👉 Tracheids are a type of bone that is found in the trachea, which is a tube-like structure that connects the lungs to the trachea. They are made up of two sets of cells called cartilaginous and cartilage, respectively. The cartilage layer is composed of collagen fibers, while the cartilage itself is a soft tissue, like cartilage. Tracheids are responsible for protecting the airway in the lungs from the harmful effects of foreign substances.