Physiology 1 - Respiratory mechanisms

Question 1

4 steps if respiration/gas exchange/external respiration.

Answer 1

1) ventilation
2) gas exchange between atmosphere & alveoli
3) gas transport in the blood
4) gas exchange at tissue level

Question 2

2 structures where air enters the lung.

Answer 2

1) trachea

2) bronchial tree

Question 3

property of the trachea that allows swallowing?

Answer 3

elasticity of the trachea

Question 4

property of hyaline cartilage that prevents trachea from collapsing during inspiration

Answer 4

curved rings of hyaline cartilage

Question 5

why mucus covers the trachea & bronchial tree?

Answer 5

to trap dirt, dust & inspired particles

Question 6

describe cilia’s role in the clearance of these particles.

Answer 6

beats the trapped dust & particles upwards towards the larynx.
Once they reach the larynx, larger particles are expelled by coughing, smaller particles are tipped into the oesophagus.

Question 7

why does air flow from the atmosphere into the alveoli?

Answer 7

due to a difference in pressure created by the contraction & relaxation of respiratory muscles.

Question 8

What is Boyle’s Law?

Answer 8

the volume of gas is inversely proportional to the pressure of the gas

Question 9

what is the pressure differences between the atmosphere and intra-alveoli BEFORE INHALATION?

Answer 9

the intra-alveolar and atmospheric pressure are the SAME

Question 10

what happens to the pressure during inhalation and why?

Answer 10

• for air to flow into the lungs, the intra-alveolar pressure must fall.
• the chest wall and lungs expand
• expansion of the lungs, increases volume of the alveoli & REDUCES the PRESSURE OF THE ALVEOLI
• therefore allowing air to enter the lungs

Question 11

in order for lungs to expand on inspiration, what muscles contract on inspiration?

Answer 11

1) diaphragm

2) external intercostal muscles

Question 12

What happens to the diaphragm when you contract it?

Answer 12

the diaphragm flattens

Question 13

what happens to the vertical diameter of the thoracic cage when the diaphragm is contracted?

Answer 13

the vertical diameter of the thoracic cage is increased

Question 14

describe the effect of contracting external intercostal muscles to the ribs and lateral and anterior-posterioir diameter of chest.

Answer 14

• ribs are elevated

- lateral and anterior-posterior diameter of the chest increases

Question 15

name the 2 forces that hold the thoracic wall and lungs in close opposition.

Answer 15

1) intra pleural fluid cohesiveness

2) negative intra pleural pressure

Question 16

describe intra pleural fluid cohesiveness

Answer 16

• water molecules in the intra pleural fluid are attracted to each other & resist being pulled apart
• hence, pleural membranes end to stick together

Question 17

Describe the negative intra pleural pressure?

Answer 17

sub-atmospheric intra-pleural pressure creates a transmural pressure gradient across the lung wall & across the chest wall.
- so the lungs are forced to expand outwards while the chest is forced to squeeze inwards

Question 18

is expiration passive or active?

Describe how expiration works?

Answer 18

PASSIVE
= no contraction necessary

• inspiratory muscles relax,
• recoil of the chest wall and lungs due to elastic connective tissue in the lungs
• alveolar surface tension produces a force which resists the stretching fo the lungs
• pressure in alveoli is higher than atmosphere so air is forced out of lungs as it moves up the trachea

Question 19

is inspiration passive or active?

Answer 19

ACTIVE

Question 20

is EXHALATION active of passive?

Answer 20

ACTIVE

Question 21

what muscles contract during exhalation?

Answer 21

1) internal intercostal muscles

2) abdominal muscles

Question 22

What does contraction of these muscles cause the ribs and diaphragm to do?

Answer 22

• inferior ribs move down
• diaphragm moves up
• the spaces between the ribs contract, increasing abdominal and thoracic pressure

Question 23

What does surfactant do?

Answer 23

= reduces the alveolar surface tension, by interspersing between the water molecules lining the alveoli

Question 24

Do smaller of larger alveoli have higher tendency to collapse?

Answer 24

smaller alveoli

- according to Law of LaPlace

Question 25

what cells secret surfactant?

Answer 25

type II alveoli

Question 26

what is alveolar interdependence?

Answer 26

• when one alveolus starts to collapse, the surrounding alveoli stretch & then recoil exerting expanding forces in the collapsing alveolus, causing it to open