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Age-related characteristics of the lungs
Last reviewed: 06.07.2025
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In a newborn, the lungs have an irregular cone shape. The upper lobes are relatively small; the size of the middle lobe of the right lung is equal to the size of the upper lobe, and the lower lobe is relatively large. In the 2nd year of a child's life, the size of the lung lobes relative to each other becomes the same as in an adult.
The mass of both lungs in a newborn is 57 g (from 39 to 70 g), the volume is 67 cm 3. The density of a non-breathing lung is 1.068 (the lungs of a stillborn child drown in water), and the density of a breathing lung is 0.490. The bronchial tree is mostly formed by the time of birth; in the 1st year of life, its intensive growth is observed (the size of the lobar bronchi increases by 2 times, and the main ones - by 1.5 times). During puberty, the growth of the bronchial tree intensifies again. The size of all its parts by the age of 20 increases by 3.5-4 times (compared to the bronchial tree of a newborn). In people 40-45 years old, the bronchial tree is small.
Age-related involution of the bronchi begins after 50 years. In old and senile age, the length and diameter of the lumen of many segmental bronchi decrease slightly, sometimes bead-like protrusions of their walls and tortuosity of the course appear.
The pulmonary acini in a newborn have a small number of small pulmonary alveoli. During the first year of a child's life and later, the acinus grows due to the appearance of new alveolar passages and the formation of new pulmonary alveoli in the walls of existing alveolar passages.
The formation of new branches of the alveolar passages ends by the age of 7-9 years, and of the pulmonary alveoli by the age of 12-15 years. By this time, the size of the alveoli doubles. The formation of the pulmonary parenchyma ends by the age of 15-25 years. In the period from 25 to 40 years, the structure of the pulmonary acinus remains virtually unchanged. After 40 years, the aging of the lung tissue gradually begins. The interalveolar septa are smoothed out, the pulmonary alveoli become smaller, the alveolar passages merge with each other, and the size of the acini increases.
During the growth and development of the lungs after birth, their volume increases: during the first year - 4 times, by 8 years - 8 times, by 12 years - 10 times, by 20 years - 20 times (compared to the volume of the lungs of a newborn).
The boundaries of the lungs also change with age. The apex of the lung in a newborn is at the level of the 1st rib. Later, it protrudes above the 1st rib and by the age of 20-25 is located 3-4 cm above the 1st rib (1-2 cm above the clavicle). The lower border of the right and left lungs in a newborn is one rib higher than in an adult. As the child ages, this border gradually drops. In old age (after 60 years), the lower border of the lungs is 1-2 cm lower than in people aged 30-40 years.
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