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Questions and Answers
What can result from malfunctions or interruptions during development?
Which of the following may cause congenital anomalies?
If cellular apoptosis did not occur during tongue development, what condition might result?
What is the primary function of the ectoderm during development?
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What impact can a cleft lip and/or palate have?
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Which nerve is responsible for the muscles of mastication?
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What type of tissue is formed from the mesoderm layer?
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What can increased oral diseases be associated with?
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Which cartilaginous structure is associated with the second branchial arch?
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Which embryonic layer is primarily responsible for developing the respiratory and digestive systems?
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What does the term 'embryogenesis' refer to?
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Which tissue layer develops into the neural crest cells crucial for the development of the head and face?
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During which weeks does face formation begin through the fusion of prominences?
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What occurs to allow the tongue to separate from the floor of the mouth during development?
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Which structure forms between the primary and secondary palate due to retraction of the tongue?
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At what point in development is the embryo officially recognized as a fetus?
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Which embryonic origin is responsible for forming the anterior 2/3 of the tongue?
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What critical change occurs to the maxilla and mandible during week 7?
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What forms as a result of the fusion of the frontonasal and medial nasal prominences?
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Which embryonic tissue layer is responsible for giving rise to all connective tissues in the body?
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Study Notes
Embryology
- Study of tissue development
- Oral embryology focuses on oral tissue development
- Embryogenesis is the process of embryological development, involving the formation of tissues and organs
- Three embryonic origins: ectoderm, mesoderm, and endoderm, form the tri-laminar embryonic disc, giving rise to all body tissues
Early Embryogenesis (Week 1-4)
- Week 1: Formation of blastocyst through fertilization, cleavage, proliferation, migration, and differentiation (Zygote - Morula - Blastocyst)
- Weeks 2-3: Three embryonic origins form the tri-laminar embryonic disc
- Weeks 3-4: Highly specialized neural crest cells, derived from ectoderm and neuroectoderm, are key for head, face, and oral cavity development
- Week 4: Embryo takes shape through folds forming the stomodeum, buccal-pharyngeal membrane, and primitive gut
- Week 4: Bulges develop, known as pharyngeal arches, which act as building blocks for the face and oral cavity
Embryogenesis (Week 5-8)
- Development of all tissues, organs, and structures
- Weeks 4-6: Face formation through the fusion of prominences: 1 frontonasal, 2 maxillary, and 2 mandibular
- Weeks 4-7: Tongue development from the 1st, 2nd, and 4th pharyngeal arches
- Anterior 2/3rd forms from the 1st and 2nd arches
- Posterior 1/3rd forms from the 4th arch
- Cellular apoptosis occurs to separate the tongue from the floor of the mouth, leaving the frenulum as an anchor
- Weeks 6-7: Primary palate development through the fusion of frontonasal and medial nasal prominences
- Weeks 7-8: Secondary palate development with palatine shelves growing and fusing at the midline with the primary palate and nasal septum
- Tongue retracts creating space, and the incisive foramen forms at the midline between the primary and secondary palate
- Week 7: Maxilla and mandible undergo ossification
- Each jaw develops neural and alveolar portions
- Support the development of teeth and secondary cartilages
- Support bone growth
Fetal Development (Week 9 - Birth)
- Begins after the first 8 weeks of development
- Embryo is now a fetus
- Development, maturation, and growth of previously formed structures, organs, and body systems
- Fingernails, eyelashes, and hair grow
- Fetus is able to move limbs
Clinical Significance
- Embryogenesis is a complex delicate process
- Malfunctions or interruptions can lead to developmental anomalies
- Aetiology: Genetic or Environmental/Congenital (radiation, medication, illness, hormones, nutritional deficiency)
- Ankyloglossia (tongue-tied): If cellular apoptosis does not occur during tongue development
- Can impact feeding, speech, oral hygiene, and breathing
- Cleft lip and/or palate: If tissues do not fuse properly during development
- Can impact feeding, speech, hearing, tooth development, and oral hygiene
- Anomalies increase the risk of oral disease
Pharyngeal Arches
| Arch | Innervation | Muscles | Artery | Cartilage or Bones |
|---|---|---|---|---|
| I | Trigeminal nerve (Cranial nerve V) | Muscles of mastication | Aortic arch 1 | Merkel's Cartilage, Mandible, Maxilla, Zygomatic, Squamous portion of temporal, Malleus and incus of ear |
| II | Facial nerve (Cranial nerve VII) | Muscles of facial expression | Aortic arch 2 | Reichert's Cartilage, Hyoid bone |
Embryonic Origins
- Ectoderm (outside layer): Protection (skin, hair, nails, enamel, neural)
- Mesoderm (middle layer): Support (muscles, blood, bone, connective tissues)
- Endoderm (inside layer): Specialist organs (respiratory, digestive systems, etc)
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Description
This quiz covers the critical stages of embryonic development from weeks 1 to 8, focusing on the formation of tissues and organs. You will explore the processes of embryogenesis, including the establishment of the tri-laminar embryonic disc and the development of key structures, such as the neural crest cells and pharyngeal arches. Test your knowledge of the complex stages that shape the early embryo.
