Trachea annular ligaments of trachea. The epiglottis closes the opening to the larynx during swallowing. The trachea develops in the second month of development. It is lined with an epithelium that has goblet cells which produce protective mucins (see "Respiratory epithelium"). An inflammatory condition, also involving the larynx and bronchi, called croup can result in a barking cough. A tracheotomy is often performed for ventilation in surgical operations where needed. Intubation is also carried out for the same reason by the inserting of a tube into the trachea. From 2008, operations have experimentally transplanted a windpipe grown by stem cells, and
Effect of spaceflight on the human body of motion sickness for the first three days of travel due to the conflict between what the body expects and what the body actually perceives. Over time however the brain adapts and although these illusions can still occur, most astronauts begin to see "down" as where the feet are. People returning to Earth after extended weightless periods have to readjust to the force of gravity and may have problems standing up, focusing their gaze, walking and turning. This is just an initial problem, as they recover these abilities quickly. NASA jokingly measures SAS using the "Garn scale", named for United