Anatomical Changes of Child Through Adolescense

Infant to Adolescent Changes Lloyd A. Hause NRSG 252 Colorado Technical University Professor Darlene Perdue 7-11-11 Abstract From infancy to adolescence many anatomical and physiological changes will occur, often in stages. From the moment a newborn leaves the womb and takes its first breath of air, a rollercoaster of events is set into motion. This is also the time that the new infant is most vulnerable to injury and infection. This is primarily due to the fact that not all of the infant’s body systems and parts are fully mature yet.

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For instance, the epidermis is very fragile and can be torn easily; the kidney, liver, neurological system, and immunological system are not developed to full capacity. Over a period of days, weeks and years and infant slowly matures and continues to grow and go through stages of change until adulthood. Growth and development of a child occurs more rapidly during infancy. During the first year of infancy, especially the first six months of life, is when the body changes rapidly. It is expected that a baby will gain 1. 5 pounds per month for about the first five to six months of its life.

At the same time, the infant is growing in height at a rate of around one inch per month. As stated by Wong, “Infants gain 680g (1. 5 pounds) per month until age 5 months, when the birth weight has at least doubled. ” and “Height increases by 2. 5cm (1 inch) per month during the first 6 months and by half that amount per month during the second 6 months. ” (Hockenberry & Wilson, 2007) After this first year of life, a child continues to grow and develop, just at a slower rate, until early adolescence, which is around 11-14 years of age.

Then once again the body begins to go thorough more rapid changes, such as rapid physical growth. From birth to adolescence, many anatomical and physiological changes occur. Skeletal and muscular growth of a human being is probably one of the most noticeable changes throughout the different stages of life. As mentioned, an infant nearly doubles its birth weight by month five as well as doubling in height by month six. At birth, a newborn’s skeletal system primarily consists of cartilage rather than bone. For instance, the nose is mainly cartilage and is often flattened by delivery.

The skull is another example, at birth the skull bones are still soft and not sutured yet. The cranial sutures usually begin to close around six to eight weeks of life. By the end of a baby’s first year, their head size has increased nearly 33%. (Hockenberry & Wilson, 2007) During preadolescence, there is another rapid acceleration of growth. This is the time period that a person reaches their peak heights, 20% to 25% of height and nearly 50% of adult weight is achieved during this time. (Hockenberry & Wilson, 2007) Once difference, between infants and adolescents is the time frame that their height and weight gains occur.

An infant achieves approximately the same height and weight gain during their first six months of life, regardless of sex. Whereas, preadolescents around the ages of eleven to fourteen gain height and weight at different ages, depending on the whether they are male or female. Females start their growth spurt around the age of twelve where boys start around the age of fourteen. As stated by Perry & Potter, “For girls, height increases 2 to 8 inches and weight increases by 15 to 55 pounds. Height for boys increases approximately 4 to 12 inches, and weight increases by 15 to 65 pounds. (Potter & Perry, 2009) Girls also typically achieve their adult maximum height before menstruation begins, normally before age fourteen. Males on the other hand, continue to grow taller until about the age of eighteen or twenty. Another growth difference between infants and adolescence is where on the body the growth is most significant. With infants the growth occurs mainly in the trunk, instead of the extremities. With adolescents, growth in the extremities occurs first, which is what makes teens appear to lanky and clumsy. At the same time, the lower jaw and nose become longer and the forehead higher and wider.

This is when a person’s appearance begins to look less like a child and more like an adult. Thermoregulation or heat regulation is very critical, but even more so to the newborn. A newborn has the ability to produce adequate heat but there are a few factors against the new baby, causing heat loss. A newborn baby has a large surface area in comparison to his/her weight at birth. This large exposed surface area allows exposure of the baby to the environment contributing to a risk for heat loss. Secondly, the infant has very little subcutaneous fat.

This lack of insulation to the environment makes for a temperature gradient that is not in favor of the child. Essentially, a baby’s core temperature is higher than that of the environment. Therefore, heat wants to cross the temperature gradient from a higher to lower temperature, causing a loss of body heat. “Since core body temperature is approximately 1° F higher than surface body temperature, this temperature gradient (difference) causes a heat transfer from a higher to lower temperature. ” (Hockenberry & Wilson, 2007) Another problem that the newborn has, is the ability to produce heat.

