1. Physiology of Respiration
Part IV
Prof. Dušan M. Mitrović, M.D., Ph.D

2. Blood flow and Metabolism
How the pulmonary Circulation
Removes Gas From the Lung
and Alters Some Metabolites

3. Systemic and Pulmonary Circulation

9. Pressures Around Pulmonary Blood Vessels
Note: around alveaolar vessels pressure is alveolar
The pressure difference between the isside and outside
of the capillaries is called transmural pressure

10. Many alveoli and an extra-alveolar vessel with its perivascular sheet

11. Pulmonary Vascular Resistance
input pressure – output pressure
Vascular resistance =
blood flow

12. Fall in pulmonary vascular resistance as the pulmonary arterial or venous pressure is raised.

13. There are two mechanisms for the decrease in pulmonary vascular
resistance that occurs as vascular pressures are raised
increase in caliber
of vessels
opening previously
closed vessels

14. Effects of lung volume on pulmonary vascular resistance
when the transmural pressure of capillaries is held constant
At low lung volumes, resistance is high because the extraalveolar vessels become narrow.
At high volumes, the capillaries are stretched, and their caliber is reduced.

15. Assesment of the pulmonary blood flow

16. Measurements of capillary blood flow by recording
nitrous oxide uptake in body plethysmograph

17. Distribution of Blood Flow

18. Measurement of the distribution of blood flow
in the upright human lung with radioactive xenon
Disolved xenon is envolved into alveolar gas from pulmonaru capilaries

19. Regional perfusion and gravity
PPA blood pressure in the pulmonary artery
PPV blood pressure in pulmonary vein
Ppc pericapillary pressure
PL,is interstitial pressure in the lung tissue
Qc capillary blood flow

20. The Starling resistors
Rubber tube
When chamber pressure exceeds downstream pressure (A), flow is independent of
downstream pressure.
When downstream pressure exceeds chamber pressure (B), flow is idetermined by
The upstream-downstream pressure difference.

21. Regional capillary blood volume

22. Active control of circulation
Hypoxic pulmonary vasoconstriction

23. Water Balance in the Lung

24. Lymph and fluid movement in the lung

25. Metabolic Function of the Lung
Peptides
Angiotenzin I Converted to angiotensin II by ACE
Bradykinin Up to 80% inactivated
Amines
Serotonin Almost completely removed
Noradrenalin Up to 30% removed
Arachidonic acid metabolites
Prostaglandin E2 and E2a Almost completely removed
Leukotriens Almost completely removed

26. Two pathways of arachidonic acid metabolism
Membrane-bound phospholipid
Phospholipase A2
Arachidonic acid
Cyclooxygenase
Lipoxygenase
Prostaglandins,
Tromboxane A2
Leukotriens