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Embryology Pedro Amarante Andrade, PhD LCSC06 BIOSCIENCES FOR SPEECH AND LANGUAGE THERAPY LCSC06 | Biosciences for SLT INTRODUCTION TO EMBRYOLOGY • Basic concepts and principles • How the embryo develops from fertilisation to implantation – brief overview (for your information) • Influences on the growth and development of the embryo; critical period concept • Important stages in development: gastrulation, neurulation, development of the nervous system • The neural crest cells – and their fate • Embryonic development of the head and neck structures LCSC06 | Biosciences for SLT DIRECTED STUDY ELEMENTS • Basic genetics • To understand how the pharyngeal arches develop and contribute to the development of the structures of the face, neck and palate • Relate this development to the structures of the head and neck you are currently studying LCSC06 | Biosciences for SLT EVERYBODIE’s JOURNEY https://en.wikipedia.org/wiki/File:HumanNew born.JPG https://en.wikipedia.org/wiki/File:Human_e mbryo_2.jpg https://insideoutsrikar.f iles.wordpress.com/20 11/12/zygote.jpg LCSC06 | Biosciences for SLT WHY STUDY EMBRYOLOGY? LCSC06 | Biosciences for SLT PREGNANCY: MEASURED IN TRIMESTERS http://americanpregnancy.org/week-by-week/7-weekspregnant/ LCSC06 | Biosciences for SLT REAL STAGES • Prenatal development: 3 stages of unequal length • Germinal stage: days 1 to 14 (i.e. from conception to implantation) • Embryonic stage: begins at implantation approximately 2 weeks after conception and continues through weeks 3 to 8 (the period oforganogenesis ) LCSC06 | Biosciences for SLT REAL STAGES • The Foetal Stage: from 9th week to the birth (40 weeks from last period, or 38 weeks from fertilisation) • Organs grow and continue differentiation • Increase in weight LCSC06 | Biosciences for SLT CHALLENGES IN STUDYING EMBRYOLOGY • • • • Complexity Personal experience Attitudes and beliefs Terminology LCSC06 | Biosciences for SLT PRE-EMBRYONIC PERIOD Germinal Stage • The first 14 days • Cells can still repair themselves • If damaged either repairs or dies (spontaneous miscarriage) LCSC06 | Biosciences for SLT CRITICAL PERIOD http://image.slidesharecdn.com/2015-150325050652-conversiongate01/95/human-embryology-2-638.jpg?cb=1427260053 LCSC06 | Biosciences for SLT WHAT CAN AFFECT PRENATAL DEVELOPMENT? LCSC06 | Biosciences for SLT WHAT CAN AFFECT PRENATAL DEVELOPMENT? • • • • Chromosomal and genetic factors Teratogens: maternal disease, drugs Mutagens: radiation Other maternal influences on development: – Diet, age, chronic illness, environmental hazards and maternal emotions LCSC06 | Biosciences for SLT CHROMOSOMAL & GENETIC FACTORS 90% of abnormal embryos are spontaneously aborted Only 1% of live new-borns have a genetic abnormality LCSC06 | Biosciences for SLT CHROMOSOMAL ABNORMALITIES • 23 pairs of chromosomes • 50+ different chromosomal abnormalities – Too many chromosomes – Too few chromosomes • Vast majority of chromosomal abnormalities are lethal (spontaneous abortion) LCSC06 | Biosciences for SLT CHROMOSOMAL ABNORMALITIES • Three copies of chromosome 21 • 1 /600 birth • Learning disability (IQ averages 50) • May have congenital eye, ear, heart defect • Distinctive physical features: protruding http://year9diseases.wikispaces.com/Dow tongue, short limbs, n's+Syndrome slightly flattened nose… Down’s Syndrome http://ehumanbiofield.wikispaces.com/JH+Downsydrome LCSC06 | Biosciences for SLT ANGELMAN’S SYNDROME AND PRADER-WILLI SYNDROME • Genetic defect on chromosome 