Summary of Embryonic and Fetal Development

A comprehensive vocabulary flashcard set detailing the milestones, structural developments, and stages from Week 1 to Week 40 of embryonic and fetal development.

Week 1 Development

The initial stage where fertilization occurs, the blastocyst begins to form, and implantation in the uterus begins.

Three Germ Layers

The embryonic layers that develop during Week 2, consisting of the Ectoderm, Mesoderm, and Endoderm.

Neural Plate

An early part of the nervous system that forms during Week 3, coinciding with the start of backbone/spinal development when the embryo is about $2\,\text{mm}$ long.

Week 4 Development

The embryonic stage when the heart, blood vessels and blood, gut, and umbilical cord begin developing, and the embryo is about $5\,\text{mm}$ long.

Week 5 Development

The developmental stage when the brain continues developing, limb buds appear, heartbeat begins and may be seen on ultrasound, and embryo length reaches about $8\,\text{mm}$.

Fetus

The designation given to the developing baby starting at Week 6, when eyes and ears begin to form and major body structures continue developing.

Week 7 Development

The fetal stage when internal organs continue forming, face begins to develop, limbs, mouth, and tongue develop, and fetal length is about $17\,\text{mm}$.

Week 10 Development

The fetal stage during which the body continues to grow, organ development continues, and fingers and toes become more distinct.

Week 12 Development

The stage where the fetus is more fully formed, sex organs begin developing, fetal movement starts, and length reaches about $56\,\text{mm}$.

Week 18 Development

The stage characterized by more noticeable fetal movement, continued development of the nervous system, and the gender anatomy ultrasound.

Week 20 Development

The stage when hair and nails begin to grow, fingerprints and a firm hand grip develop, fetal movement can be felt, and fetal length is about $160\,\text{mm}$.

Week 24 Development

The fetal stage marked by the opening of eyelids and continued lung and nervous-system development.

Week 26 Development

The stage at which the fetus has a good chance of survival if born prematurely, although intensive medical care would generally be needed.

Week 28 Development

The fetal stage when the fetus responds to touch and sound, swallows amniotic fluid, and begins urinating.

Week 30 Development

The stage where the head is positioned downward in preparation for birth and fetal length is about $240\,\text{mm}$.

Week 37 Development

The stage of fetal development at which the pregnancy is considered early term.

Week 39 Development

The stage of fetal development when pregnancy is full term and most organs are ready to function outside the uterus.

Week 40 Development

The final stage when birth occurs and pregnancy reaches the typical end of the $40\text{-week}$ period.