Lung Physiology

Question 1

What lines the lungs?

Answer 1

• Visceral pleura (inside)

- Paretial pleura (outer)

Question 2

What is inside the pleural cavity?

Answer 2

Liquid

- serous pleural fluid, allows the two layers to slide

Question 3

What are the alveolar sacs composed of?

Answer 3

• Surrounded by elastic fibres
• Can expand during inhalation
• composed of no cartilage, instead collagenous and elastic smooth muscle

Question 4

What is the significance of surface tension in the alveoli?

Answer 4

• Intermolecular forces within a liquid form the droplet shape
• As alveolar shape expands, more force needed to bring back
• Surfactant reduced surface tension

Question 5

During inspiration what occurs?

Answer 5

• Pressure inside lungs is lower than on the outside
• Volume of lungs is increased by the diaphragm moved down
• Intercostal muscles move up and out

Question 6

During expiration what occurs?

Answer 6

• Pressure is greater inside the lungs than outside
• elastic recoil of chest wall and lungs
• Diaphragm up
• Surfactant prevents lungs from collapsing as air is forced out

Question 7

What are the important nerve impulses linked with ventilation?

Answer 7

• Basic impulses, generated by the inspiratory centre in the brain and trigger the phrenic nerves of the diaphragm
• Cerebral cortex has connections wih the respiratory centre, so we can voluntarily alter our breathing
• Nervous stimulation is however involuntary, would pass out before death
• The carotid body contains the vagus nerve which monitors gas levels
• The common caroti artery is also here

Question 8

Where does air intake occur?

Answer 8

• 70% in alveoli
• Each constituent will diffuse across into the cappillaries
• Partial pressure of O2 is less in cappillaries and CO2 less in the alveoli