29 - The developmental environment: clinical perspectives on effects on the musculoskeletal system

Summary

Introduction

The ability to move, the protection of vital organs and stable support for the body are the principal roles of the musculoskeletal system (muscle, bone and cartilage) (Simkin 1994). This system accounts for a large proportion of the body mass; for example, the muscle mass of a healthy adult 70-kg individual is about 20 kg (Kreisberg et al. 1970). The musculoskeletal system develops embryonically from the mesodermal layer, differentiating into dermatomes containing skeletal and muscle cell precursors in the first trimester. At this stage the embryo is only a few millimetres long. The growing fetus usually obtains nourishment at the expense of the mother, who tends to suffer in periods of adversity, but placental size and unrestricted blood flow through placental vessels to and from the fetus are important for optimal growth, especially during the last trimester. Fetal nutrition and the uterine environment are likely to play a part in the transcription of the genomic blueprint acquired at conception into the phenotypic newborn. Some of these developmental adaptations are now known to have long-term effects on the later risk of osteoporosis, sarcopenia and osteoarthritis. During early childhood, growth is rapid and there are windows of opportunity for environmental or lifestyle factors to have long-term effects, especially on the skeleton.

Puberty, which occurs much earlier in girls, brings growth to an end and its timing will have long-term consequences for adult stature.