The part from the vocal cord to the fifth thoracic vertebra is called the trachea. It is a hollow tube. Its length is 12 cm and diameter is 2 cm. It is also known as Wind pipe. It is composed of 16-20 hyaline cartilage rings in a C (semi ring) shape. The cartilage is called the tracheal ring. Because the rings are connected by fibrous tissue, the trachea does not collapse. The inner wall of the trachea is covered by ciliated mucous membrane and the outer wall by connective tissue.
Function: Moves air through the trachea. The cilia of the mucous membrane prevent the entry of foreign matter.