2. EMBRYOLOGY YR1 SLT EMILY BURTENSHAW

3. Introduction to embryology Basic cncepts and principles How the embryo develops from fertilisation to implantation – brief overview, for information only 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

4. 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

5. https://insideoutsrikar.files.wordpr ess.com/2011/12/zygote.jpg

6. https://en.wikipedia.org/wiki/File:Human_embryo_2.jpg

7. https://en.wikipedia.org/wiki/File:HumanNewborn.JPG

8. Why study embryology??

9. Pregnancy: measured in trimesters http://totorus.blogspot.co.uk/

10. In reality … Prenatal development: 3 stages of unequal length. Germinal stage: days 1 to 14 ie from conception to implantation Embryonic stage: begins at implantation approximately 2 weeks after conception and continues through weeks 3 to 8 (the period oforganogenesis )

11. The Foetal Stage: from 9 th week to the birth (40 weeks from last period, or 38 weeks from fertilisation) Organs grow and continue differentiation Increase in weight

12. Challenges in studying embryology: Complexity –CD rom and websites Personal experience Attitudes and beliefs Terminology

13. Pre-embryonic period The first 14 days Cells can still repair themselves If damaged either repairs or dies (spontaneous miscarriage)

14. Critical period: http://veganimal.wikispaces.com/4.1.7.-EL+DESAROLLO+EMBRIONARIO+EN+LOS+ANIMALES

15. What can affect prenatal development?

16. Chromosomal and genetic factors Teratogens: maternal disease, drugs Mutagens: radiation Other maternal influences on development: Diet, age, chronic illness, environmental hazards and maternal emotions

17. Chromosomal & Genetic factors 90% of abnormal embryos are spontaneously aborted Only 1% of live newborns have a genetic abnormality

18. Chromosomal abnormalities 23 pairs of chromosomes Over 50 different chromosomal abnormalities Too many chromosomes Too few chromosomes Vast majority of chromosomal abnormalities are lethal (spontaneous abortion)

19. http://year9diseases.wikispaces.com/Down's+Syndrome

20. http://ehumanbiofield.wikispaces.com/JH+Downsydrome

21. eg:Down Syndrome Three copies of chromosome 21 1 in every 600 birth Learning disability (IQ averages 50) May have congenital eye, ear, heart defect Distinctive physical features: protruding tongue, short limbs, slightly flattened nose…

22. Eg Angelman’s syndrome and Prader-Willi syndrome Genetic defect on chromosome 15 (maternal in case of Angelman’s syndrome, paternal in case of Prader-Willi syndrome)

23. eg: Klinefelter’s Syndrome Sex chromosomes: XXY (boys) 1/500 births Poor coordination May have mild learning difficulties

24. http://genmolecular.com/alteraciones-cromosomicas/

25. Turner’s syndrome https://en.wikipedia.org/wiki/Turner_syndrome

26. Genetic disorders Through dominant or recessive genes Eg 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

27. Mutagens: Physical or chemical agents eg ionising radiation, certain chemicals Act on the DNA in cells, especially during cell division Alters the genes Mutation can be passed on, if it occurs in the gametes

28. 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

29. 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

30. Toxoplasmosis –¼ adults have this mild disease – similar to common cold. –Parasite (cat) –Powerful teratogen –Serious eye or brain damage, induce spontaneous abortion

31. http://talubrinandoescritoschapadadoarapari.blogspot.co.uk/2012/09/a-minha-solidariedade-as-vitimas-da.html

32. Drugs Thalidomide –In 60s –Drug against sickness given to pregnant women in first trimester –Violent teratogen –Badly deformed eyes, ears, nose, even missing limbs

33. Smoking –Low birth weight (less than 2.5 kg) –Nicotine constricts blood vessels  Reduces blood flow to placenta

34. W Eugene Smith, 1972

35. Alcohol: Foetal alcohol syndrome (FAS): –Microcephaly –Malformation of heart, limbs, joints, face –Smaller –Lower IQ - More likely to have learning difficulties (IQ < 85) –Even low drinking, social drinking

36. http://disindevt3.wikispaces.com/Foetal+Alcohol+Syndrome

37. Iterative processes in embryological development: Cell division (proliferation) Cell adhesion Separation of cell sheets to form cavities Cell migration Cell differentiation Cell induction

38. http://eorif.com/syndactyly- 7551 APOPTOSIS

39. 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

40. ♫♪Let’s start at the very beginning♪♫

41. Embryonic development: Weeks 1 and 2: Fertilisation Implantation Formation of the placenta and the early embryo

42. l http://www.wisegeek.com/what-is-the-fertilization-process.htm

43. Fertilisation to implantation: http://humanphysiology2011.wikispaces.com/15.+Reproductive+Physiology SYMBRYO video

44. Day 1 Day 2 2 cells; Genes ‘switch on’

45. 8 to 16 cell stage (morula) Day3 https://en.wikipedia.org/wiki/File:Embryo,_8_cells.jpg

46. Development of the blastocyst: http://www.conceive.ca/fertility-treatments/in-vitro-fertilization-ivf/

47. Three sources of embryonic stem cells: http://www.intechopen.com/books/pluripotent-stem-cells/de-differentiation-of-somatic-cells-to-a-pluripotent-state

48. Day 14: https://quizlet.com/7189248/bilaminar-and-trilaminar-flash-cards/

49. "It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life." Lewis Wolpert (1986)

50. 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.

