Chest Structure And Bronchopulmonary Movement
• Chest shape and anteroposterior diameter:
Infant: rounded chest where diameter equals transverse diameter;
School-age: changes gradually to lateral diameter ratio of 1:2 or 5:7 as chest assumes a more flattened anteroposterior diameter with growth.
• Narrow, smaller lumen of airway system with increased airway resistance until age of five years.
• Ability to respond to irritating stimuli by age 4 to 5 months as smooth muscle develops in airways, gradually reaching smooth muscle development of an adult by age of one year.
• Glottis has more cephalad location in the infant than in the child; epiglottis is longer, and the narrowest part of the larynx located at the same level as the cricoid cartilage; larynx grows slowly during infancy and childhood, with a spurt of growth after childhood phase during preadolescence (voice change).
• Airways grow faster than cervical and thoracic spine, causing a descent of the larynx and trachea; the tracheal bifurcation gradually descends from opposite T3 in the infant to T4 by the end of the growth period, and the cricoid cartilage descends from C4 in the infant to C6 by the end of the growth period.
• Diaphragm in the infant is attached higher in front and is longer, causing a decreased ability to contract with the same force of an older infant or child.
• Lung growth changes from globular to lobular shape by 12 years of age.
• Lung growth produces an increase in alveoli numbers and size as septa in the alveoli develop, divide, and increase their numbers at each terminal airway.
• Branching of terminal bronchioles is increased as alveoli are increased as the child grows.
• Collateral pathways develop between bronchioles and growth pores in alveolar walls during child's growth.
Post a comment