Trachea are generally highly elastic but they may calcify with age. The trachealis muscle connects the ends of the incomplete rings and contracts during coughing, reducing the size of the lumen of the trachea to increase the rate of air flow. The esophagus lies posteriorly to the trachea, adjoining along the tracheoesophageal stripe. Circular horizontal bands of fibrous tissue called the annular ligaments of trachea join the tracheal rings together. The cartilaginous rings are incomplete to allow the trachea to collapse slightly so that food can pass down the esophagus. A flap-like epiglottis closes the opening to the larynx during swallowing
Explorers of the Human Body weeks. It was later decided that instead of a hiatus, the program will end the season with thirteen episodes. Super Junior decided to leave the show due to their occupied schedules and busy preparations for their upcoming Asia-wide concert tour, Super Show. However, representatives of the program stated if there is a chance, a second season is considered. "Change", the variety program hosted by Lee Hyo-ri and Shin Dong-yup with Noh Hong-chul, Kangin, Son Ho-young and Min Kyung-hoon as regulars, took over the time slot. Explorers of the Human Body Explorers of the Human Body (Hangul: 인체탐험대; Hanja: 人體探險隊) was