In theory teaching,we let students know the knowledge of some important discovery and invention in the history of physiology and while in experiment teaching,we added the experiments designed by students in addition to traditional experiments,so as to enhance the students,ability of innovation.

Objective: To investigate the vitamin A nutritional status of 6- to 17-year-old urban children and adolescents by analyzing serum retinol level, between 2010 and 2012 in China. Methods: Data were obtained from the China Nutrition and Health Survey in 2010-2012. Using multi-stage stratified sampling and the population proportional stratified random sampling method, 6 617 children aged 6-17 years from 32 metropolis and 41 middle-sized and small cities of China were selected. The questionnaire survey was used to collect demographic information. Blood samples were analyzed using high-performance liquid chromatography to determine serum retinol concentration, and the World Health Organization guidelines were used to evaluate the nutritional status of vitamin A. Vitamin A levels, vitamin A deficiency, and marginal vitamin A deficiency in children with different characteristics were compared. Results: A total of 3 785 cases with valid samples were obtained. The overall mean serum retinol concentration level was (1.49±0.71) μmol/L; the mean serum retinol concentration was (1.55±0.69) μmol/L for metropolis and (1.49±0.75) μmol/L for middle-sized and small cities (P>0.05). The mean serum retinol concentration was (1.52±0.78) μmol/L for boys and (1.47±0.68) μmol/L for girls (P>0.05). The mean serum retinol concentration level was (1.46±0.70) μmol/L for 6- to 11-year-old children and (1.54±0.65) μmol/L for 12- to 17-year-old children (P<0.05). The total vitamin A deficiency rate and marginal vitamin A deficiency rate was 7.69% (291/3 785) and 18.57% (703/3 785), respectively. The vitamin A deficiency rate was 8.00% (36/450) for metropolis and 7.64% (65/3 335) for middle-sized and small cities; 8.12% (155/1 908) for boys and 7.25% (136/1 877) for girls; and 8.04% (171/2 115) for 6- to 11-year-old children and 7.18% (120/1 670) for 12- to 17-year-old children. No significant differences were observed for region, sex, or age (P>0.05). The marginal vitamin A deficiency rate was 19.11% (86/450) for metropolis and 18.50% (617/3 335) for middle-sized and small cities; 18.19% (347/1 908) for boys and 18.97% (356/1 877) for girls, with no significant differences observed (P>0.05). The marginal vitamin A deficiency rate was 16.54% (350/2 115) for 6- to 11-year-old children and 21.13% (353/1 670) for 12- to 17-year-old children (P<0.05). Conclusion The vitamin A nutritional status of 6- to 17-year-old Chinese urban children and adolescents between 2010 and 2012 has improved, and the gap between cities is narrowing. However, vitamin A deficiency overall remains high, especially in younger children, and requires specific attention.