The narrowest point in the child's airway is within the cricoid cartilage. See croup. Endotracheal tubes seal in the child by fitting (loosely) within that ring, whereas in the adult a more distal balloon is necessary and used.
The cricoid is the complete ring of cartilage about the trachea, this permits the importnat anaesthetic manouver named after sellick in which pressure on the cricoid closes off the oesophagus and prevents regurgitation at emergency induction of anaesthesia which otherwise might kill the patient.
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