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Lectured by:

Pn. Anwarul Hidayah Zulkifli

BIOLOGY 2 (FB 1020)

10th January 13th January 2011

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The general process by which animals andplants control solute concentrations andbalance water gain and loss

Also known as homeostasisOsmoregulation is essential in the fluidenvironment of cells, tissues and organs.

Based largely on controlled movement ofsolutes between internal fluids and the

external environment.

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Na+ and Ca+ must be maintained at

concentrations that permit normal activity

of:

MusclesNeurons

Body cells

Water follows solutes by osmosis ->regulate

both solute and water content

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All animals face the need forosmoregulation regardless of:Phylogeny

HabitatType of waste produced

Water uptake = loss

If water uptake is excessive, animal cells

swell and burst.If water loss is substantial, they shriveland die.

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Osmolarity: total solute concentrationexpressed as molarity, or moles of soluteper liter of solution.

The unit of measurement for osmolarity:milliOsmoles per liter (mOsm/L)

1 mOsm/L equivalent to a total soluteconcentration of 10-3 M.

Osmolarity of human blood = 300 mOsm/LOsmolarity of seawater = 1,000mOsm/L

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Isoosmotic: 2 solutions separated by a

selectively permeable membrane have the

same osmolarity.

No net movement of water by osmosisHyperosmotic: the one with greater

concentration of solutes

Hypoosmotic: the one which is more diluted.

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Animal can maintain water balance in two ways:1. Osmoconformer

Internal osmolarity the same as that of its environment

No tendency to gain or lose water

Live in water that has a stable composition/constant

internal osmolarity e.g: marine animals

1. Osmoregulator Controls its internal osmolarity independent of that of

its environment.

Hypoosmotic environment: Osmoregulator dischargeexcess water

Hyperosmotic environment: osmoregulator take inwater to offset osmotic loss.

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Most animals cannot tolerate substantial

changes in external osmolarity =>

stenohaline.

Able to survive large fluctuations in externalosmolarity => euryhaline.E.g. Barnacles and mussels (euryhaline

osmoconformers)

Striped bass and salmon (euryhalineosmoregulators)

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Most marine invertebrates are osmoconformers.

The sum of the concentrations of all dissolved

substances is the same as that of seawater.They must actively transport these solutes(specific solutes) to maintain homeostasis.

They drink seawater to compensate fluid loss

Little urine excreted by the kidneys with small orno glomeruli.

High protein diet of these animals results in the production oflarge amounts of urea, excrete in urine without losing much

water.

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Osmoregulators live in a stronglydehydrating environment.

Marine vertebrates constantly lose water by

osmosis => balance the water loss by

drinking large amounts of seawater and

make use of their gills and kidneys to ridthemselves of salts.

In the gills, specialized chloride cells

actively transport chloride ions out and

sodium ions follow passively.In the kidneys, excess calcium, magnesium

and sulfate ions are excreted with the loss of

only small amounts of water.

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Retain and can tolerate large amounts of urea allows them to take in water osmotically through

their gills

Excrete large volume of hypotonic urine

Tissues adapted to function at concentrations of

urea that will be toxic to other animals

Example: Shark kidney reabsorbs urea in high

concentration=> tissues become hypertonic toseawater

Therefore, water enters the shark by osmosis and

excretes a large quantity of dilute urine.

CARTILAGINOUS FISHES

(SHARKS AND RAYS)

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Gains salts by

diffusionWater loss by

osmosis

Drinks

salt

water

Small volume ofisotonic urineSalt excreted

through gillsKidney with small or

no glomeruli

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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

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Are specialized cells that regulate solute movement

single sheet of cells, joined by impermeabletight junctions, facing theexternalenvironment.

Are essential components of osmotic regulation and metabolic wastedisposal

Are arranged into complex tubular networksMaintain the composition of cellular cytoplasm

An example of transport epithelia is found in the saltglands of marine birdsWhich remove excess sodium chloride from the blood

Salt glands are usually inactive, function ONLY in response toOSMOTIC STRESS.

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But most animal do this indirectly by managing the

composition of internal body fluid that bathes the

cells. In insects with an open circulatory system, the fluid

is the hemolymph.

In vertebrates and other animals with a closed

system, the cells are bathed in an interstitial fluid.

