transport of oxygen and carbon dioxide. session format at the end of this lecture the student will...

Transport of oxygen and Transport of oxygen and carbon dioxidecarbon dioxide

Session formatSession format

At the end of this lecture the student will be At the end of this lecture the student will be able to:able to:

understand how Ounderstand how O22 and CO and CO22 are transported are transported around the body.around the body.

describe the structure, function and location describe the structure, function and location of RBC, haemoglobin and myoglobin.of RBC, haemoglobin and myoglobin.

describe the oxygen dissociation curve for describe the oxygen dissociation curve for haemoglobin.haemoglobin.

understand the Bohr effect.understand the Bohr effect.

RecapRecap

The cardiovascular system is composed of The cardiovascular system is composed of the heart, blood and the heart, blood and

The main job of the cardiovascular system is The main job of the cardiovascular system is to transport respiratory gases (Oto transport respiratory gases (O22 and CO and CO22) ) around the body. around the body.

This is in the form of oxygenated and This is in the form of oxygenated and deoxygenated blood.deoxygenated blood.

Q: Which blood has the highest concentration Q: Which blood has the highest concentration of COof CO22; oxygenated or deoxygenated blood?; oxygenated or deoxygenated blood?

RecapRecap

During exercise the demand for oxygen During exercise the demand for oxygen Especially at the Especially at the This is because OThis is because O22 is required for the is required for the

production of (Energy).production of (Energy). The energy is used for muscular contraction The energy is used for muscular contraction

and hence movement of the body.and hence movement of the body. During exercise the cardiac output is During exercise the cardiac output is

increased by increasing increased by increasing

RecapRecap

Remember that:Remember that: Heart rate is the amount of heart beats per Heart rate is the amount of heart beats per

minute.minute. Stroke volume is the amount of blood Stroke volume is the amount of blood

ejected from the heart with each beat.ejected from the heart with each beat. Cardiac output is the total amount of blood Cardiac output is the total amount of blood

pumped out of the heart in one minute.pumped out of the heart in one minute. Cardiac output = Cardiac output =

RecapRecap

Sympathetic activity = Sympathetic activity = Parasympathetic activity = Parasympathetic activity = Increase in heart rate is due to an increase Increase in heart rate is due to an increase

in sympathetic activity.in sympathetic activity. Accompanied by a decrease in Accompanied by a decrease in

parasympathetic activity.parasympathetic activity. Hormonal control by adrenaline and Hormonal control by adrenaline and

RecapRecap

Blood is shunted away from certain organs Blood is shunted away from certain organs during exercise and redirected to the during exercise and redirected to the working muscles.working muscles.

““Supply and Demand”Supply and Demand” This is achieved through vasoconstriction This is achieved through vasoconstriction

and vasodilation of the and vasodilation of the Q: Will the blood vessels supplying the Q: Will the blood vessels supplying the

working muscles vasodilate or vasoconstrict working muscles vasodilate or vasoconstrict during exercise?during exercise?

Transport of OTransport of O22 Oxygen picked up by the blood at the lungs ( Oxygen picked up by the blood at the lungs (

) must be transported to the ) must be transported to the tissues.tissues.

Oxygen is transported in the blood in two forms:Oxygen is transported in the blood in two forms:– physically dissolved in the blood ( )physically dissolved in the blood ( )– bound to haemoglobin ( )bound to haemoglobin ( )

Very little OVery little O22 is dissolved in the plasma of the is dissolved in the plasma of the blood as it poorly soluble.blood as it poorly soluble.

Due to the small amount of ODue to the small amount of O22 dissolved in the dissolved in the blood there must be an additional mechanism of blood there must be an additional mechanism of transporting oxygen from the lungs to the transporting oxygen from the lungs to the tissues.tissues.

Transport of OTransport of O22

This mechanism is (Hb)This mechanism is (Hb) Haemoglobin - iron bearing protein molecule Haemoglobin - iron bearing protein molecule

contained within red blood cells (RBC).contained within red blood cells (RBC). 280 million haemoglobin molecules crowded into 280 million haemoglobin molecules crowded into

each RBC. each RBC. Men have more haemoglobin than women.Men have more haemoglobin than women. Due to male testosterone increasing RBC Due to male testosterone increasing RBC

production. production. Haemoglobin has the ability to form a reversible Haemoglobin has the ability to form a reversible

combination with oxygen.combination with oxygen. Q: What does reversible mean?Q: What does reversible mean?


