Embryology General Terminology

Gestational Age vs Fetal Age

Gestational = first day of last menstrual period

Fetal = First day of conception/fertilization

2 weeks difference (gestational is more)

Fetal Development Stages & Durations

0-2 weeks, germinal

3-8 weeks, embryo

9 weeks-birth, fetal

Germinal fetal development stage

Zygote formation

Cell division

Blastocyte in uterine walls

Embryonic fetal development stage

Organogenesis

Body structure

Fetal in fetal development stage

Refinement of body systems

Maturation of organs

Zygote

Diploid cell from two haploid cells

Fertilized ovum

Teratogen

Something that defects embryo/fetus

Drugs, alcohol, infection

Organogenesis

Embryonic stage

Primary organs & systems form

Primary germ layers

Ectoderm

Mesoderm

Endoderm

Ectoderm derives what

Nervous system, skin

Mesoderm derives what

Cardiovascular, muscle, skeletal

Endoderm derives what

Digestive, respiratory

Gastrulation

Week 3

Single layer → multiple layers

Blastula → gastrula

Gametes

Reproductive cells

Half the genetic information

Eggs in female, sperm in males

Totipotent cells

Cells capable of developing into entire organism, both embryonic and extraembryonic

Totipotent cell example

Zygote

Pluripotent cells

Cells capable of developing to all cell types, EXCEPT extraembryonic tissues

Pluripotent cell example

Embryonic stem cells

Mesenchymal cells

Multipotent cells → variety of cell types

Mesenchymal cells examples

Bone, cartilage, fat cells