Canalization and catch-up growth (Answer in 150 words)

- Canalization and catch-up growth (Answer in 150 words)
Introduction
Growth is not a free trajectory but a buffered one. Canalization names the buffering, catch-up growth the return to the path after it has been pushed off; together they describe a self-correcting, target-seeking system.
Body
1. Canalization: Waddington's term for developmental buffering. Growth follows a genetically specified pathway, or creode, in his epigenetic landscape, and resists moderate nutritional or infectious insult. Tanner accordingly called human growth target-seeking rather than merely age-graded.
2. Catch-up growth: described by Prader, Tanner and von Harnack in 1963. Once the constraint lifts, velocity rises far above the age norm until the original centile is regained, then falls back. The mechanism proposed is a growth-plate tally of chondrocyte divisions, not a central clock.
3. Limits and critical periods: recovery is incomplete if deprivation is early, severe or prolonged. Undernutrition in the first thousand days leaves permanent stunting, and catch-up in weight without stature carries later cardiometabolic risk.
Conclusion
Canalization explains why most children resist minor insult; catch-up explains recovery from a defined one. Neither guarantees full restitution once a critical period has passed.