When not combined to OWhen not combined to O22, haemoglobin is , haemoglobin is referred to as referred to as reduced haemoglobinreduced haemoglobin..

When combined with OWhen combined with O22, it is called , it is called

Hb + OHb + O22 HbO HbO22

HaemoglobinHaemoglobin Oxygen OxygenOxyhaemoglobinOxyhaemoglobin


The haemoglobin molecule has four atoms The haemoglobin molecule has four atoms of iron.of iron.

Each of the four iron atoms has the ability Each of the four iron atoms has the ability to combine with .to combine with .

Each Hb molecule can carry up to 4 Each Hb molecule can carry up to 4 molecules of Omolecules of O22..

Hb is considered to be Hb is considered to be fully saturatedfully saturated when all iron atoms combine with a when all iron atoms combine with a molecule of Omolecule of O22..


The percent haemoglobin saturation (%Hb) is The percent haemoglobin saturation (%Hb) is a measure of the extent to which Hb in the a measure of the extent to which Hb in the blood is combined with Oblood is combined with O22..

Can vary from 0 to 100%Can vary from 0 to 100% 100% = all of the haemoglobin molecules 100% = all of the haemoglobin molecules

within the blood are fully saturated with Owithin the blood are fully saturated with O22.. Healthy individuals = Healthy individuals = Hb Hb Influenced by POInfluenced by PO22 of the blood. of the blood. POPO22 = partial pressure of Oxygen. Caused by = partial pressure of Oxygen. Caused by

movement of dissolved oxygen in the blood.movement of dissolved oxygen in the blood.


Gases (OGases (O22 and CO and CO22) move down partial pressure ) move down partial pressure gradients.gradients.

POPO22 is high at the (pulmonary capillaries). is high at the (pulmonary capillaries). POPO22 is low at the (systemic capillaries). is low at the (systemic capillaries). When POWhen PO22 is high oxygen combines readily with is high oxygen combines readily with

haemoglobin, until the haemoglobin becomes haemoglobin, until the haemoglobin becomes saturated. Called oxygenationsaturated. Called oxygenation

When the POWhen the PO22 is low haemoglobin releases O is low haemoglobin releases O22 to to the tissues. Called deoxygenationthe tissues. Called deoxygenation


Because of the difference in POBecause of the difference in PO22 at the at the lungs and the tissues, Hb automatically lungs and the tissues, Hb automatically loads up on oxygen at the lungs loads up on oxygen at the lungs (oxygenation) and unloads it at the tissues (oxygenation) and unloads it at the tissues (deoxygenation).(deoxygenation).

The relationship between POThe relationship between PO22 and % and % haemoglobin saturation is known as the:haemoglobin saturation is known as the:

Oxygen -Haemoglobin Dissociation CurveOxygen -Haemoglobin Dissociation Curve S - shaped curve (see graph)S - shaped curve (see graph)

Oxygen - Haemoglobin Dissociation Oxygen - Haemoglobin Dissociation CurveCurve

100100

8080

% sat 60% sat 60

of Hbof Hb

4040

2020

00

00 20 20 40 40 60 60 80 80 100 100 POPO22


Note: from the Oxygen haemoglobin Note: from the Oxygen haemoglobin dissociation curve that the % saturation of dissociation curve that the % saturation of haemoglobin is higher at the lungs and haemoglobin is higher at the lungs and lower at the tissues.lower at the tissues.

Oxygen is attaching to haemoglobin at the Oxygen is attaching to haemoglobin at the lungslungs

Oxygen is unloading Oxygen is unloading

The Bohr effectThe Bohr effect Oxygen - haemoglobin curve shown Oxygen - haemoglobin curve shown

previously is at normal conditions (pH 7.4, previously is at normal conditions (pH 7.4, tissue Temp of 37tissue Temp of 37ooC).C).

Any increase in acidity, temperature or Any increase in acidity, temperature or concentration of carbon dioxide causes the concentration of carbon dioxide causes the dissociation curve to shift downwards and dissociation curve to shift downwards and to the right.to the right.

In other words the haemoglobin releases In other words the haemoglobin releases oxygen more readily.oxygen more readily.

