UN Thread Types. UN (Unified) is a specification of the shape and dimensions of the thread for a given size (diameter) of fastener and number of threads per inch of fastener length. UN bolts and machine screws are the type of fastener in everyday use in the US, UK, and Canada. UN, UNR, and UNJ thread dimensions are measured in Imperial units.
Causes The airway can become narrowed or blocked due to many causes, including: Allergic reactions in which the trachea or throat swell closed, including allergic reactions to a bee sting, peanuts, antibiotics (such as penicillin), and blood pressure medicines (such as ACE inhibitors) Chemical burns and reactions. Epiglottitis (infection of the structure separating the trachea from the esophagus)
The trachea, commonly known as the windpipe, is a tube about 4 inches long and less than an inch in diameter in most people.The trachea begins just under the larynx (voice box) and runs down behind the breastbone (sternum).The trachea then divides into two smaller tubes called bronchi: one bronchus for each lung. A procedure called bronchoscopy is usually needed to remove a foreign body from the trachea. 2  Tracheal cancer: Cancer of the trachea is quite rare. 3  Symptoms can include coughing or difficulty breathing. 4  Tracheomalacia: The trachea is soft and floppy rather than rigid, usually due to a birth defect.