Development of the human hypoglossal nucleus: a morphometric study.

Development of the human hypoglossal nucleus was studied using complete serial sections of the brains of 9 fetuses at 16, 18, 21, 23, 27, 32, 33, 35 and 40 weeks of gestation, a 2-month-old infant, a 16-year-old adolescent and a 63-year-old adult. Morphometric analysis produced the following three findings pertaining to the development of the human hypoglossal nucleus: (1) development may accelerate after 32 weeks of gestation; (2) postnatal maturation is observable, and (3) natural cell death, as indicated by a decrease in the number of neurons and the appearance of degenerating neurons, may occur during fetal development.