The maintenance of fluid composition depends on

specialized structures ranging from cells that regulate

solute movement (epithelial cells) to complex organs

such as the kidney.

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Nasal salt gland

Nostril

with salt

secretions

Lumen of

secretory tubule

NaCl

Blood

flowSecretory cell

of transport

epithelium

Centralduct

Direction

of salt

movement

Transport

epithelium

Secretory

tubule

Capillary

Vein

Artery

(a) An albatrosss salt glands

empty via a duct into thenostrils, and the salty solution

either drips off the tip of the

beak or is exhaled in a fine mist.

(b) One of several thousand

secretory tubules in a salt-

excreting gland. Each tubule

is lined by a transport

epithelium surrounded by

capillaries, and drains into

a central duct.

(c) The secretory cells actively

transport salt from the

blood into the tubules.

Blood flows counter to the

flow of salt secretion. By

maintaining a concentrationgradient of salt in the tubule

(aqua), this countercurrent

system enhances salt

transfer from the blood to

the lumen of the tubule.

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Freshwater animalsConstantly take in water from their hypoosmoticenvironment

Lose salts by diffusion.

Freshwater animals maintain water balanceBy excreting large amounts of dilute urine

Salts lost by diffusion

Are replaced by foods and uptake across the gills

Gills excrete most of nitrogenous wastes

Main: ammonia; 10%: urea

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AMPHIBIANS

Least known as semiaquaticMechanism of osmoregulation: Similar to freshwater fishes

Produce large amount of dilute urine

Frog can lose an amount of water (throughurine and skin) equivalent to 1/3 of its body

weight in one day.

Active transport of salt inward by special

cells in the skin compensates for loss of salt(through skin and urine)

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Some aquatic invertebrates living in temporary

pondsCan lose almost all their body water and survive in adormant state

This adaptation is called anhydrobiosis

(a) Hydrated tardigrade (b) Dehydrated tardigrade

100 m

100 m

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Land animals manage theirwater budgets By drinking and eating moistfoods and by using metabolicwater

Lung, skin and digestive

system vital inosmoregulation and wastedisposal.

Sweat glands of humans andother mammals excrete 5% to10% of all metabolic wastes.

Liver produces both urea anduric acid, transported by the

blood to the kidneys.

Amniotes (reptiles, birds andmammals): minimizes water lossby evaporation and excreteuric acid.

Water

balance

in

a human

(2,500

mL/day

= 100%)

Water

balance in a

kangaroo rat

(2 mL/day

= 100%)

Ingested

in food (0.2)

Ingested

in food (750)

Ingested

in liquid

(1,500)

Derived from

metabolism (250)Derived from

metabolism (1.8)

Water

gain

Feces (0.9)

Urine

(0.45)

Evaporation (1.46)

Feces (100)

Urine

(1,500)

Evaporation (900)

Water

loss

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Birds and mammals are endothermic and

have a high rate metabolism => produce a

relatively large volume of nitrogenous

wastes.

Have efficient kidneys for conserving water.

Birds conserve water by excreting nitrogen as

uric acid and reabsorb water from the cloaca

and intestine.Mammals excrete urea and their kidney

produce very concentrated urine.

LIVER ALL CELLS

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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

SKINLUNGS

Exhaled air

containing water

vapor and carbon

dioxide

Excretion Urine Feces Sweat

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Kangaroo rat: loses so little water that 90% is replaced bywater generated metabolically Other 10% comes from the small amount of water in itsdiet of seeds.

Camels: fur of camels exposed to full sun in the desertcould reach over 70C, while the skin remained more than

30C cooler. Skin insulation reduces the need for evaporative cooling bysweating (If skin removed, water loss increased by up to50%)

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ANIMALS

NITROGENOUS

WASTE

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Reflect its phylogeny and habitat

The type and quantity of an animals waste

products

May have a large impact on its water balanceAmong the most important wastesAre the nitrogenous breakdown products of

proteins and nucleic acids

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Proteins Nucleic acids

Amino acids Nitrogenous bases

NH2Amino groups

Most aquatic

animals, including

most bony fishesMammals, most

amphibians, sharks,

some bony fishes

Many reptiles

(including

birds), insects,

land snails

Ammonia Urea Uric acid

NH3NH2

NH2

O C

C

C

N

C

ON

H H

C O

NC

HN

O

H

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Ammonia (very toxic, soluble)

Ammonia is excreted directly by most aquatic animals.

