Lung Defects
Respiratory Distress Syndrome
Infants born prematurely, with weights up to 1 to 1.5 kg, are most susceptible
to the respiratory distress syndrome. Shortly after birth, the infant
develops rapid and labored breathing.
A deficiency of pulmonary surfactant appears to be a major cause of hyaline
membrane disease, a common cause of death in the perinatal period.
The lungs are underinflated and the alveoli contain a fluid of high protein
content that resembles a hyaline (glassy) membrane.
Hyaline membrane distress is a major cause of the respiratory distress syndrome
in newborn infants. This membrane is believed to be derived from a
combination of substances in the circulation and injured pulmonary epithelium.
It is suggested that prolonged intrauterine asphyxia may produce irreversible
changes in the alveolar cells, making them incapabel of producing surfactant.
However, there are probably several causes fro absence or deficiency of
surfactant in premature and full-term infants.
Lobe of the Azygos Vein
Abnormal fissures and lobes of the lungs are common and usually insignificant.
A lobe of the azygos vein appears in the right lung in about 1 percent of
people. It develops when the apical bronchus grows superiorly medial
to the arch of the azygos vein instead of lateral to it. As a result,
the azygos vein comes to lie at the bottom of a deep fissure in the superior
lobe of the right lung.
Sources:
1. The Developing Human.
3rd ed. Keith L. Moore. W. B. Sauders Co., 1982.