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Human respiratory system
A system of organs, functioning in the process of gas exchange between the body and the environment, consisting of the trachea, bronchi, alveoli and lungs
Gaseous exchange
The process where oxygen is taken in and exchanged for carbon dioxide which is a waste product of respiration
Oxygen
A gas that is needed for aerobic respiration to release energy, oxygen is transported into the body by the respiratory system and around the body by the circulatory system
Carbon dioxide
A waste product of respiration that needs to be removed from cells via the blood and removed from the body via the respiratory system
Bronchioles
Airways in the lungs that are made up of multiple branches, leads from the bronchi to the alveoli
Alveoli
Tiny sacs of lung tissue where gaseous exchange takes place with the blood
Diaphragm
A large muscle at the bottom of the chest cavity that helps control breathing, when the diaphragm pulls down and contracts to become flat, air can easily enter the lungs
Intercostal muscles
Muscles in between the ribs which move the rib cage during breathing
Bell jar model
A simple model of the lung made up of a transparent jar and two balloons, demonstrates ventilation by pulling down on or pushing up on the elastic base which causes the balloons to automatically inflate or deflate due to changes in pressure
Limitations of the bell jar model
The glass jar is not flexible to show the action of intercostal muscles, the glass trachea are not flexible, the elastic base does not correctly show the shape of the diaphragm, the balloons contain open space as opposed to many small alveolar sacs
When breathing in
Intercostal muscles contract pulling the ribcage upwards and outwards, the diaphragm contracts pulling downwards, volume of the thorax increases and pressure decreases, air is drawn into the lungs down a pressure gradient
When breathing out
Intercostal muscles relax pulling the ribcage downwards and inwards, the diaphragm relaxes and domes upwards, volume of the thorax decreases and pressure increases, air is pushed out of the lungs
Ventilation
The movement of air in and out of the lungs in response to muscular action that changes the volume and internal pressure of the thorax or chest, needed to efficiently regulate the exchange of oxygen and carbon dioxide
Percentage composition of inspired air
21% Oxygen, 0.04% Carbon Dioxide, 78% Nitrogen, percentage of water vapour varies
Percentage composition of exhaled air
16% Oxygen, 4% Carbon Dioxide, 78% Nitrogen, saturated with water vapour
