Infancy and Childhood Flashcards

Flashcards for Infancy and Childhood lecture review.

Growth

Increase in the size of the body or body parts. Occurs mainly in the first 20 years of life. Occurs through an increase in the number of cells (hyperplasia), increase in cell size (hypertrophy), and increase in intercellular substance (accumulation). Focus is on the size attained at a specific time.

Maturation

The process of growing to maturity or toward the state of being mature biologically. Occurs in all organs and their systems and tissues. E.g., skeletal maturation = fully ossified adult skeleton. Timing and rate of maturation vary.

Development

2 scenarios: Biology: stem cells developing into functional cells and systems. Behavioral: development of behavioral competence: motor/skill acquisition, socially acceptable behavior, intellect, emotion.

Human Lifespan Definitions

Chronological age = how old you are. Biological age = how old you are biologically. Prenatal Period = period of growth and development before birth (approx. 9 months). Germinal Period = fertilization to the end of blastocyst formation (Weeks 1-2 of development).

Human Lifespan Definitions (cont.)

Embryonic Period = day 14-56 after fertilization (Weeks 3-8). The developing human is called an embryo. Fetal Period = 56 days to birth (last 30 weeks).

Age Group

Postnatal = period after birth. Infancy = first year of life (0-1 year). Perinatal = first week. Neonatal = first month.

Age Group

Childhood = 1 year – puberty. Toddlerhood = preschool years (1 – 4 years). Mid-childhood = elementary school years (5 years to puberty).

Adolescence

Generally between 10-18 years. Start and end of puberty varies widely. Males: 10 - 22 years. Females: 8 - 19 years.

Adulthood

20 years to death. Young adulthood = 20-40 years. Middle adulthood = 40-65 years. Older adulthood = 65 years to death. Three-age: 65-75 years, 75-85 years, 85+ years.

Infancy and Childhood

Periods of rapid growth in most systems. Toddlerhood = continued rapid growth, but rate slows. Mid-childhood = steady development.

Fetal Circulation

Mother provides O2 and nutrition, and removes CO2 and waste for the fetus. This is accomplished by the placenta. Allows for exchange to occur, without mixing maternal and fetal blood. Umbilical Vein = carries O2 and nutrients from the placenta to the fetus. 2 Umbilical Arteries = carry venous blood from the fetus to the placenta for re-oxygenation and waste removal.

Fetal Circulation

Fetal lungs are non-functional – they are filled with fluid. Fetal heart does pump blood, but only 10-15% of the blood pumped out by the heart goes through the lungs. Two shunts divert blood from the right side to the left side of the heart, thus bypassing the lungs: Foramen Ovale: one-way opening in the septum separating the right and left atria. Allows blood to bypass the right ventricle and go directly to the left atrium. Once blood flows through RA, the pressure on the left side closes the valve, thus preventing backflow.

Ductus Arteriosus

Small blood vessel, connecting the pulmonary artery to the aorta. Acts as right to left shunt. Allows the small amount of blood that is pumped by the RV to the lungs to be diverted to the aorta. Ductus Venosus – temporary blood vessel from the umbilical vein to the inferior vena cava. Allows oxygenated blood coming from the maternal circulation to be diverted directly from the umbilical vein to the IVC – bypassing the liver.

Circulatory Changes at Birth

At birth, metabolic link between mother and fetus is cut = Lungs inflate = decreases resistance to blood flow to the lungs = increases blood flow to the pulmonary artery = more blood flows from the RA to RV to the pulmonary artery = reduces flow through the foramen ovale, more blood returns to the left atrium via the pulmonary veins = increases LA pressure = Foramen Ovale closes (fossa ovalis). Ductus arteriosus constricts = complete, permanent closure = replaced by connective tissue = ligamentum arteriosum. Umbilical cord is cut = No more blood flow through it, umbilical vein and arteries degenerate = No blood through the ductus venosus = ligamentum venosum.

Heart Size

After birth, the left side grows faster than the right side. Why? The LV pumps against higher pressure or resistance than the RV. Continue to increase in size until adolescence. Birth = 40 cm3. 6 months = doubles. 2 years = x 4. Heart size is proportional to body size. Allometric relationship – not linear.

Changes in Cardiac Functionality – Heart Rate

Fetal heart rate begins at 4 weeks, prenatally. HR is very fast. Labor contractions may cause the fetal heart rate as high as 200 bpm. Newborn HR = 140±20 bpm. Newborn can have a heart rate up to 170 bpm when crying. Over one year, heart rate will decrease by about 40 bpm. Heart rate at 6 years = approx. 80 bpm. Heart rate at 10 years = approx. 70 bpm.

