Andrea Heinzlmann Embryology Course 2018 GASTRULATION Andrea Heinzlmann Embryology Course 2018

GASTRULATION 1. the undifferentiated blastomeres move in small masses to form sheets of cells 2. these cells differentiate into three germ layers- ectoderm, mesoderm and endoderm - these are called primary germ layers 3. these movements are called morphogenetic movements 4. the over all event is called gastrulation https://hu.pinterest.com/pin/544231936193074372/

GASTRULATION GASTRULATION: is a process by wich the bilaminar embryonic disc is converted into a trilaminar embryonic disc involves the movement of prospective organ forming areas from the blastodermic vesicle to their definitive positions in the embryo and their reorganisation into three primary layers https://is.muni.cz/el/1411/jaro2015/VSET0411p/um/5_-_nervous_system.txt https://www.memorangapp.com/flashcards/61308/Embryology/

GASTRULATION These primary germ layers give rise to: 1. Ectoderm 2. Endoderm 3. Mesoderm http://biology4isc.weebly.com/human-embryonic-development.html https://www.researchgate.net/figure/Formation-of-Mesoderm-Formation-and-segregation-of-the-mesodermal-germ-layer-is_fig1_309620633

GASTRULATION Ectoderm forms: the outermost layer differentiates into: 1. skin 2. brain 3. spinal cord 4. nerves https://openi.nlm.nih.gov/detailedresult.php?img=PMC3521957_fphys-03-00453-g001&req=4

GASTRULATION 2. Endoderm forms: the innermost layer gives rise to: the digestive system the respiratory systems urinary bladder middle part of the ear https://openi.nlm.nih.gov/detailedresult.php?img=PMC3521957_fphys-03-00453-g001&req=4

GASTRULATION Mesoderm forms: the middle layer differentiates into: 1. notochord 2. muscles 3. heart 4. blood vessels 5. kidneys 6. gonads https://openi.nlm.nih.gov/detailedresult.php?img=PMC3521957_fphys-03-00453-g001&req=4

GASTRULATION GASTRULATION: is the biginning of MORPHOGENESIS

GASTRULATION MORPHOGENESIS: development of the form, structures of various organs and body parts begins with the formation of the PRIMITIVE STREAK 1 2 3 4 5 6 7 8 9 NB Primitive groove Primitive pit Primitive node Oropharyngeal membrane Cardial plate Sectional edge of amniotic membrane Mesoderm Endoderm Future cloacal membrane 1+2+3 primitive streak

GASTRULATION Dorsal view of the primitive  streak at around the 17th day Dorsal view of the primitive  streak at around the 19th day Dorsal view of the primitive streak at around the 23rd day Dorsal view of the primitive streak at around the 25th day 1 2 3 Primitive streak Prechordal plate Primitive node 4 5 6 Neural plate Cloacal membrane Chordal process 1 2 3 Primitive streak Primitive node Neural tube 4 5 6 Cloacal membrane Prechordal plate Chordal process

GASTRULATION PRIMITIVE STREAK: at the biginning og the 5th weekthe primitive streak (thickened linear band of epiblast) appears caudally in the median plane of the dorsal aspect of the embryonic disc the primitive streak elongates by the addition of cells to its caudal end the cranial ends of the primitive streak proliferates to form the PRIMITIVE NODE A PRIMITIVE GROOVE develops in the primitive streak ending in the PRIMITIVE PIT (depression in the primitive node) cells leave the the deep surface of primitive streak to form MESOBLAST (a loose connective network of embryonic connective tissue known as mesenchyme – which forms the supporting tissues of the embryo) 1 2 3 4 5 6 7 8 9 NB Primitive groove Primitive pit Primitive node Oropharyngeal membrane Cardial plate Sectional edge of amniotic membrane Mesoderm Endoderm Future cloacal membrane 1+2+3 primitive streak 1 2 3 4 5 6 Primitive groove Epiblast Extraembryonic mesoblast Definitive endoblast Invading epiblastic cells forming  the intraembryonic mesoblast Hypoblast

GASTRULATION MESENCHYME: mesenchymal cells have the potential to proliferate and diferentiate into: fibroblasts chondroblasts osteoblasts

GASTRULATION 6. epiblast cells migrate through the primitive groove to become ENDODREM and MESODERM 7. the primitive streak actively forms mesoderm till the early part of the 4th week – then its production slows down – the primitive streak diminishes in size – becomes an insignificant structure in the sacrococcygeal region of the embryo 1 2 3 4 5 6 7 8 9 NB Primitive groove Primitive pit Primitive node Oropharyngeal membrane Cardial plate Sectional edge of amniotic membrane Mesoderm Endoderm Future cloacal membrane 1+2+3 primitive streak

NOTOCHORDAL PROCESS AND NOTOCHORD some mesenchymal cells migrate cranially from the primitive node and pit forming the NOTOCHORDAL PROCESS the notochordal process acquires a lumen, the NOTOCHORDAL CANAL the notochordal process grows cranially between the ectoderm and endoderm reaching the PRECHORDAL PLATE The red arrow shows schematically the migration direction of the epiblast cells coming from the primitive node to form the notochordal process and later the notochord

NOTOCHORDAL PROCESS AND NOTOCHORD The chordal process at  roughly the 21rst day (Stage 7)  The chordal process at  roughly the 19th day (Stage 7 The chordal process at  roughly the 19th day (Stage 7)  The chordal process at roughly the 21rst day (Stage 7) 1 3 Chordal process Embryonic endoblast 1 2 3 4 Chordal process Primitive node Embryonic endoblast Amniotic cavity 5 6 7 Body stalk Extraembryonic mesoblast Allantois 4 5 6 7 Amniotic cavity Body stalk Extraembryonic mesoblast Allantois The chordal process at  roughly the 23rd day (Stage 8)  The chordal process at  roughly the 23rd day (Stage 8) 1 2 3 4 5 6 Fused chordal process Prechordal plate Pharyngeal membrane Embryonic endoblast Amniotic cavity Neural groove 7 8 9 10 11 Canalis neurentericus Intraembryonic mesoblast Cloacal membrane Umbilical vesicle  Allantois

