- Air is not dense enough to support and protect these delicate structures - The body as a whole would otherwise lose a great deal of water and dry out
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What structure are the lungs protected by?
The ribcage
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What muscles can move the ribs?
Intercostal muscles
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Describe the structure of the lungs
A pair of lobed structures made up of a series of highly branched tubules
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What are the tubules called?
Bronchioles
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What structure are found at the end of the bronchioles?
Alveoli
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Describe the structure of the trachea?
It is a flexible airway that is supported by rings of cartilage
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What is the function of the rings of cartilage lining the outside of the trachea?
They prevent the trachea from collapsing as the air pressure inside decreases as we inhale
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What are the inner tracheal walls made up of?
Muscle, lined with ciliated epithelium and goblet cells
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What is a goblet cell?
It's a glandular whose function is to secrete gel-forming mucins, which is a major component in mucus
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Why is mucus produced?
Mucus helps trap dirt and dust particles that may enter the airways so that they can be moved towards the throat by cilia, to protect the alveoli
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Describe the structure of the bronchi
They are two divisions of the trachea, each leading to one lung. They are similar in structure to the trachea
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Describe the structure of the bronchioles
They are a series of branching subdivisions of the bronchi
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Why are the inner walls of the bronchioles lined with muscle?
So that the muscles can contract to control how much airflow there is to the alveoli
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Describe the structure of the alveoli
They are minute air sacs at the end of the bronchioles
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What is there between the alveoli sacs?
Collagen and elastic fibres
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What is the function of the elastic fibres?
They allow the alveoli to stretch as they fill with air when breathing in
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