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
What Is Life "Rolling Stone" readers' poll, titled "10 Greatest Solo Beatle Songs", the song placed fourth, with the editor commenting: "The track is deceptively simple, and more layers become apparent the more often you play it." "What Is Life" has featured in Bruce Pollock's book "The 7,500 Most Important Songs of 1944–2000", Treble website's "The Top 200 Songs of the 1970s" (ranked at number 101) and Dave Thompson's "1000 Songs That Rock Your World" (at number 247). "What Is Life" was included on the 1976 compilation "The Best of George Harrison" as well as 2009's "". The song has also been featured