51. 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

52. Birth defects originating during gastrulation: situs inversus Teratoma (formed from epiblast cells – contain hair, skin, bone, liver etc cells) Caudal dysgenesis

53. http://radiopaedia.org/cases/situs-inversus-9

54. https://beyondthedish.wordpress.com/2013/05/

55. http://body-system-broadcast.wikispaces.com/Musculo-Skeletal+System

56. http://designermetin.deviantart.com/art/3D-Origami-Swan-303043684

57. Weeks 3 to 4 Formation of the neural and gut tubes Embryo transformed from a trilaminar disc into something more recognisable!

58. Neurulation: Formation of neural plate Elevation and curling of lateral edges ‘zippering’ and formation of the neural tube

59. https://en.wikipedia.org/wiki/Neural_tube_defect,_folate-sensitive

60. http://www.intechopen.com/books/neuroblastoma/

61. neurulation video epic neurulation!

62. 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 Parasympathetic ganglia of the GI tract Adrenal medulla Schwann cells Glial cells Arachnoid and pia mater melanocytes

63. http://sharonap-cellrepro-p3.wikispaces.com/Creating+Bodies

64. Week 3: 0.5 mm https://en.wikipedia.org/wiki/Somite

65. https://en.wikipedia.org/wiki/Spina_bifida#/media/File:Spina-bifida.jpg

66. 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

67. https://www.studyblue.com/notes/note/n/em bryology/deck/3740268

68. http://philschatz.com/anatomy-book/contents/m46319.html

69. 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

70. folding of the embryo in two planes

71. http://pregnancyweeks.wikispaces.com/Your+Baby%E2%80%99s+Development+and+Improvement+in+Week+4+of+Pregnancy Week 4 embryo

72. Ontogeny replicates phylogeny

73. https://en.wikipedia.org/wiki/Recapitulation_theory

74. http://3-cups-of-tea.wikispaces.com/Pai+Yu+Cha+Tea

75. http://sharonap-cellrepro-p3.wikispaces.com/Creating+Bodies

76. 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

77. https://www.studyblue.com/notes/note/n/em bryology/deck/3740268

78. Week 3: 0.5 mm https://en.wikipedia.org/wiki/Somite

79. 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.

80. 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

82. viscerocranium http://medical-dictionary.thefreedictionary.com/neurocranium

83. 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)

84. www.en.wikipedia.org

85. (rhombencephalon) Primary Brain Vesicles https://en.wikipedia.org/wiki/File:Embry onicBrain.svg

86. http://bookcoverimgs.com/fetal-brain-development-stages /

87. 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

88. 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

89. Synaptic pruning occurs: Prenatally In childhood At puberty “use it or lose it” Learning causes synaptic connections to increase in strength

90. 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?

91. 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?

92. 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.

93. https://it.wikipedia.org/wiki/Cauda_equi na https://quizlet.com/24950848/spinal-cord-flash-cards

94. By the end of the 4 th week: Neural folds have closed Head region distinguished by presence of 3 brain vesicles

95. Lens and otic placodes for eye and ear development; Primitive oral cavity (stomatodeum) 3 pairs of pharyngeal arches

96. http://pregnancyweeks.wikispaces.com/Your+Baby%E2%80%99s+Development+and+Improvement+in+Week+4+of+Pregnancy Week 4 embryo

97. 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

98. http://www.med.umich.edu/lrc/coursepages/m1/embryology/embryo/09faceandpharynx.htm

100. http://center-for-nonverbal-studies.org/pharynx.htm

101. https://commons.wikimedia.org/wiki/File:PharyngealArchHuman.jpg

103. https://odontologi.wikispaces.com/cranio-facial+development

104. http://scienceblogs.com/pharyngula/2006/06/21/deep-homologies-in-the-pharyng

105. http://medchrome.com/basic-science/anatomy/general-embryology-mnemonics/

106. First arch deformities: Micrognathia Cleft palate (indirectly) Conductive hearing loss External ear malformations

107. Abnormal neural crest migration/differentiation: Treacher-CollinsRobin sequence http://byebyedoctor.com/treacher-collins-syndrome/

108. Goldenhar syndrome First AND second pharyngeal arches malformed https://en.wikipedia.org/wiki/Goldenhar_sy ndrome http://health9.org/goldenhar-syndrome/

109. http://wps.aw.com/wps/media/objects/443/454121/developmentofexternalear.html

110. https://syllabus.med.unc.edu/courseware/embryo_images/unit-ear/ear_htms/ear015.htm

113. FORMATION OF THE FACE: formation of the face development of the head, neck, face and palate

114. http://www.med.umich.edu/lrc/coursepages/m1/embryology/embryo/09faceandpharynx.htm

115. Formation of the palate https://web.duke.edu/anatomy/embryology/craniofacial/craniofacial.html

116. https://en.wikipedia.org/wiki/Incisive_foramen

117. http://praxisprep.wikispaces.com/Cleft+Palate

118. https://en.wikipedia.org/wiki/Embryo

119. Week 8 https://en.wikipedia.org/wiki/Embryo