Embryology of Teeth Tongue Thyroid Dr Shivaram Bhat
Embryology of Teeth, Tongue, Thyroid Dr Shivaram Bhat
Learning objectives • Embryology of teeth from dental lamina • Development of tongue from floor of pharyngeal pouches • Development of thyroid from thyroid diverticulum • Applied embryology related to above organs
Questions • Embryology & anomalies thyroid • Embryology & Anomalies of tongue • Embryology & nerve supply of tongue • Development of teeth • • Anomalies of tongue Thyroglossal duct Thyroglossal cyst Anomalies of thyroid
Time line of events • • 4 weeks – lingual swellings and tuberculum impar 5 weeks – hypopharyngeal eminence, thyroid 6 weeks – dental lamina 7 weeks – thyroid in definitive position 8 – 10 weeks – enamel organs 6 months – enamel, dentine, tongue 9 months – cementum Birth – periodontal ligaments
TEETH
Dental lamina
Stages
Stages
Deciduous teeth
Dental buds for permanent teeth
Permanent teeth
Embryological origin • Ectoderm – Ameloblasts – Enamel • Mesoderm ( neural crest ) – Odontoblasts – Dentine • Mesenchyme – Cementoblasts – Cementum, Periodontal ligament
Morphology
Applied aspects • • Anodentia Gemination Natal teeth Amelogenesis imperfecta Dentinogenesis imperfecta Tooth impaction Dentigerous cyst
TONGUE
Floor of primitive pharynx
Nerve supply
Nerve supply
To summarise • Anterior 2/3 rd - 2 lateral lingual swellings and 1 median lingual swelling • Posterior 1/3 rd - hypobranchial eminence • Posterior most part – 4 th pharyngeal arch • Muscles of tongue – occipital myotomes
Anomalies of tongue • • Aglossia. Microglossia Macroglossia Ankyloglossia Cleft tongue Bifid tongue Lingual thyroid
THYROID GLAND
Thyroid development
Floor of primitive pharynx
Caudal pharyngeal complex
To summarise Thyroid develops from • Thyroid diverticulum from foramen cecum at the junction of tuberculum impar and copula • Caudal pharyngeal complex from 4 th arch and also probably disappearing 5 th arch. • Starts functioning by 3 -4 months
• Absence of isthmus, + 1 lobe • Presence of pyramidal lobe • Levator glandulae thyroidae
THYROID GLAND- Pyramidal lobe
- Slides: 45