Function
- supplies oxygen to cells and removes carbon dioxide
- defending the body against invasion of microorganisms
- control the body’s blood pH
Components:
Ventilation (breathing) > inhalation and exhalation; take in oxygen and dispose of carbon dioxide
External Respiration > the exchange of gases between the alveoli and the blood
Internal Respiration > exchange of gases between the blood and tissue cells
Organ | Structure | Function |
Nasal cavity | – lined with capillaries; warm air to 37°C- secrete mucus; moisten and filter air
– lined with cilia; filter out debris in the air | – warms, moistens and filters air entering the respiratory system |
Pharynx | – path that connects nasal cavity to the trachea | |
Epiglottis | – a tiny flap of connective tissue | – prevents food from entering the trachea during swallowing- prevents air from entering the stomach when breathing in |
Larynx | – made up of cartilage- contains the vocal cords; two highly elastic folds | – to produce sound for communication |
Trachea | – a hollow tube surrounded by tough, flexible C-shaped cartilage rings- lined with cilia
– lined with mucus secreting cells | – allows air to pass from the pharynx into the lungs- cartilage rings prevent the trachea from collapsing and provide it with support |
Lung | – composed of the bronchi, bronchioles and alveoli | – the main organs of the respiratory system |
Bronchi | – branch out of the trachea- hollow tubes surrounded by cartilage rings
– lined with cilia and mucus secreting cells | – to carry the air into the lungs |
Bronchioles | – branch out of the bronchi- large bronchioles secrete mucous and are lined with cilia | – to decrease in size and carry air to the alveoli |
Alveoli | – clusters of tiny hollow air sacs; the ends of the smallest bronchioles- surrounded by an extensive network of capillaries
– very small structures with very high surface area | – are the sites of gas exchange |

Respiratory Membrane
- wall of alveoli and wall of capillaries come together for form a respiratory membrane
- gas exchange occurs across the respiratory membrane
Gas Exchange
- exchange of gases (O2 & CO2) between the alveoli & the blood occurs by simple diffusion
- diffusion requires a concentration gradient
- the surface of the alveoli must be moist so that diffusion can occur
I learned lots about the respiratory system
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