Biological and Medical Application - 2F B

8/3/2019 Biological and Medical Application - 2F B

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OSMOSIS


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Osmosis Is usually defined as the transport of water

through a semi-permeable membrane due to

an imbalance on its concentration on eitherside of the membrane.

Reverse osmosis takes place when the pressure opposing

osmosis exceeds the osmotic pressure.


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If one of the solution is pure water, then thepressure necessary to stop the flow of water fromthe region of high concentration to the region oflower concentration.

Relative osmotic pressureThe pressure on the right is then greater than thepressure on the left by amount ofhpg ;where p is

the density of the liquid, this extra pressure wascreated by osmosis, and once h becomes largeenough, the pressure forces water back throughthe membrane as the same rate as it moves

through osmosis.


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EXAMPLES OF OSMOSISIN BIOLOGICAL

ORGANISMWater intake by Roots and turgor in plantsEpsom saltsRegulation of fluid between cells (interstitial

fluid)

Swelling (edema) due to heart failureEffect of electrolyte balance


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Water intake by roots and turgor in

plants-osmosis between water and roots is thought o be

responsible for the transfer of water into many plants.

Ground water is purer and has a higher concentration thansap, so osmosis moves water into roots. Water in sap isthen transferred by osmosis into cells causing them toswell with increased pressure. This pressure is called

turgorpressure partly responsible for availability forplants to stand up.


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Epsom salt

-soaking a sprinkled ankle in epsom salt is acommon method of reducing swelling. The concentrationof the water in the swollen part of the ankle is greater thanin he epsom salts solution. Osmosis therefore transportswater out of the ankle into the soaking solution.

Regulation of the fluids between cells-I n humans and other animals the interstitial fluid

is regulated by exchange of substances with blood incapillaries. Many substances are moved across thecapillary but the transport of water is of immediateinterest.


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Swelling edema due to heart failure

-if the patient suffers from right heart failure, thenthe heart is less effective in taking up the blood sent to it,the pressure at the right capillary rises.

Edema-causes reverse osmosis all along thecapillary and the build up of interstitial fluid.

PulmonaryEdema-If the patient is experiencingleft heart failure, the pressure increases in the lungs,causing reverse osmosis.And there is the water build up.


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Effect of electrolyte balance

-too much salt consumption causes water retentionbecause osmosis carry water from the salty blood into theinterstitial region.

Electrolyte-essentially dissolved salts.


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Dialysis


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Dialysis

-is the diffusion of substances other than waterthrough semi permeable membrane and occurs in kidneysand many other places in biological organisms.

ReverseDialysis-also called filtration-occurs in high concentration side is large enough

to reverse the normal direction of dialysis.


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Two examples of dialysis in humans

Kidney functionEffects of diuretics

Kidney failureCan cause high blood pressure. If filtrationslows or stops in glomerulus, the kidney emits ahormone called renin that causes blood pressure

to rise so that filtration recommences. high blood pressure can even cause capillaries

in the glomerulus to burst.


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Effects of Diuretics

Diuretics- any substance that increased urine outputs.-the presence of such molecule decreases the

concentration of water in the tube and its

reabsorption , resulting in a greater production ofwater in the urine.


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Active transport

-in which the living membrane itself suppliesenergy to cause the transport of a substance.

-can also aid ordinary osmosis or dialysis and

explains why some transport proceeds faster than osmosisand dialysis alone.


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The Cardiovascular System

- many of the characteristics of vascular system canbe explained in terms of laws of physics.

-cardiovascular system is consist of two pumps

the right side of the heart and the left side of theheart and complex arrangement of vessels thattransports blood through nearly every part of thebody.

-the maximum and minimum pressure is systolicand diastolic.Diastolic-due to the elasticity of the arteries*minimum pressure is 80mm Hg.


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The Heart as aDouble Pump

-the purpose of any pump is to create pressureexerting a force directly in the fluid.

-the heart of some animals including humans,consist of two pumps and two reservoirs preceding thosepumps.

-right side of the heart pumps blood trough thelungs to the left side of the heart.

-left side of the heart pumps blood through the restof circulatory system , returning it to the right side of heheart , where the process begins again


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Pressures around the system

-resistance in the system causes pressure to drop asblood flows in the system.

P1 P2=FR

*where P1 is the pressure at the entrance of a tube and P2at its exit

-pressure drop is equal to the resistance and flowrate. The resistance R depends strongly on the radius, sothe pressure drop in the aorta is fairly small, while in thecapillaries is fairly large.


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Blood Velocities and branching

-the velocities of the blood is much greater in themajor arteries about 30cm/sec than in the capillaries about

310cm/sec.-the total flow rate in the major arteries is the same

as in the aorta since all the blood which passes throughthe aorta passes through the major arteries. Therefore,

F aorta=F major arteries


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Effect of gravity in the Circulatory

System-gravity affects pressure but not flow rate in the

Circulatory System. In any closed system, pressure due togravity has no net effect on flow rate, much at theatmosphere has no effect in a flow of IV.

-gravity can have effect in fluid balance.P=hpg

*where h is depth in the fluid, p is density and g is theacceleration of gravity.*where h is positive in any point below the heart andnegative in any point above the heart.


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The blood pressure in the major arteries on the head isthen:

P head= P heart-h head pg*can cause fainting if P head is too low.

Pressure in the major arteries in the legs isP legs=p heart + h head pg

* the larger fluid in the legs can cause edema.


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Flow regulation in the circulatory

system.-blood flow is adjusted by both changes in vessel

radii and by changes in blood pressure.

In tube of uniform diameter, fluid flows obeyrelationship.

F= (P1-P2)/R


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Poiseuilles law

-a resistance always decreases when radiusincreases and increases when viscosity increases.

Applicability of Poiseuilles law- does not quantitatively

describe blood flow very accurately for a no. of reasons.First-blood is not an ideal fluid.Second-vessel wall are not rigid.Third- Poiseuilles law is only valid for non turbulent

flow*Poiseuilles law is widely applied to blood flow anddoes not give a good qualitative description of thedependence of flow on radius and viscosity.


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Biological and Medical Application - 2F B

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