Embryology of the Head, Face, and Oral Cavity (Student Copy)

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...

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 Formative – to support your learning Workbooks Discussions in consolidation session Quiz Summative – 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 Define the embryonic origins (cellular layers) of structures of the head, face and oral cavity Explain the consequences of interruptions in the development process on the structures of the face and oral cavity GDC Learning Outcomes: 1.1.5, 1.1.6 Definitions Embryology The study of the development of tissues. Oral The study of the development of oral tissues. Embryology Embryogenesis The process of embryological development, the forming of tissues and organs Embryonic the three tissue layers (ectoderm, mesoderm, endoderm) of origins the tri-laminar embryonic disc that give rise to all tissues in the human body Derivatives the structures that the origins/tissue layers form Fertilisation, cleavage, proliferation, migration and differentiation 3 key phases of embryogenesis and development  Blastocyst 3 embryonic Early origins Embryogene Neural crest cells sis: Week 1-4: 3 Key Phases Pharyngeal arches Embryogenesis and development Developmen t of all tissues: Embryogene Face, sis: Week 5-8: palate, tongue, jaws, skull, etc Fetal Growth of Development fetus : Week 9 – Maturation term: Overview of the process Video: Development of the face video link https://www.youtube.com/watch?v=FhhWG3XzARY Overview Early Embryogenesis Weeks 2-4 Embryogenesis Weeks 4-6 Images source: Yamanda and Takauwa 2012 Early Embryogenesis: Week 1 Embryoblast – cluster of Blastocoel – cells within the primary yolk sac, cavity fluid filled space Trophoblast – cells lining the cavity Zygote (2-cell), 4-cell, (8-cell) Morula (16 Blastocyst (70-100 cell) cells) Fertilisati Cleavag Proliferati Migratio Differentiat on e on n ion Images: https://smart.servier.com/category/medical-specialties/embryology/ Early Embryogenesis: Weeks 2-3 Embryoblast -> Bilaminar embryonic disc 1. Ectoderm 2. Endoderm Bilaminar -> Trilaminar embryonic disc 3. Mesoderm These 3 layers are called the Image credit: embryonic origins for all the https://www.easynotecards.com/notecard_set/85381#&image tissues/organs in the body – they  Early Embryogenesis: Week 3-4 Ectoderm Neuroectode rm Neural crest cells Neural Plate 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 derivatives The neural Ectoderm Mesoderm crest cells are key to the Oral epithelial cells Neuroectoderm Somites development of the head, face and oral Neural crest cells Mesenchyme cavity. They are highly Cranial and sensory ganglia Peripheral Ectomesenchyme Stem cells Connective tissue in the rest of the nervous system specialised. and nerves body They migrate connective tissue throughout the in the head, face and oral cavity embryo and give rise to the Dentine, pulp & cranial nerves, cementum NOT enamel peripheral Early Embryogenesis: Week 4 The embryo starts to take shape through folds forming: Stomodeum (primitive mouth) Bucco-pharyngeal membrane Primitive gut As the embryo develops, this membrane ruptures to allow communication 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. Each arch has its own: nerve supply, blood supply and Image: Magreni and cartilage Endoderm May 2015 Mesoderm Therefore, structures that are formed in Neural crest cells different arches will have different Pharyngeal Arches and derivatives Arches Nerves Blood Muscles Cartilag Bones that form e (eventually) 1st (I) Trigeminal 1st Muscles of Merkel’s Mandible, Maxilla, Mandibul nerve (cranial aortic mastication Cartlidge zygomatic bones, the ar arch nerve V) arch squamous portion of the blood temporal bone, malleus vessel and incus of ear 2nd (II) Facial Nerve 2nd Muscles of Reichert’ Part of the hyoid bone, Hyoid (VII cranial aortic facial s body of hyoid, styloid arch nerve) arch expression Cartlidge process, blood the stapes vessel 3rd (III) Glossopharyn 3rd aortic Stylopharynge None Part of the hyoid bone and geal Nerve arch al muscle body, (cranial nerve blood (supports connective tissue of the IX) vessel swallowing) thymus, inferior parathyroid 4Bold th (IV)indicates key structures Superior 4threlevant to your learning and aortic Laryngeal practice. Cartlidge This table Thyroid, is not and corniculate exhaustive,laryngeal it includes key points. arch muscles of the cuneiform. Development of the head, face and oral cavity including jaws, tongue, palate and skull. Embryogenesis: Weeks 5-8 Developm ent of the face: Week 4-6 Note the colour shading relating to the different prominences that fuse together to form the face: - 1x Frontonasal prominence - 2x Maxillary prominences - 2x Mandibular prominences Video: Development of the face, start at 2:48 link The face continues to https://www.youtube.com/watch?v=FhhWG3XzARY Development of the primary palate: Week 6-7 The palate forms in 2 parts. 