Trachea

The trachea (syn. windpipe) is a flexible fibrocartilaginous tube forming the beginning of the lower respiratory tract. Its lumen is kept patent by 16–20 C-shaped rings of hyaline cartilage.

The gap between the posterior free ends of C-shaped cartilages is bridged by a band of smooth muscle (trachealis) and a fibroelastic ligament, which permit expansion of esophagus during the passage of bolus of food. The arrangement of cartilages and elastic tissue in the tracheal wall prevents its kinking and obstruction during the movements of the head and neck.

LOCATION The trachea extends from the lower border of cricoid cartilage (corresponding to the lower border of C6 vertebra) in the neck to the lower border of T4 vertebra in the thorax. Thus upper half of the trachea is located in the neck (cervical part) and lower half in the superior mediastinum (thoracic part). N.B. The extent of trachea varies as follows: • C6 to T4 in cadaver placed in supine position. • C6 to T6 in living individuals in standing position. • C6 to T3 in newborn. DIMENSIONS Length: 10–12 cm. External diameter: 2 cm in males and 1.5 cm in females. Internal diameter: 12 mm in adult, 3 mm in newborn. Lumen of trachea: 1. The lumen of trachea is smaller in living human beings than in the cadavers. 2. It is 3 mm at 1 year of age; during childhood it corresponds to the age in years