15 – Angelman’s syndrome (maternal case) – Prader-Willi syndrome (paternal case) LCSC06 | Biosciences for SLT KLINEFELTER’S SYNDROME • Sex chromosomes: XXY (boys) • 1/500 births • Poor coordination • May have mild learning difficulties http://genmolecular.com/alteraciones-cromosomicas/ LCSC06 | Biosciences for SLT TURNER’S SYNDROME • Only affect girls • Occur randomly • 23rd X missing https://en.wikipedia.org/wiki/Turner_syndrome LCSC06 | Biosciences for SLT GENETIC DISORDERS • Through dominant or recessive genes (E.g. Cystic fibrosis) • Phenylketonuria (PKU) – Lack of enzyme to digest food containing amino acid phenylalanine (e.g.milk) – Phenylpyruvic acid accumulates in the body and attacks the developing nervous system – Hyperactivity; learning difficulties – Test routinely given at birth – Treatment: diet LCSC06 | Biosciences for SLT MUTAGENS • Caused by physical or chemical agents (e.g. ionising radiation) • Act on the DNA in cells, especially during cell division • Alters the genes • Mutation can be passed on, if it occurs in the gametes LCSC06 | Biosciences for SLT TERATOGENS • Any disease, drug or other environmental agent that can harm the developing embryo or foetus • The effect is worse on a body part when that structure is forming or growing rapidly • Critical period: Period when a body part is most sensitive to teratogenic agents LCSC06 | Biosciences for SLT MATERNAL DISEASE Rubella – Most dangerous in first trimester – Blindness, deafness, cardiac abnormalities, mental retardation Syphilis – Most harmful in middle or later stages – Miscarriage, serious eye, ear, bone, brain damage LCSC06 | Biosciences for SLT TOXOPLASMOSIS • ¼ adults have this mild disease – similar to common cold • Parasite (cat) • Powerful teratogen • Serious eye or brain damage, induce spontaneous abortion LCSC06 | Biosciences for SLT DRUGS Thalidomide – In 60s – Drug against sickness given to pregnant women in first trimester – Violent teratogen – Badly deformed eyes, ears, nose, even missing limbs http://talubrinandoescritoschapadadoarapari.blogspot.c o.uk/2012/09/a-minha-solidariedade-as-vitimas-da.html LCSC06 | Biosciences for SLT DRUGS Smoking • Low birth weight (less than 2.5 kg) • Nicotine constricts blood vessels Reduces blood flow to placenta LCSC06 | Biosciences for SLT DRUGS Alcohol: • Foetal alcohol syndrome (FAS): • Microcephaly • Malformation of heart, limbs, joints, face • Smaller • Lower IQ - More likely to have learning difficulties (IQ < 85) http://disindevt3.wikispaces.com/Foetal+Alcoh ol+Syndrome • Even low drinking, social drinking LCSC06 | Biosciences for SLT DRUGS Mercury Poisoning • Minamate disease W Eugene Smith, 1972 LCSC06 | Biosciences for SLT EMBRYOLOGICAL DEVELOPMENT LCSC06 | Biosciences for SLT ITERATIVE PROCESSES IN EMBRYOLOGICAL DEVELOPMENT • • • • • • Cell division (proliferation) Cell adhesion Separation of cell sheets to form cavities Cell migration Cell differentiation Cell induction LCSC06 | Biosciences for SLT TIMING IS EVERYTHING • Cell proliferation : embryo/organ system vulnerable to genetic or environmental factors • Cell migration: cells move into position; can be affected by matrix through which they travel • Cell differentiation: cells assume their ultimate form or phenotype – less vulnerable to insult LCSC06 | Biosciences for SLT APOPTOSIS http://eorif.com/syndactyly-7551 LCSC06 | Biosciences for SLT EMBRYONIC DEVELOPMENT • Weeks 1 and 2: –Fertilisation –Implantation –Formation of the placenta and the early embryo http://www.wisegeek.com/what-is-thefertilization-process.htm LCSC06 | Biosciences for SLT FERTILISATION TO IMPLANTATION http://humanphysiology2011.wikispaces.com/15.