History of embryology

Study day 1 material

Embryology

The study of biological development from a fertilized egg to a multicellular organism

Why is embryology important?

Historical high rates of pre-implantation and embryonic pregnancy losses, as well as neonatal loss in both humans and livestock

Preformism

Originated from Hippocrates

• Organisms exist fully formed in miniature inside the womb before birth

Neoformism

Originated from Aristotle

• Organs form progressively from initially undifferentiated, homologous material

Albertus Magnus

Conducted chick and fish embryology studies and proposed the existence of male and female gametes

Hieronymus Fabricus

Proposed comparative embryo dissections across species, considered as the true Father of Embryology

William Harvey

Stated that all organisms arise from eggs

Casparr Wolff

Demonstrated epigenesis through tissue layers and identified the Wolffian ducts

Epigenesis

The biological process by which a complex organism develops step-by-step from a fertilized egg

Karl-Ernst von Baer

Formulated Baer’s Laws, establishing that general structural features appear earlier in embryonic development than specialized features

First Baer Law

The more general characters of a large group appear earlier in the embryo than the more special characters

Second Baer Law

From the most general forms the less general are developed, and so on, until finally the most special arises

Third Baer Law

Every embryo of a given animal form, instead of passing through the other forms, rather becomes separated from them

Fourth Baer Law

The embryo of a higher form never resembles any other form, but only its embryo.