PhysioEX Ex. 7 Act. 3 The effect of surfactant and intrapleural pressure on respiration

surface tension

molecules of liquid are attracted more stongly to each other than they are to gas molecules. this causes surface tension

• resists any force that tends to increase surface area, such as the alveoli or microscopic air spaces within the lungs

what would happen if the film lining the lung were pure water

it would be very difficult, if not impossible to inflate the lungs

surfactant

contained in the aqueous film covering the alveolar surfaces. a detergent-like mixture of lipids and proteins that decreases surface tension by reducing the attraction of water molecules to each other

intrapleural pressure

pressure in the pleural cavity between breaths

• is less than the pressure in the alveoli

Two forces cause this negative pressure condition

1. the tendency of the lung to recoil because of its elastic properties and the surface tension of the alveolar fluid

2. the tendency of the compressed chest wall to recoil and expand outward.

these two forces pull the lungs away from the thoracic wall, creating a partial vacuum in the pleural cavity

pneumothorax

opening created in pleural membranes to equilize the intrapleural pressure with atmospheric pressure

• due to pressure in intrapleural space being lower than atmospheric pressure

atelectasis

pneumothorax can lead to lung collapse, causing atelestasis

intrapleural space

space between wall and outer layer of lung

which of the following statements about surface tension is FALSE?

1. molecules of a liquid are attracted more strongly to each other than they are to gas molecules

2. surface tension resists any force that tends to increase the surface area of the gas-liquid boundry

3. surface tension acts to increase the size of the alveoli within the lungs

4. surface tension occurs at any gas-liquid boundary

3. surface tension acts to increase the size of the alveoli within the lungs

which of the following statements about surfactant is false?

1. surfactant is detergent-like mixture of lipids and peptides that decrease surface tension

2. surfactant is part of the aqueous film covering the alveolar surfaces

3. surfactant reduces the amount of work required to inflate the lung

4. surfactant works by increasing the attraction of water molecules to each other

4. surfactant works by increasing the attraction of water molecules to each other

just before and inspiration begins, the pressure within the intrapleural cavity

1. is referred to as the intrapleural pressure

2. is less than the pressure within the alveoli

3. is influenced by the tendency of the chest wall to collapse

4. is responsible for causing lung collapse

2. is less than the pressure within the alveoli

the respiratory condition of the pneumothorax refers to

1. the pressure in the intrapleural space becoming lower than atmospheric pressure

2. the removal of air from the intrapleural cavity

3. any opening that equilizes the intrapleural pressure with the atmospheric pressure

4. a bacterial infection

3. any opening that equilizes the intrapleural pressure with the atmospheric pressure

a pneumothorax can lead to

1. excessive lung expansion

2. atelectasis

3. intrapleural pressures that are more negative than normal

4. severe admonishments from the lorax

2. atelectasis

what effect will adding more surfactant have on these lungs?

1. airflows will decrease

2. airflows will further increase

3. airflows will remain the same

2. airflows will further increase

why did the sequential additions of surfactant change this lung system

1. surface tension was sequentially decreased

2. the addition of more fluid to the lungs will always improve airflow

3. surface tension was sequentially increased

4. the addition of more fluid to the lungs increased the pressure in the lungs

1. surface tension was sequentially decreased

premature infants often have difficulty breathing because the amount of surfactant in their lungs is

1. too high

2. too low

3. irrelevant to the problem

2. too low

what happened to the left side of the bell jar when the valve was opened

1. the intrapleural pressure became more negative

2. the intrapleural pressure equilized w atmospheric pressure

3. the lungs on the right side of the glass bell jar became larger

4. airflows increased

2. the intrapleural pressure equilized w atmospheric pressure

what will happen to the collapsed lung in the left side of the glass bell jar if you close the valve

1. the lung will reinflate in one breath

2. the lung will reinflate over several breaths

3. the lung will remain collapsed

4. the lung will collapse further

3. the lung will remain collapsed

the addition of surfactant to the lung interior

1. decreased the magnitude of the intrapleural pressure changes

2. increased surface tension

3. increased airflow

4. increased the magnitude of the intrapleural pressure changes

3. increased airflow

opening the valve in the side of the glass bell jar

1. allowed the surfactant to drain out of the lungs

2. altered the atmospheric pressure

3. allowed the changes to intrapleural pressure to be greater

4. stimulated pneumothorax

4. simulated pneumothorax

the best way to rapidly reinflate a persons collapsed lung is to

1. pump air out of the intrapleural space to recreate negative pressure

2. remove a portion of the surfactant from the lung interior

3. pump air out of the collapsed lung to recreate negative pressure

4. induce strong and frequent contractions of the diaphragm muscle

3. pump air out of the intrapleural space to recreate negative pressure

what effect does the addition of surfactant have on airflow?

airflow increased

why does surfactant effect airflow by increasing it

surfactant affects airflow by decreasing the resistance, but increases the gas exchange surface

what effect did opening the valve have on left lung? why did this happen?

When opening the valve on the left lung, the lung shrunk in size and was unable to function. This occurred because the pressure of the intrapleural space and intrapulmonary are equal, thus making the pressure of the atmosphere of the intrapulmonary are the same so the air could not get to the left lung

What effect on the collapsed lung in the left side of the glass bell jar did you observe when you closed the valve?

the lung remained collapsed. This occurred because the pressure difference with intrapleural space and lung did not re-established

What emergency medical condition does opening the left valve simulate?

The medical emergency condition opening the left valve stimulates pneumothorax.

In the last part of this activity, you selected the Reset button to draw the air out of the intrapleural space and return the lung to its normal resting condition. What emergency procedure would be used to achieve this result if these were the lungs in a living person?

The emergency procedure used on a living person would be inserting a chest tube. The chest tube would create a partial vacuum from the intrapleural space and creating a valve below the atmospheric pressure.

What do you think would happen when the valve is opened if the two lungs were in a single large cavity rather than separate cavities?

If both the lungs were in one single large cavity, the lungs would collapse if the valve was open.