The physiological characteristics of infants and young children, the birth and development of infants conform to the laws of human growth. These standard laws can make novice parents know their children's development more intuitively, but infants and young children need to pay more attention and look at their physiological characteristics.

Physiological characteristics of infants 1 (1) Physiological characteristics of newborns

A newborn refers to a baby from birth to 28 days.

The newborn has just left the mother to live independently, and the surrounding environment suddenly changes, forcing the newborn to adapt to the new and ever-changing external environment. The average weight of newborns at birth is 2500 ~ 4500g, and the average height is 45 ~ 51cm.

In terms of nutrition, the newborn can not adapt well to the environment outside the mother's body from the over-nutrition provided by pregnant women to the nutrition provided by gastrointestinal tract. If it is not properly fed, it will easily lead to malnutrition and even illness of the newborn.

(2) Physiological characteristics of infancy

A baby is a child under 1 one year old. Babies grow and develop particularly rapidly at this stage, which is the most vigorous stage of human life.

① The body weight can reach 3 times of that at birth, about 9000 ~10000g.

② The body length is about 50 cm at birth, generally increasing by 3 ~ 3 and 5 cm per month, and increasing by 1 0 ~ 1 2 cm at 4 months, and it can reach about 5 times of1at birth.

③ The head circumference is about 34 cm at birth, which increases by 8 ~ 1 0 cm in the first half of the year, and 2 ~ 4 cm in the second half of the year, with an average of 46 cm at1year. After that, the growth rate slowed down, and it was about 56 ~ 58 cm when it reached adulthood.

④ The chest circumference is smaller than the head circumference at birth1~ 2cm, and by the end of 4th month, the chest circumference is basically the same as the head circumference.

⑤ The baby is still in the rapid development period of the brain for a period of time after birth, and the number of brain cells continues to increase, which requires the support of sufficient, balanced and reasonable nutrients (especially high-quality protein), so the demand for calories, protein and other nutrients is particularly strong.

Thus, to meet the needs of fast-growing babies, we must provide adequate, balanced and reasonable nutrition.

(3) Developmental characteristics of digestive system and related organs in infants.

In order to feed the baby correctly and reasonably, it is very necessary to know the development of the baby's digestive organs in this period, so as to feed the baby reasonably according to the special physiological characteristics and nutritional needs of the baby and ensure the nutritional needs of the baby.

Oral cavity: Full-term newborns have good sucking and swallowing function at birth, and there is a thick fat pad on the cheek, which is helpful for sucking activities, but premature infants are worse. Sucking is a complex natural reflex, which can be affected by serious diseases, making sucking weak and powerless. Newborns and infants have thin and tender oral mucosa, rich blood vessels, imperfect salivary gland development, less saliva secretion, dry oral mucosa, and are vulnerable to injury and bacterial infection; Saliva secretion began to increase at 3 months; It increased significantly at 5 months. The content of amylase in saliva of children under 3 months is less, so it is not suitable to feed starch food. Babies with shallow mouth floor will not swallow all the saliva secreted in time, and often have physiological salivation.

Esophagus: the esophagus has two main functions: one is to push food and liquid into the stomach from the mouth; The second is to prevent reflux of stomach contents during swallowing. The esophagus of newborns and infants is funnel-shaped, with delicate mucosa, lack of glands, underdeveloped elastic tissue and muscularis, immature sphincter of cardia in the lower esophagus, and poor control ability. Gastroesophageal reactions often occur, and most of the symptoms disappear in 8 ~10 months. Babies often swallow too much air when sucking milk, which is easy to overflow milk.

Stomach: The stomach capacity of newborns is about 30 ~ 60ml, and then it increases with age, 90 ~ 1 50ml at13 months, and 250 ~ 300ml at1year. Because the stomach capacity of newborns is small, newborns should be fed a few times, and the feeding times should be more than that of older children. The baby's stomach is horizontal, and its position becomes vertical when it begins to walk; The development of gastric smooth muscle is not perfect, and it is easy to expand the stomach after being filled with liquid food. Due to low cardiac muscle tension, well-developed pyloric sphincter and poor autonomic nerve regulation, it is easy to cause pyloric spasm and vomiting. Gastric mucosa is rich in blood vessels, but there are few glands and goblet cells, and the secretion of hydrochloric acid and various enzymes is less than that of adults, with low enzyme activity and poor digestive function.

