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Chapter 4


Exchange ­ Summary Notes
Exchange Surfaces

Large organism = large surface area and volume
Volume increases more than SA
Must have:
Large surface area ­ for gas exchange
Thin ­ shorter diffusion distance
Diffusion gradient ­ substances move down gradient
Moist ­ cells don't dry out
Emphysema ­…

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Chapter 4

Alveoli:
Air spaces
divided by thin walls
Surrounded by capillaries
Elastic fibres ­ strength
and flexibility
Macrophages:
Patrol alveolar surfaces
Phagocytes
Engulf and digest harmful materials
Some can't be digested ­ a sbestos

Breathing

Movements that cause air to enter and leave lungs
Movement ­ caused by diaphragm…

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