmoregulationosmoregulation in freshwater fishes, marine bony fishes, in freshwater fishes, marine bony fishes, sharks, marine mammals, and terrestrial sharks, marine mammals, and terrestrial vertebratesvertebrates

Freshwater Freshwater FishesFishes

• Take in water Take in water osmoticallyosmotically

• excrete large volume excrete large volume of hypotonic urineof hypotonic urine

Fig. 47-5a, p. 1015

Loses salt by diffusionWater gain by osmosis

Drinks no

water

Large volume of hypotonic urine

Salt uptake by gills

Kidney with large glomeruli

Marine Bony Fishes Marine Bony Fishes

• Lose water osmotically Lose water osmotically

• Compensate by drinking sea water and Compensate by drinking sea water and excreting salt through their gillsexcreting salt through their gills

• Produce only a small volume of isotonic Produce only a small volume of isotonic urine urine

Fig. 47-5b, p. 1015

Gains salts by diffusionWater loss by

osmosis

Drinks salt

water

Small volume of isotonic urineSalt excreted

through gillsKidney with small or

no glomeruli

Sharks and Other Marine Sharks and Other Marine Cartilaginous FishesCartilaginous Fishes

• Retain large amounts of ureaRetain large amounts of urea• allows them to take in water osmotically allows them to take in water osmotically

through their gills through their gills

• Excrete large volume of hypotonic urine Excrete large volume of hypotonic urine

Fig. 47-5c, p. 1015

Water gain by osmosis

Salts diffuse in through gills

Salt-excreting gland

Some salt water swallowed with

foodKidney with large

glomeruli—reabsorbs urea

Large volume of hypotonic urine

Marine MammalsMarine Mammals

• Ingest sea water with their food Ingest sea water with their food • produce concentrated urineproduce concentrated urine

Terrestrial VertebratesTerrestrial Vertebrates

• Must conserve water Must conserve water • adaptations include efficient kidneysadaptations include efficient kidneys

• EndothermsEndotherms• have a high metabolic rate have a high metabolic rate • produce large volume of nitrogenous wastes produce large volume of nitrogenous wastes

Fig. 47-6b, p. 1016

LIVER ALL CELLS

Wastes produced

Hemoglobin breakdown

Breakdown of nucleic acids Cellular respiration

Deamination of amino acids

Uric acid

WastesBile pigments Water Carbon dioxide

Urea

Organs of excretion

KIDNEY DIGESTIVE SYSTEM

SKIN LUNGS

Exhaled air containing water vapor and carbon

dioxide

Excretion Urine Feces Sweat


• Freshwater, marine, and terrestrial Freshwater, marine, and terrestrial animals have different adaptations to meet animals have different adaptations to meet the challenges of these diverse the challenges of these diverse environmentsenvironments


• Describe (or label on a diagram) the Describe (or label on a diagram) the organs of the organs of the mammalian urinary systemmammalian urinary system

• Give the functions of eachGive the functions of each

The Urinary SystemThe Urinary System

• Principal excretory system in mammals Principal excretory system in mammals

• Mammalian kidneys produce urineMammalian kidneys produce urine• passes through passes through uretersureters • to to urinary bladderurinary bladder for storage for storage

• Urine is released from the body (urination)Urine is released from the body (urination)• through the through the urethra urethra

Human Urinary SystemHuman Urinary System

Fig. 47-7, p. 1017

Adrenal gland

Left renal arteryRight kidney

Right renal vein

Left kidney

Inferior vena cava Abdominal aorta

Ureteral orifices

Right and left ureters

Urinary bladder

Urethra

External urethral orifice

Kidney Structure 1Kidney Structure 1

• Renal cortexRenal cortex• outer portion of kidneyouter portion of kidney

• Renal medullaRenal medulla • inner portion of kidneyinner portion of kidney• contains 8 to 10 contains 8 to 10 renal pyramids renal pyramids

• Renal pyramids Renal pyramids • tip of each pyramid is a tip of each pyramid is a renal papillarenal papilla

