Embryology of the Head, Face and Oral Cavity GN 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  very beginning Blastocyst Early 3 embryonic origins Embryogenesis: Neural crest cells Week 1-4: Pharyngeal arches 3 Key Phases Embryogenesis and development Development of all 6ssues: Embryogenesis: Development Face, palate, Week 5-8: of all tissues, organs and tongue, jaws, structures skull, etc Everything is formed, needs to grow and Fetal mature 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 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) Grows a lot FerClisaCon Cleavage ProliferaCon MigraCon DiRerenCaCon Images: https://smart.servier.com/category/medical-specialties/embryology/  Early Embryogenesis: Weeks 2-3 Formation of embryonic disc and 3 embryonic layers Collection of cells within blastocyst, proliferates and changes to form bilaminar embryonic disc Embryoblast -> Bilaminar embryonic disc 2 layers 1. EctodermOutside, protection; skin, hair, nails, enamel, neural 2. EndodermInside; specialised organs, live, respiratory, digestive. This grow more and changes into Bilaminar -> Trilaminar embryonic disc 3. Mesoderm Middle layer; between ecto and endoder; support; muscles, blood, bone, connective tissues. Support inside and outside to work together. 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  Neurogenisis Early Embryogenesis: Week 3-4 This point; if there are interruption it can have impact of neuro development. Ectoderm Ectoderm Neuroectoderm Neural plate Neural crest cells Neural tube Neuroectoderm Neural crest cells Mesoderm 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 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 connective tissue rise to the cranial in the head, face and oral cavity nerves, peripheral nervous system Dentine, pulp & cementum NOT and the teeth. enamel Early Embryogenesis: Week 4 The embryo starts to take shape through folds forming: Stomodeum (primiCve mouth) Early mouth Bucco-pharyngeal membrane Separates mouth from primitive gut PrimiCve gut 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. Each arch has its own: nerve supply, blood supply and Foundations for all structures car6lage 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 Foundation 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. 1. The primary palate: forms at the same 6me as the face the frontonasal prominence and the medial nasal prominences fuse together – see diagram Not enough space for palate to form in one. 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 Palatine shelves form from maxilla prominence Palatine shelves grow one from either side then fuse together at midline and with primary palate. Also forms nasal septum. 2. The secondary palate forms aner the primary palate: Tongue retracts to create space. 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) 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 (2 arch) nd - 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 If cells didn’t die, tongue would remain attached; tongue tied. Clinical signiEcance if this was disrupted? Feeding can be impacted. Can be different degrees.  Only called alveolar bone when tooth in place 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 Throughout life 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 Environmental (congenital) – infec6ons, radia6on, hormones, nutri6onal deEciencies, medica6ons etc Clea lip and palate Happen due to local cause or disruption in process 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.