1. The primary palate: forms at the same time as the face the frontonasal prominence and the medial nasal prominences fuse together – see diagram The developing tongue fills the space where the secondary Image adapted: Magreni and May 2015 palate will form hence the Indicates processes that fuse to primary palate forms first due to form the primary palate  Development of the secondary palate: Week 7-8 2. The secondary palate forms after the primary palate: The palatine shelves develop and grow around the developing tongue. (A) The palatine shelves fuse together along the midline with the primary palate and nasal septum as the tongue retracts creating space. (B) The incisive foramen forms at the midline between the secondary and primary palates. (C) 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 Showing the swellings where the tongue forms from the different arches. Image credit: Magreni and May 2015 Cellular apoptosis (cell death) allows Development of the alveolar bone: Week 7 The maxilla and mandible jaws undergo ossification similar to normal bone starting in the respective prominences. Each jaw develops: A neural and alveolar portion to support the development of the teeth Secondary cartilages 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 sections: 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 Cranial base fuse until 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 After the first 8 weeks of development, the fetal development phase starts which focuses mostly on growth of the fetus. The structures that have formed continue 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 significance Clinical significance of Embryology Remember the clinical significance of the tongue not separating from the floor of the mouth? This is an example of an Embryogenesis is a very complex and anomaly. Tongue tied. delicately balanced set of processes that can unfortunately result in malfunctions or be subject to interruptions. These issues may result in developmental anomalies that can have an impact on people’s health and quality of life. Anaolgy for anomalies: Aetiology of anomalies: jigsaw piece that doesn’t fit Genetic Environmental (congenital) – infections, radiation, hormones, nutritional deficiencies, medications etc Cleft lip and palate Facial clefts (space/gap) are congenital anomalies that affect the face and oral cavity. They may be complete or incomplete and unilateral or bilateral. The most common type of facial cleft in the UK is cleft lip and palate where around 1 in 700 live births. If not diagnosed or treated they can significantly impact on feeding, speech, hearing and development. Figures A,B&C showing the range of cleft Image: lip and Shkoukani palate et al 2013 anomalies. Types of facial clefts Figure showing range of cleft lip and palate anomalies from the ventral view. Cleft lip (CL) results from failure of fusion of the two medial nasal processes and/or the maxillary and mesial nasal processes. Cleft palate (CP) results from failure of fusion of the palatine 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 Cleft lip and palate (CLP) Management of cleft lip and palate Diagnosis and treatment are effective and can reduce the impact for patients especially when identified early. Multi-disciplinary teams can start treatment very young. Patients may remain at a higher risk for oral disease as it may impact on the development of teeth requiring additional orthodontic, restorative or periodontal management. See the NHS for more details https://www.nhs.uk/conditions/cleft-lip-and-palate/ Figure showing the repair of a Image: bilateral Shkoukani et al cleft lip 2013 case. 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 - https://youtu.be/wFY_KPFS3LA Learning resources: It does take time to get your Workbook head 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: https://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, Operative Techniques in Otolaryngology-Head and Neck Surgery, 26 (3), pp. 110-114. DOI: https://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. https://doi.org/10.1007/978-1-4614-8341-0_1. Shkoukani, M. A., Chen, M., & Vong, A. (2013). Cleft lip - a comprehensive review. Frontiers in pediatrics, 1, 53. https://doi.org/10.3389/fped.2013.00053.