The gastric emptying time varies with different kinds of food, and the milk with thick milk curd is slow to empty. The emptying time of water is 1 and 5-2 hours; Breast milk for 2 ~ 3 hours; Milk for 3 ~ 4 hours. Premature infants have slower gastric emptying and are prone to gastric retention.

Intestine: The intestine of children is relatively longer than that of adults, which is generally 5 ~ 7 times of the body or 10 times of the sitting height, which is beneficial to digestion and absorption. Intestinal mucosa is tender, rich in blood vessels and lymphatic vessels, with good villi development and poor muscularis development. The mesentery is soft and long, the mucosal tissue is slack, especially the colon has no obvious colon band and fat pendant, and the ascending colon is poorly fixed with the posterior wall, which is prone to volvulus and intussusception. Thin intestinal wall, high permeability, poor barrier function, intestinal endotoxin, indigestion products and allergens can enter the body through intestinal mucosa, which is easy to cause systemic infection and allergic diseases.

Liver: The younger you are, the bigger your liver is. Infants' liver connective tissue is poorly developed, and their liver cells have strong regenerative ability, so they are not prone to cirrhosis. However, they are easily affected by various unfavorable factors, such as hypoxia, infection and drug poisoning, which can cause liver cells to swell, fat infiltration, degeneration and necrosis, fiber proliferation and swelling, thus affecting their normal physiological functions. There is less bile secretion in infancy, so the digestion and absorption of fat are poor.

Pancreas: It is divided into two parts: endocrine and exocrine. The former secretes insulin to control glucose metabolism, while the latter secretes pancreatic juice, which contains various digestive enzymes, interacts with bile and intestinal secretions, and participates in the digestion of protein, fat and carbohydrates. The secretion of pancreatic juice and its digestive alcohol in infants is easily inhibited by hot weather and various diseases, and indigestion is easy to occur.

Kidney: several months after birth, the renal tubules gradually grow before they have the ability to absorb back. The glomerular filtration rate is low, that is to say, the kidney has a weak ability to deal with the "waste" produced by nutrient metabolism. The baby's renal tubule has not grown to a sufficient length, and its function is insufficient, and its ability to excrete sodium is limited. The chronic retention of sodium will cause edema. If you eat too much salt, it will lead to high blood pressure in adulthood. Therefore, for infants before 4 months, special attention should be paid to the intake of salt in food, and it is generally advocated that infants within 4 months should control the intake of sodium salt.

Digestive enzymes: 4 months ago, the baby's salivary gland secretion function was weak, the saliva secretion was very small, and the salivary amylase activity was very low. All digestive enzymes except pancreatic amylase were available in the intestinal cavity. At this stage, besides the protein and fat digestibility of breast milk, the digestibility of starch food and other animal milk is relatively weak. From these characteristics of human newborn babies, we know that babies are born with the ability to breastfeed. Therefore, breastfeeding is a suitable feeding method for infants. In addition, the low enzyme activity in the newborn's liver and the insufficient activity of glucuronic acid converting enzyme are one of the important reasons for neonatal physiological jaundice. When the enzyme is insufficient, the detoxification ability of some drugs is also poor, and a slightly larger dose will cause serious toxic reactions.

Intestinal bacteria: in the mother's body, the fetus's intestine is sterile, and bacteria invade the intestine from air, nipples and utensils through the mouth, nose and anus several hours after birth; In general, the stomach is almost sterile, and there are fewer duodenum and upper small intestine, and the colon and rectum are the most bacteria. Intestinal flora is influenced by food composition, and Bifidobacterium is dominant in breast-fed children. The proportion of Escherichia coli, acidophilus, Bifidobacterium and enterococcus in the intestine of artificially fed and mixed fed children is almost equal. Normal intestinal flora has a certain antagonistic effect on pathogenic bacteria invading the intestine. When the digestive function is disordered, intestinal bacteria can multiply in large quantities and enter the small intestine or even the stomach to cause disease.

Physiological characteristics of infants 2 1, growth and development

The growth and development of infants and young children is the process of the growth and functional maturity of various tissues and organs of the body, which is determined by the interaction of genetic factors and environmental factors, among which nutritional factors are very important.

