Structure of the Breathing System (Edexcel IGCSE Biology)
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Structure of the Breathing System
The thorax is the human chest cavity; it consists of:
the ribs
intercostal muscles
diaphragm
trachea
bronchi
bronchioles
alveoli
pleural membranes
The lungs are the gas exchange surface in humans
All gas exchange surfaces have features in common which allow the maximum amount of gases to be exchanged across the surface in the smallest amount of time
They include:
Large surface area to allow faster diffusion of gases across the surface
Thin walls to ensure diffusion distances remain short
Good ventilation with air so that diffusion gradients can be maintained
Good blood supply to maintain a high concentration gradient so diffusion occurs faster
Structures in the human breathing system
Breathing Structures Table
Examiner Tips and Tricks
You may notice that several of the features of alveoli that make them suited to their function are the same as those that make villi suited to their function or root hair cells suited to their function – the reason for this is because all of these structures are involved in transporting substances across their surfaces – by diffusion, active transport, osmosis or a combination. So if you learn the features for one, you also know many of the features of the others!
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