Trachea the trachea. The trachea is no more than 4mm diameter during the first year of life, expanding to its adult diameter by late childhood. The trachea is more mobile and of more variable length, deeper, and smaller in children. The trachea is lined with a layer of pseudostratified ciliated columnar epithelium. The epithelium contains goblet cells, which are glandular, modified simple columnar epithelial cells that produce mucins, the main component of mucus. Mucus helps to moisten and protect the airways. Mucus lines the ciliated cells of the trachea to trap inhaled foreign particles that the cilia then waft upward toward
Effect of spaceflight on the human body Effect of spaceflight on the human body Venturing into the environment of space can have negative effects on the human body. Significant adverse effects of long-term weightlessness include muscle atrophy and deterioration of the skeleton (spaceflight osteopenia). Other significant effects include a slowing of cardiovascular system functions, decreased production of red blood cells, balance disorders, eyesight disorders and a weakening of the immune system. Additional symptoms include fluid redistribution (causing the "moon-face" appearance typical in pictures of astronauts experiencing weightlessness), loss of body mass, nasal congestion, sleep disturbance, and excess flatulence. The engineering problems associated with leaving Earth and developing