-easily permeates membrane since molecules are small

and very water soluble

-In soft-bodied invertebrates, ammonia just diffuses out.

-In freshwater fishes, it is excreted as ammonium ions

(NH4+) across gill epithelium.

-Very toxic, excreted in very dilute solutions.

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Urea (less toxic, soluble)

Urea is the nitrogenous waste excreted by mammals and

most adult amphibians

-Can be much more concentrated since it is much less toxic

than ammonia; reduces water loss for terrestrial animals.

-produce in liver by a metabolic cycle combining ammoniawith CO2. It is transported to kidneys via the circulatory

system.

-Amphibians that undergo metamorphosis and move as

adults to land to land, switch from excreting ammonia toexcreting urea.

-Disadvantage: animals must expend energy to produce

urea from ammonia.

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Uric acid (nontoxic, insoluble in water)

Insects, land snails, reptiles, birds

excreted in solid paste with little water loss

(advantage for animals with little access to

water)

Disadvantage: Uric acid is even moreenergetically expensive to produce than

urea, require more ATP to produce/synthesis

uric acid from ammonia.

Genetic defect in purine (uric acid) metabolism:

Dalmatian dogs to form uric acid stones in their bladder

Humans develop gout, painful inflammation of joints caused

by deposits or uric acid crystals

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EXCRETION

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Function of excretory systems:Regulate solute movement between internalfluids and the external environment

The process ofremoval waste products of

metabolism from the body.

Produce urine by refining a filtrate derived frombody fluids

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Filtration. The excretory tubule collects a filtrate from

the blood. Water and solutes are forced by blood

pressure across the selectively permeable membranes

of a cluster of capillaries and into the excretory tubule.

Reabsorption. The transport epithelium reclaims

valuable substances from the filtrate and returns themto the body fluids.

Secretion. Other substances, such as toxins and

excess ions, are extracted from body fluids and added to

the contents of the excretory

tubule.

Excretion. The filtrate leaves the system and the

body.

Capillary

ExcretorytubuleFiltrate

Urine

1

2

3

4

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What are the waste products?- Nitrogenous waste, eg. Urea, ammonia

- Waste products of metabolism, eg. CO2,bile pigments

- Toxic substances

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What is the principal organ?Kidneys (two, one on each side of the abdomen)

Function of Kidneys:

- Controls the composition of water and solutes inthe blood.

How does it control the system?

- By retaining the important substances &removing the unwanted substances.

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Posterior vena cava

Renal artery and vein

Aorta

Ureter

Urinary bladder

Urethra

Excretory organs and major

associated blood vessels

Kidney

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How does the blood goes to the kidneys?

- Blood flows to the kidneys by the renal

artery.

What happens in the kidneys?

- The blood flowing through the kidney, is

collected into the renal vein posterior venacava.

- Unwanted substances are removed from the

blood pelvis to bladder via ureter

- Fluids in the bladder is called urine

expelled by urination via urethra.

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Excretion: removal wastes products ofmetabolism from cells.

Kidney: bean shaped, about 10 cm long,supply blood by a renal artery and drained bya renal vein.

The mammalian kidney consists of an outer

cortex and an inner medulla. It is composed of units called nephrons.

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UreterSection of kidney from a rat

Renal

medullaRenal

cortex

Renal

pelvis

Juxta-

medullary

nephron

Cortical

nephron

Collecting

duct

Torenal

pelvis

Renal

cortex

Renal

medulla

20 m

Afferent arteriole

from renal artery

GlomerulusBowmans capsule

Proximal tubulePeritubular

capillaries

SEM

Efferentarteriole from

glomerulus Branch ofrenal vein

Descending

limbAscending

limb

Loop

of

Henle

Distal

tubule

Collecting

duct

Nephron

Vasa

recta

Filtrate and blood flow

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Nephron=functional unit of kidneyConsists of a single long tubule (renal tubule) anda ball of capillaries called the glomerulus

process 180L offiltrate per day, and the transportepithelium, lining the renal tubule, processes this

filtrate1.5L urine excreted daily. The rest of the filtrate is reabsorbed into the blood.

