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Breathing involves exchange of gases in the lungs. - Oxygen is taken in, Carbon dioxide is released


Nasal cavity

Bronchus Bronchiole Alveolus

Diaphragm

Trachea Trachea Left lung Intercostals muscle


ALVEOLUS BLOOD CAPILLARY


Pathway taken by air during inhalation Nostril → Nasal Cavity → Trachea → Bronchus → Bronchiole → Alveolus

Pathway taken by air during exhalation Alveolus → Bronchiole → Bronchus → Trachea → Nasal Cavity → Nostril


INHALATION Rib cage moves upwards and outwards

EXHALATION Rib cage moves downwards and inwards


Comparison between inhalation and exhalation Inhalation

Parts involved

Exhalation

Contracts

External intercostals Relaxes muscles

Relaxes

Internal intercostals muscles

Moves upwards and outwards

Contracts and flattens Volume increases, air pressure decreases, atmospheric air is pushed into the lungs

Contracts

Rib cage

Moves downwards and inwards

Diaphragm

Relaxes and curves upwards

Thoracic cavity

Volume decreases, air pressure increases, atmospheric air is pushed out of lungs


Comparison of the composition of inhaled and exhaled air Gas

Inhaled Air (%)

Exhaled Air (%)

Nitrogen

78

78

Oxygen

21

16

Carbon dioxide

0.03

4

Inert gas Water vapour

0.9 Less

0.9 More



Human Respiratory System