Embryology: Head, Face & Oral Cavity Revision PDF

Embryology; head, face & oral cavity Embryology = Study of the development of tissues. Oral embryology = Study of development of oral tissues. Embryogenesis = Process of embryological development, forming of tissues & organs. Embryonic origins = 3 tissue layers (ectoderm, mesoderm, endoderm) of...

Embryology; head, face & oral cavity Embryology = Study of the development of tissues. Oral embryology = Study of development of oral tissues. Embryogenesis = Process of embryological development, forming of tissues & organs. Embryonic origins = 3 tissue layers (ectoderm, mesoderm, endoderm) of tri- laminar embryonic disc layer that give rise to all tissues in the body. Derivatives = Structures that the origin/tissue layers form. 3 key phases of embryogeneis = Early embryogenesis: (Week 1-4) Week 1 - Formation of blastocyst through; fertilisation, cleavage, proliferation, migration and differentiation. (Zygote—morula—blastocyst) Weeks 2-3 - Three embryonic origins; ectoderm, mesoderm, endoderm form tri- laminar embryonic disc. Weeks 3-4 - Highly specialised neural crest cells derivatives from ectoderm and neuroectoderm. Key component for development of head, face and oral cavity. Week 4 - Embryo starts to take shape through folds forming; stomodeum, buccal- pharyngeal membrane, primitive gut. Bulges are developed; pharyngeal arches. These are building blocks for structure of face and oral cavity. Embryogenesis: (Week 5-8) Development of all tissues, organs and structures. Weeks 4-6 - Face starts to form through the fusion of prominences; 1x frontonasal, 2x maxillary and 2x mandibular. Weeks 4-7 - Tongue develops from 1st, 2nd & 4th pharyngeal arches. Anterior 2/3rd forms from 1st and 2nd arch; Posterior 1/3rd forms from 4th arch. Cellular Development of tongue; 4-7 weeks apoptosis occurs to allow tongue to separate from floor of mouth, leaving frenulum as anchor. Weeks 6-7 - Primary palate development; frontonasal and medial nasal prominences fuse together. Weeks 7-8 - Secondary palate development; palatine shelves grow and develop to fuse together at midline with primary palate and nasal septum. Tongue retracts to create space and the incisive foramen is formed at midline between primary and secondary palate. Week 7 - Maxilla and mandible jaws undergo ossification. Each jaw develops; neural and alveolar portion; support development of teeth and secondary cartilages; support growth of bone. Fetal development: (Week 9 - birth) Clinical signignificance: Embryogenesis is very complex and a Begins after first 8 weeks of development. delicate set of processes. Embryo is now officially a fetus. Malfunctions/interruptions may result in Development, maturation and growth of developmental anomalies. previously formed structures, organs and body systems. Aetiology - Genetic OR Environmental/ Fingernails, eyelashes and hair grow. congenital (radiation, medication, illness, hormones, nutritional deficiency). Fetus is able to move limbs. If cellular apoptosis did not occur during the Morula tongue development, it would leave an individual ‘tongue-tied’ (Ankyloglossia). Can impact; feeding, speech, oral hygiene and breathing. If tissues do not fuse together properly during development, cleft lip and/or palate may occur. Significantly impact; feeding, speech, hearing, development of teeth and oral hygiene. Anomalies increase the risk of oral disease. Branchi Innervation Muscles Artery Cartilage or al / bones Pharyen Ectoderm = Outside layer for protection. gealArc (Skin, hair, nails, enamel, neural) hes I Trigeminal nerve Muscles of Aortic Merkel’s (Cranial nerve V) mastication arch 1 cartilage. Mandible, Mesoderm = Middle layer for support. maxilla, (Muscles, blood, bone, connective tissues) zygomatic, squamous portion of temporal and Endoderm = Inside layer for specialist organs. malleus and (Respiratory, digestive systems etc.) incur of ear. II Facial nerve Muscles of Aortic Reichert’s (Cranial nerve facial arch 2 cartilage. VII) expression Hyoid bone. III Glossopharyngea Stylopharyngeal Aortic Hyoid bone. l arch 3 Connective nerve tissue of (Cranial nerve IX) thymus. IV Superior Laryngeal Aortic Thyroid, laryngeal branch arch 4 corniculate and of vagus nerve cuneiform (Cranial nerve X) cartilage. V ??Vagus nerve?? Doe not give rise to adult structure. VI Recurrent Intrinsic muscle Aortic Laryngeal laryngeal of layrynx. arch 6 cartilages branch of vagus (Not epiglottis) nerve (Cranial nerve X)