Filtrate: Water, salts, urea and other small molecules

that are separated from the blood passing through thecapillaries and flow through the renal tubule.

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The blind end of the renal tubule that receivesfiltrate from the blood forms a cup-shapedBowmans capsule which embraces a ball ofcapillaries, the glomerulus.

Filtrate then passes through the proximalconvoluted tubule, the loop of Henle (a longhairpin turn with a descending limb and anascending limb) and the distal convolutedtubule, which empties into a collecting duct.

The collecting duct receives filtrate from manyother nephrons.

Filtrate, now called urine, passes from thecollecting ducts into the renal pelvis. Urine thendrains from the renal pelvis into the ureter.

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The bowmans capsules and the proximal anddistal convoluted tubules are located in thecortex. The loops of Henle and collecting tubes extend intomedulla.

Cortical nephrons= Nephrons that havereduced loops of Henle and are confined tothe cortex. 80% of the nephrons in human are corticalnephrons.

Juxtamedullary nephrons= Nephrons that

have long loops of Henle that are extend intothe medulla and are found only in mammalsand birds. 20% of the nephrons are juxtamedullary nephrons.

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The cortex:

- is covered by a fibrous capsule.

- contains Malpighian bodies (Bowmans capsule

and a glomerulus),proximal convolutedtubule, distal convoluted tubule, part of thecollecting duct and blood capillaries.

The medulla:

- Contains the loop of Henle, collecting duct andblood capillaries.

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Nephrons wall consists ofone layer of

epithelial cells.At the proximal end of the nephron isMalphigian body (spherical).

The Malphigian body consists ofBowmans capsule and a glomerulus.

The glomerulus is a dense network ofcapillaries contained in the Bowmanscapsule.

The inside of the Bowmans capsule(called the capsule space) is separatedfrom the lumen of the glomerularcapillary by three thin layers, namely:

(1) Endothelium of glomerular capillary

(2) Basement membrane of glomerularcapillary

(3) Epithelium of the Bowmans capsule

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Each nephron is closely associated with vessels:

Afferent arteriole is a branch of the renal artery thatdivides to form the capillaries of the glomerulus.

Efferent arteriole forms from converging capillaries

as they leave the capsule. This subdivides to form theperitubular capillaries which intermingle with theproximal and distal convoluted tubules.

Vasa recta is the capillary system branchingdownward from the peritubular capillaries that servethe loop of Henle

Materials are exchanged between capillaries andnephrons through interstitial fluid.

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Nephrons regulate blood compositionby:

- Filtration

- Secretion- Reabsorption

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Blood pressure forces fluid from the glomerulusacross the Bowmans capsule epithelium intothe lumen of the renal tubule. Porous capillaries and podocytes (specialized cellswrapped around the capillaries in the glomerulus)nonselectively filter out blood cells and large

molecules

Any molecule small enough to be forced through thecapillary wall enters the renal tubule.

Filtrate contains a mixture of glucose, salts, vitamins,

nitrogenous wastes and small molecules inconcentrations similar to that in blood plasma.(filtrate= blood plasma)

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Filtrate is joined by substances from thesurrounding interstitial fluid, transportedacross the tubule epitheliumAdds plasma solutes to the filtrate

Proximal and distal convoluted tubules (PCTand DCT) are most common sites of secretion

Very selective (involves both passive and activetransport)

Controlled secretion of H+

ions helps maintainconstant body fluid pH.

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Reabsorption is the selective transport offiltrate substances from the renal tubuleback to the interstitial fluid.Recovers essential molecules and water fromthe filtrate and returns them to the body fluids

Occurs in the convoluted tubules, the loop ofHenle and the collecting duct.

Valuable solutes: glucose, certain salts,vitamins, hormones, amino acids and water areabsorbed.

Regulates salt concentration

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The composition of filtrate ismodified by selective

secretion and reabsorption.-The concentration ofbeneficial substances isreduced as they are returnedto the body.

-The concentration of wastes

and non-useful substances isincreased and excreted fromthe body

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Small molecules and water from the filtrate as it flowsthrough the renal tubules

Collecting duct converts the filtrate into urine.

(1)The proximal convoluted tubule alters the volume andcomposition of filtrate by reabsorption and secretion.

