Outline the structures involved in the mammalian gaseous exchange system. For each structure explain how it increases the efficiency of gaseous exchange [6 marks]

Trachea- c shaped cartilage provides structure and support, goblet cells and ciliated epithelium, secrete mucus to trap dust and pathogens and waft the mucus up the tracheaBronchi- smooth muscle relaxes to allow air into the lungsAlveoli- branched, have a large surface area to uptake oxygen. Thin walls, one cell thick, short diffusion distance. Good blood supply, oxygen diffuses down the concentration gradient into the bloodDiaphragm- contracts to increase the area of the lungs, decreases pressure so air moves into the lungs, down the pressure gradient. causing inspiration