Shivering is the method that a child or adult uses to generate heat, unfortunately a newborn is unable to perform this function. Unlike an adolescent, a newborn produces heat via thermogenesis by way of brown fat otherwise known as brown adipose tissue (BAT). As described by Hockenberry & Wilson, “BAT has a greater capacity for heat production through intensified metabolic activity than does ordinary adipose tissue. Heat generated in the brown fat is distributed to other parts of the body by the blood, which is warmed as it flows through the layers of this tissue. Hockenberry & Wilson, 2007) Another difference between newborns and adolescence is the ability to cool the body down in an overheated environment. Infants lack the ability to sweat like an adolescent, which increases their chances of hyperthermia. The gastrointestinal system is limited at birth. Compared to a preadolescent child, the newborn has issues with eating fatty food, the liver is not well developed and in relation to body size their intestine is quite long. Infants make enzymes to break down proteins and simple carbohydrates.

The problem lies with the insufficient production of pancreatic amylase which impairs the ingestion of complex carbohydrates. This therefore limits foods that have high saturated fat content, such as cow’s milk. So, an infant has difficulty breaking down these types of food, where an adolescent has the ability to make the enzyme necessary to digest complex carbohydrates. The liver is the most underdeveloped of the gastrointestinal organs. Because of this, the liver has a reduced amount of the enzyme glucuronyl transferase, which contributes to jaundice in newborn babies. The activity of the enzyme glucuronyl transferase is reduced, jaundice of the newborn. ” (Hockenberry & Wilson, 2007) The liver stores less glycogen at birth, which puts the baby at an increased risk for hypoglycemia. This may be prevented by a feeding soon after birth, preferably breast milk. Compared to an adolescent the infant has a larger intestine in relation to body size. Therefore, there are more secretory vessels and a larger surface area for absorption. A common occurrence in a newborn that does not happen in adolescents is regurgitation after feeding.

Because of the size of the intestine, peristalsis occurs rapidly. The waves created, called migrating motor complex, force food forward causing the child to vomit. Essentially, this is caused because of the immaturity of this motor complex and weak lower esophageal sphincter along with delayed stomach emptying. Fluid and electrolyte imbalance is quite common in an infant compared to an older child or adult. A newborn is 73% fluid compared to 58% in an adult. (Hockenberry & Wilson, 2007) Infants need more water and are at greater risk for fluid and electrolyte imbalances.

Much of an infant’s susceptibility to water loss is due to a larger body surface area, increased metabolic rate, immature kidney function and their fluid requirements. Because an infant has a larger body surface area and larger intestine they are more prone to water loss through the skin and diarrhea. Newborns have a higher metabolic rate compared to adolescents. This high metabolic rate in conjunction with a larger body surface area causes greater heat production, which leads to water loss. An infant’s kidney is immature at birth and therefore cannot perform its job properly.

As a result, the kidney doesn’t excrete waste products properly. The infant compared to an older child is more likely to get dehydrated because the kidney has difficulty with the concentration and dilution of urine and saving or eliminating sodium. Therefore, the infant is at greater risk of dehydration when given concentrated formulas or overhydrated when fed too much water or diluted formula. Because of all these factors infants have to consume and eliminate more fluid compared to an older child or adolescent. The integumentary system is another difference between an infant and an adolescent.

Compared to adolescent children a newborn’s skin is quite immature and very fragile. As stated by Hockenberry & Wilson, “The two layers of the skin, the epidermis and dermis, are loosely bound to each other and are very thin. ” (Hockenberry & Wilson, 2007) So the slightest trauma to the epidermis, such as pulling off a band aide or removal of tape can tear the skin. The sweat glands or eccrine glands are active by three weeks of age and noticeable on the palms. Since infants are not able to convey their needs verbally, this sweating may indicate anxiousness or pain.

Another sweat gland, the apocrine gland, which is attached to hair follicles are small and don’t become functional until puberty. Newborns are also more susceptible to ultraviolet light from the sun. This is primarily because at birth they have low levels of melanin. A baby’s pigmentation, because of the lack of melanin, is light skinned. As they age, and produce more melanin, they become darker skinned and are better protected from the sun. Compared with older children, a newborn’s neurologic system is not quite as developed.

Newborns unlike adolescents have limited motor skills and their sensory functions are not as acute. A newborn is developed to the point of being able to survive outside of the womb, but is limited to basic reflexes. Although, the baby’s automatic nervous system is developed enough to maintain life. At birth, the automatic nervous system makes breathing and temperature control possible, as well as, regulates acid-base balance. As an infant ages, myelination of the nervous system follows, which is when an infant begins to master motor skills.

Myelination of the nerves is important because it allows for transmission of nerve impulses. The sensory, cerebellar and extrapyramidal tracts develop myelin first. This allows a baby its basic senses such as smell, taste and hearing and sensing pain. Swallowing is the ability to collect food and propel it into the esophagus. As a newborn this ability is lacking. Therefore, children under six months of age should not be fed solid foods. As stated by Potter & Perry, “Developmentally, infants are not ready for solid food before 6 months.