In this area, ammonia, drugs and poisons processed in theliver are secreted to join the filtrate.

Helps to maintain a constant body fluid pH by controlledsecretion of H+.

Nutrients such as glucose and amino acids are reabsorbed(active transport) from the filtrate and returned to the interstitialfluid.

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Epithelial cells in thisregion have numerousmicrovilli facing thetubule lumen (a brush-border), provide extensivesurface area forreabsorption ofpotassium, nutrients andNaCl into the interstitialfluid and from there intothe peritubularcapillaries.

Na+ and Cl- diffuse acrossthe brush border into theepithelial cells; themembrane facing theinterstitial fluid thenactively pump Na+ out ofthe cells, which isbalanced by passivetransport of Cl-. Waterfollows passively by

osmosis.

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ASCENDING LOOP OF HENLE DESCENDING LOOP OF HENLE

In the ascending limb of the loop ofHenle, transport epithelium is verypermeable to salt, but not to thewater.

In the thin segment near the looptip, NaCl diffuse out passively and

contributes to the high osmolarity ofthe interstitial fluids of themedulla.

In the thick segment leading to thedistal convoluted tubule, Cl- isactively pumped out and Na+ flowspassively.

FILTRATE becomes more dilute dueto the removal of salts withoutlosing water.

In the descending limbof the loop of Henle,transport epithelium isvery permeable towater, but not to saltand other small solutes.

Filtrate moving down thetubule from the cortex tothe medulla continues tolose water by osmosissince interstitial fluid inthis region increases inosmolarity

NaCl concentration of thefiltrate increases.

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The distal convoluted tubuleregulates K+and Na+ concentration of body fluids byregulating K+ secretion into the filtrate andNa+ reabsorption from the filtrate.

This region also contributes to pH regulation byquantitative secretions of H+ and reabsorption ofbicarbonate (HCO

3

-,an important body fluid

buffer)

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The collecting duct carries filtrate backtowards the medulla and renal pelvis.

The epithelium here is permeable to water butnot to salt, so filtrate loses water by osmosis to

the hyperosmotic fluid outside the duct and theurea is concentrated.

The bottom portion of the duct is permeableto urea, some of which diffuse out.

This contributes to the high osmolarity of theinterstitial fluid of the kidney medulla, whichenables the kidney to conserve water byexcreting a hyperosmotic urine.

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Two solutes: NaCl and urea,

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H2O

H2O

H2O

H2O

H2O

H2O

H2O

NaCl

NaCl

NaCl

NaCl

NaCl

NaCl

NaCl

300

300 100

400

600

900

1200

700

400

200

100

Active

transport

Passivetransport

OUTER

MEDULLA

INNER

MEDULLA

CORTEX

H2O

Urea

H2O

Urea

H2O

Urea

H2O

H2O

H2O

H2O

1200

1200

900

600

400

300

600

400

300

Osmolarity of

interstitialfluid

(mosm/L)

300

,

contribute to the osmolarity of

the interstitial fluid

-causes the reabsorption

of water in the kidney and

concentrates the urineThe countercurrent multiplier

system involving the loop of

Henle

-Maintains a high salt

concentration in the

interior of the kidney,

which enables the kidney

to form concentrated urine

Urea diffuses out of the

collecting duct

-As it traverses the innermedulla

Urea and NaCl

-Form the osmotic

gradient that enables the

kidney to produce urine

that is hyperosmotic to theblood

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ADH makes the collecting ducts morepermeable to water so more water

reabsorbed.

Small volume of concentrated urine

produced.

ADH acts on aquaporin-2, membrane protein

that forms gated water channels in the wall

of the collecting ducts.Gated water channelsallow water to pass

rapidly through the plasma membrane.

