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
What Is Life During the verses, Gordon moves to a square, Motown-style beat – or "rock-steady Northern soul backbeat" in Leng's words – before returning to the "galloping rhythm" of the more open, "knockout" choruses, and the song is driven equally by Badfinger drummer Mike Gibbins' powerful tambourine work. On "What Is Life", Spector provided what music critic David Fricke terms "echo-drenched theater", in the form of reverb-heavy brass, soaring strings (arranged by John Barham) and "a choir of multitracked Harrisons". The vocals and Barham's contribution, along with a brief slide-guitar commentary from Harrison over the final verse, were overdubbed at Trident Studios,