Embryology of the Head, Face and Oral Cavity PDF

Embryology of the head, face and oral cavity Tutor: Lauren Stockham Module: Biomedical Sciences Year 1 Outline for Embryology sessions Session Title Mode Learning Acti...

Embryology of the head, face and oral cavity Tutor: Lauren Stockham Module: Biomedical Sciences Year 1 Outline for Embryology sessions Session Title Mode Learning Activity 1 Embryology of the head, face and oral cavity Self-directed Workbook 2 Embryology of oral tissues Self-directed Workbook 3 Embryology of the crown Self-directed Workbook 4 Embryology of the root Self-directed Workbook 5 Embryology of eruption and exfoliation Self-directed Workbook 6 Oral embryology consolidation session Live Group work + quiz Assessment for Embryology FormaCve – to support your learning Workbooks Discussions in consolida6on session Quiz SummaCve – counts towards your grade E-assessment for Biomedical Sciences module Intended Learning Outcomes By the end of this session students should be able to: Outline the key phases of embryogenesis and development of the structures of the head, face and oral cavity DeEne the embryonic origins (cellular layers) of structures of the head, face and oral cavity Explain the consequences of interrupCons in the development process on the structures of the face and oral cavity GDC Learning Outcomes: 1.1.5, 1.1.6 DeIniCons Embryology The study of the development of 6ssues. Oral Embryology The study of the development of oral 6ssues. Embryogenesis The process of embryological development, the forming of 6ssues and organs Embryonic origins the three 6ssue layers (ectoderm, mesoderm, endoderm) of the tri-laminar embryonic disc that give rise to all 6ssues in the human body Deriva6ves the structures that the origins/6ssue layers form Fer6lisa6on, cleavage, prolifera6on, migra6on and diSeren6a6on 3 key phases of embryogenesis and development  Blastocyst Early 3 embryonic origins Embryogenesis: Neural crest cells Week 1-4: Pharyngeal arches 3 Key Phases Embryogenesis and development Development of all key structure of tissues and organs Development of all 6ssues: Embryogenesis: Face, palate, Week 5-8: tongue, jaws, skull, etc Everything isformed Fetal Growth of fetus Development: Matura6on Week 9 – term: Overview of the process Video: Development of the face video link hYps://www.youtube.com/watch?v=FhhWG3XzARY Overview Early Embryogenesis Weeks 2-4 Embryogenesis Weeks 4-6 Images source: Yamanda and Takauwa 2012  Congregates one side and is the foundation of the Early Embryogenesis: Week 1 embryonic disk and 3 embryonic layers. Embryoblast – cluster of cells Blastocoel – within the primary yolk sac, cavity fluid filled space Trophoblast – cells lining the cavity Moves and forms even bigger Zygote (2-cell), 4-cell, (8-cell) Morula (16 collection of Blastocyst (70-100 Fertilised egg Cells split cell) cells called cells) blastocysts FerClisaCon Cleavage ProliferaCon Grows a lot to form MigraCon DiRerenCaCon a collection of cells Changing and growing Images: https://smart.servier.com/category/medical-specialties/embryology/  Formation of embryonic disk containing 3 embryonic layers & Early Embryogenesis: Weeks 2-3 ' Two layers / Embryoblast -> Bilaminar embryonic disc Outermost layer of embryo , gives rise to 1. Ectoderm Skin, hair, nails , enamel and nervous system - 2. Endoderm Everything on ' i'nside such as liver, - digestive system , respiratory tract Grows some more creating trilaminar embryonic disk Bilaminar -> Trilaminar embryonic disc - 3 layers 3. Mesoderm Layer sits in the middle , muscles, bone, connective tissues , blood These 3 layers are called the embryonic origins for all the 6ssues/organs in the body – they are our building blocks. Image credit: hYps://www.easynotecards.com/notecard_set/85381#&image  Early Embryogenesis: Supports Week 3-4 Ectoderm Differentiates and Neuroectoderm forms neural plate Neural crest lines the neural tubes cells comes from neuroectoderm ' Foundations Neural Plate Neural plate folds and forms neural tube Neural tube Figure above shows key stages in development during weeks 3-4 of the embryo. Image right shows the development of neuroectoderm, neural tube, neural crest cells and somites. This Photo by Unknown Author is licensed under CC BY Early Embryogenesis: Neural Crest Cells derivaCves Ectoderm Mesoderm The neural crest cells are key to the development of Oral epithelial cells Neuroectoderm Somites the head, face and oral cavity. They Neural crest cells Mesenchyme are highly specialised. They migrate Cranial and sensory ganglia Peripheral Ectomesenchyme Stem cells Connective tissue in the rest of the nervous system throughout the and