WEEK 1 WEEK 2(week of 2’s) WEEK 3 WEEK 4

Blastocyst(1)Fertilisation 1. Capacitation (P1)Penetrate CR 2. Acrosome (digest ZP) (P2)Penetrate ZP 3. Zona Reaction (impermeable) (P3)Fusion (2)Cleavage Zygote(2)-> (4)-> Morula(16)-> blastocyst(32) (3)Implantation

Inner cell mass (bilaminar germ disc)

Epiblast

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(2)T

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Ectoderm Neural tube Brain, SC

Neural crest Cranial n, meninges

Mesoderm Notochord (INDC) Nucleus pulposus

Paraxial mesoderm

Sclerotome Vetebral bodies

Myotome Muscles

Dermatome CT, Dermis

Intermediate mesoderm

Intraembryonic visceral

Intra soma mesoderm Parietal serous membrane

Intra splanchnic mesoderm

Visceral serous membrane

Endoderm(folding) Epithelial lining of gut, resp, other organs

Hypoblast

Urinary system

Pleural membrane, pericardium membrane, peritoneal cavity

Trophoblast Syncytiohyphoblast Chorionic villi Placenta

Cytotrophoblast Cytotrophoblast shell

Cavities (primitive yolk sac = extracoelem cavity)

Amniotic cavity Amniotic cavity

Amniotic cavity

Exocoelamic cavity

Extraembryonic mesoderm

Extraembryonic somatic meso

Chorionic cavity

Chorionic plate

Extraembryonic splanchnic mso

Extraembryonic cavity

Chorionic cavity

Chorionic cavity