Give reason: Rings of cartilages are present in trachea.
Trachea:
Functions of the trachea:
Rings of cartilage are present in the trachea because:
They are incomplete because this permits the trachea to collapse slightly to allow food to pass down the oesophagus.
The open part of the cartilage rings faces the oesophagus, permitting the trachea to be compressed slightly when the oesophagus bulges outward when the food is swallowed.