Characteristics of Body Parts in Children

Note: The information in this article is for reference only and is not a substitute for professional medical advice.

Skin

• Vernix caseosa: A white or pale yellow greasy substance that covers newborn babies.

• Function: Protects the skin, prevents heat loss, contains immunoglobulins, and is a skin nutritional product.

• Note: Vernix caseosa should be cleaned after 48 hours to avoid diaper rash.

• Skin surface area to body weight ratio: Higher in children than in adults.

• Subcutaneous fat layer:

• 3-month-old babies: 6-7 mm

• 1-year-old babies: 10-12 mm

• 7-10-year-old children: 7 mm

• Subcutaneous fat composition: Contains more saturated fatty acids than unsaturated fatty acids.

• Water loss through skin: Children lose more water through their skin than adults.

Muscles

• Muscle to weight ratio: Lower in children than in adults.

• Development: Muscle development is uneven in children:

• Large muscle groups develop first (e.g., leg muscles, arm muscles).

• Small muscle groups develop later (e.g., finger muscles, hand muscles).

• Note: Children under 6 years old cannot perform precise movements requiring the use of fingers.

Bones

• Ossification: Children’s bones ossify gradually, completing around 20-25 years of age.

• Development:

• Skull: Develops fastest in the first year of life.

• Anterior fontanel: Closes by about 12 months, with a maximum of 18 months.

• Posterior fontanel: Closes by about 3 months.

• Frontal and ethmoid sinuses: Develop after 3 years of age.

• Note: Children under 3 years old do not have frontal sinusitis.

• Pelvic bones: The two iliac bones, sacrum, and coccyx begin to fuse together at age 7 and finish around 20-21 years of age.

• Rib cage:

• Young children: Anterior-posterior diameter equals transverse diameter.

• Older children: Transverse diameter is twice the anterior-posterior diameter.

Teeth

• Tooth eruption: Begins in the sixth month.

• Formula for calculating the number of teeth: Number of teeth = Number of months – 4.

• Molars: Erupt at 5-7 years of age.

• Deciduous teeth replacement: Begins at 6-7 years of age.

Respiratory system

• Nose: The ability to warm and filter air is less than in adults.

• Tonsils:

• Children under 1 year old: Less susceptible to infection.

• Children over 1 year old: Prone to infection.

• Adenoids:

• Children under 1 year old: More susceptible to infection than older children.

• Normal respiratory rate:

• Newborn: 40-60 breaths/minute

• 2-6 months: 35-40 breaths/minute

• 7-12 months: 30-35 breaths/minute

• 2-3 years: 25-30 breaths/minute

• 4-6 years: 20-25 breaths/minute

• 7-15 years: 18-20 breaths/minute

• Breathing pattern:

• Newborn, breastfeeding: Primarily abdominal breathing.

• 2-year-old children: Mixed chest-abdominal breathing.

• 10-year-old children: Boys breathe abdominally, girls breathe with their chests.

Circulatory system

• Normal heart rate:

• Newborn: 140-160 beats/minute

• 1-year-old children: 120 beats/minute

• 5-year-old children: 100 beats/minute

• 7-year-old children: 90 beats/minute

• Systolic blood pressure:

• Newborn: 75 mmHg

• 3-12-month-old babies: 75-80 mmHg

• Diastolic blood pressure: 3-12-month-old babies: 50 mmHg

• Formula for calculating blood pressure in children over 1 year old: 80 + 2N (age in years)

• Circulatory volume: 110-150 ml/kg

• Heart-to-chest ratio:

• Newborn: 0.6

• Children over 1 year old: 0.55

Digestive system

• Stomach capacity:

• Newborn: 35 ml

• 3 months: 100 ml

• 1 year: 250 ml

• Liver: Located 1 cm below the costal margin in children under 2 years of age.

• Ability to digest starch: Children under 4 months old cannot digest starch.

Excretory system

• Kidneys: The left kidney is higher than the right kidney.

• Specific gravity of newborn urine: Very low.

• Kidney function: Similar to adults by the age of 2.

• Average daily urine volume in children over 1 year old: ml = 600 + 100*(n-1) (n = age in years).

Blood

• Red blood cell count (RBC):

• Newborn: 5-6 * 10^12/l

• Children under 1 year old: 3.2-3.4 * 10^12/l

• Children over 1 year old: 3.5 * 10^12/l

• Hemoglobin (Hb):

• Children under 1 year old: 110-120 g/l

• Children over 1 year old: 120-140 g/l

• Glycated hemoglobin A1:

• Children over 1 year old: 97-98%

• At birth: 20-40%

• Fetal hemoglobin (HbF):

• At birth: 60-80% of total Hb

• Children over 1 year old: < 1%

• HbA2:

• Newborn: 0.03-0.6%

• Children over 1 year old: 2-3%

• Conus medullaris: At the L1-L2 level similar to adults by the age of 4.

• Neutrophil count:

• Children under 1 year old: 10-12 * 10^9/l

• Children over 1 year old: 6-8 * 10^9/l

• Platelets: 150-300 * 10^9/l

Note: This information is for general reference only. Each child may develop at a different rate. It’s important to consult a doctor to best monitor your child’s health.