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 to Be Done? What Is to Be Done? What Is To Be Done? Burning Questions of Our Movement () is a political pamphlet written by the Russian revolutionary Vladimir Lenin (credited as N. Lenin) in 1901 and published in 1902. Lenin said that the article represented "a skeleton plan to be developed in greater detail in a pamphlet now in preparation for print". Its title is inspired by the novel of the same name by the 19th century Russian revolutionary Nikolai Chernyshevsky. In "What Is to Be Done?", Lenin argues that the working class will not spontaneously become political simply by fighting economic