nerves body embryo and give rise to the cranial - connective tissue in the head, face Specialized tissue that forms and oral cavity connective tissues in head nerves, peripheral face,oral cavity eg, denting, pulp, cementum. NOT nervous system Dentine, pulp & ENAMAL cementum NOT and the teeth. enamel Early Embryogenesis: Week 4 read - The embryo starts to take shape through folds forming: Stomodeum (primiCve mouth) Bucco-pharyngeal membrane Separates primitive mouth from primitive gut I PrimiCve gut opening mouth As the embryo develops, this membrane ruptures to allow communicaCon between the stomodeum and gut. Early Embryogenesis: Week 4 The embryo develops bulges called: Pharyngeal Arches (Branchial arches) These arches are the building blocks to the structures of the face and oral cavity. O Each arch has its own:. nerve supply, blood supply and car6lage -Foundations Therefore, structures that are formed in diSerent Image: Magreni and Endoderm May 2015 arches will have diSerent nerve supplies ie the Mesoderm tongue. Neural crest cells Pharyngeal Arches and derivaCves Arches Nerves Blood Muscles CarClage Bones that form (eventually) 1st (I) Trigeminal nerve 1st aor6c Muscles of Merkel’s Mandible, Maxilla, zygoma6c Mandibular (cranial nerve V) arch blood masCcaCon Cartlidge bones, the squamous por6on of arch vessel the temporal bone, malleus and incus of ear 2nd (II) Facial Nerve (VII 2nd aor6c Muscles of facial Reichert’s Part of the hyoid bone, body of Hyoid arch cranial nerve) arch blood expression Cartlidge hyoid, styloid process, vessel the stapes 3rd (III) Glossopharyngeal 3rd aor6c Stylopharyngeal None Part of the hyoid bone and body, Nerve (cranial arch blood muscle (supports connec6ve 6ssue of the thymus, nerve IX) vessel swallowing) inferior parathyroid 4th (IV) Superior laryngeal 4th aor6c Laryngeal muscles Cartlidge of Thyroid, corniculate and branch of arch blood the larynx cuneiform. Vagus nerve vessel (cranial nerve X) Bold indicates key structures relevant to your learning and prac6ce. This table is not exhaus6ve, it includes key points. Development of the head, face and oral cavity including jaws, tongue, palate and skull. Embryogenesis: Weeks 5-8 Development of the face: Week 4-6 - Note the colour shading rela6ng to the diSerent prominences that fuse together to form the face: - - 1x Frontonasal prominence - 2x Maxillary prominences - 2x Mandibular - prominences The face con6nues to develop in detail. Video: Development of the face, start at 2:48 link hYps://www.youtube.com/watch?v=FhhWG3XzARY Development of the primary palate: Week 6-7 The palate forms in 2 parts. Frontal prominence and medial nasal 1. The primary palate: prominence fuses together to form the primary plate - limited space to start with. forms at the same 6me as the face the frontonasal prominence and the medial nasal prominences fuse together – see diagram The developing tongue Ills the space where the secondary palate will form hence the primary palate forms Erst due to limited space. Image adapted: Magreni and May 2015 Indicates processes that fuse to form the primary palate  Development of the secondary palate: Week 7-8 2. The secondary palate forms aner the primary palate: The palaCne shelves develop and grow around the developing tongue. (A) The pala6ne shelves fuse together along the midline with the primary palate and nasal septum as the tongue retracts crea6ng space. (B) The incisive foramen forms at the midline between the secondary and primary palates. (C) - fromprominance come Diagram showing the developing secondary palate. Image credit: Magreni and May 2015 Development of the tongue: Week 4-7 The tongue develops from the 1st, 2nd & 4th pharyngeal arches. The anterior 2/3 of the tongue forms from: 2x lateral lingual swellings (1st arch) the tuberculum impar (2nd arch) The posterior 1/3 of the tongue forms from: The copula/hypobranchial eminence Cellular apoptosis (cell death) allows the tongue to separate from the ooor of the Showing the swellings where the tongue forms from mouth leaving a frenulum as its anchor. the different arches. Image credit: Magreni and May 2015 Clinical signiEcance if this was disrupted? Tongue Tied Development of the alveolar bone: Week 7 The maxilla and mandible jaws undergo ossiIcaCon similar to normal bone star6ng in the respec6ve prominences. Each jaw develops: A neural and alveolar porCon to support the development of the teeth Secondary carClages to support growth of the bone These Photos by Unknown Author is licensed under CC BY-SA https://upload.wikimedia.org/wikipedia/commons/7/7f/Maxilla_anterior.png Development of the skull The skull development takes place in 3 sec6ons: Cranial