The eyelids develop from surface ectoderm that gives rise to the epidermis, cilia, and conjunctival epithelium. Neural crest cell mesenchyme gives rise to deeper structures including the dermis and tarsus. The eyelid muscles, orbicularis and levator, are derived from mesoderm. By 6 weeks of gestation, the upper and lower eyelid buds are visible (see Fig. 1-15). They come from mesenchymal accumulations called frontonasal (upper lid) and maxillary (lower lid) processes. The lid folds grow together and elongate to cover the developing eye. Upper and lower lids fuse together at approximately 10 weeks. By 6 months gestation, glandular structures and cilia develop, and the lids gradually separate.
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