a summary of the grade 11 section Gaseous Exchange. provided all the necessary info needed for ieb syllabus as well as diagrams required to understand and those to assist with understanding the content in this section.
- the exchange of O2 and CO2at a respiratory surface
occurs at two places in mammals:
1. at a gaseous exchange
surface (lungs) and the
blood
2. between the blood and
the body cells at the tissue
level
Di erence between cellular respiration, breathing and
gas exchange:
- Breathing is the taking of air in and out of the lungs.
- Gas exchange is the intake of oxygen and the excretion of carbon dioxide at the lung surface.
Oxygen moves into the blood and carbon dioxide moves out of the blood.
- Cell respiration is the process that releases energy from the food
Requirements of an E ective Gaseous:
• Large – to ensure the maximum exchange of gases can take place.
• Thin and permeable – so that di usion can take place easily and rapidly.
• Moist – so that gases can dissolve to form a solution.
• Well ventilated – good oxygen supply and carbon dioxide removal.
HUMAN GASEOUS EXCHANGE
The human gas exchange system consists of the following distinct sections:
- air passages
- lung
- muscles involved in the
mechanism of
breathing (ventilation)
ff ff ff
, Structure and function:
nostrils = air inhale air into the nose
Nasal cavities = cilia trap dirt and sweep it out of the nose; keeps cavity moist
trachea = C-shaped cartilage rings protect trachea and keep it open for easy movement of air
bronchus /bronchi = held open by O-shaped cartilage rings; lined with mucous membranes
bronchioles/ bronchioles = Transport air from bronchi to alveolus
alveoli = increase the surface area to maximise the gas Exchange right bronchus bronchiole
alveolus (air sac) Ribs diaphragm intercostal muscles
lungs = Contains the alveoli for gaseous exchange , also aid in inhalation and exhalation
ribs = protect the lungs from injury
Intercostal muscles = contract and relax during inhalation and exhalation altering the volume of
air in the chest (thoracic cavity)
diaphragm = contracts and attens altering the volume of the chest cavity and is important in the
breathing
The mechanism of breathing (Ventilation of the lungs):
- The process of breathing is a mechanical process.
- Air moves in and out of the lungs as a result of di erences in atmospheric air pressure
and the air pressure inside the lungs.
- It involves di erent muscles and volume and pressure changes in the thoracic cavity.
- Inhalation: the breathing in of air
- Exhalation: the breathing out of air
ff fl ff
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