Respiration mechanics (1)

Question 1

what is external respiration?

Answer 1

Sequence of events that lead to the exchange of O2 and CO2 between external environment and the cells of the body

Question 2

what is internal respiration?

Answer 2

Intracellular mechanisms which consumes O2 and produces CO2

Question 3

What are the 4 steps of external respiration?

Answer 3

1) Ventalation- gas exchange between atmosphere and air sacs(alveoli) in the lungs
2) Exchange of O2 and CO2 between the air in the alveoli and blood coming to the lungs
3) Transport of O2 and CO2 in the blood between the lungs and the tissues
4) Exchange of O2 and CO2 between the blood and the tissues

Question 4

What 4 systems are involved in external respiration ?

Answer 4

Respiratory, cardiovascular, haematology, nervous

Question 5

What is Boyles law?

Answer 5

At any constant temperature the pressure exerted by a gas varies inversely with the volume of the gas

Question 6

What 2 forces hold the thoracic wall and lungs together?

Answer 6

• Intrapleural fluid cohesiveness- water molecules in the intrapleural fluid are attracted to each other and so resist being pulled apart
• negative intrapleural pressure- sub atmospheric intrapleural pressure creates transmural pressure gradient across lung wall and chest wall and so lungs forced to expand outwards and chest forced to squeeze inwards

Question 7

What happens during inspiration?

Answer 7

Volume of the thorax is increased vertically by contraction of the diaphragm and the contraction of external intercostal muscles lift the ribs and move out the sternum. This increase in the size of lungs cause intra-alveolar pressure to fall and air enters lungs down a pressure gradient and stops when pressure becomes equal.

Question 8

What happens during expiration?

Answer 8

The chest wall and lungs recoil making the intra-alveolar pressure rise and air leaves lungs down the pressure gradient

Question 9

What causes the lungs to recoil?

Answer 9

Elastic connective tissue and alveolar surface tension

Question 10

what reduces alveolar surface tension and how does it do this?

Answer 10

Surfactant- it intersperses its lipids/proteins between water molecules lining the alveoli

Question 11

What value is atmospheric pressure?

Answer 11

760mm Hg

Question 12

what is pneumothorax and what does it cause?

Answer 12

air in the pleural space abolishes the transmural pressure gradient and causes a collapsed lung

Question 13

what is traumatic pneumothorax?

Answer 13

puncture wound in chest wall

Question 14

what is spontaneous pneumothorax ?

Answer 14

Hole in lung

Question 15

what is the law of Laplace?

Answer 15

the smaller alveoli (smaller radius) have a higher tendency to collapse