NOTOCHORDAL PROCESS AND NOTOCHORD  The chordal process at  roughly the 25th day (Stage 9) The chordal process at  roughly the 28th day (Stage)10)  The chordal process at  roughly the 25th day (Stage 9)  The chordal process at  roughly the 28th day (Stage 10) 1 2 3 4 5 6 7 Chordal process Embryonic endoderm Amniotic cavity Neural groove Body stalk Intraembryonic mesoblast Prechordal plate 1 2 3 4 5 6 7 Chordal process Embryonic endoblast Amniotic cavity Neural tube Body stalk Intraembryonic mesoblast Prechordal plate 8 9 10 11 12 13 Pharyngeal membrane Cloacal membrane Aortae  Umbilical veins Cardiogenic plate Allantois 8 9 10 11 12 13 Pharyngeal membrane Cloacal membrane Aortae Umbilical veins Cardiogenic plate Allantois

NOTOCHORDAL PROCESS AND NOTOCHORD PRECHORDAL PLATE is an important organizer of the head region it is attached to the ovarlaying ectoderm – these fused layers, the ecto – and endoderm form the OROPHARYNGEAL MEMBRANE (located at the future site of the oral cavity) https://aalraddadi.weebly.com/cardiogenic-field.html https://github.com/obophenotype/uberon/issues/271

NOTOCHORDAL PROCESS AND NOTOCHORD 4. some mesenchymal cells from the primitive streak and the notochordal process migrate laterally and cranially between the ecto – and endoderm reaching the margins of the embryonic disc 5. these mesenchymal cells are continous with the extraembryonic mesoderm – which covers the amnion and the umbilical vesicle 1 2 3 4 5 6 7 8 9 NB Primitive groove Primitive pit Primitive node Oropharyngeal membrane Cardial plate Sectional edge of amniotic membrane Mesoderm Endoderm Future cloacal membrane 1+2+3 primitive streak

NOTOCHORDAL PROCESS AND NOTOCHORD 6. some mesenchymal cells from the primitive streak migrate cranially on each side of the notochordal process and around the prechordal plate – these cells meet each other to form the CARDIOGENIC MESODERM in the cardiogenic area (primordium of the heart) http://medicinembbs.blogspot.hu/2013/12/cardiovascular-embryology.html https://hu.pinterest.com/timfluenze/embryology/

NOTOCHORD NOTOCHORD: is a cellular rod extends from the oropharyngeal membrane to the primitive node Induces the overlying ectoderm to form the NEURAL PLATE (primordium of the central nervous system) defines the axis of the embryo serves as the basis for the development of the axial skeleton (bone, head, vertebral column) indicates the future site of the vertebral bodies Dorsal view of the primitive  streak at around the 17th day Dorsal view of the primitive  streak at around the 19th day Dorsal view of the primitive streak at around the 23rd day Dorsal view of the primitive streak at around the 25th day 1 2 3 Primitive streak Prechordal plate Primitive node 4 5 6 Neural plate Cloacal membrane Chordal process 1 2 3 Primitive streak Primitive node Neural tube 4 5 6 Cloacal membrane Prechordal plate Chordal process

VERTEBRAL COLUMN forms around the notochord the notochord degenerates and disappears as the bodies of the vertebrae form parts of the notochord persist as the NUCLEUS PULPOSUS of each intervertebral disc https://en.wikipedia.org/wiki/Intervertebral_disc https://skeletalsystemdev.weebly.com/uploads/7/0/4/3/7043675/2458583_orig.png

NOTOCHORDAL PROCESS AND NOTOCHORD CLOACAL MEMBRANE: caudal to the primitive streak Indicates the future site of the anus

NOTOCHORDAL PROCESS AND NOTOCHORD ALLANTOIS: appears approx. Day 16 as a small diverticulum extends from the caudal wall of the umbilical vesicle into the connecting stalk involved with early blood formation associated with the urinary bladder http://www.digopaul.com/english-word/allantois.html

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BIBLIOGRAPHY The developing human : clinically oriented embryology by Moore, Keith L Langman's Medical Embryology Thomas W. Sadler Essentials of Domestic Animal Embryology, 1st Edition, Poul Hyttel, Fred Sinowatz, Morten Vejlsted, Keith Betteridge http://www.embryology.ch/anglais/hdisqueembry/triderm01.html http://www.embryology.ch/anglais/hdisqueembry/triderm01.html#formligneprim http://www.embryology.ch/anglais/hdisqueembry/triderm02.html http://www.embryology.ch/anglais/hdisqueembry/triderm03.html http://www.embryology.ch/anglais/hdisqueembry/triderm04.html http://www.embryology.ch/anglais/hdisqueembry/triderm05.html https://is.muni.cz/el/1411/jaro2015/VSET0411p/um/5_-_nervous_system.txt https://www.memorangapp.com/flashcards/61308/Embryology/ https://healtheappointments.com/chapter-8-third-month-to-birth-essays/3/

BIBLIOGRAPHY https://www.youtube.com/watch?v=dAOWQC-OBv0 https://www.youtube.com/watch?v=iZbCXZh_fQs https://www.youtube.com/watch?v=iHmBIJs77ZQ