Human Growth & Development

• The study of development begins at the moment of conception
• Prenatal Development:

  • From the Latin word natalis, meaning relating to birth
  • The time between conception and birth
  • Stages of development during pregnancy: Fetal Stage, Germinal Stage, Embryonic Stage
• Prenatal Development:

  • Life-giving oxygen and nutrients are passed from the mother to the child
  • Differentiation of bodily structures occurs during the embryo’s first two months
  • By the end of the second month, all major organs have begun to develop and sexual differentiation occurs
• Germinal Stage:

  • Two-week period after conception
  • Conception occurs when a sperm cell combines with an egg cell to form a zygote
  • Zygote divides quickly and moves to the uterus
  • Implantation process starts around seven days after conception
  • Formation of the placenta, which passes oxygen and nutrients to the embryo or fetus and removes waste materials
• Embryonic Stage:

  • Lasts from the end of the germinal stage to two months after conception
  • Begins when the zygote implants in the uterine wall
  • All major organs form and the embryo becomes fragile
  • Critical period for rapid development
  • Biggest dangers are teratogens, which can cause deformities in the embryo or fetus
• Fetal Stage:

  • Lasts from two months after conception until birth
  • Sex organs begin to form about one month into this stage
  • Organ systems develop further and start to function
  • Brain increases rapidly in size, fat layer forms under the skin, and respiratory and digestive systems start to work independently
• Fetal Viability:

  • Around twenty-two to twenty-six weeks after conception, fetus reaches viability
  • Chances of premature baby's survival increase with each additional week in the mother's uterus
• Factors affecting Prenatal Development:

  • Maternal nutrition
  • Vitamin deficiency
  • Maternal health
  • Drugs
  • X-ray
  • Alcohol
  • Tobacco
  • Maternal emotions
  • Uterine crowding
• Month 1:

  • Formation of amniotic sac
  • Placenta development
  • Primitive face formation with blood cells, circulation, and heartbeat
• Month 2:

  • Continued development of facial features, arms, legs, fingers, toes, eyes
  • Formation of neural tube, digestive tract, sensory organs, and bones
  • Head is large in proportion to the body
  • Heartbeat can usually be detected around 6 weeks
• Month 3:

  • Arms, hands, fingers, feet, and toes fully formed
  • Fingernails, toenails, external ears, and beginnings of teeth develop
  • Reproductive organs develop, gender is difficult to distinguish
  • Baby is fully formed with all organs and extremities present
• Month 4:

  • Audible heartbeat
  • Defined fingers, toes, eyelids, eyebrows, eyelashes, nails, and hair
  • Teeth and bones become denser
  • Nervous system starts to function
  • Reproductive organs and genitalia fully developed
• Month 5:

  • Quickening felt by the mother
  • Hair growth on baby's head
  • Presence of lanugo
  • Baby's skin covered with vernix caseosa
• Month 6:

  • Reddish skin color, visible veins
  • Finger and toe prints visible, eyelids begin to part and eyes open
  • Baby responds to sounds, moves, and increases pulse
  • Survival possible after 23rd week if born prematurely
• Month 7:

  • Baby continues to mature and develop body fat reserves
  • Hearing fully developed, responds to stimuli
  • Amniotic fluid diminishes
  • Likely survival after the seventh month if born prematurely
• Month 8:

  • Continued maturation and body fat development
  • Increased kicking, brain development, and sensory functions
  • Most internal systems well developed, lungs may still be immature
• Month 9:

  • Continued growth and maturation, lungs nearly fully developed
  • Reflexes coordinated, baby moves less due to tight space
  • Position changes to prepare for labor and delivery
  • Baby about 18-20 inches long and weighs about 7 pounds
• The Neonate:

  • Newly born individual in the first month of life
  • Capable of reacting to the environment
  • Has reflexes at birth
• Reflexes:

  • Involuntary movements or actions
  • Help identify normal brain and nerve activity
  • Some reflexes occur only in specific periods of development
• Rooting reflex:

  • Baby turns head and opens mouth to find breast or bottle for feeding
• Suck reflex:

  • Baby begins to suck when roof of mouth is touched
  • Premature babies may have weak sucking ability
• Moro reflex:

  • Startle reflex with arms and legs extending in response to loud sound or movement
• Tonic neck reflex:

  • Arm and head movement when baby's head is turned to one side
• Grasp reflex:

  • Closing fingers in a grasp when palm is stroked
• Babinski reflex:

  • Big toe bends back and other toes fan out when sole of foot is stroked
• Step reflex:

  • Walking or dancing reflex when baby is held upright with feet touching a solid surface
• Blinking reflex:

  • Blinking eyes when touched or sudden bright light appears
• Swimming reflex:

  • Bradycardic response makes babies hold breath and open eyes when submerged in water