REGULATION

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REGULATIONOF URINEVOLUME BY

ADH

Osmoreceptors

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Osmoreceptors

in hypothalamus

Drinking reduces

blood osmolarity

to set point

H2O reabsorption

helps prevent

further

osmolarity

increase

STIMULUS:

The release of ADH is

triggered when osmo-

receptor cells in the

hypothalamus detect anincrease in the osmolarity

of the blood

Homeostasis:

Blood osmolarity

Hypothalamus

ADH

Pituitary

gland

Increased

permeability

Thirst

Collecting duct

Distal

tubule

*Increasedblood

osmolarity

* water*Low

waterpotential

Figure 44.16a:

Antidiuretic hormone(ADH) enhances fluid

retention by making the

kidneys reclaim more

water

WATER GAIN

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No drinking

No feeling of thirst

Osmoreceptors in

hypothalamus

become

less stimulated

Decrease in osmotic

concentration(too much water

relative to salts)

Kidney reabsorbs

less water

Posterior pituitary

gland secretes

less ADH

Increase in osmotic

concentration

Correct osmotic

concentration

(normal)

WATER GAIN

WATER LOSS

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Drinking

Feeling of thirst

Osmoreceptors in

hypothalamus

become

more stimulated

Increase in osmotic

concentration(too little water

relative to salts)

Kidney reabsorbs

more water

Posterior pituitary

gland secretes

more ADH

Decrease in osmotic

concentration

Correct osmoticconcentration

(normal)

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DIABETES INSIPIDUSDue to pituitary gland malfunctioning

Does not release sufficient amount of ADH

Develop from an acquired insensitivity of the

kidney to ADH.Water is not efficiently reabsorbed from the

ducts => large volume of urine produced.

Person with severe diabetes insipidus may

excrete up to 25 quarts of urine each day, aserious water loss.

Treatment: injections of ADH or use of ADH

nasal spray.

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Main function: increase Sodium reabsorption and regulatesodium concentration

The juxtaglomerular apparatus (JGA) is a specialized tissuenear the afferent arterioles leading to kidney glomeruli.

It responds to a decrease in blood pressure or Na+concentration by releasing the enzyme, renin into the blood.

Reninconverts inactive angiotensin to active angiotensin II (hormone) Angiotensin II directly increases blood pressure by causing arterioleconstriction; increased blood pressure increases filtration rate.

Angiotensin II acts indirectly by signaling the cortex of the adrenalglands to release aldosterone, which stimulates Na+ reabsorptionacross distal convoluted tubules (water follows by osmosis)

The increased Na+ concentration in blood and increased blood volumeand pressure suppresses further release renin.

R i A i t i Ad l t

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Renin-Angiotensin-AdolsteronePathway 1

When blood pressure decreases juxtaglomerular apparatus secretes renin

Renin (enzyme)converts the plasma protein angiotensinogen toangiotensin I.

Angiotensin-converting enzyme (ACE) converts

angiotensin I into its active form, angiotensin II

(peptide hormone). ACE produced by the endothelial cells in the walls

of pulmonary capillaries.

RENIN ANGIOTENSIN ADOLSTERONE

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RENIN-ANGIOTENSIN-ADOLSTERONEPATHWAY 2

Angiotensin II (hormone) constricts arterioles (raises blood pressure) stimulates aldosterone release Also stimulates the posterior pituitary to release ADH=> stimulates thirst

All actions help increase extracellular fluid volumeand raise blood pressure Individuals with hypertension, ACE inhibitors sometimesused to block the production of angiotensin II.

Aldosterone (hormone) secretion stimulated both by hormones and by adecrease in blood pressure (caused by a decrease involume of blood and interstitial fluid).

increases sodium reabsorption (raises blood pressure)

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S i i gi t i

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Summaries on renin-angiotensin-adolsterone pathwayBlood volume decreasesBlood pressure decreasesCells of JGA secrete reninRenin catalyzes conversion ofangiotensinogen to angiotensin I

ACE catalyzes conversion of angiotensin I toangiotensin II

Angiotensin II constricts blood vessels andstimulates aldolsterone secretion

Aldolsterone increases sodium reabsorptionBlood pressure increases

ATRIAL NATRIURETIC PEPTIDE

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ATRIAL NATRIURETIC PEPTIDE(ANP)

Main function: Inhibits sodium reabsorption

ANP (hormone) produced by the heart and

stored in atrial muscle cells: Increases sodium excretion

Decreases blood pressure

Both ANP and RAAS regulate fluid balance,electrolyte balance and blood pressure

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SUMMARIES ON ANP Blood volume increases (when Na+ concentrationincreases)

Blood pressure increases Atrial muscle cells (heart) stretched

ANP released into circulation Sodium reabsorption by the collecting ducts directlyinhibited

Adolsterone secretion inhibited ANP reduces plasma adolsterone concentration by

inhibiting renin release Lowers blood volume Large sodium excretion and urine output Blood pressure decreases

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Liver: is the LARGEST gland in the body. (about 2% of the body weight in an adult) Accessory digestive gland

receives blood, through the hepatic portal vein(~75% of the blood supply), and arterial blood,

through the hepatic artery (~25% of the bloodsupply). The liver has two blood vessels supplying it withblood:

Hepatic portal vein (often portal vein for short) is aportal vein in the human body that drains blood fromthe digestive system.

