Pulmonary circulation and gas transport (physio)

Question 1

Route of pulmonary circulation after birth

Answer 1

Deoxy blood from tissues flow in right atrium (RA) -> right ventricle (RV) -> main pulmonary artery -> branches successively into small pulmonary arteries -> arterioles -> capillary bed around alveoli -> gas exchange -> oxygenated blood flow into small pulmonary veins (PV) -> 4 large PV -> left atrium (LA) -> left ventricle (LV) -> systemic circulation

Question 2

Does pulmonary or systemic circulation have higher pressures?

Answer 2

Systemic

Question 3

Features of pulmonary circulation

Answer 3

Low pressure

High flow -> lungs receive whole of CO at all times

Distribution of blood flow in lungs is not uniform

Question 4

Other fns of pulmonary circulation

Answer 4

Metabolism of hormones
- angiotensin converting enzyme (ACE) converts angiotensin 1 -> angiotensin 2

Question 5

What influences distribution of blood flow in lungs?

Answer 5

Gravity -> posture
- upright -> more blood flow at bottom

Muscular tone of pulmonary arterioles -> change diameter of arteriole
- distension
- pulmonary artery and arterioles have less muscular walls (compared to systemic) -> distend more easily w/ increased blood flow
- vasoconstriction
- decreased blood flow through capillaries

Question 6

Describe pulmonary circulation in fetus

Answer 6

Lungs collapsed -> non-functional -> little blood floe thru lungs

Oxygenated blood from placenta enter via umbilical vein -> right heart -> left heart via foramen ovale (opening btw RA and LA) -> pulmonary artery -> aorta via ductus arteriosus -> systemic circulation

Question 7

Special properties of pulmonary circulation in foetus

Answer 7

High pressure, low flow sys

Lungs are collapsed -> not useful for gas exchange

Question 8

Special properties of pulmonary circulation after birth

Answer 8

Low pressure, high flow sys

Gravity-dependent

Blood flow through capillaries regulated by arteriolar tone

Question 9

Factors affecting O2 transport

Answer 9

Respi sys
- lung fn

CVS
- CO, vascular constriction/dilation affecting blood flow in capillaries

Blood
- capacity to carry O2

Question 10

Sources of O2 in blood

Answer 10

Hb in RBC

Dissolved free O2 molecules
- exerts pO2 in blood

Question 11

Sources of CO2 in blood

Answer 11

Converted to HCO3-

Bound to proteins including Hb -> carbamino cmpds

Dissolved free CO2 molecules
- exerts pCO2 in blood

Question 12

What do dissolved gases in fluid do?

Answer 12

Create gas pressure within fluid

Question 13

What happens when there is increased dissolved gas in fluid?

Answer 13

Increase gas pressure in fluid

Question 14

High vs low solubility gas

Answer 14

High solubility -> more free gas molecules dissolve to create a particular gas pressure in fluid

Low solubility -> fewer free gas molecules dissolve to create similar gas pressure in fluid

Question 15

At equilibration, is the amt of gas dissolved in liquid in both compartments the same?

Answer 15

No, amt of gas dissolved depends on the solubility of the gas

If A more soluble than B in fluid, more A molecules will be dissolved in fluid when equilibrium reached

Question 16

Does O2 have good solubility in blood?

Answer 16

No -> dissolved O2 is insufficient for physiological needs

Question 17

Eqn for Hb fusion w/ O2

Answer 17

Hb + O2 <-> HbO2

Question 18

Type of Hb for normal adult and foetus

Answer 18

Adult -> HbA

Fetal -> HbF

Question 19

Does normal adult or foetus Hb have a higher affinity for O2?

Answer 19

HbF > HbA
- HbF have higher affinity -> Hb binds w/ higher efficiency than adult Hb -> extract O2 from mother

Question 20

How many O2 molecules can 1 molecule of Hb bind to?

Answer 20

4 O2 molecules
- 1 Hb have 4 Fe -> bind to 4 O2
- each Fe atom bind reversibly to 1 O2 -> oxygenate tissue

Question 21

Factors affecting amt of O2 carried by Hb

Answer 21

pO2 in blood
- higher pO2 -> more O2 binds to Hb up till saturation capacity

Conc of Hb in blood
- more Hb -> more O2 can bind

Affinity of Hb for O2
- higher affinity -> more O2 can bind

Question 22

Factors affecting affinity of Hb for O2

Answer 22

pH
- low pH -> lower affinity

Temp
- higher temp -> lower affintiy

2,3-diphosphoglycerate
- increased levels -> lower affinity

Question 23

Shape of HbO2 dissociation curve

Answer 23

Sigmoid shape (S-shaped curve)

Question 24

What is the HbO2 dissociation curve?

Answer 24

Relate HbO2 and pO2 of blood

Question 25

What happens when blood pO2 drops?

Answer 25

pO2 drop <100 - 60mmHg -> minimal drop in %HbO2 (based on curve)
- sufficient O2 supply in blood for tissues

pO2 drop to <60mmHg -> severe drop in %HbO2 -> decreased O2 supply in blood for tissues

Question 26

How does affinity for O2 shift the HbO2 dissociation curve?

Answer 26

Higher affinity -> increased O2 binding to Hb -> increased %HbO2 -> shift left

Lower affinity -> decreased O2 binding to Hb -> decreased %HbO2 -> shift right

Question 27

Purpose of Cl- in gas CO2 transport

Answer 27

Cl- shift maintains electrical neutrality -> move from plasma into RBC as HCO3- moves into plasma
- because RBC loses negatively charged ion

Question 28

What happens when CO2 is excreted?

Answer 28

Removes H+

Question 29

CO2 vs O2 dissociation curve

Answer 29

CO2 curve is much steeper and more linear
- as long as blood pCO2 decrease -> CO2 content in blood decrease