Questions and Answers
Where does the mesenchyme for the formation of the head region come from?
Neural crest cells
What does the paraxial mesoderm contribute to in the head region formation?
Base and flat bones of the skull
Which region does the lateral plate mesoderm specifically form?
Laryngeal cartilages
What structures do the neural crest cells form in the head and neck region?
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Which tissues are formed by ectodermal placodes cells in collaboration with neural crest cells?
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What is the most significant feature in the development of the head and neck according to the text?
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During neurulation, which part of the neural tube communicates with the amniotic cavity by way of the cranial neuropore?
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What is the initial structure that forms the optic vesicle during eye development?
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What part of the ear is derived from the otic vesicle?
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During neurulation, what happens as the neural folds elevate and fuse?
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What part of the optic cup initially forms two separated layers?
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Which part of the ear develops from the 1st pharyngeal cleft?
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When does fusion of the lips of the choroid fissure occur during eye development?
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Which part of the ear is derived from the 1st pharyngeal pouch?
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Which parts of the ear are derived from the 1st and 2nd pharyngeal arches?
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What happens to neural crest cells as they leave the neuroectoderm during neurulation?
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At what stage does invagination of the optic vesicle occur during eye development?
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Where do eyes initially develop in relation to the head?
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Which structure forms from the mesoderm of the 2nd, 3rd, and part of 4th pharyngeal arch?
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What marks the development of the epiglottis and is supplied by the superior laryngeal nerve?
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What contributes to the conotruncal endocardial cushion, separating the outflow tract of the heart into pulmonary and aortic channels?
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What results from a lack of fusion of the palatine shelves?
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What contributes to severe craniofacial malformations if disrupted during development?
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What appears as an epithelial proliferation in the floor of the pharynx between the tuberculum impar and the copula?
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What contributes to the formation of the nasal prominences?
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What forms the side (alae) of the nose?
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What separates the outflow tract of the heart into pulmonary and aortic channels?
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Which cranial nerve is responsible for innervating the muscles of mastication, anterior belly of digastric, mylohyoid, tensor tympani, and tensor palatine?
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Which pharyngeal arch gives rise to the stapes, styloid process of the temporal bone, stylohyoid ligament, lesser horn, and upper part of the body of the hyoid bone?
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What forms a stalk-like diverticulum that comes in contact with the epithelial lining of the 1st pharyngeal cleft, the future external auditory meatus?
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Which nerve innervates the muscles of facial expression, stapedius, stylohyoid, and posterior belly of digastric?
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What does the superior parathyroid gland develop from?
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Which cranial nerve innervates the muscles of the 3rd pharyngeal arch, specifically the stylopharyngeus muscle?
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During further development, Meckel's cartilage disappears except for two small portions at its dorsal end, forming which bones of the middle ear?
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What gives rise to the trigeminal nerve's ophthalmic, maxillary, and mandibular branches, providing sensory supply to the skin of the face?
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Which cranial nerve innervates the muscles of the 4th pharyngeal arch, including cricothyroid, levator palatini, and constrictors of the pharynx?
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Study Notes
Head Region Formation
- Mesenchyme for head region formation comes from neural crest cells, paraxial mesoderm, and lateral plate mesoderm.
- Paraxial mesoderm contributes to the formation of sclerotome, which forms the cartilage and bone of the skull.
Mesoderm Derivatives
- Lateral plate mesoderm forms the muscles of the head and neck.
- Mesoderm of the 2nd, 3rd, and part of 4th pharyngeal arch forms the styloid process of the temporal bone, stylohyoid ligament, lesser horn, and upper part of the body of the hyoid bone.
Neural Crest Cells
- Neural crest cells form the craniofacial skeleton, dentin, pulp of teeth, and dermis of the face.
- They also form the walls of the large arteries, and the outflow tract of the heart.
Ectodermal Placodes
- Ectodermal placodes cells in collaboration with neural crest cells form the olfactory epithelium, lens of the eye, and otic epithelium.
Development of the Head and Neck
- Most significant feature in the development of the head and neck is the formation of the pharyngeal arches.
- During neurulation, the cranial neuropore communicates with the amniotic cavity.
- As the neural folds elevate and fuse, the neural tube forms.
Eye Development
- Initial structure that forms the optic vesicle is the optic pit.
- Invagination of the optic vesicle occurs at the 3-week stage.
- Eyes initially develop laterally in relation to the head.
- Fusion of the lips of the choroid fissure occurs at the 5-week stage.
Ear Development
- Otic vesicle forms the otic capsule, cochlea, and vestibule.
- The 1st pharyngeal cleft forms the external auditory meatus.
- The 1st pharyngeal pouch forms the eustachian tube.
- The 1st and 2nd pharyngeal arches form the malleus and incus bones.
Cranial Nerves
- The trigeminal nerve (V) is responsible for innervating the muscles of mastication, anterior belly of digastric, mylohyoid, tensor tympani, and tensor palatine.
- The facial nerve (VII) innervates the muscles of facial expression, stapedius, stylohyoid, and posterior belly of digastric.
- The glossopharyngeal nerve (IX) innervates the muscles of the 3rd pharyngeal arch, specifically the stylopharyngeus muscle.
- The superior laryngeal nerve supplies the epiglottis.
Pharyngeal Arch Derivatives
- The 2nd pharyngeal arch gives rise to the stapes, styloid process of the temporal bone, stylohyoid ligament, lesser horn, and upper part of the body of the hyoid bone.
- The 3rd pharyngeal arch forms the greater horn of the hyoid bone and the lower part of the body of the hyoid bone.
- The 4th pharyngeal arch forms the conotruncal endocardial cushion, separating the outflow tract of the heart into pulmonary and aortic channels.
Other Developmental Structures
- Meckel's cartilage disappears except for two small portions at its dorsal end, forming the malleus and incus bones.
- The superior parathyroid gland develops from the 4th pharyngeal pouch.
- The 1st pharyngeal pouch forms the eustachian tube.
