Physiology Lecture 3.7: Pulmonary Circulation

What is the total blood volume in the body?

5000 ml

How much of the total blood volume is in systemic circulation?

84%

How much of the total blood volume is in pulmonary circulation?

9%

How much of the total blood volume is in the heart?

7%

What are the circulations of the lung?

1. Pulmonary

2. Bronchial

3. Lymphatics

What are the functions of the pulmonary circulation?

1. Oxygenate blood

2. Excrete CO2

How high is the pressure and flow of the pulmonary circulation?

Low pressure

High flow

What is the function of the bronchial circulation?

Supply lung tissue blood

How high is the pressure and flow of the bronchial circulation?

High pressure

Low flow

What is the function of the lymphatic system?

Remove intestinal fluid

What disease does the lymphatic system work to prevent?

Edema

Do pulmonary arteries and arterioles have larger or smaller diameters than systemic vessels?

Larger

Do pulmonary arteries have more or less smooth muscle in their walls than systemic arteries?

Far less

Do pulmonary arteries have high or low compliance?

High

Do pulmonary veins have more or less compliance than systemic veins?

About the same

Which pulmonary vessel is much more numerous and has a greater total cross sectional area?

Pulmonary capillaries

What are the consequences of the pulmonary anatomic features?

1. High flow rate

2. Distensible

3. Low pressure

4. Low flow resistance

How much of cardiac output does pulmonary circulation receive?

100%

Which pulmonary vessels have thinner walls that allow for distensibility?

Pulmonary arteries

How much lower is flow resistance in pulmonary flow than systemic flow?

1/10

Compared to the systemic vessels, do pulmonary arteries have thick or thin smooth muscle walls?

Thin

What are the triggers to pulmonary vasculature remodeling that leads to thicker pulmonary arteries?

1. EC injury

2. Hypoxia

3. Stress

4. Inflammation

5. Genetics

Is the range of arterial pressure higher or lower in pulmonary circulation than systemic circulation?

Lower

What is the distensibility of the pulmonary system vital for?

Keeping low pressure in arteries and capillaries

At resting, what pressure in the pulmonary circulation is potentially fatal?

> 20 mmHg

What is the mean pressure in systemic and pulmonary circulation?

Systemic - 100

Pulmonary - 15

What is the pressure of the pulmonary system after goin through the capillaries?

5 - 6 mmHg

What are the assumptions of Ohm's Law?

1. Homogenous fluid

2. Consistent

3. Laminar flow

4. Fixed geometry

What is the average value of pulmonary resistance?

2 mmHg.min/l

What is the average value of systemic resistance?

20 mmHg.min/l

Is the relationship between left atrial pressure and pulmonary arterial pressure linear?

No

Where do bronchial arteries originate from?

Thoracic aorta

How much of left ventricular output is diverted by the bronchial arteries?

2%

Where do the bronchial veins empty?

Pulmonary veins

What is the consequence of bronchial circulation?

Dip in oxygenation

Where are pulmonary arteries widely distributed along?

1. Arteries

2. Veins

3. Airways

Where are pulmonary arteries NOT widely distributed along?

Alveolar walls

Why is pulmonary lymphatics crucial for pulmonary function?

1. Vascular resistance

2. Diffusion

What is the main component of the colloid portion of pulmonary fluid?

Albumin

Which pressure is identical in both systemic and pulmonary pressure?

Capillary oncotic pressure

What causes lower capillary pressure in pulmonary circulation than systemic circulation?

Low ventricular pressure and resistance in lung

What causes lower interstitial pressure in pulmonary circulation than systemic circulation?

More active lymphatic pump in lungs

What causes lower interstitial oncotic pressure in pulmonary circulation than systemic circulation?

More protein leak out in lung

Where does pulmonary fluid move to from the pulmonary capillaries?

Interstitial space

Where does some pulmonary fluid leak through in the pulmonary capillaries?

Porous alveolar epithelium

What does removing alveolar fluid prevent?

Flooding

What does increasing the difference in capillary and interstitial pressure cause?

1. Fluid extrusion

2. Pulmonary edema

What are the causes of pulmonary edema?

1. Acute rise in pulmonary arterial pressure

2. Left ventricular failure

Where does the left ventricle draw blood from?

Left atrium

What does the remaining pleural fluid in the lungs do?

Lubricate pleural surfaces

What are the factors affecting pulmonary circulation?

1. Gravity

2. Exercise

3. Alveolar gas

How much does the pressure change in the pulmonary arteries at the apex of the lung?

- 15 mmHg

How much does the pressure change in the pulmonary arteries at the base of the lung?

+ 8 mmHg

How can you determine capillary diameter using pressures?

Pulmonary Capillary Pressure - Adaptive Lung Ventilation Pressure

What is the blood flow in Zone 1?

Zero flow

Where can Zone 1: Zero flow occur in the lungs?

Apex (Potentially)

What is the blood flow in Zone 2?

Intermittent flow

Where can Zone 2: intermittent flow occur in the lungs?

Apex and Middle Lung

When does Zone 2: intermittent flow occur?

During systole

Which zone has the greatest change in alveolar diameter?

Zone 2

What is the blood flow in Zone 3?

Continuous flow

Where can Zone 3: continous flow occur in the lungs?

Base

Do pulmonary vessels constrict or dilate during hypoxia?

Constrict

What is the physiological mechanism to improve ventilation, perfusion, and oxygenation in the pulmonary system?

Hypoxic pulmonary vasoconstriction

What is the function of Hypoxic pulmonary vasoconstriction?

Redirect blood flow to alveoli with higher oxygen content

How does strenuous exercise affect cardiac output and pulmonary perfusion?

Dramatically increases

What capillary mechanisms keep a modest increase in pulmonary arterial pressure?

1. Recruitment

2. Distention

During forced expiration, how much can the Adaptive Lung Ventilation Pressure increase?

+ 100 mmHg

What happens to the lung capillaries during forced expiration?

Squeezed

What happens to the blood volume distribution during forced expiration?

Less blood contained in lung

What blood flow zone occurs due to forced expiration?

Zone 1