Kidney Structure 2Kidney Structure 2

• Urine flows into Urine flows into collecting ductscollecting ducts• which empty through a which empty through a renal papillarenal papilla into the into the

renal pelvisrenal pelvis (funnel-shaped chamber) (funnel-shaped chamber)

• NephronsNephrons • functional units of kidney functional units of kidney • each kidney has more than 1 million each kidney has more than 1 million

Internal Kidney StructureInternal Kidney Structure

Fig. 47-8a, p. 1018

Renal pyramids (medulla)

Capsule

Renal cortex

Renal medulla

Renal artery

Renal vein

Renal pelvis

Ureter

Internal structure of the kidney.

Fig. 47-8b, p. 1018

Juxtamedullary nephron

Distal convoluted tubule Cortical nephron

Capsule

Proximal convoluted tubule

Renal cortexGlomerulus

Bowman’s capsule

Artery and vein

Loop of Henle

Renal medulla

Collecting duct

Papilla

Juxtamedullary and cortical nephrons.

Insert “Human kidney”Insert “Human kidney”

kidney_anatomy_v2.swfkidney_anatomy_v2.swf


• Describe (or label on a diagram) the Describe (or label on a diagram) the structures of a structures of a nephronnephron (including (including associated blood vessels)associated blood vessels)

• Give the functions of each structureGive the functions of each structure

Nephron StructureNephron Structure

• Each Each nephronnephron consists of consists of • a cluster of capillaries (a cluster of capillaries (glomerulusglomerulus))• surrounded by a surrounded by a Bowman’s capsuleBowman’s capsule • that opens into a long, coiled that opens into a long, coiled renal tubulerenal tubule

• Renal tubuleRenal tubule consists of consists of • proximal convoluted tubule proximal convoluted tubule • loop of Henle loop of Henle • distal convoluted tubuledistal convoluted tubule

Types of NephronsTypes of Nephrons

• Cortical nephronsCortical nephrons • located mostly within cortex or outer medullalocated mostly within cortex or outer medulla• have small glomeruli have small glomeruli

• Juxtamedullary nephronsJuxtamedullary nephrons • extend deep into medulla extend deep into medulla • have large glomeruli and long loops of Henlehave large glomeruli and long loops of Henle• important in concentrating urineimportant in concentrating urine

Blood Vessels 1Blood Vessels 1

• Blood flows Blood flows • from small branches of from small branches of renal arteryrenal artery • to to afferent arteriolesafferent arterioles • to to glomerular capillariesglomerular capillaries • into an into an efferent arterioleefferent arteriole

Blood Vessels 2Blood Vessels 2

• Efferent arterioleEfferent arteriole • delivers blood into delivers blood into peritubular capillariesperitubular capillaries that that

surround the renal tubule surround the renal tubule

• Blood leaves kidney through Blood leaves kidney through renal veinrenal vein

Nephron StructureNephron Structure

Fig. 47-9a, p. 1019

Proximal tubule

Bowman's capsule

Glomerulus

Efferent arteriole

Afferent arteriole

Peritubular capillaries

Distal tubule

Collecting duct

From renal artery

To renal vein

To renal pelvisLoop of

Henle

(a) Location and basic structure of a nephron.

Fig. 47-9b, p. 1019

Distal tubule Proximal tubuleBowman's capsule

Podocyte

Glomerular capillaries

Afferent arteriole Afferent arteriole

Juxtaglomerular apparatus

Efferent arteriole

Distal tubule

(b) Cutaway view of Bowman’s capsule.


