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 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 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 Embryology The study of the development of oral tissues. Embryogenesis The process of embryological development, the forming of tissues and organs Embryonic origins the three tissue layers (ectoderm, mesoderm, endoderm) of 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 Early 3 embryonic origins Embryogenesis: Neural crest cells Week 1-4: Pharyngeal arches 3 Key Phases Embryogenesis and development Development of all tissues: Embryogenesis: Face, palate, Week 5-8: tongue, jaws, skull, etc Fetal Growth of fetus Development: Maturation Week 9 – 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 cells Blastocoel – 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) Fertilisation Cleavage Proliferation Migration Differentiation 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 embryonic origins for all the tissues/organs in the body – they are our building blocks. Image credit: https://www.easynotecards.com/notecard_set/85381#&image  Early Embryogenesis: Week 3-4 Ectoderm Neuroectoderm 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 Ectoderm Mesoderm The neural crest cells are key to the development of Oral epithelial cells Neuroectoderm Somites the head, face and oral cavity. They are highly Neural crest cells Mesenchyme specialised. They migrate Cranial and sensory ganglia Peripheral Ectomesenchyme Stem cells Connective tissue in the rest of the throughout the and nerves nervous system body embryo and give connective tissue rise to the cranial in the head, face and oral cavity nerves, peripheral nervous system Dentine, pulp & and the teeth. cementum NOT enamel 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 cartilage Therefore, structures that are formed in different Image: Magreni and Endoderm arches will have different nerve supplies ie the Mesoderm May 2015 tongue. Neural crest cells Pharyngeal Arches and derivatives Arches Nerves Blood Muscles Cartilage Bones that form (eventually) 1st (I) Trigeminal nerve 1st aortic Muscles of Merkel’s Mandible, Maxilla, zygomatic Mandibular (cranial nerve V) arch blood mastication Cartlidge bones, the squamous portion of arch vessel the temporal bone, malleus and incus of ear 2nd (II) Facial Nerve (VII 2nd aortic 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 aortic Stylopharyngeal None Part of the hyoid bone and body, Nerve (cranial arch blood muscle (supports connective tissue of the thymus, nerve IX) vessel swallowing) inferior parathyroid 4th (IV) Superior laryngeal 4th aortic 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 practice. This table is not exhaustive, 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 relating to the different prominences that fuse together to form the face: - 1x Frontonasal prominence - 2x Maxillary prominences - 2x Mandibular prominences The face continues to develop in detail. Video: Development of the face, start at 2:48 link 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 palate will form hence the primary palate forms first 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 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 Cellular apoptosis (cell death) allows the tongue to separate from the floor 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 significance if this was disrupted? 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 fuse Cranial base 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 delicately anomaly. Tongue tied. 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. Aetiology of anomalies: Anaolgy for 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 lip and palate Image: anomalies. Shkoukani et al 2013 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- Cleft lip and palate (CLP) and-embryology.com/wp-content/uploads/2020/08/cleft-palate-1.png results from a combination of each of the above. 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 bilateral cleft 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 - https://youtu.be/wFY_KPFS3LA Learning resources: It does take time 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: 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.