what is the difference in size and function of the thymus in infants and adults
The thymus gland is large in infants and continues to grow through childhood. During this phase, the thymus matures more than enough T-cells to last throughout your child's life, so the gland begins to decrease in size at puberty. Fat slowly replaces the thymus until it becomes quite small in older adults.
At birth it is about 5 cm in length, 4 cm in breadth, and about 6 mm in thickness. The organ enlarges during childhood, and atrophies at puberty. Unlike the liver, kidney and heart, for instance, the thymus is at its largest in children. The thymus reaches maximum weight (20 to 37 grams) by the time of puberty.