Changes in Cardiac Functionality – Heart Rate

Why is the heart rate of infants and children higher than adults? Less blood volume. Still need blood to reach a large surface area. Myocardium has less contractility / heart’s force of contraction is less. Due to heart not being fully developed. All these factors result in less Blood per beat (SV) thus a higher HR is needed to maintain Cardiac Output (CO). Why does it decrease as the child grows? As the heart grows and blood volume increases, Blood per beat (SV) increases, so HR can decrease to maintain CO

Changes in Blood per Beat (Stroke Volume)

Infants are not bipedal ambulating = Limits the venous muscle pump. Infant/child has a lower stroke volume (SV) than an adult due to the smaller heart and blood volume Birth SV = 3-4 ml per contraction. By adolescence, SV increases to = 60 ml per contraction.

Changes in Cardiac Function - Cardiac Output

Children have a smaller quiescent force of contraction. Newborn = 0.5 L / min. Child (3-12 years) = 3.6-4.8 L / min. The heart rate in children is higher than adults, but not enough to make up for the lower stroke volume, so cardiac output is still lower compared to adults.

Respiratory System Formation in Weeks 2-38 of Gestation

-Formation of main airways Embryonic lungs -Formation of the bronchial tree and part of the respiratory substance - Surfactant is detectable

Respiratory System at Birth

Prenatal lungs are filled with fluid = pulmonary resistance is very high, and no gas exchange occurs. Because the fetus blood is oxygenated by the mother, respiratory movements are not needed, so the brain doesn’t tell the respiratory muscles to move, thus decreasing O2 demand. First Breath: This fluid is pushed out when the thorax is compressed during delivery. Decreased O2, increased CO2, light, slight cooling, sound and touch stimulate the respiratory center in the brain to take the first breath. Alveoli expand and fill with air. Lung vessels allow more blood flow.

Respiratory System

Lung growth is proportional to height/stature. At birth lungs weigh approx. 60-70 grams, increasing 20x by maturity. Most alveoli continue to develop after birth. 20 – 70 million alveoli at birth, approx. 300 million by 8 years old. Newborn can inhale approx. 3 ml air/gram of tissue. Mature state 8-10 ml air/gram of tissue. Respiratory Rate at Birth = 40 / min, 1 year = 30 / min , 5-6 years = 22 / min, Respiratory tree is completely developed by 8 years of age

Thermoregulation in Infants and Children

Body surface area (BSA) to mass ratio is very important to thermoregulation This ratio changes as a person grows = decreases 33% between the ages of 2 and 16 years Infants and children have: > BSA relative to Mass = faster rate of heat loss Which is advantageous If skin temperature is higher than the environment Not advantageous in cold climates

Thermoregulation in Infants and Children

Have low evaporative capacity Sweat glands Produce less sweat = low sweat rate per BSA Pre-pubescent sweat rate is less than post-pubescent males High sweating threshold Sweating is activated at a higher intensity or higher core temperature Therefore, children rely more on cutaneous blood flow Rely on heat loss by convection Vasoconstriction mechanism is not well developed Minimal subcutaneous fat Shivering mechanisms are immature

Digestive System

Low levels of enzymes Lactase - enzyme needed for milk digestion is high at birth and gradually declines = milk diet As infant grows, amount of digestive enzymes increases At 30 months of age all the deciduous teeth(n=20; no molars)are present Blunt shaped Limited mastication = decreased the mechanical breakdown of food Stomach capacity increases with age Lower esophageal sphincter is immature = result in reflux

Endocrine System

Anterior pituitary gland secretes specific hormones to promote growth and development Growth Hormone (GH) Works by: Hormone directly exerts growth promoting actions on target tissue Stimulates liver to produce Insulin-like growth factors Insulin-like growth factors (growth promoting molecules) IGF1 – regulates linear growth – long bone development, protein synthesis, increase cell proliferation

Endocrine System

IGF2 – especially important for creation of organs and muscle differentiation during fetal period GH content in the pituitary increases, peaking at 12-18 years Content in pituitary = content in circulation Circulating levels are higher in children compared to adults Secreted in a pulsatile manner, more bursts in children Average peak levels of GH are higher during adolescence

Endocrine System

GH needs thyroxine to work Affects growth and maturation Skeletal growth and maturation Sexual maturation Muscle development Accelerates most biological processes TSH is at highest levels in infancy and childhood Levels decline from birth Adrenal Hormones Adrenal medulla= used for normal growth and development Adrenal cortex= regulates growth and development