• The nephron is the functional unit of the The nephron is the functional unit of the vertebrate kidneyvertebrate kidney


• Trace a drop of filtrate from Bowman’s Trace a drop of filtrate from Bowman’s capsule to its release from the body as capsule to its release from the body as urineurine

Urine ProductionUrine Production

• FiltrationFiltration • of plasma of plasma

• ReabsorptionReabsorption • of needed materialsof needed materials

• SecretionSecretion • of potassium, hydrogen ions into renal tubuleof potassium, hydrogen ions into renal tubule

Urine ProductionUrine Production

Fig. 47-10, p. 1020

REABSORPTION AND SECRETION

Proximal tubule

FILTRATION

Bowman's capsuleGlomerulus

REABSORPTION AND SECRETION REABSORPTION OF

H2O; URINE CONCENTRATED

Distal tubuleCollecting duct

CapillariesRenal arteryRenal vein To renal pelvis

Loop of Henle

Insert “Structure of the Insert “Structure of the glomerulus”glomerulus”

glomerulus.swfglomerulus.swf

Filtration 1Filtration 1

• Plasma filters through glomerular Plasma filters through glomerular capillaries into Bowman’s capsule capillaries into Bowman’s capsule

• Filtration membraneFiltration membrane • permeable walls of capillaries permeable walls of capillaries • filtration slitsfiltration slits between between podocytespodocytes

• PodocytesPodocytes • specialized epithelial cells specialized epithelial cells • make up inner wall of Bowman’s capsulemake up inner wall of Bowman’s capsule

Filtration MembraneFiltration Membrane

Fig. 47-11a, p. 1021

GlomerulusBowman's capsule

Afferent arteriole

Efferent arteriole

Fig. 47-11b, p. 1021

Blood cells restricted from passing through Endothelial cell of

capillaryRed blood cell

Capillary pores

Nucleus

Podocyte

Filtration slits

Foot processes

Filtration 2Filtration 2

• Filtration is nonselectiveFiltration is nonselective• small molecules become part of filtratesmall molecules become part of filtrate• glucose, other needed materials, metabolic glucose, other needed materials, metabolic

wasteswastes

Reabsorption 1Reabsorption 1

• About 99% of filtrate is reabsorbed from About 99% of filtrate is reabsorbed from renal tubules into blood renal tubules into blood

• Highly selective processHighly selective process• returns usable materials to bloodreturns usable materials to blood• leaves wastes, excess substances to be leaves wastes, excess substances to be

excreted in the urine excreted in the urine

Reabsorption 2Reabsorption 2

• Tubular transport maximum (Tm)Tubular transport maximum (Tm)• maximum rate at which a substance can be maximum rate at which a substance can be

reabsorbed reabsorbed

Insert “Tubular Insert “Tubular reabsorption”reabsorption”

tubular_reabsorption_m.swftubular_reabsorption_m.swf

SecretionSecretion

• Hydrogen ions, certain other ions, and Hydrogen ions, certain other ions, and some drugs are actively transported into some drugs are actively transported into renal tubule to become part of urinerenal tubule to become part of urine

Water, Ion and Urea MovementWater, Ion and Urea Movement

Fig. 47-12, p. 1022

Bowman's capsule

Proximal tubule

Distal tubuleAfferent arteriole

Efferent arteriole

Filtrate NaCl MEDULLA

NaCl CORTEX

NaClCollecting ductH2O NaCl

NaClUrea

Descending limb Ascending

limb

Loop of Henle

H2O

H2O

H2O H2O

Urine Concentration 1Urine Concentration 1

• Depends on high concentration of salt and Depends on high concentration of salt and urea in interstitial fluid of kidney medulla urea in interstitial fluid of kidney medulla

• Concentration gradient Concentration gradient • salt most concentrated around bottom of loop salt most concentrated around bottom of loop

of Henle of Henle • maintained by salt reabsorption from various maintained by salt reabsorption from various

parts of renal tubule parts of renal tubule


• Counterflow of fluid through two limbs of Counterflow of fluid through two limbs of loop of Henleloop of Henle

• concentrates filtrate moving down concentrates filtrate moving down descending loop descending loop

• dilutes filtrate moving up ascending loopdilutes filtrate moving up ascending loop

• Water is drawn from filtrate by osmosisWater is drawn from filtrate by osmosis• as it passes through collecting ductsas it passes through collecting ducts• concentrating urine in collecting ductsconcentrating urine in collecting ducts


