Child Development Unit Four

Prenatal Development

Period of rapid and dramatic change

Preformationism

The person is already formed in the sperm or the egg at conception (saw a mini person in a microscope somehow)

Epigenesis

Similar to today’s view, fetuses start out as a single cell and new structures and functions emerge during prenatal development

Prenatal Period

Conception to birth, meiosis takes 23 chromosomes from each parent and creates a 46 chromosome cell (zygote) that develops

First Trimester

Conception to 3rd month

Second Trimester

4th month through 6th month

Third Trimester

7th month through 9th month

Three periods of prenatal development

Germinal, Embryonic, Fetal

Germinal Period

Conception to week 2, rapid mitosis, differentiation starts to occur, cells move from stem cells to specialized cells, fetus becomes group of cells, ends when the placenta moves from fallopian tube and implants in uterine wall

Blastocyst

Inner core of group of cells (becomes the baby)

Trophoblast

Outer core of group of cells that become the supporting materials

What are the three supporting materials in the Trophoblast?

Amniotic sac, placenta, and umbilical cord

Amniotic Sac

Bag filled with amniotic fluid

Placenta

A plate-like structure that acts as the baby’s lung, liver, and kidneys while in the womb

Umbilical Cord

Tube that connects placenta and developing organ, provides blood vessels

Embryonic Period

Third week through eight weeks (first two months), can see cephalocaudal development and proximodistal development, 3 layers of cells start to develop

Organogenesis

Formation of organs

Cephalocaudal Development

Head to toe development (head develops first)

Proximodistal Development

Inner to outer (fingers develop last)

Three layers of cells that start to develop in Embryonic Period

Ectoderm, mesoderm, endoderm

Ectoderm

Outer layer (skin, hair, teeth, sense cells, brain, and spinal cord)

Mesoderm

Middle layer (muscles, bones, excretory, reproductive, and circulatory systems)

Endoderm

Inner layer (liver, pancreas, and digestive and respiratory systems)

Fetal Period

Week 9 to birth, spans all three trimesters, baby is a fetus, physical structures continue to develop, refinement of organ systems

Viability

Baby can live outside womb in week 24/25

Quickening

First movement

Neuron

Single cell nerve cell, building block of nervous system

Neurogenesis

Neurons start to generate

Primitive streak

Nervous system that begins forming as a long hollow tube and eventually closes at top and bottom at 24 days

Four developmental cell processes

Cell division, migration, differentiation, and apoptosis

Cell division

Mitosis (results in proliferation of cells)

Cell migration

Movement of cells from point of origin to somewhere else in embryo

Cell differentiation

Transforms stem cells into specialized cells

Cell apoptosis

Cell death that is genetically programmed

Teratogens

Environmental agents that have potential to cause harm during prenatal development

What effect can timing have on teratogen

Can be a crucial factor in severity of effects, whether it was during a sensitive or critical time