All are true regarding trachea except:

C i.e. More than 20 hyaline cartilagesRef: Gray's Anatomy, The Anatomical Basis of Clinical Practice, 41st edition, 2016, page 965 & 966 Version - 2TRACHEALength of trachea is 10-11 cm.Diameter: External transverse diameter is typically 2 cm in adult males and 1.5 cm in adult females.Mean transverse diameter is greater than anteroposterior diameter up to the age of 6 years, after that the two diameters are nearly equal.Internal transverse diameter (lumen) is about 12 mm.In the first postnatal year, the tracheal diameter does not exceed 4 mm.The second to fourth tracheal cartilages are crossed by the isthmus of the thyroid gland.Trachea is lined by respiratory epithelium, i.e., ciliated pseudostratified columnar epithelium with more number of goblet cells.Extent: Trachea extends from the level of C6 (Cricoid cartilage) to the upper border of T5 (Just below the sternal angle). At T5 it divides into right and left principal bronchi.Structure: Wall is made up of cartilage and fibromuscular membrane.Tracheal rings are varies from 16-20 in number. Consists of 16-20 shaped incomplete rings of hyaline cartilage and intervening fibroelastic tissue.Isthmus of thyroid gland related at 2, 3, 4th tracheal rings.