• Vasa rectaVasa recta• system of capillaries extending from efferent system of capillaries extending from efferent

arterioles arterioles • removes some water that diffuses from filtrate removes some water that diffuses from filtrate

into interstitial fluidinto interstitial fluid

Urine ConcentrationUrine Concentration

Fig. 47-13, p. 1023

Bowman's capsuleProximal tubule

Distal tubuleAfferent arteriole

300 300 100 100

200Efferent arteriole

CORTEX

Filtrate300 100 300 300

MEDULLA

400 200 400 400

600 400 600 600

600Interstitial

fluid

Collecting duct

1200 1200 1200

Loop of Henle

UrineUrine

• A watery solution of nitrogenous wastes, A watery solution of nitrogenous wastes, excess salts, and other substances not excess salts, and other substances not needed by the bodyneeded by the body

Watch renal processes in action Watch renal processes in action by clicking on the figures in by clicking on the figures in

ThomsonNOW.ThomsonNOW.


• Describe the hormonal regulation of fluid Describe the hormonal regulation of fluid and electrolyte balance by and electrolyte balance by antidiuretic antidiuretic hormone (ADH),hormone (ADH), the the renin–angiotensin– renin–angiotensin– aldosterone systemaldosterone system, and , and atrial natriuretic atrial natriuretic peptide (ANP)peptide (ANP)

Antidiuretic Hormone (ADH)Antidiuretic Hormone (ADH)

• Posterior pituitary increases Posterior pituitary increases ADHADH release release • when body needs to conserve waterwhen body needs to conserve water• responds to increase in osmotic concentration responds to increase in osmotic concentration

of blood (caused by dehydration) of blood (caused by dehydration)

• ADH increases permeability of collecting ADH increases permeability of collecting ducts to water ducts to water

• more water is reabsorbedmore water is reabsorbed• small volume of urine is producedsmall volume of urine is produced

Regulation by Regulation by ADH ADH

Fig. 47-14, p. 1024

1 Fluid intake is low. Receptors in the hypothalamus

2 Blood volume decreases, and osmotic pressure increases.

Posterior pituitary

ADH secretion is inhibited.

Posterior pituitary secretes ADH.

Blood volume increases, and osmotic pressure decreases.

36 7

Collecting ductNephron

H2O

Kidney

5Water reabsorption increases.

Collecting ducts become more permeable.

4

Lower urine volume

H2OH2O

H2O

H2O

H2O

Renin-Angiotensin-Aldosterone Renin-Angiotensin-Aldosterone Pathway 1Pathway 1

• When blood pressure decreasesWhen blood pressure decreases• juxtaglomerular apparatusjuxtaglomerular apparatus secretes secretes reninrenin

• ReninRenin (enzyme) (enzyme)• activates pathway to production of activates pathway to production of angiotensin IIangiotensin II

Renin-Angiotensin-Aldosterone Renin-Angiotensin-Aldosterone Pathway 2Pathway 2

• Angiotensin IIAngiotensin II (hormone) (hormone) • constricts arterioles (raises blood pressure)constricts arterioles (raises blood pressure)• stimulates stimulates aldosteronealdosterone release release

• AldosteroneAldosterone (hormone) (hormone)• increases sodium reabsorption (raises blood increases sodium reabsorption (raises blood

pressure)pressure)

Atrial Natriuretic Peptide (ANP)Atrial Natriuretic Peptide (ANP)

• When blood pressure increasesWhen blood pressure increases• ANPANP increases sodium excretion, inhibits increases sodium excretion, inhibits

aldosterone secretion aldosterone secretion • increases urine output, lowers blood pressure increases urine output, lowers blood pressure

• Renin-angiotensin-aldosterone pathway Renin-angiotensin-aldosterone pathway and atrial natriuretic peptide work and atrial natriuretic peptide work antagonistically antagonistically

Osmoregulation and Disposal of Metabolic Wastes

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