+Reproductive+Physiology LCSC06 | Biosciences for SLT DAY 1 DAY 2 2 cells; Genes ‘switch on’ 8 to 16 cell stage (morula) LCSC06 | Biosciences for SLT https://en.wikipedia.org/wiki/File:Embryo,_8_cells.jpg DAY 3 DEVELOPMENT OF THE BLASTOCYST http://www.conceive.ca/fertility-treatments/in-vitro-fertilization-ivf LCSC06 | Biosciences for SLT THREE SOURCES OF EMBRYONIC STEM CELLS http://www.intechopen.com/books/pluripotent-stem-cells/de-differentiation-ofsomatic-cells-to-a-pluripotent-state LCSC06 | Biosciences for SLT DAY 14 https://quizlet.com/7189248/bilaminar-and-trilaminar-flash-cards/ LCSC06 | Biosciences for SLT "It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life." Lewis Wolpert (1986) LCSC06 | Biosciences for SLT GASTRULATION A PROCESS THAT LASTS 2 WEEKS • Gastrulation: At this point, I suggest you do a Google search of gastrulation images, as the best ones are unfortunately subject to copyright LCSC06 | Biosciences for SLT THE FATE OF THE 3 GERM LAYERS • Ectoderm: CNS, PNS, epidermis, hair, nails, sensory epithelium (nose, ear, eye) • Mesoderm: part of skull, muscles, vertebrae, urogenital system, serous membranes, body wall, limbs • Endoderm: gut tube and its derivatives; glands, lungs, liver, gall bladder, pancreas LCSC06 | Biosciences for SLT BIRTH DEFECTS ORIGINATING DURING GASTRULATION • Situs inversus • Teratoma (formed from epiblast cells – contain hair, skin, bone, liver etc cells) • Caudal dysgenesis http://radiopaedia.org/cases/sit us-inversus-9 https://beyondthed ish.wordpress.com/ 2013/05/ http://body-system-broadcast.wikispaces.com/Musculo-Skeletal+System LCSC06 | Biosciences for SLT WEEKS 3 TO 4 • Formation of the neural and gut tubes • Embryo transformed from a trilaminar disc into something more recognisable! LCSC06 | Biosciences for SLT NEURULATION • Formation of neural plate • Elevation and curling of lateral edges • ‘zippering’ and formation of the neural tube neurulation video https://en.wikipedia.org/wiki/Neural_tube_defect ,_folate-sensitive LCSC06 | Biosciences for SLT NEURAL CREST http://www.intechopen.com/books/neuroblastoma/ LCSC06 | Biosciences for SLT FINAL DESTINATION NEURAL CREST CELLS • Connective tissue and bones of the face and skull • C cells of thyroid gland • Septum of the heart • Odontoblasts • Dermis in the face and neck • Dorsal root ganglia • Sympathetic chain and pre-aortic ganglia LCSC06 | Biosciences for SLT FINAL DESTINATION NEURAL CREST CELLS • • • • • • Parasympathetic ganglia of the GI tract Adrenal medulla Schwann cells Glial cells Arachnoid and pia mater melanocytes LCSC06 | Biosciences for SLT FINAL DESTINATION NEURAL CREST CELLS http://sharonap-cellrepro-p3.wikispaces.com/Creating+Bodies LCSC06 | Biosciences for SLT WEEK 3: 0.5 MM https://en.wikipedia.org/wiki/Spina_bifida#/m edia/File:S a-bifida.jpg https://en.wikipedia.org/wiki/Somite LCSC06 | Biosciences for SLT FOLDING OF THE EMBRYO • Dorsal surface – formation of the neural tube – ‘zippering’ effect – cervical first, then caudally • Ventral surface – formation of gut tube and body cavities • Body stalk – eventual umbilical cord LCSC06 | Biosciences for SLT FOLDING OF THE EMBRYO https://www.studyblue.com/notes/note/n/embryology/deck/3740268 LCSC06 | Biosciences for SLT FOLDING OF THE EMBRYO http://philschatz.com/anatomy-book/contents/m46319.html LCSC06 | Biosciences for SLT FORMATION OF THE UMBILICAL RING • Proliferation and differentiation