Embryology 1 PDF

ANAT20006 EMBRYOLOGY 1 A/Prof Dagmar Wilhelm Dept Anatomy & Physiology The University of Melbourne [email protected]  COPYRIGHT REGULATIONS 1969 Schedule 4...

ANAT20006 EMBRYOLOGY 1 A/Prof Dagmar Wilhelm Dept Anatomy & Physiology The University of Melbourne [email protected]  COPYRIGHT REGULATIONS 1969 Schedule 4 (regulation 4D) FORM OF NOTICE FOR PARAGRAPH 49 (7A) (c) OF THE COPYRIGHT ACT 1968 COMMONWEALTH OF AUSTRALIA Copyright Regulations 1969 WARNING This material has been provided to you pursuant to section 49 of the Copyright Act 1968 (the Act) for the purposes of research or study. The contents of the material may be subject to copyright protection under the Act. Further dealings by you with this material may be a copyright infringement. To determine whether such a communication would be an infringement, it is necessary to have regard to the criteria set out in Part 3, Division 3 of the Act. Poll Everywhere Live interactive audience participation Web and SMS text message – based response system (also option to download app) You respond with your phone/tablet/computer - activity will be displayed on screen Respond at PollEv.com/dwilhelm Text DWILHELM to +61 480 025 509 to join Any questions during the lecture?  Objectives At the end of the three lectures, students should be able to Describe the critical events that take place during embryo development to form a functional human body Understand the cellular basis of the mechanisms of these events Use this knowledge to predict what would happen if things do not go to plan WHY STUDY EMBRYOLOGY? Human Chicken Rabbit WHY STUDY EMBRYOLOGY? - Logical framework for understanding adult anatomy - Provides information about many issues: reproduction, contraception, stem cells, etc. - Informs about when things go wrong: birth defects, cancer Congenital disorders - Congenital disease, birth defect - Structural or functional (e.g. metabolic disorder) defects - Condition present at or before birth (regardless of cause) - Genetic, infectious, nutritional and/or environmental in origin - Occurs in approximately 3% of live birth Some examples: - Orofacial clefts (lip, palate) 1:1000 - Trisomy 21 (Down) 1:700-900 (1:380 if early termination and death also counted) - Heart defects 1:110 - Neural tube defects 1:2400 - Polydactyly 1:1100 Periods of human embryology Conceptus: Fertilization to end of 2nd week Embryo: Beginning of 3rd week to end of 8th week Fetus: 3rd month to birth http://schoolbag.info/biology/humans/25.html Early stages cell become smaller(half of mother * cell) -> identical DNA. Vellutini and Migotto, PLoS One (2010) Early stages Author’s own  - Differentiation ↳ start certain pathway to become specific. - Cavity formation ↳ cell move out. http://schoolbag.info/biology/humans/25.html Blastocyst Two types of cell Outer epithelial layer (trophoblast) Inner cell mass Trophoblast forms extraembryonic structures (part of placenta) Between 5 and 10 days, blastocyst implants into uterine wall Zona pellucida Blastocyst Modified from Wikipedia genetic modify. occur ↳ where  - Implantation - Differentiation - Cavity formation form cavities. - http://schoolbag.info/biology/humans/25.html Two germ layer stage Two germ layer stage - Inner cell mass splits - Cavities form - Forming embryonic disc Blastocyst: Epiblast Hypoblast ↑ amniotic carity http://schoolbag.info/biology/humans/25.html form yolk saz disk. embryonic Gastrulation - Formation of primitive streak: defines all major body axes - Formation of the three germ layers: ectoderm, mesoderm, endoderm - Give rise to distinct tissues in adult Gastrulation – formation of primitive streak On upper surface of bilaminar disc (on epiblast) a line of thickened cells appear (primitive streak) Primitive streak invaginates to form primitive groove cranial ventral-hypoblast end -only & on one - candal http://www.visembryo.com/ surface of epliblast. invagination. (dorsal Embryonic body axes Cranial (anterior) Ventral Dorsal Left Right Caudal (posterior) Adult body axes  Cells of epiblast migrate medially and into primitive groove First cells move into hypoblast to form embryonic endoderm Later cells move into space between epiblast and endoderm become embryonic mesoderm Cells left in epiblast become embryonic ectoderm = Three layer stage transverse view Larson’s Human Embryology, Figure 3-7  Primitive groove epiblast push the hypoblast to the yolk. sac hypoblast Bilaminar embryonic disc (Transverse view) Primitive groove epiblast Embryonic