Introduction to Embryology Carolyn Joy Rodgers MD FACOG
Introduction to Embryology Carolyn Joy Rodgers MD FACOG
AIM • Begin your study of embryology • Outline the early major developmental events and anatomical landmarks of a human embryo • Understand be able to use the terminology of early human development • Act as an introduction to the systems embryology you will encounter in the phase one modules • Begin to identify relevance of these processes to clinical practice
Learning Outcomes: lecture one • Describe simply the processes from fertilisation to implantation • Describe simply the second week of human development • Describe simply the early stages of placental development
What is embryology? • Development from single diploid cell…. to…. • Multicellular organism • Organised body structure • Specialised tissues
Development • Growth • Morphogenesis • Differentiation
Role and relevance of embryology • • Understand normal body structure Maturation of adult structures Anatomical relationships Links prenatal development to clinical medicine • Values in medicine
How is it studied? • • • Starting with anatomy Teratology Experimental Molecular / Cellular Genetic
The embryonic period • • • Conception Eight weeks Body axes Organ primordia Three layers Early placenta
First Week • • Fertilisation Cleavage Blastocyst formation Implantation
The first day • • • Gametes and fertilisation-zygote A unique new individual Ampulla Cleavage Blastomeres
Day 3 • Compaction • Morula
Entering the uterus: day 4 -5 • Blastocoele / Blastocyst • Outer cells-Trophoblast • Inner cell mass-embryoblast -pluripotent
Implantation: day 6 -7 • Hatching • Cytotrophoblast • Syncytiotrophoblast • Invasion
Implantation process: day 7 • Uterus has been prepared • Usually in upper part of uterus • Specific orientation and maternal/embryonic communication mechanisms • Immunologically complex • Very little information in humans • IVF- most likely stage of failure
Second week • Two layers • Amniotic cavity • Yolk sac • Extraembryonic mesoderm-splanchnic • - somatopleural
The two layers: Bilaminar disc: day 8 -9 • Epiblast and hypoblast • Amniotic cavity • Primitive yolk sac
Day 10 -12 • Utero-placental • circulation • Extra-embryonic • mesoderm • Chorionic cavity • (Extra-embryonic coelom)
Day 13 -14 • • • Implantation bleed Human chorionic gonadtrophin HCG Villous formation Secondary yolk sac Chorionic plate Connecting stalk
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