Hepatic artery, which supplies oxygen.functions as an exocrine gland because itsecretes bile.

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Is a pear-shaped bag, with a capacity of about50ml.

Break down products

Bile salts, bilirubin, cholesterol, phospholipids,proteins, electrolytes and water: secreted byhepatocytes

they are eventually transported down the bileduct.

Structure of the liver

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The basic structural units of the liver: "classical"

liver lobules.Portal triads are embedded in interlobular

connective tissue

Classical liver lobule is asix-sided prism, it is delimited

by interlobular connective

tissue.

The lobule is filled by cords of

hepatic parenchymal cells,

hepatocytes which radiate

from the central vein and

separated by vascular

sinusoids.

central vein

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Between the hepatocyte plates are the liversinusoids (capillaries). Blood from both the hepatic portal vein and the hepaticartery percolates (filter through pores) from triad regionsthrough these sinusoids and empties into the central vein.

Inside the sinusoids are star-shaped hepatic

macrophages, called Kupffer (koopfer) cells. Remove debris such as bacteria and worn-out blood cellsfrom the blood as it flows past.

Secreted bile flows through tiny canals, called bilecanaliculi (little canals), that run betweenadjacent hepatocytes toward the bile duct branchesin the portal triads.

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Hepatocytes are metabolically active cellsthat take up glucose, minerals andvitamins from the blood and store them.

can produce many important substancesneeded by the body, such as bloodclotting factors, transporter proteins,cholesterol, and bile components.

regulating blood levels of substances suchas cholesterol and glucose liver helps maintain body homeostasis.

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Glucose.plays a key role in the homeostatic control ofblood glucose, by storing or releasing it asneeded, in response to the pancreatic hormonesinsulinand glucagon.

Proteins.Most blood proteins (except antibodies) aresynthesized and secreted by the liver, e.g.albumin

Decreased amounts of serum albumin may lead

to oedema - swelling due to fluid accumulationin the tissues.The liver also produces most of the proteinsresponsible for blood clotting, called clottingfactors.

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Bile.a greenish fluid synthesized by hepatocytes

secreted into the bile duct; stored in the gallbladderbefore being emptied into the duodenum.

Bile is both excretory and secretory

In addition to bile salts, it contains cholesterol,phospholipids, and bilirubin (from the breakdown ofhaemoglobin).

Bile salts act as "detergents" that aid in thedigestion and absorption of dietary fats.

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Lipids.

Cholesterol (a type of lipid), is an essentialcomponent of cell membranes.

The liver synthesizes cholesterol, which thencirculates in the body to be used or excreted into

bile for removal.

Increased cholesterol concentrations in bile maylead to gallstone formation.

The liver also synthesizes lipoproteins, whichcirculate in the blood and shuttle cholesterol andfatty acids between the liver and body tissues.

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The liver stores glucose in the form of

glycogen,Fat-soluble vitamins (A, D, E and K),

Vitamins B6, and B12

Minerals such as copper and iron.

However, excessive accumulation of certainsubstances can be harmful.

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Ammonia.The liver converts ammonia to urea, which is

excreted in urine by the kidneys =>

deamination.

The liver can also convert one amino-acid into

a keto acid to form a different amino acid (but

not essential amino-acids) => transamination

(via the citruline-ornithine pathway)

In adult humans only 11 of 20 amino acids canbe made by transamination.

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Bilirubin.a yellow pigment formed as a breakdown product

ofred blood cell haemoglobin.

The spleen, which destroys old red cells,

releases bilirubin into the blood, where it

circulates to the liver which excretes it in bile.

Excess bilirubin results in jaundice, a yellowpigmentation of the skin and eyes.

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Hormones.

The liver plays an important role in hormonalmodification and inactivation, e.g. the steroidstestosterone and oestrogen are inactivated by theliver.

