浙江大学医学院：人胚胎早期发生（二）Trilaminar Germ Disc（Third Week of Development）

人胚胎早期发生II Trilaminar Germ disc (Third Week of Development) 周俊 浙江大学医学院 20180612

Trilaminar Germ Disc (Third Week of Development) 人胚胎早期发生II 周俊 浙江大学医学院 20180612

OBJECTIVES 1. Bilaminar and trilaminar germ discs 2. Describe the formation and derivatives of ectoderm mesoderm and endoderm 3. The components of fetal membrane and their functions 4. Structure and function of placenta 5.comPositionofPlacentabarrier

OBJECTIVES 1.Bilaminar and trilaminar germ discs. 2.Describe the formation and derivatives of ectoderm, mesoderm and endoderm. 3.The components of fetal membrane and their functions. 4.Structure and function of placenta. 5.Composition of Placenta barrier

End of the week of twos Buccopharyngeal Primary 2 major ce‖! masses_membrane Trophoblasts Maternal inner cell mas Amniotic . Trophoblasts cavity Cytotrophoblasts Syncytiotrophoblasts .Embryonic Cavities Extraembryonic somatopleure mesoderm (chorionic plate -Amniotic cavity Extraembryonic coelom Yolk sac ● Germ disc Epiblasts 2GCP89000303000CB00GOLC -hypoblast

End of the Week of Twos •2 major cell masses –Trophoblasts –Inner cell mass •Trophoblasts –Cytotrophoblasts –Syncytiotrophoblasts •Embryonic Cavities –Amniotic cavity –Yolk sac •Germ Disc –Epiblasts –Hypoblasts

Formation of trilaminar disc ● early of three weeks Buccopharyngeal embrane Primitive streak(原条): Cut edge of amnion caudal end a midline Primitive node indentation on the epiblast X-section at"B Primitive streak surface Cloacal membrane Primitive node/knot(原结) Primitive Primitive Primitive pit(原凹) node streak Proliferation Invagination of esbls Amnioblasts epiblasts Intra-embryonic mesoderm Invaginating B erm c Hypoblast

Formation of trilaminar disc •Early of three weeks •Primitive streak（原条）: caudal end, a midline indentation on the epiblast surface •Primitive node/knot（原结） •Primitive pit（原凹） •Proliferation & Invagination of epiblasts Intra-embryonic mesoderm

Gastrulation Cut edge of amnion Migrating epiblasts will form X-section at"B Primitive streak Cloacal membrane Endoderm(内胚层): migrated cells displace hypoblast cells Mesoderm(中胚层): cells btw the endo and ector voblasts Ectoderm(外胚层) (Note-epiblasts=>all layers) Invaginating mesoderm colls Mesoderm cranial and lateral extension fused membranes Oral: oropharyngeal membrane(口咽膜) Cloaca!: cloacal membrane(泄殖腔膜) Cloven membane

Gastrulation •Migrating epiblasts will form: -Endoderm（内胚层）: migrated cells displace hypoblast cells -Mesoderm（中胚层）: cells btw the endo and ecto -Ectoderm（外胚层） (Note - epiblasts=>all layers) •Mesoderm cranial and lateral extension •Fused membranes –Oral: oropharyngeal membrane（口咽膜） –Cloacal: cloacal membrane（泄殖腔膜）

Review/ Background ● First week Buccopharynge Second Week Prenotochordal cells o Third- 8th week Primitive node X-section at"B" Primitive streak Gastrulation Cloacal membrane A primitive pit Primitive Primitive .Primitive node ● Primitive streak Epiblast Am mniobla notochord(脊索) Invaginating Hypoblast

Review/Background •First Week •Second Week •Third- 8th week –Gastrulation •Primitive pit •Primitive node •Primitive streak •Notochord（脊索）

Expansion and Elongation Migration of Epiblasts to of amni form Endoderm Mesoderm amative Ectoderm 16 days o Expansion of the disk aryngeal Cloacal Notochord mbrane membrane ● Notochord midline rod of mesoderm Yolk sac orientation the germ disc

Expansion and Elongation •Migration of Epiblasts to form –Endoderm –Mesoderm –Ectoderm •Expansion of the disk •Notochord: -midline rod of mesoderm -orientation the germ disc

Differentiation of trilaminar germ disc 3rd -8th weeks embryonic period(胚期): the major body form and organ structure take Bilaminar disc: flat and round elongated with a broad cephalic and a narrow caudal end Trilaminar disc: a pear-shaped appearance

Differentiation of trilaminar germ disc 3 rd –8 th weeks embryonic period（胚期）: the major body form and organ structure take Bilaminar disc: flat and round→elongated with a broad cephalic and a narrow caudal end Trilaminar disc: a pear-shaped appearance

Ectoderm(外胚层)- Neurulation Overlying notochord Anterior neuropore Thickens- Neural plate (神经板) eDges- Neural Folds (神经褶) oFuse at future neck region Posterior B neuropore 23 day Zippers shut - Neural Tube(神经管) ●Ant/ Post Neuropores (前/后神经孔) Notochord

Ectoderm （外胚层）- Neuralation •Overlying notochord Thickens – Neural Plate （神经板） •Edges - Neural Folds （神经褶） •Fuse at future neck region •Zippers shut –Neural Tube（神经管） •Ant/Post Neuropores （前/后神经孔）

Ectoderm- Neuralation oVerlying notochord Anterior neuropore Thickens- Neural plate 1st and 2nd Lens Pericardial arches o edges -Neural Folds bulge Cut edge of amnion Heart bulge oFuse at neck region Connection vitelline duct Umbilical cord Zippers shut yolk sac Allantois Connecting -Neural Tube Posterior .Ant Neuropore: 25th days 25 days neuropore 28 days Post Neuropore: 27th days

Ectoderm - Neuralation •Overlying notochord Thickens – Neural Plate •Edges - Neural Folds •Fuse at neck region •Zippers shut –Neural Tube •Ant Neuropore: 25th days •Post Neuropore: 27th days