1- Overview of Respiration & Respiratory mechanics

Question 1

what is internal respiration?

Answer 1

intracellular mechanisms which consumes oxygen and produces carbon dioxide (once in tissues)

Question 2

what is external respiration?

Answer 2

sequence of events that lead to exchange of oxygen and carbon dioxide between external environment and cells of the body
(has 4 steps)

Question 3

what are the 4 steps of external respiration?

Answer 3

1. Ventilation = mechanical process of moving gas in & out of lungs
2. gas exchange between alveoli & blood = exchange of O2 and CO2 between air in alveoli and blood in pulmonary capillaries
3. Gas transport in the blood = The binding and transport of of O2 and CO2 in the circulating blood
4. gas exchange at tissue level = The exchange of O2 and CO2 between the blood in the systemic capillaries and the body cells

Question 4

what 4 body systems are involved in external respiration?

Answer 4

• respiratory system
• cardiovascular system
• Haematology system
• Nervous system

Question 5

what is ventilation?

Answer 5

first step of external respiration which is mechanical process from moving air between atmosphere & alveolar sacs

Question 6

what influences movement of lungs? is it passive or active?

Answer 6

movement is entirely passive of the lungs - results form forces external to lungs

Question 7

is inspiration active or passive? and what causes?

Answer 7

active process brought about contraction respiratory muscles

Question 8

is expiration active or passive? and what causes it?

Answer 8

passive process brought about relaxation of inspiratory muscles

Question 9

what are the opposing forces that act on the lungs?

Answer 9

= forces keeping alveoli open and forces promoting alveoli collapse

keeping open:
- transmural pressure gradient (important)
- pulmonary surfactant
- alveolar interdependence

promoting collapse:
- elastic recoil of lungs & chest wall
- alveolar surface tension

Question 10

what is transmural pressure gradient?

Answer 10

gradient that can be across lung wall & across thoracic wall

(intrapleural should be lower so allows alveoli to expand more)

2 different transmural pressure gradients:
across lung wall= intra-alveolar pressure - intrapleural pressure

across thoracic wall = atmospheric pressure - intrapleural pressure

Question 11

what are 2 factors that allow the lungs to adhere to chest and follow movement?

Answer 11

1. transmural pressure gradient
2. intrapleural fluid cohesiveness (water molecules in intrapleural fluid attracted to each other & resist being pulled apart)

Question 12

what is normal pressure in
a) atmosphere
b) intra-alveolar pressure
c) intrapleural pressure

Answer 12

a) 760 mmHg
b) 760 mmHg
c) 756 mmHg

Question 13

what is intrapleural/intrathoracic pressure?

Answer 13

pressure exerted outside the lungs within pleural cavity (usually less than atmospheric pressure)

Question 14

what is intra-alveolar/intrapulmonary pressure?

Answer 14

pressure within lung alveoli - 760 mmHg when equilibrated with atmospheric pressure

Question 15

what does increased transpulmonary pressure gradient mean?

Answer 15

=another name for transmural pressure gradient across lung wall
means lungs will expand (as increased gradient means lower intrapleural pressure so alveoli can spread out)

Question 16

what is pneumothorax?

Answer 16

air in pleural space

Question 17

what effect does pneumothorax have on transmural pressure gradient?

Answer 17

abolishes transmural pressure gradient as liquid in pleural space so disrupts the normally negative intrapleural pressure and raises it

= this can lead to lung collapse

Question 18

what can cause pneumothorax?

Answer 18

can be spontaneous, traumatic, iatrogenic
= air enters pleural space from outside lungs or lung itself

Question 19

what are symptoms of pneumothorax?

Answer 19

shortness of breath and chest pain

Question 20

what are signs of pneumothorax?

Answer 20

hyperresonant percussion note and decreased/absent breath sounds

Question 21

what must pressure levels be like to allow inspiration?

Answer 21

intra-alveolar pressure must be less than atmospheric pressure air to flow into lungs in inspiration (as air flows from high pressure to low pressure)

Question 22

how does intra-alveolar pressure change during inspiration and expiration?

Answer 22

before inspiration = intra-alveolar pressure is same as atmospheric pressure

during inspiration = thorax & lungs expand (because of muscle contraction) and this expansion makes intra-alveolar pressure fall to become less than atmospheric due to Boyle’s law (as volume of gas increases the pressure exerted by gas decreases)

during expiration = muscles relax so intra-alveolar pressure rises (relax muscle = less space = higher pressure). higher intra-alveolar pressure allows air flow to leave again

Question 23

how does contraction of diaphragm affect volume of thorax?

Answer 23

volume of thorax increased vertically by contraction of diaphragm - flattens out it’s dome shape

Question 24

what does contraction of external intercostal muscles do?

Answer 24

causes elevation of ribs which increases side-side dimension of thoracic cavity. this pushes diaphragm down increasing vertical dimension of thoracic cavity

Question 25

what happens in inspiration?

Answer 25

= active process brought about by contraction of inspiratory muscles

• chest wall & lungs stretched
• increase in size of lungs makes intra-alveolar pressure fall
• because air molecules become contained in a larger volume (Boyle’s Law)
• The air then enters the lungs down its pressure gradient until the intra-alveolar pressure become equal to atmospheric pressure

Question 26

what happens in expiration?

Answer 26

= passive process brought by relaxation of inspiratory muscles

• The chest wall and stretched lungs recoil to their pre-inspiratory size because of their elastic properties
• The recoil of the lungs make the intra-alveolar pressure to rise because air molecules become contained in a smaller volume (Boyle’s Law)
• The air then leaves the lungs down its pressure gradient until the intra-alveolar pressure become equal to atmospheric pressure

Question 27

what allows lungs to recoil during inspiration?

Answer 27

1. elastic connective tissue in the lungs (bounces back whole structure)
2. alveolar surface tension - IMPORTANT

Question 28

what is alveolar surface tension and how does it help lungs recoil during expiration?

Answer 28

attraction between water molecules (alveoli lined with water molecules that are attracted to each other creating surface tension) - this tension would collapse the alveoli if not for surfactant

surfactant is interspersed between water molecules lowering surface tension = preventing collapse and therefore helping recoil

Question 29

what is surfactant and it’s role in expiration?

Answer 29

surfactant = a complex mixture of lipids and proteins secreted by type II alveoli

Surfactant acts to decrease surface tension, particularly at smaller alveolar sizes. This reduces the pressure needed to keep the alveoli open and prevents their collapse during expiration

Question 30

what does LaPlace’s Law help support?

Answer 30

supports the idea about alveolar surface tension and surfactant
the law says that the smaller alveoli the higher tendency to collapse so surfactant has to help smaller alveoli most

Question 31

how can surfactant link to respiratory distress in newborns?

Answer 31

the developing fetal lung is unable to synthesize surfactant until late pregnancy so premature babies may not have enough causing respiratory distress by strenuous inspiratory efforts in attempt to overcome high surface tension & inflate the lungs

Question 32

what is alveolar interdependence?

Answer 32

= factor that helps keep alveoli open

If an alveolus start to collapse the surrounding alveoli are stretched and then recoil exerting expanding forces in the collapsing alveolus to open it