Infant refers to the period from birth to 1 year. Infantile period is the first peak of human life growth and development, especially in the 6 months after birth. The growth and development of infants and young children is first manifested in the increase of their weight, which can be increased to twice the birth weight at 5 ~ 6 months, and will be increased to three times the birth weight at 1 year. Body length is an index reflecting the growth of skeletal system. The average body length increases by 25cm in infancy, and it will increase to 75cm when 1 one year old, which is 5 times of that at birth. The size of the head circumference reflects the development of the brain and skull. The average head circumference is 34cm at birth and increases to 46cm at 1 year. In this period, the number of brain cells continued to increase, and the brain weight increased to 2 times (600 ~ 700 g) at the age of 6 months, and reached 900 ~ 1 000 g at the age of/kloc-0, which was close to 2/3 of the adult brain weight. Chest circumference reflects the development of chest and chest back muscles. It is smaller than the head circumference by 1 ~ 2 cm, but it grows rapidly. By1year, it is basically equal to the head circumference and begins to exceed the head circumference (head-chest circumference crosses).

Childhood refers to from 1 year to 3 years old. Although children's growth and development are not as rapid as babies, they are also very vigorous compared with adults. The body weight increased by about 2kg every year, the body length increased by113 cm in the second year, 8-9 cm in the third year, and the head circumference increased by about 1cm every year. During this period, intelligence developed rapidly, and language and thinking abilities were enhanced.

2. Digestion and absorption

The digestive system of infants is still in the development stage, and its function is not perfect enough, so the digestion, absorption and utilization of food are limited to some extent.

(1) Oral cavity: The oral cavity of infants is narrow, the oral mucosa is quite tender, and the blood vessels are rich, so it is easy to be damaged. Therefore, special attention should be paid to keeping the oral cavity of infants clean, and it is not advisable to eat overheated and hard food to avoid damaging the oral mucosa of infants. Infants and young children have well-developed fat pads on their cheeks to help them suck milk. The development of salivary glands in newborns is not perfect, the secretion of saliva is low, and the content of amylase in saliva is low, which is not conducive to the digestion of starch.

(2) Teeth: Primary teeth begin to erupt around 6-8 months. Because the growth of teeth affects the chewing function of infants, the ability of infants to chew food is poor.

(3) Esophagus and stomach: The mucosa and muscularis of the esophagus and stomach wall of infants are thin, and the elastic tissues are not well developed, so they are easily damaged. The esophagus of infants is thinner and shorter than that of adults, and the stomach capacity is small. The stomach capacity of newborn infants is only 25 ~ 50 ml, about 200ml at 6 months and about 300 ~ 500 ml at 1 year. Because the gastric pyloric sphincter is well developed, the cardiac sphincter is poorly developed, and the autonomic nerve regulation function is poor, it is easy to cause pyloric spasm and galactorrhea and vomiting.

(4) Intestine: The intestine is relatively long, with poor fixation and prone to intussusception. The intestinal mucosa is tender, rich in blood vessels and lymph, and has strong permeability, which is conducive to the absorption of nutrients. However, the intestinal wall muscles are weak and the intestinal peristalsis is worse than that of adults, which makes the food stay in the intestinal cavity for a long time. On the one hand, it is beneficial to the digestion and absorption of food. On the other hand, if the peristalsis function of the large intestine is not coordinated, stool retention or functional intestinal obstruction may occur. The shielding function of the intestinal wall of infants is poor, and microorganisms, toxins and allergic substances in the intestinal cavity can penetrate into the intestinal wall and enter the blood to cause disease. Babies are born with lactase and sucrase, which is beneficial to the absorption of lactose and sucrose. The brush border of intestinal wall can produce enterokinase and peptidase, which contributes to the digestion and absorption of protein.

(5) Pancreas: The pancreas of infants is immature, and the digestive enzyme secreted is low. Infants under 5 ~ 6 months only secrete a small amount of pancreatic amylase, so infants before 3 ~ 4 months should not add starch complementary food. The content of pancreatic lipase was low at birth, which increased 5 times in the first 1 week and 20 times in1~ 9 months. Therefore, the fat digestion ability of younger infants is weak, but trypsin and chymotrypsin are sufficient at birth.

(6) Liver: The infant's liver is relatively large, and the newborn's liver accounts for 4% of the body weight (2% of the adult's body weight), and it increases 1 times at 10 months. Before 1 years old, the liver is often touched at1~ 2 cm under the right rib. Infants' liver is rich in blood vessels, but the liver cells are not fully differentiated, the liver function is poor, and bile secretion is less, which affects the digestion and absorption of fat.

