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From the beginning of life to adulthood,children are always in the dynamic process of growth and development.For children of different ages,their physical,physiological and pathological aspects have different characteristics,and disease types,pathological changes and clinical manifestations are different too,therefore,there are different requirements for nurturing,health care,disease prevention and control.At present,children under the age of 18 are regarded as the scope of pediatric visits.According to the anatomical,physiological and psychological characteristics of children,the whole period of childhood is divided into 7 stages,so as to better guide child rearing and disease prevention.
The prenatal period starts at fertilization and ends when the umbilical cord is cut at parturition.The gestational age is 40 weeks or 280 days from the first day of the last menstruation.During gestation,the fetus is connected to its parent with the umbilical cord attached to the placenta and relies on maternal blood qi for its growth and development in the uterus.In this period the fetus is influenced not only by the parents’ physical constitution and heredity but also by the mother’s nutritional,psychological,hygienic and environmental conditions.For example,trauma,infection,drug abuse,fatigue,exposure to radioactive substances,nutritional deficiencies and adverse psychological factors may result in abortion,malformation or intrauterine growth retardation etc.
The neonatal period begins from the beginning to the full 28 days after the birth of the fetus umbilical cord ligation.The newborn baby separates from the mother and lives independently.The internal and external environment has undergone fundamental changes,but its ability to adapt to the outside environment and resist evil capabilities are poor,in addition to fetal injury,birth injury and improper care and other reasons,therefore morbidity and mortality in this period are much higher,and infection,birth trauma,asphyxia,scleredema and umbilical wind are particularly common.Besides,the period from the gestational age of 28 weeks to 7 days after birth is defined as perinatal period.Perinatal mortality is an important indicator to measure the level of health education,obstetrics and neonatal quality in a country or region.
Infancy is the stage between ligation of the umbilical cord after birth and the first year of life.This period is the most rapid growth and development period.The body is growing rapidly and requires a large number of nutrients.However,the spleen’s functions of transportation and transformation are still weak,and the ability to digest,absorb and transport food is relatively inadequate.As a result,the baby is prone to diseases of spleen and stomach,such as enterorrhea,indigestion,abdominal pain,vomiting,and infantile malnutrition.Meanwhile,the lung is delicate and immature,the defensive exterior is insecure,the immunity from the mother gradually disappears,self-immunity is still at a low level,and the ability to resist pathogens is weak,seasonal epidemic diseases and pulmonary diseases can easily develop in infants.
Toddler period is defined as 1–3 years of age.During this period,the children’s physical growth and development slow down,and their intelligence develops rapidly.Learning to walk,they have more opportunity to get into contact with the surroundings,and the ability to speak,think,and move is reinforced.At the same time,after weaning,if not reasonably fed,they are prone to diseases of spleen system; engaging in increased outdoor activities,the toddlers will have more opportunities to contact exogenous pathogens and to catch a variety of contagious diseases.In addition,toddlers lack the ability to identify dangers,and their self-protection is poor,so they are prone to poisoning,burns and other accidents.
The pre-school period is from 3–6 or 7 years old before primary school.At this time,the physical growth and development of children grow steadily,the intelligence development gradually is improving,the understanding comprehension is gradually strengthening,the psychological changes are more prominent,and there is a strong curiosity,which is the key period for the formation of children’s personal character.Due to the enhancement of their resistance to disease,lung spleen syndrome incidence decreases,and diseases related to immunoreaction like asthma,juvenile rheumatoid disease,nephritis,and nephropathy are increasing.Because of expansion of activities,and lack of experience in life,the children are prone to trauma,drowning,electric shock,wrong medication,poisoning and other accidental injuries.
School age refers to the period between entering primary school (6–7 years) and adolescence (female 12 years,male 13 years).Children’s physical development in this period is still increasing steadily.Except the reproductive system,the development of other organs is approaching the adults.The shedding of deciduous teeth,the eruption of permanent teeth,and the development of brain morphology are basically the same as those of adults.The development of intelligence is more mature,and the abilities of self-control,understanding,analysis and synthesis are further enhanced,and the scientific and cultural education of the system can be accepted.In this period,the disease resistance in children is enhanced; the incidence decreases,types and manifestations of diseases are similar to that of adults.
Adolescence refers to the period from the appearance of secondary sexual characteristics to the basic development of reproductive function with the ceasing of height growth.Generally,the females,adolescence is from ages 11–12 to 17–18 and for males 13–14 to 18–20 years old.Adolescence is a transitional period from childhood to adulthood,when the main characteristics include kidney qi becoming sufficient, tiān kuí (reproduction-stimulating essence) arriving,yin and yang harmonizing and reproductive system maturating.Gender differences become significant.Girls commence menarche and boys have their first ejaculation.Secondary sexual characteristics become apparent.There are the second peaks in growth of their body weight and length.In spite of physical growth,increased knowledge and skills,and enhanced social adaptability and disease resistance,their psychological changes are so great that a variety of psychological and behavioral disorders may also appear.