Known as theKnown as the

The Bohr EffectThe Bohr Effect

100100

8080 rightward shift due to increased rightward shift due to increased

carbon dioxide, acidity and temp.carbon dioxide, acidity and temp.

% sat 60% sat 60

of Hbof Hb

4040

2020 CO2, acidity, Temp CO2, acidity, Temp

00

00 20 20 40 40 60 60 80 80 100 100 POPO22

Carbon MonoxideCarbon Monoxide Carbon Monoxide (CO) is a poisonous gas.Carbon Monoxide (CO) is a poisonous gas. Found in such things as motor car fumes.Found in such things as motor car fumes. Carbon Monoxide and Oxygen compete for Carbon Monoxide and Oxygen compete for

the same binding sites on Haemoglobin.the same binding sites on Haemoglobin. CO is times more likely to attach to CO is times more likely to attach to

haemoglobin than Ohaemoglobin than O22.. Therefore if CO is present oxygen Therefore if CO is present oxygen

is transported in the blood.is transported in the blood. Death can occur due to oxygen starvation of Death can occur due to oxygen starvation of

the tissues.the tissues.

MyoglobinMyoglobin

Myoglobin is an iron containing protein.Myoglobin is an iron containing protein. Found in skeletal and muscleFound in skeletal and muscle It’s function is as a storage site for .It’s function is as a storage site for . Similar to haemoglobin - combines reversibly Similar to haemoglobin - combines reversibly

with oxygen.with oxygen. Each myoglobin molecule contains 1 iron atom, in Each myoglobin molecule contains 1 iron atom, in

contrast to haemoglobin which contains 4 atoms.contrast to haemoglobin which contains 4 atoms. High concentration of myoglobin in slow twitch High concentration of myoglobin in slow twitch

muscle fibres (generate ATP aerobically).muscle fibres (generate ATP aerobically).

MyoglobinMyoglobin

Facilitates (helps) the transfer of oxygen to the Facilitates (helps) the transfer of oxygen to the tissues.tissues.

Especially during beginning of exercise and duringEspecially during beginning of exercise and during

During rest and moderate levels of exercise the During rest and moderate levels of exercise the myoglobin stays attached to the oxygen.myoglobin stays attached to the oxygen.

Unlike haemoglobin, myoglobin is not affected by Unlike haemoglobin, myoglobin is not affected by acidity, carbon dioxide and temperature.acidity, carbon dioxide and temperature.

Therefore does not display theTherefore does not display the

Transport of Carbon dioxide Transport of Carbon dioxide (CO(CO22))

Remember - gases flow a Remember - gases flow a pressure gradient.pressure gradient.

When blood flows through the tissue When blood flows through the tissue capillaries COcapillaries CO22 diffuses down its pressure diffuses down its pressure gradient from the tissue cells into the blood.gradient from the tissue cells into the blood.

The blood then becomes . The blood then becomes . COCO22 is produced as a by product of is produced as a by product of

metabolism (energy production).metabolism (energy production).

Transport of Carbon dioxide Transport of Carbon dioxide (CO(CO22)) COCO22 is transported in the blood in three is transported in the blood in three

ways:ways:– physically dissolved (10%)physically dissolved (10%)– bound to haemoglobin (30%)bound to haemoglobin (30%)– as bicarbonate ( )as bicarbonate ( )

When COWhen CO22 combines with haemoglobin the combines with haemoglobin the product is known as carbomino-product is known as carbomino-haemoglobin (HbCOhaemoglobin (HbCO22).).

The unloading of OThe unloading of O22 at the tissues facilitates at the tissues facilitates the picking up of COthe picking up of CO22 by Haemoglobin. by Haemoglobin.

Transport of Carbon dioxide (COTransport of Carbon dioxide (CO22)) By far the most important means of By far the most important means of

transporting COtransporting CO22 from the tissues to the lungs from the tissues to the lungs is as a bicarbonate (HCOis as a bicarbonate (HCO33--).).

60% of the CO60% of the CO22 is converted to a bicarbonate. is converted to a bicarbonate. The chemical reaction takes place in theThe chemical reaction takes place in the

It is essential both at rest and during exercise It is essential both at rest and during exercise that Othat O22 and CO and CO22 are transported around the are transported around the body. This is achieved through various body. This is achieved through various mechanisms within the blood.mechanisms within the blood.

transport of oxygen and carbon dioxide. session format at the end of this lecture the student will...

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