Infants and young children have immature digestive system, small stomach capacity, low activity of various digestive enzymes and weak digestive function, which is obviously different from that of adults. If it is not properly fed, it is easy to have diarrhea and cause nutrient loss.

3. Development of brain and nervous system

The baby's brain weighs about 370g at birth, accounting for about 1/8 of the body weight, and it weighs about 600 ~ 700 g at 6 months. The development of the brain, especially the proliferation, enlargement and differentiation of cortical cells, is mainly in the third trimester of pregnancy and the first year after birth, especially in the first six months after birth, which is a key period for the development of the brain and intelligence.

Physiological characteristics of infants 3 1-2 babies' developmental characteristics

1-2-month-old baby can only see things 20-30cm away from his eyes, so he is very interested in faces. Bao Ma can hold the baby and play the game of "Get to know me quickly" with him. Eyes looking at each other, speaking softly, hugging and stroking can all promote the baby's perceptual development. When a baby hears his mother's kind voice and touches his mother's skin, he will feel safe, happy and promote brain development.

Developmental characteristics of 2-3 month-old babies

Babies aged 2-3 months can hold small socks, toys of different colors, black and white cards, etc., and put them 30cm away from the baby's eyes, and then slowly move left and right to train the baby to turn his head while staring at the items.

This is also one of the items that doctors visit when we take our baby for a physical examination. At that time, my little monkey's prone position was a little unstable, which affected the posture of swinging his head left and right. He didn't do very well and was criticized by the doctor.

Developmental characteristics of 3-4 month-old babies

Babies aged 3-4 months can start to train their hand-eye coordination ability and reach out for things. I bought a fitness rack for the little monkey. There are some toys hanging on it. He can try to reach it by himself. It doesn't matter if there is no fitness rack at home. You can tie an elastic band on the railings on both sides of the cot and hang 1-2 small toys. Just lie down and reach the height.

Don't underestimate this play process, which combines the senses of touch, hearing, vision, taste and smell, and also exercises the activity ability of the baby's head and body, and promotes the development of bones and joints.

Developmental characteristics of 4-5 month-old babies

4-5 months old baby, when lying on his stomach, can already support himself quite high. Put a toy near him. If he can wriggle to find it, or even catch it successfully, remember to praise him. During this time, the doctor gave us advice that we should lie down if there is nothing to do. The baby is sunbathing on the balcony, and I let him lie down.

After 5 months, you can try to let the baby sit on you and play. After the baby sits firmly alone, he can train himself from lying down to sitting up.

Developmental characteristics of babies aged 5-6 months.

Babies aged 5-6 months have been able to express their feelings initially, and they will be happy and afraid until they know they are strangers. When meeting a stranger, the baby will gradually eliminate the fear after the mother has communicated with the stranger. At this time, let the baby greet and communicate with the stranger, promote the baby's social communication ability, and stimulate the baby's brain's observation, memory and expression.

Developmental characteristics of 7-8 month-old babies

At the age of 7-8 months, the baby's mobility has been greatly enhanced, and he can turn over, sit alone, crawl and stand. His big movements are more and more refined and flexible, and his hand-eye coordination ability is more mature. Hearing is more sensitive. Through imitation and repetition, the more you learn, the more you know yourself, the more you begin to express your feelings, and the more you begin to say hello to strangers other than family members. Babies need to know themselves and their body parts in front of the mirror, and practice crawling on the abdomen to prepare for crawling.

Developmental characteristics of 9- 10 month baby

9- 10 months old, crawling is a compulsory course for babies, and it is a necessary stage to promote the intellectual development of the brain. Some babies learn to walk very early, so the crawling time is compressed, and they miss a good opportunity for the coordinated development of their brains and brains.

Please remember that the two most important movements in 0- 1 year-old are lying down and crawling, not walking.

The baby has a strong interest in the things around him. Read some simple color picture books and show the baby the things at home, starting with the shape and color. Look at the pictures, from top to bottom, from left to right, in order and without omission.

1 1- 12-month-old baby's developmental characteristics

1 1- 12 months old, the baby began to stand up and walk with the edge of the bed, fence and stool. Walking requires the lower limbs to support the weight of the whole body, the cooperation of other muscle joints and sound brain command. Training your baby to walk often takes several months, and you can't rush it.

My family didn't buy a toddler belt and a walker, only a fence. The baby often stood on the fence and slowly learned to walk on his own.

Babies begin to play role-playing, and taking care of dolls is the most common. Learning to care about others will help to deal with interpersonal relationships in the future.