endoderm Bilaminar embryonic disc (Transverse view)  Trilaminar embryonic disc Embryonic Embryonic ectoderm mesoderm Embryonic endoderm Bilaminar embryonic disc (Transverse view) Fate of cells moving through primitive groove Larson’s Human Embryology, Figure 3-8 Lecture 1 Lecture 2 Lecture 3 Adapted from Gilbert 9/10  outside inside Left-right symmetry or asymmetry? Cranial (anterior) fluid-filled Node - DorsalVentral Left Right I cilid Caudal (posterior)  Node = Important for setting up left-right asymmetry - Cilia within node rotate - Leftward fluid flow - bend S bend L R I rotate - mechano-sensor - Cilia on left are bend due to fluid moving towards them => give. signal - Increased Ca2+ = signal in the cell Journal.pbio.0030268.g002.png Left-right asymmetry Sugrue and Zohn, PLoS One (2017) Situs invertus (1:8,000) - Organs are mirrored from their normal position - Only some organs or partial: Situs ambiguus or heterotaxis - Often associated with other problems, especially heart defects Normal position From: www.uludagsozluk.com Summary - early development Blastocyst Inner cell mass Trophoblast Primitive endoderm Epiblast (hypoblast) Cytotropho Embryonic tissues blast Extraembryonic Amniotic Embryonic Syncytiotro endoderm ectoderm epiblast phoblast Yolk sac Primitive streak Embryonic Embryonic Embryonic mesoderm endoderm ectoderm Extra-embryonic tissues Formation of the notochord Cartilage-like, transient Towara structure Important for induction of e.g., neural tube Cranial midline extension from primitive node to form hollow tube Tube grows in length (cells added from primitive node) Primitive streak regresses Larson’s Human Embryology, Figure 3-8 Formation of the notochord mesoderm - ectoderm  streak did not disappear. when primitive - Teratomas from primitive streak Primitive streak should disappear Sometimes cells of primitive streak retained Most common tumour in newborns 1:35,000 births Benign, corrected by surgery Moore and Perseaud 2008 The Developing Human 8 Ed Saunders Elsevier9781416037064 Fig 4_6.jpg Formation of neural plate and neural tube - Ectodermal cells above notochord thicken and differentiate - Extension and folding of neural plate - Convergence of neural folds - Neural tube closure endodermis http://schoolbag.info/biology/humans/25.html Formation of neural plate and neural tube Neural plate Induced by notochord Cranial to primitive node Ectodermal cells differentiate into thick plate of pseudostratified, columnar neuroepithelial cells = neuroectoderm Neural tube Formation = Neurulation Invagination of neural plate = neural groove Closure Neural crest cells ↓ under o Mesenchymal phenotype Epithelial phenotype MET EMT & mesenchymal phenotype Neural crest cells ↳ migrate - form different part of body. Give rise to e.g.: - Dorsal root ganglia - Enteric ganglia - Schwann cells - Melanocytes - Sympathetic and parasympathetic ganglia - Dentine Neural crest cells in chicken embryo  form (NS - Segmentation of neural tube - Neural tube initially one cell layer thick and hollow Cranial end starts to swell forming vesicles Vesicles give rise to brain Remainder to spinal cord Human Embryology and Developmental Biology, BM Carlson 3rd Ed, Mosby, 1999, 0 Bear, Connors and Paradiso, Neuroscience, Exploring the Brain, 3rd 323 03649 X Fig 6.4 Ed, 07187600038 Lippincott, Williams and Wilkins Fig 07.003ap Lecture 1 Lecture 2 Lecture 3 Adapted from Gilbert 9/10 Development of skin Two layers: epidermis and dermis Epidermis: from embryonic ectoderm, colonized by melanocytes (neural crest) and Langerhans cells (immune cells from bone marrow) Dermis: mesodermal (except face: neural crest) y head 3D Atlas of Human Embryology https://www.3dembryoatlas.com/ Lecture 1 Lecture 2 Lecture 3 Adapted from Gilbert 9/10 Review questions Why is it important to study embryology? Why are the early cell divisions called “cleavages”? What are the two cell types of the blastocyst? What is gastrulation? What is the function of the notochord? From which germ layer does the neural tube form? Where do neural crest cells come from? What organs are formed by the ectoderm? Further reading - Wolpert, Tickle, Lawrence, Meyerowitz, Robertson, Smith and Jessell (2011) “Principles of Development” (Oxford University Press) - Gilbert (2010) “Developmental Biology” (Sinauer Assoc., Sunderland, MA) - “Larson’s Human Embryology” (Elsevier) - Fitzgerald & Fitzgerald “Human embryology” (Bailliere Tindall) - Moore ”The Developing Human”, clinically oriented embryology (Elsevier)