The document outlines the stages of human prenatal development, starting from conception to birth, and emphasizes the importance of understanding these stages for physiotherapists. It describes the germinal, embryonic, and fetal periods, detailing the key processes and structures involved in embryonic development. Additionally, it highlights the significance of early development stages, including fertilization, cleavage, and the formation of the blastocyst.

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.