of mesoderm • Causes ventral folding along sides of embryonic axis; amnion surrounds embryo • Formation of gut tube • Brain grows • Head and tail folding • ‘purse strings’ effect folding of the embryo in two planes LCSC06 | Biosciences for SLT Week 4 embryo http://pregnancyweeks.wikispaces.com/ Your+Baby%E2%80%99s+Development+ and+Improvement+in+Week+4+of+Preg nancy LCSC06 | Biosciences for SLT ONTOGENY REPLICATES PHYLOGENY LCSC06 | Biosciences for SLT ONTOGENY REPLICATES PHYLOGENY https://en.wikipedia.org/wiki/Recapitulation_theory LCSC06 | Biosciences for SLT NEURAL CREST CELLS: IN THE HEAD AND NECK REGION…… • Form ganglia of the cranial nerves • Connective tissue and some of the bones of the skull and face • Dermis in the face and neck • Odontoblasts • Arachnoid and pia mater • Glial cells LCSC06 | Biosciences for SLT https://www.studyblue.com/notes/note/n/embryology/deck/3740268 LCSC06 | Biosciences for SLT WEEK 3: 0.5 MM https://en.wikipedia.org/wiki/Somite LCSC06 | Biosciences for SLT FATE OF THE MESODERM • Paraxial mesoderm forms paired somites from occiput caudally along the length of the neural tube • In the head region, somitomeres form part of skull, muscles, vertebrae, and dermis of the skin. LCSC06 | Biosciences for SLT DEVELOPMENT OF THE SKULL • Neurocranium (protective covering of the brain) derived from paraxial mesoderm – Membranous portion (flat bones) – Cartilagenous portion = Chondrocranium (base of the skull) • Viscerocranium (skeleton of the face – the ‘middle third’ - & including the mandible) derived entirely from neural crest cells LCSC06 | Biosciences for SLT DEVELOPMENT OF THE SKULL viscerocranium http://medical-dictionary.thefreedictionary.com/neurocranium LCSC06 | Biosciences for SLT DEVELOPMENT OF THE BRAIN VESICLES • • • • • Cranial end of neural tube expands Neural tube closure complete in week 4 Brain vesicles form the future brain Anterior vesicle: prosencephalon This subdivides: telencephalon (future cerebral hemispheres) and diencephalon (optic and thalamic tissues and other structures) LCSC06 | Biosciences for SLT www.en.wikipedia.org LCSC06 | Biosciences for SLT PRIMARY BRAIN VESICLES (rhombencephalon) https://en.wikipedia.org/wiki/File:EmbryonicBrain.svg LCSC06 | Biosciences for SLT PRIMARY BRAIN VESICLES http://bookcoverimgs.com/fetal-brain-development-stages/ LCSC06 | Biosciences for SLT FURTHER DEVELOPMENT OF THE NS • The nervous system continues to develop and changes occur up until the early 20’s • The main changes include: • Myelination • Formation of synapses • Synaptic pruning • Apoptosis LCSC06 | Biosciences for SLT SYNAPTIC PRUNING • Microglia -nerve cells which are usually involved in response to injury in the NS • They also pluck off or ‘prune’ some of the synapses between neurons • In conjunction with apoptosis of neurons, ensures that only the most-used ie strongest connections, remain • Keeps the brain operating efficiently LCSC06 | Biosciences for SLT SYNAPTIC PRUNING OCCURS • Prenatally • In childhood • At puberty • “use it or lose it” • Learning causes synaptic connections to increase in strength LCSC06 | Biosciences for SLT IMPLICATIONS FOR SLT • Aberrant synaptic pruning may be at the root of MND, MS • AD – by the time it is identified, people have lost over HALF their synapses • Children with ASD have increased cerebral volume, ? ? have not undergone the same extent of synaptic pruning? LCSC06 | Biosciences for SLT MYELINATION • Starts late in embryonic development and continues into adolescence/early adulthood • Forebrain the last part to complete myelination • Q what is the function of the myelin sheath? LCSC06 | Biosciences for SLT THE SPINAL CORD • Extends from the foramen magnum to the level of the second lumbar vertebra • Shorter than the vertebral column because it does not grow as rapidly during embryonic development. • Because the spinal cord is shorter, spinal nerves do not always exit the vertebral column at the same level as their origin in the spinal cord. LCSC06 | Biosciences for SLT THE SPINAL CORD https://quizlet.com/24950848/spinal-cord-flash-cards https://it.wikipedia.org/wiki/Cauda_equina LCSC06 | Biosciences for SLT BY THE END OF THE 4TH WEEK • Neural folds have closed • Head region distinguished by presence of 3 brain vesicles • Lens and otic placodes for eye and ear development; • Primitive oral cavity (stomatodeum) • 3 pairs of pharyngeal arches LCSC06 | Biosciences for SLT BY THE END OF THE 4TH WEEK http://pregnancyweeks.wikispaces.com/Your+Baby%E2%80%99s+ Development+and+Improvement+in+Week+4+of+Pregnancy LCSC06 | Biosciences for SLT FORMATION OF THE PHARYNGEAL ARCHES • Neural crest material grows from the rhombencephalic region (rhombomeres) • Migrates and forms 6 paired bands • These form the pharyngeal arches • Each is accompanied by its own artery, nerve and cartilage LCSC06 | Biosciences for SLT FORMATION OF THE PHARYNGEAL ARCHES http://www.med.umich.edu/lrc/cou rsepages/m1/embryology/embryo/ 09faceandpharynx.htm LCSC06 | Biosciences for SLT FORMATION OF THE PHARYNGEAL ARCHES LCSC06 | Biosciences for SLT FORMATION OF THE PHARYNGEAL ARCHES http://center-for-nonverbal-studies.org/pharynx.htm LCSC06 | Biosciences for SLT FORMATION OF THE PHARYNGEAL ARCHES https://commons.wikimedia.org/wiki/File:Phar yngealArchHuman.jpg LCSC06 | Biosciences for SLT FORMATION OF THE PHARYNGEAL ARCHES LCSC06 | Biosciences for SLT FORMATION OF THE PHARYNGEAL ARCHES https://odontologi.wikispaces.com/cranio-facial+development LCSC06 | Biosciences for SLT FORMATION OF THE PHARYNGEAL ARCHES http://scienceblogs.com/pharyngula/2006/06/21/deep-homologies-in-thepharyng LCSC06 | Biosciences for SLT FORMATION OF THE PHARYNGEAL ARCHES http://medchrome.com/basicscience/anatomy/generalembryology-mnemonics LCSC06 | Biosciences for SLT FIRST ARCH DEFORMITIES • Micrognathia • Cleft palate (indirectly) • Conductive hearing loss • External ear malformations LCSC06 | Biosciences for SLT http://byebyedoctor.com/treacher-collins-syndrome/ ABNORMAL NEURAL CREST MIGRATION/DIFFERENTIATION Treacher-Collins Robin sequence LCSC06 | Biosciences for SLT GOLDENHAR SYNDROME First AND second pharyngeal arches malformed http://health9.org/goldenhar-syndrome/ LCSC06 | Biosciences for SLT DEVELOPMENT OF EXTERNAL EAR http://wps.aw.com/wps/media/objects/443/454121/developmentofexternalear.html LCSC06 | Biosciences for SLT DEVELOPMENT OF EXTERNAL EAR https://syllabus.med.unc.edu/courseware/embryo_images/unit-ear/ear_htms/ear015.htm LCSC06 | Biosciences for SLT FORMATION OF THE FACE development of the head, neck, face and palate LCSC06 | Biosciences for SLT FORMATION OF THE FACE http://www.med.umich.edu/lrc/coursepages/m1/embryology/embryo/09faceandpharynx.htm LCSC06 | Biosciences for SLT FORMATION OF THE PALATE https://en.wikipedia.org/wiki/Incisive_foramen https://web.duke.edu/anatomy/embryology/craniofacial/craniofacial.html LCSC06 | Biosciences for SLT FORMATION OF THE PALATE http://praxisprep.wikispaces.com/Cleft+Palate LCSC06 | Biosciences for SLT WEEK 8 https://en.wikipedia.org/wiki/Embryo LCSC06 | Biosciences for SLT
