fig1

Figure 1. Human vs. rabbit trachea. (a) Human trachea measures 10 cm ± 9 cm;^[10] (b) rabbit trachea measures on average 6.5 cm; (c) human cartilage rings comprise two-thirds of tracheal circumference vs. 90% in rabbits (d). The blue (c) and green (d) arrows represent the trachealis muscle; (e and f) Masson's trichrome stain: human trachea (e) contains more submucosal glands, compared to the better-developed submucosal capillaries in rabbits (f)