Height mainly depends on the length of long bones (such as femur and tibia of lower limbs). The growth of long bones includes the longitudinal growth of bones and the maturity of bones. The main long bones at birth, such as the epiphysis at both ends of humerus, femur and tibia, are all cartilage except the distal femur. Later, ossification centers appeared in epiphyses of different ages, and the number of ossification centers gradually increased, and bone tissue replaced cartilage tissue. But there is still a section of cartilage between the diaphysis and epiphysis, which is called epiphyseal plate cartilage. During the growth and development period, this section of chondrocytes continuously divide and reproduce vertically to generate new cartilage. At the same time, the process of bone formation near the shaft is also going on. Long bones grow little by little, and people grow taller gradually. At the age of 20~22, the epiphyseal cartilage gradually disappears, the epiphysis closes, the longitudinal growth of bones stops, and people are not tall. The growth of epiphyseal cartilage is the basis of human growth, and the growth of epiphyseal cartilage is completed under the synergistic effect of growth hormone, thyroid hormone and other hormones in human body. Among them, the main power source to promote the division and proliferation of chondrocytes is growth hormone, which is secreted by human pituitary gland, promotes the growth of cartilage, widens the epiphyseal plate and plays a leading role in the growth of human height. "Long bone" here refers to the proliferation and differentiation of epiphyseal cartilage layer, and the growth of bone is expressed by bone age. Bone age is an independent growth index, independent of age and growth rate. That is to say, a boy of 10 is about 125 cm tall, which may be older or younger than his actual age. The difference between normal children's bone age and actual age can reach about 1 year. If a child is shorter than normal children of the same age and has a bone age less than the actual age, then the child may grow slowly, while the bone age is older than the actual age, and the child may be precocious. If the epiphysis is closed, there is little possibility of growth. Children's puberty growth will accelerate again, with boys 25-28 cm long and girls about 25 cm long. While sex hormones accelerate the growth of puberty, they also accelerate the maturity of bones and the closure of epiphysis, which slows down the growth to a stop. Normal children 13 years old enter puberty. Children with precocious puberty enter puberty early, and their height can increase rapidly in a period of time, but the growth time is relatively short, that is to say, puberty is shortened, and children can't get enough time to develop, which eventually makes their adult height shorter than the average person. Experts suggest that children should not eat supplements such as ginseng, royal jelly, medlar and astragalus, and should not drink adult functional drinks, which are the chief culprits of precocious puberty in children. Factors affecting children's height: 1. Nutrition. When children's nutrition can't meet the needs of bone growth, the growth rate of body length will slow down. Nutrients closely related to bone growth are vitamin D, calcium and phosphorus. Insufficient iodine and zinc can also lead to short stature of children. Step 2 sleep. The secretion of human growth hormone during sleep is higher than that during awakening. Lack of sleep will affect children's growth, 3. Exercise. Exercise can promote blood circulation, improve bone nutrition, accelerate bone growth, make bones tight and promote body length growth. Parents should cultivate the ability of turning over, climbing, standing and walking in time with the growth of months. 4. Long sunshine time is helpful for children's growth and development. For example, the annual sunshine time in Beijing is 2778.7 hours, and the height of children is well developed; The annual sunshine in Wuhan is 2085.3 hours, and the height development is slightly less; Chengdu is foggy, and the annual sunshine is only 1239.2 hours, so the height development is poor. Therefore, increasing outdoor activity time can promote its growth and development. 5. heredity. 6. disease. Generally, acute diseases only affect weight, while chronic diseases affect body length.