Lung volumes, functions on the lungs and lung mechanics

Question 1

Tidal volume

Answer 1

vol of air insp and exp in a normal breath

Vt = Vd + Va

Question 2

Inspiratory reserve volume

Answer 2

extra vol that can be expired after normal tidal insp

Question 3

Expiratory reserve volume

Answer 3

extra vol that can be exp after a normal tidal exp

Question 4

Residual volume

Answer 4

vol of air remaining after max exp effort; unable to be removed from lungs

Question 5

Vital capacity

Answer 5

vol of gas contained in lungs after max insp

Question 6

Total lung capacity

Answer 6

vol of gas contained in lungs at end of max insp

Question 7

Functional residual capacity

Answer 7

vol remaining in lungs after normal exp

Question 8

Inspiratory capacity

Answer 8

max vol that can be inspired from resting end-exp level

Question 9

What are the functions of the lungs?

Answer 9

• inactivation - destruction of prostoglandins
• -biological activation - angiotensin I –> angiotensin II
• filters blood of thombi
• defence - change in temp/humidity
• reservoir for blood
• gas exchange

Question 10

What is Ficks’ Law?

Answer 10

amount of gas moved is proportional to area and inversely proportional to thickness

Question 11

What are the three factors that must be overcome to move air in/out of lungs?

Answer 11

1. elastic recoil: of chest wall and lungs
2. frictional resistance: of lungs chest wall, tissues, airways
3. inertia - matter continuing in existing state in uniform motion or straight line

Question 12

What is the major inspiratory muscle during quiet breathing?

Answer 12

diaphragm

Question 13

Which muscles increase the antero-posterior diameter of the chest cavity?

Answer 13

parasternal muscles and scalenes

Question 14

Which muscles cause lateral expansion of the chest cavity?

Answer 14

lower intercostals and diaphragm

Question 15

What is compliance?

Answer 15

ease with which something can be stretched/distorted and return to it’s original configuration

Question 16

Intra-pleural pressure

Answer 16

between visceral and parietal pleura; slightly below atmospheric

Question 17

Alveolar pressure

Answer 17

inside alveoli

Question 18

Trans-mural pressure

Answer 18

across airways or lung walls

Question 19

Trans-pulmonary pressure

Answer 19

difference between inside and outside of lungs, keeps lungs from collapsing

Question 20

trans-airway pressure

Answer 20

keeps airways open

Question 21

What is interdependence?

Answer 21

each alveolus supports each other to prevent collapse

Question 22

Wha are factors reponsible for keeping alveoli open?

Answer 22

• surfactant to decrease surface tension
• interdependence
• frictional residual capacity

Question 23

What are the functions of surfactant?

Answer 23

• decrease muscular effort of breathing - more compliant lungs
• decrease elastic recoil - prevent alveoli from collapsing
• maintain equilibrium of size of alveoli
• lower surface tension during deflation