Prenatal Development

1
Prenatal Development

• Ovum and spermatozoon fuse Growth process begins
• All genetically controlled
• Embryo and fetus Sensitive to environmental
  factors
• These factors may later affect skill potential

2
Embryonic Development

• Formation of sex cells
• DNA determines hair and eye color, height
  potential, skeletal structure
• Genes are on chromosomes
• 23 pairs of chromosomes

3
Cell Growth and Differentiation

• Fertilized egg undergoes mitosis
• After 4 days becomes bundle called a blastocyst
• Implants in uterus forms three tissues
• Ectoderm skin, tooth enamel, nervous system,
  parts of glands and sensory receptors
• Endoderm epithelial linings, auditory tube,
  larynx, bladder, urethra, prostate
• Mesoderm muscles, blood, connective tissues,
  teeth, adrenal cortex, skeleton
• Differentiation Cells dividing and becoming
  specialized
• Happens during first 8 weeks after conception

4
Fetal Development

• Fetal stage follows embryonic stage
  Characterized by further growth
• Hyperplasia increased of cells e.g. blood,
  bone, liver tissue
• Hypertrophy increased size of cells e.g. brain,
  lungs, muscle
• Direction of growth
• Cephalocaudal Head to tail
• Proximodistal Near to far
• Most cells simply grow but others have
  plasticity

5
Environmental Factors and Prenatal Growth

• Fetal nourishment
• Placenta network of blood capillaries that form
  early from embryos outer membrane and maternal
  tissue
• Blood flows through umbilical cord and contains
  the nourishment
• Nutrients include proteins, amino acids,
  polypeptides, carbohydrates, water, inorganic
  ions (NA, K, Fe-), vitamins

6
Maternal Health Status

• There are increased demands on the mother during
  pregnancy
• Increased energy requirements
• Increased nutrient requirements
• Increased oxygen consumption
• Increased cardio respiratory function
• If nutrients, oxygen or energy are in short
  supply
• Socioeconomic differences Lower birth weight,
  increased risk of disease, infection and death

7
Abnormal Prenatal Development

• Two causes genetic and environmental
• Genetic
• May inherit genetic abnormalities (dominant or
  recessive disorders)
• Dominant one normal copy of a gene and one
  abnormal, 50 chance the defective gene overrides
  
• Recessive get a defective gene from each parent
  (no normal copy to take over)

8
Sex-Linked Recessive Disorders

• Defective gene on X chromosome
• ¼ male children e.g. color blindness, muscular
  dystrophy
• Mutations
• Alteration or deletion of a gene in egg or sperm
  cell
• Genetic abnormalities vary in appearance and
  severity

9
Environmental

• Teratogens
• Viruses, drugs, chemicals get to fetus through
  placenta
• Especially hazardous to tissues undergoing rapid
  growth

10
Others

• Pressure on infant
• Extreme temperatures
• X-rays, gamma-rays
• Atmospheric pressure
• Environmental pollutants

11
Normal Prenatal Development

• Overall growth
• Distinct predictable pattern, consistent but not
  linear
• In early childhood, gender differences are
  negligible

12
Growth

• Height
• Peak growth Girls 9-12, Boys 11-14
• Girls taper off at 14 and end at 16, boys taper
  at 17, end at 18
• Older adulthood Slight decrease in stature
• Weight
• Peaks follow those for height by 2-5 months for
  boys, 3-10 months for girls
• Increase in adults (early 20s) due to lifestyle
  changes

13
Secondary Sex Characteristics

• Girls breasts enlarge, pubic hair appears,
  menarche
• Boys testes and scrotum enlarge, pubic hair
  appears
• Environmental Factors
• Nutrition and sickness in growing phase
• Body weight and menarche

14
Regular Growth Assessment

• Can help detect abnormalities
• Children and teens above 90 or below 10
  percentile
• Percentiles generally stay the same, large
  fluctuations abnormal
• Important to educate children about nature of
  development

15
Relative Growth

• Proportions change dramatically through life
• Reflects cephalocaudal and proximodistal growth
• May account for skill differences when compared
  to adults

16
Skeletal System

• Embryonic life Only have cartilage model
• In 2months, develop primary ossification centers
• Postnatal bone growth Secondary ossification
  centers at each end
• 400 ossification centers at birth an additional
  400 after
• At epiphyseal plates cartilage zone eventually
  disappears and shaft (diaphysis) fuses with
  epiphysis
• Also increase in girth Appositional growth
• Use this process of bone growth to asses skeletal
  age
• Measures of stature only reflect linear growth of
  bone

17
Skeletal Injuries

• Heal quickly, efficiently
• Potential for injury of epiphyseal plate
• May cut off blood supply to bone and slow or stop
  growth
• Epiphyses also exist where muscle tendons attach
  to bones (traction epiphyses) and are susceptible
  to overuse injuries

18
Older Adults

• Bone loss occurs in aging process
• Change in composition (more inorganic material
  vs. organic)
• Osteoporosis e.g. prolonged deficiency of calcium
• Bones become more porous and susceptible to
  fracture
• In women, decreased estrogen can lead to
  osteoporosis
• Can treat with dietary supplements, physical
  activity