vault (brain case) Cranial base Facial bones The skull bones derive from neural crest cells and mesoderm. The cranial vault bones do not fully fuse Cranial base un6l 6-7 years old to allow for brain growth and development. This Photo by Unknown Author is licensed under CC BY https://pressbooks-dev.oer.hawaii.edu/anatomyandphysiology/wp-content/uploads/sites/ 29/2017/09/703_Parts_of_Skull-01.jpg Fetal Development – Week 9 - birth Aner the Irst 8 weeks of development, the fetal development phase starts which focuses mostly on growth of the fetus. The structures that have formed con6nue to develop and mature. This Photo by Unknown Author is licensed under CC BY-ND http://www.medicalgraphics.de/images/joomgallery/details/free_pictures_11/miscellaneous_16/ week-12-th_20190920_1115842888.jpg Developmental anomalies and defects Clinical signiIcance  Remember the clinical Clinical signiIcance of Embryology significance of the tongue not separating from the floor of the mouth? This is an example of an Embryogenesis is a very complex and delicately anomaly. Tongue tied. balanced set of processes that can unfortunately result in malfuncCons or be subject to interrupCons. These issues may result in developmental anomalies that can have an impact on people’s health and quality of life. AeCology of anomalies: Anaolgy for anomalies: jigsaw piece that doesn’t Et GeneCc Down Sybrome cestic fibrosis - , Environmental (congenital) – infec6ons, radia6on, hormones, nutri6onal deEciencies, medica6ons etc Clea lip and palate Facial clens (space/gap) are congenital anomalies that aSect the face and oral cavity. They may be complete or incomplete and unilateral or bilateral. The most common type of facial clen in the UK is clea lip and palate where around 1 in 700 live births. If not diagnosed or treated they can signiEcantly impact on feeding, speech, hearing and development. Figures A,B&C showing the range of clen lip and palate Image: anomalies. Shkoukani et al 2013 Types of facial cleas Figure showing range of clen lip and palate anomalies from the ventral view. Clea lip (CL) results from failure of fusion of the two medial nasal processes and/or the maxillary and mesial nasal processes. Clea palate (CP) results from failure of fusion of the palaCne shelves together and/or the nasal septum. This Photo by Unknown Author is licensed under CC BY-SA-NC https://histology- and-embryology.com/wp-content/uploads/2020/08/cleft-palate-1.png Clea lip and palate (CLP) results from a combina6on of each of the above. Management of clea lip and palate Diagnosis and treatment are eSec6ve and can reduce the impact for pa6ents especially when iden6Eed early. MulC-disciplinary teams can start treatment very young. Pa6ents may remain at a higher risk for oral disease as it may impact on the development of teeth requiring addi6onal orthodon6c, restora6ve or periodontal management. See the NHS for more details hYps://www.nhs.uk/condi6ons/clen-lip-and-palate/ Figure showing the repair of a bilateral clen Image: lip case. Shkoukani et al 2013 Summary 3 Key phases in embryogenesis and development: 1. Early embryogenesis Embryonic origins Neural crest cells Pharyngeal arches 2. Embryogenesis Development of the face, palate, tongue, alveolar bone, skull 3. Fetal development Clinical significance Aeitiology of developmental anomalies Example - cleft lip and palate Video Recap Take note of the changes in shape of the embryo, the pharyngeal arches and the prominences, the pieces of the puzzle that combine to fit the face together. Development of the face video link - hYps://youtu.be/wFY_KPFS3LA Learning resources: It does take 6me to get your head Workbook around this content. activities Oral embryology reading list Online resources and videos References BBC, 2011. Face Development in the womb – inside the human body: creation. Youtube. Available online: hYps://youtu.be/wFY_KPFS3LA Accessed 04/08/2023. Faculty of dentistry, university of toronoto. 2015. DPES EarlyEmbryonicFacialDevelopment. Youtube. Available online: DPES EarlyEmbryonicFacialDevelopment – YouTube Accessed: 04/08/2023. Magreni, A. and May, J. G. (2015) Embryology of the oral structures, Opera&ve Techniques in Otolaryngology- Head and Neck Surgery, 26 (3), pp. 110-114. DOI: hYps://doi.org/10.1016/j.otot.2015.06.002. Taub P.J., Mesa J.M. (2015) Embryology of the Head and Neck. In: Taub P., Patel P., Buchman S., Cohen M. (eds) Ferraro's Fundamentals of Maxillofacial Surgery. Springer, New York, NY. hYps://doi.org/10.1007/978-1-4614-8341-0_1. Shkoukani, M. A., Chen, M., & Vong, A. (2013). Clen lip - a comprehensive review. Fron&ers in pediatrics, 1, 53. hYps://doi.org/10.3389/fped.2013.00053.