ISSN:
0003-276X
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Medicine
Notes:
This study covers the period from the fortieth day after ovulation to the thirty-eighth day after birth. In addition, lungs of two mature monkeys have been analyzed. Birth occurs about the one hundred sixty-eighth day (24 weeks after ovulation). By the fortieth day the patterns of the bronchopulmonary segments are well established. These are the tools of the investigator. The curve of growth for the first 60 days parallels that of the rhesus monkey but is steeper than the human curve. At 63 days (9 weeks) pairs of rosette-like clusters of epithelial buds (future alveolar ducts) have appeared on peripheral branches of the segmental bronchi and continue to grow in size until the twelfth week. Then they resemble the paired rosettes of human acini of the seventeenth postovulatory week (Boyden, ′74) and probably represent the primitive unit from which the human was derived. In both man and monkey, canalization of the rosettes starts at about the same relative time (the 17th and 12th week, respectively) and spreads centralwards from the rosettes along the bronchioles of each segmental bronchus. In man, canalization forms acini (alveolar ducts and respiratory bronchioles). In the monkey, due to the monopodial pattern of branching, it produces racemes of alveolar ducts, each raceme ending basally in a pseudorespiratory bronchiole (127th day). By the one hundred fortieth day, enough surfactant has been secreted to support a premature infant. At one hundred fifty days, 11 generations of bronchi, followed by 16 of pseudorespiratory bronchioles, are present in the medial basal segment, followed in turn by 19 generations of prealveolar ducts (the latter provided with delicate spiral muscles) each giving off alternate branches of alveolar ducts. After one hundred fifty days of gestation, generations of bronchi, pseudorespiratory bronchioles, prealveolar ducts and cartilages (15) remain virtually constant for at least 38 days after birth. By the adult stage the number of generations of pseudorespiratory bronchioles has been reduced to three and the prealveolar ducts increased (at the former's expense) to 27. This study is concluded with a comparison of the lungs of the newborn monkey with those of the human/neonate and puppy.
Additional Material:
25 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/ar.1091860103
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