Terminal bronchiolar duct ending number does not increase post-natally in normal infants

Organ development may be assessed by estimating the total number of functio nal units within an organ over time; the potential functional capacity of t hat organ may be represented by the total number of functional units presen t in the fully developed, mature organ. Relative development of the lung at birth is essential to provide sufficient oxygenation of body tissues and s o maintain ex utero life. Estimation of the number of one type of functiona l unit of the lung - terminal bronchiolar duct endings - provides important information regarding development of the lung. This investigation used ste reological techniques, specifically Cavalieri's Principle and the "physical disector", to estimate total number of terminal bronchiolar duct endings i n the upper lobe of the right lung of a group of 14 control infants between 0 and 66 weeks post-natal age. Results demonstrate that total terminal bro nchiolar duct ending number does not increase significantly over the first 24 weeks of post-natal life in normal infants (P = 0.997). The unbiased, de sign-based techniques used in this paper confirm previous model-based resea rch that indicates that terminal bronchiolar duct ending: development is co mpleted before birth. (C) 2000 Elsevier Science Ireland Ltd. All rights res erved.