Department of medical physiology5th week

Semester: winterStudy program: Dental medicineLecture: RNDr. Soňa Grešová, PhD.Department of medical physiologyFaculty of Medicine PJŠU

Department of medical physiology5th week

1. Pressures in the pulmonary system

2. Transport of the respiratory gases by blood

3. Respiratory gases exchange

4. Blood flow through the lungs and ventilation-perfusion ratio

1. Pressures in the Pulmonary System• The systolic pressure in the right

ventricle about 25 mm Hg, and the diastolic pressure averages about 0 to 1 mm Hg

• During systole, the pressure in the pulmonary artery is essentially equal to the pressure in the right ventricle about 25 mm Hg, the diastolic pulmonaryarterial pressure is about 8 mm Hg, and the mean pulmonary arterial pressure is 15 mm Hg.

• The mean pulmonary capillary pressure, is about 7 mm Hg

• The mean pressure in the left atrium and the major pulmonary veins averages about 2 mm Hg (varying from as low as 1 mm Hg to as high as 5 mm Hg)

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

The systemic arteriesMean BP= 100 mmHg

Pulmonary arteriesBP=25 mm Hg/8mmHg (Mean BP= 15 mmHg)

Pulmonary capillariesMean BP =7 mmHg

Calculation of mean arterial bloodpressure (MAP)

𝑀𝐴𝑃 = 𝐷𝐵𝑃 +1

3(SBP-DBP)

Right ventricleBP= 25 mm Hg/0-1 mmHg

The left ventricleBP= 120mmHg/0mmHg

The major pulmonaryveins andthe left atriumMean BP= 5 mmHg

1. Pressures in the pulmonary system

1. Pulmonary Capillary Dynamics

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

2. Transport of Oxygen

O2 transport

• Transported two ways:

1) Dissolved in blood (3%)

– partial pressure of oxygen (Po2)

2) In chemical combination with Hb (97%)

– oxyhemoglobin

2. Uptake of Oxygen by pulmonaryblood and Po2

• The alveolus

Po2 = 104 mmHg

• the venous blood entering thepulmonary capillary

Po2 = 40 mmHg

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

2. Transport of oxygen in the arterialblood and Po2

• Blood is mixed withpulmonary shunt blood

• the bronchial circulation(2%)

– venous admixture of blood

– Po2 falls = 95 mmHg

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

2. Diffusion of oxygen from the peripheralcapillaries into the tissue fluid and Po2

• the arterial blood

Po2 = 95 mmHg

• the interstitial fluid

Po2 = 40 mmHg

• the blood leaving the tissue capillaries and entering the systemicveins

Po2 = 40 mmHgCopyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

2. Effect of blood flow and rate of oxygen consumption on tissue PO2

• Effect of rate of bloodflow on interstitial fluidPO2

– points A, B, C

• Effect of rate of tissue metabolism on interstitial fluid PO2

– curves O2 consumption

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

2. Transport of carbon dioxide

CO2 transport

• Transported three ways:

1) Dissolved in blood (7%)

– partial pressure of carbon dioxide (Pco2)

2) In the form of bicarbonate ion (70%)

3) In combination with Hb (23%)

– carbaminohemoglobin

2. Diffusion of Carbon Dioxide and Pco2

• Intracellular Pco2, = 46 mm Hg

• Interstitial Pco2,= 45 mm Hg

• The arterial blood entering the tissuesPco2 = 40 mm Hg

• The venous blood leaving the tissuesPco2 = 45 mm Hg

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

2. Diffusion of Carbon Dioxide and Pco2

• the blood entering the pulmonary capillaries at the arterial end

Pco2 = 45 mmHg

• Pco2 of the alveolar air

= 40 mm Hg

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

2. Effect of blood flow and metabolic rate on peripheral tissue Pco2

• Effect of rate of bloodflow on interstitial fluidPco2

– points A, B, C

• Effect of rate of tissue metabolism on interstitial fluid Pco2

– curves of metabolic rate

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

3. Exchange of O2 and CO2 in pulmonary capillaries

3. Exchange of O2 and CO2 in systemiccapillaries

Oxygen-hemoglobin dissociation curve.The Bohr effect

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

Carbon dioxide dissociation curve. The Haldane effect

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

Transport of the respiratory gases by blood

VO2= 5ml/100mlVCO2= 4ml/100ml

VCO2= 4ml/100mlVO2= 5ml/100ml

VO2= 20ml/100mlVCO2= 48ml/100mlPCO2= 40 mmHgPO2= 95 mmHgpH= 7,4Hgsaturation=97%

VO2= 15ml/100mlVCO2= 52ml/100mlPCO2= 45 mmHgPO2= 40 mmHgpH=7,36Hgsaturation=75%

4. Blood flow through the lungsand its distribution

• Zone 1:

– no blood flow during all portions of the cardiac cycle

• Zone 2:

– intermittent blood flow

• Zone 3:

– continuous blood flow

• Normally, the lungs have only zones 2 and 3 blood flow—zone 2 (intermittent flow) in the apices, and zone 3 (continuous flow) in all the lower areas.

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

Lung Ventilation/Perfusion ratioV/Q

• Alveoli at apex are underperfused(overventilated)

V=more than 4000ml/minQ=less than 5000ml/min

(V/Q >0,8)

• Alveoli at the base are underventilated(overperfused)

V=less than 4000ml/minQ=more than 5000ml/min

(V/Q<0,8)

Ventilation – Perfusion Mismatching

• Blood goes to parts of the lung that do nothave oxygen to give it

Obstruction of airways(regulation-constriction of vessels)

• Blood does not go to parts of the lung thathave oxygen

Thrombus(regulation-bronchoconstriction)

Copyright: https://quizlet.com/101536103/pathophysiology-chapter-21-respiratory-function-alterations-in-gas-exchange-flash-cards/