alveoli

• alveoli often known as alveolus are the tiny sacs inside the lungs where exchange occurs. when air is inhaled it travels through parts of the respiratory system to arrive at the alveoli
• the layer of the membrane/surface of the alveoli is one cell thick which provides a short distance diffusion pathway and like all membranes it is partially permeable so gasses can pass through the membrane of the alveoli cells into the red blood cells found in the surrounding capillaries
• the alveoli has a good blood supply surrounding each alveolus to allow for efficient and rapid diffusion of oxygen
• example of an alveolus however it can be shaped in other ways some are bumpy and some are smooth

  
• the alveoli has a moist lining and a large surface area which helps the diffusion maximise