TRANPORT OF OXYGEN

DR NILESH KATE

MBBS,MDASSOCIATE PROF

DEPT. OF PHYSIOLOGY

TRANSPORT OF OXYGEN.

OBJECTIVES. Uptake of oxygen by pulmonary blood. Transport of oxygen in arterial blood. Release of oxygen in tissue. Vehicle for transport of oxygen.

Wednesday, May 3, 2023

INTRODUCTION Transport of gases occurs along

the conc gradient. Alveolar air PO2 : 104 mm Hg. Arterial blood PO2 :95 mm Hg Venous blood PO2: 40 mm Hg. Tissue interstitial fluid: 40

mm Hg.


UPTAKE OF OXYGEN BY PULMONARY BLOOD.

Alveolar PO2 -104 mm Hg.

Arterial blood po2 40 mm Hg.

Conc gradient of 64 mm Hg, transport is rapid.


TRANSPORT OF OXYGEN IN ARTERIAL BLOOD.

PO2 in pulmonary veins 104 mm Hg & in aorta 100 mm Hg.

Due to venous admixture Bronchial veins mix with

pulmonary capillaries Coronary blood through

Thebesian Veins.


TRANSPORT OF OXYGEN IN ARTERIAL BLOOD.

Dissolved form In combination with

haemoglobin. Oxygen in Arterial blood –

20ml/100 ml, in venous blood 15ml/100ml So 5ml/100 ml

transported from lungs to tissue.


DISSOLVED FORM Out of 5 ml transported 0.3 ml in

dissolved form & rest with Hb. As per Henry’s law dissolved gas

is proportional to Po2, so there is NO LIMIT for this transport as long as Po2 is high.

So dissolved O2 at high Po2 ( Hyperbaric Oxygen) is used for oxygenation in certain poisoning (CO)where Hb is denatured.


IN COMBINATION WITH HAEMOGLOBIN.

Oxygenation of haemoglobin Oxygen carrying capacity of haemoglobin O2-Hb dissociation curve. Shifts in O2-Hb dissociation curve. Concept of P50 & its significance. O2-Hb dissociation curve of Hb-F Effect of carbon monoxide on tranport of O2 Oxygen dissociation curve for myoglobin.


OXYGENATION OF HAEMOGLOBIN

Oxygen combine with Hb to form loose & reversible bond, this is oxygenation & Not Oxidation, convert Deoxyhaemoglobin into Oxyhaemoglobin.

Time taken 0.1 sec.


OXYGEN CARRYING CAPACITY OF HAEMOGLOBIN

1 gm of Hb bind with 1.34ml of O2

100 ml blood containing Hb 15gm% (15Χ 1.34) bind 20.1 ml of O2

But due to different shunts decreases to 19.8 ml out of which 0.3 ml in dissolved form & 19.5 ml as Oxyhemoglobin.


DISADVANTAGE Only Disadvantage

with this method is there is Ceiling with this transport due to Hb saturation.

% Saturation is Avg saturation of entire Hb molecule in the blood.


O2-HB DISSOCIATION CURVE. When relation between

PO2 & % of Hb saturation is plotted on graph we get OXYGEN-HAEMOGLOBIN DISSOCIATION CURVE.

It shows that % of Hb saturation increases with increase in PO2, but this relationship is not linear


SIGMOID SHAPED CURVE - CAUSE

When 1 molecule of O2 combines with Hb , affinity of Hb increases & so on

This is called Co-operative binding Kinetics.

Due to this O2-Hb dissociation curve is Sigmoid.


SIGMOID SHAPED CURVE - Advantage

Loading Zone – Related to process of O2 uptake in lungs. Even Po2 falls below 60

mmHg saturation is still 90%, so loading zone provide margin of safety.


SIGMOID SHAPED CURVE - Advantage

Unloading zone – related to O2 delivery in tissue, steep portion below Po2 60mmHg.

So that relatively large Oxygen is liberated at minor fall in o2 tension.( Buffering Effect)


SHIFTS IN O2-HB DISSOCIATION CURVE.

Shift to Right -Decreased affinity of Hb for O2.

Causes PCO2 & pH – Increase in

Pco2 shift curve to Right – Bohr’s effect.



Temperature – increase temperature is due to increase heat production, increased PCo2 due to rapid metabolism, decreased PO2 due to rapid consumption & decreased pH due to lactic acid accumulation.

2,3-Diphosphoglycerate – formed during Glycolysis via EMBEDEN-MEYERHOF pathway.



Shift to left – increase affinity of haemoglobin for oxygen.

Causes – Pco2 H + ion conc Temperature Fetal haemoglobin


CONCEPT OF P50 & ITS SIGNIFICANCE.

P50 – partial pressure of oxygen that produces 50% of saturation

Normal P50 – 25-27 mmHg. Significance – Hb affinity inversely proportional to

P50 value. Decreased p50 – Hb gets saturated at low po2, i.e shift to

left Increased p50 - Hb gets saturated at high po2, i.e shift to

right.


O2-HB DISSOCIATION CURVE OF HB-F

O2-Hb dissociation curve shifted to Left

As its affinity for 2,3-DPG is less than HbA

So its affinity to combine with oxygen is more than HbA.


EFFECT OF CARBON MONOXIDE ON TRANSPORT OF O2

CO has 200 more affinity for Hb.

Combines with Hb forms- Carboxyhaemoglobin

Decreases functional Hb conc.

And decreases O2 tension & O2 transport.


OXYGEN DISSOCIATION CURVE FOR MYOGLOBIN.

Present in Muscle specialised for sustained contraction

Dissociation curve is Rectangular Hyperbola – as it takes O2 at low pressure readily

It does not show Bohr’s effect At po2 40 mm Hg it is 95%

saturated & Hb 75% Act as temporary store house

of Oxygen


RELEASE OF OXYGEN IN TISSUE.

O2 release at Rest O2 release during

exercise.


O2 RELEASE AT REST

Oxygen Delivery – Normal o2 delivery is 1L/min

Oxygen Consumption – 5ml/100ml/min, so total

is 250 ml/min

Utilization Coefficient - % of O2 consumed out of

oxygen delivered to tissue.

250/1000 × 100 = 25%


O2 RELEASE DURING EXERCISE.

Depend on Severity of exercise

Delivery of oxygen – increased by Increase blood flow due to

increase cardiac output, local arteriole dilatation, increase in open capillaries.

Increase RBC count due to splenic contraction

Release of oxygen – by right sift of curve.


VEHICLE FOR TRANSPORT OF OXYGEN.

At PO2 100 mm Hg Whole blood – 19.8ml Hb soln – 19.5 ml plasma soln – 0.3 ml

At PO2 40 mm Hg Whole blood – 5 ml Hb soln – 1.5 ml plasma soln – 0.18 ml


Thank You

TRANPORT OF OXYGEN

Health & Medicine

Transcript of TRANPORT OF OXYGEN