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Breathing and Gas Exchange | Anatomy Snippets

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Breathe in…breathe out… 🧘‍♀️ 🧘‍♂️

Each time you breathe in, air travels down the trachea and into the lungs. Inside the lungs, there is a tree-like structure that disperses air to different parts of the lungs. 🌳

The trachea is in the midline and divides into left and right primary bronchi. These primary bronchi then divide into smaller branches supplying each lobe of the lung. They divide again and again until they are microscopic in size, about 300 micrometers 🔬. At the end of these bronchi are alveolar sacs, like leaves on a tree. 🌿

Bronchial Tree
Bronchial Tree in Complete Anatomy

It is within these alveolar sacs that gas exchange occurs. The alveolar sac is made up of 20 – 30 alveoli, all fused together and sharing a common bronchiole. The walls of these alveoli have two distinct features which make them ideal for gas exchange:

  1. cell walls which are only one cell thick
  2. an abundant blood supply of both arteries ❤️ and veins 💙

Also, on the walls of the alveoli are elastic fibres, allowing for distension and relaxation of the structure during breathing.

The alveoli can be damaged by excessive exposure to smoke or pollutants. The fragile walls are damaged and the internal structure of the alveolar sac is lost, resulting in a reduction of surface area for gaseous exchange. This leads to a condition called emphysema and usually presents as a shortness of breath 😯.