Men with cirrhosis (chronic inflammation of theliver, results from chronic alcoholism or severechronic hepatitis), especially those who abusealcohol, have increased circulating oestrogen,which may lead to body feminization.

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Drugs.

Nearly all drugs are modified or degraded in theliver.

oral drugs are absorbed by the gut and transportedto the liver, where they may be modified orinactivated before they enter the blood.

Alcohol, in particular, is broken down by the liver,and long-term exposure to its end-products can

lead to cirrhosis.

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Toxins.

The liver is generally responsible for detoxifyingchemical agents and poisons.

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Most liver disease is symptomless and whenthere are symptoms they are often vague.

Jaundice (a yellow discoloration of the skin andthe whites of the eyes).

Hepatitis (cause by virus) Hepatitis A, spread by food and drinking water Hepatitis B, spread by blood-to-blood contact and alsosexually

Hepatitis C, by blood borneCholestasis (reduction or stoppage of bile flow)Cirrhosis (results from infection with hepatitis Band C, alcohol misuse)

Liver enlargement, portal hypertension (abnormally high blood pressure in the veins thatbring blood from the intestine to the liver)

Gall bladder disease (gallstone)Paracetamol poisoning

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Higher risk in women is mostly due to the shortness of the female urethra,which is 1.5 inches compared to 8 inches in men. Bacteria from fecal matterat the anal opening can be easily transferred to the opening of the urethra.

Men become more susceptible to UTIs after 50 years of age, when they beginto develop prostate problems.

common type of infection caused by bacteria (most often E.

coli) that travel up the urethra to the bladder.Cystitisbladder infection

Pyelonephritisbacterial infection spreads to the kidneysand uretersReasons of UTI:

women urethra is shorterfrequent sexual intercoursecontraceptive spermicides and diaphragm usewomen reach menopause, the loss of estrogen thins the

lining of the urinary tractincrease the risk of developing a serious infection

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Strong urge to urinate frequently, evenimmediately after the bladder is emptied

Painful burning sensation when urinating

Discomfort, pressure, or bloating in thelower abdomen

Pain in the pelvic area or back

Cloudy or bloody urine, which may have a

strong smell

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Boys who are uncircumcised are about 10 - 12 times morelikely than circumcised boys to develop UTIs by the time theyare 1 year old. (2%)

After the age of 2 years, UTIs are far more common in girls.(8%)

Vesicoureteral reflux: If leftuntreated, urinary infections can cause

kidney damage, renal scarring

(potentially stunting kidney growth),and high blood pressure later in life.

Catheterization: surgical procedures to theurethra, in unconscious patients (due to surgical

anesthesia or coma), or for any other problem inwhich the bladder needs to be kept empty

(decompressed) and urinary flow assured.

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Appropriate hygiene and cleanliness of the genital area may helpreduce the chances of introducing bacteria through the urethra. FOOD INTAKE

Cranberries, blueberries, andlignonberry containcompounds called tannins (orproanthocyanadins).

1- 2 cups of cranberry juicedaily

Probiotics: lactobacilli strains,such as acidophilus, which isfound in yogurt and otherfermented milk products(kefir), as well as in dietarysupplement capsules.

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Most kidney diseases attack thenephrons, causing them to losetheir filtering capacity.

Damage to the nephrons canhappen quickly, often as theresult of injury or poisoning.

But most kidney diseases destroythe nephrons slowly and silently.

Only after years or even decadeswill the damage becomeapparent.

Most kidney diseases attack both

kidneys simultaneously.

Only one kidney is enough for alifetime and you can live a

normal healthy life just byhaving a single kidney.

When one of your kidneys isremoved the remaining kidneytakes on or does the work ofboth the kidneys.

Certain changes also take placein the remaining kidney so that itcan maintain homeostasis.

Involves change in glomerularfiltration rate

people born with one kidney and

those who donate a kidney fortransplantation can also lead anormal healthy life.

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Even if you don't haveboth the kidneys youcan still survive withthe help of dialysis.

When a person is leftout with only onekidney: 4 - 7% risk ofpermanent dialysis

If a part of it needs tobe removed: 3 - 4%risk of temporarydialysis.

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Hemodialysis

Pentoneal dialysis

Transplantation