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1. Infant development
Introduction
Physical Development

2. Rationale
• What do you expect from this course?
• Why we study pre-natal development?
– Child related problems
– Mother related problems
****Importance for physiotherapists:
– Congenital problems
– Developmental problem

7. FROM ZYGOT TO BIRTH
• conception-- when a sperm unites with an
ovum to form a single cell, zygote
• germinal period-- begins with conception,
continues with zygotic cell division (mitosis),
ends with attachment of the zygote to the uterine
wall (implantation) about 10 days later
• embryonic period-- begins with implantation,
after which the rate of cell differentiation
intensifies, and organs appear (2 to 8 weeks
after conception)
• fetal period-- development of the organ systems
(9 weeks to birth)

8. The Germinal Period
• First two weeks after conception
• Zygote is created & attaches to uterine wall
• Cell division begins
• Blastocyst; inner layer of cells which later
develop into embryo.
• Trophoblast: outer layer of cells that
provide nutrition & support for embryo.
• Implantation: attachment of zygote to
uterine wall

9. The Embryonic Period
• ORGANOGENESIS PERIOD
• Placenta life-support system consisting of group
of tissues in which small blood vessels from
mother & offspring intertwine
• Umbilical Cord life-support system, containing
two arteries & one vein, that connects baby to
placenta.
– filters in nutrients, oxygen and filters out waste
products.
• Amnion bag or envelope containing clear fluid
where developing embryo floats
– controls temperature and makes the environment
shockproof.

11. The Fetal Period
• From two months following conception to birth
• First Trimester from conception to 12 weeks.
features growth of arms, legs, brain & face; & is
where heartbeat is detectable
• Second Trimester between 12 to 24 weeks.
features development of skin, hair, &
finger/toenails; where movement such as
thumb-sucking & hiccups are noticeable.
• Third Trimester from 24 to 38 weeks, where
increased activity, periods of sleep &
assumption of birth position are noticed.

12. Human Development
Fertilization - fusion of male and female gametes
- forms a zygote
Cleavage - Period of rapid cell division without
growth of cells
Blastula - hollow ball of cells
Outer cells - trophoblasts
- extraembryonic membranes
Inside cells
- inner cell mass - embryo

13. Fertilization
- Fertilization is the joining of sperm and ovum.
- Meiosis II in the ovum is completed at the time of
fertilization forming one ovum and one polar body.
- Following fertilization, chemical reactions occur
preventing additional sperm from entering the ovum.

14. Early development: ovulation to implantation

16. Cleavage
• Mitotic cell division creates more cells.
• Cells are called blastomeres.

17. Blastocyst
The developing embryo becomes a
hollow ball of cells and is called a
Blastocyst.
The cells around the ICM become the
extraembryonic membranes:
role in implantation
supports embryo’s growth
Group of cells within the hollow space forms
the inner cell mass (ICM).
develops into the embryo.