Applied Developmental Biology The Hashemite University Dr. Lubna Tahtamouni The Hashemite University 7/2/2010 Week # 1 Introduction

But Difference between developmental biology and embryology Embryo: The stage between fertilization and birth But Do organisms ever cease to develop??????????? So, developmental biology is Discipline that studies embryonic and other developmental* processes * Development: slow process of progressive change

What is developmental biology? - Discipline that studies embryonic and other developmental processes Study of transient stages Initiation and construction rather than maintenance science of becoming, science of process

Questions of developmental biology - “ It is owing to wonder that people began to philosophize, and wonder remains the beginning of knowledge” (Aristotle, Metaphysics, ca. 350 B.C.E ) - A field of science is defined by the questions it asks! 1) How does the fertilized egg give rise to the adult body? Question of differentiation: cellular diversity Question of morphogenesis: creation of ordered form (tissues, organs…..) Question of growth: control over cell division 2) How does the adult body produce another adult body? - Question of reproduction

We…Developmental biologists owe a lot to Aristotle Different ways animals are born: oviparity, viviparity, or ovovivparity Different ways cells of the embryo (blastomere) divide: holoblastic, meroblastic Functions of placenta and umbilical cord He thought that menstrual fluids formed the materials of embryo while semen gave it form and animation! Harvey Ex ovo omnia….all from the egg Blastoderm and germ layers Function of amniotic fluid

The Aristotelian theory of male semen and female blood coagulum in the uterus A-B. The uterus appears to be filled with the menstrual blood, C-F. upon which the semen progressively acts, building up the vessels and shaping the body's organ G. After approximately forty or ninety days, the fetus appears as formatus

Epigenesis Vs preformation Organs formed from scratch Or Organs are already present, in miniature form, within the egg or sperm

vertebrates , invertebrates or Animal kingdom vertebrates , invertebrates or protozoa (unicellular) , metazoa (multicellular) Metazoan = multicellular animals Parazoa: sponges Eumetazoa: 1. radial symmetry (diploblastic) : Cnidaria, Ctenphora 2. Bilateral symmetry (triploblastic): deuterostomes. protostomes

Embryogenesis

Embryogenesis = Fertilization + Cleavage Gastrulation Organogenesis

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