Carina
The carina is a keel-shaped cartilage lying at the tracheal bifurcation--it separates the right main stem bronchus from the left main stem bronchus. The carina is a little to the left of the tracheal bifurcation, so if there is an inhaled body the carina will tend to divert foreign objects to the right main bronchus. The cricoid cartilage is the inferior and posterior cartilage of the larynx. The costal cartilages prolong the ribs anteriorly and contribute to the elasticity of the thoracic wall. They increase in length through the first seven and then gradually decrease. The pulmonary ligament is a fold of pleura located below the root of the lung. Tracheal rings are the cartilagenous structures which support the trachea and keep it patent.