The extrusion (protrusion) reflex cases food to be pushed out of the mouth. (Potter & Perry, 2009) Instead, infants have a swallowing reflex. Basically, food lies in a groove on the top of the tongue. Then, as the tongue is pressed forward and up, gravity takes over and the milk flows down the tongue and along the sides of the mouth and in grooves between the tongue, cheek, and gums. As an infant ages, the swallowing reflex changes. This is largely due to the tongue decreasing in size, having better motility, and development of face muscles and teeth.

This is best described by Hockenberry & Wilson, “The tongue remains behind the central incisors, and the mandible no longer thrusts forward. The dorsum of the tongue is less concave and remains higher and parallel, not inclined, against the palate; the lateral furrows are absent because of teeth eruption. Tongue pressure and movement against the hard palate push the bolus back into the pharynx. ” (Hockenberry & Wilson, 2007) At birth, due to passive acquired immunity, a baby inherits the mother’s immunity for about the first three months of life.

Passive immunity as described by Medical-Surgical Nursing, “Passive acquired immunity implies that the host receives antibodies to an antigen rather than synthesizing them. This may take place naturally through the transfer of immunoglobulins across the placental membrane from mother to fetus. ” (Lewis, Heitkemper, Dirksen, O’Brien, ; Bucher, 2007) The newborn receives IgG, which gives it protection from the many antigens that the mother was exposed to. From birth though, the maternal IgG levels begin to dwindle and the baby produces limited amounts on its own.

Only about 40% of adult levels of IgG are reached by the first year of age. (Hockenberry ; Wilson, 2007) Therefore, the infant is at the highest risk for infections during the first six to twelve months of life. Babies that are breastfed have an advantage over formula fed babies. A mother’s colostrum contains large amounts of IgA. This IgA is believed to protect an infant from bacteria like Escherichia coli and viruses such as poliovirus within the gastrointestinal tract.

Other immunoglobulin’s such as IgM reach their adult levels by 9 to 12 months, whereas, IgA, IgD, and IgE take longer and do not reach their adult levels until early childhood. During infancy, a child’s respiratory system is quite stable but not yet matured to the level of an adolescent. Upon birth an infant has a high respiration rate, of about 30-35 breaths per minute compared to 16-19 breaths per minute for a person age 12-18. (Hockenberry ; Wilson, 2007) One reason for the rapid respiratory rate is that the infant’s rib cage has less elastic recoil, which makes it more work to breathe.

Also, the amount of air needed to fill the respiratory passage with each breath, is large, which requires the infant to breathe nearly twice as fast as adults to provide the adequate amount of oxygen. Another large difference between an infant and a teenager is the infant’s susceptibility to respiratory infections. Because of an infant’s size, the trachea and bronchi are very close together. Because of their close proximity, infectious agents are easily passed back and forth.

Another problem is that the Eustachian tube in the ear is short and straight, allowing for infection to easily travel from the pharynx to the middle ear. An infant’s heart is larger in comparison with its body size and the heart occupies a larger space within the mediastinum. An infant has a blood pressure around 90/50 with a heart rate of around 100-180 beats while resting and awake. A thirteen year old adolescent has a blood pressure around 125/80 and a heart rate around 55-90 beats while resting and awake. (Hockenberry ; Wilson, 2007) The systolic blood pressure after birth is low because of a weak left ventricle.

Over about six weeks the pressure rises quickly and will continue to do so until just before puberty, where it then rises rapidly to adult levels. During adolescence a child’s heart increases in size with a higher blood pressure and a decreased heart rate, to accommodate growth spurts. An infant will also commonly have sinus arrhythmia with breathing, which typically increases with inspiration and decreases with expiration. At birth, the ventricular walls are about equal thickness. The left ventricular wall becomes thicker than the right ventricular wall, and the pressure on the left side of heart rises.

As pressure increases arteries and veins will elongate and thicken to keep up with the increased pressure and body size. Essentially, an infant is typically born with all the proper anatomical and physiological equipment to survive outside the womb. But many of these systems and or parts of the body need time to mature to where they function at normal levels. This process normally takes place within a couple days to weeks and usually by the end of the first year of life. Then as a child develops through the stages of growth and reaches adolescent age, he/she basically hits puberty.

At this stage of life the child develops into an adult and once again the body changes and goes through stages. References Hockenberry, M. J. , ; Wilson, D. (2007). Wong’s Nursing Care of Infants and Children. St. Louis: Mosby Elsevier. Lewis, S. L. , Heitkemper, M. M. , Dirksen, S. R. , O’Brien, P. G. , ; Bucher, L. (2007). Medical-Surgical Nursing: Assessment and Management of Clinical Problems. St. Louis: Mosby Elsevier. Potter, P. A. , ; Perry, A. G. (2009). Fundamentals of Nursing 7th Edition. St. Louis: Mosby Elsevier.


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