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SKIN

No significant changes are apparent in the ectoderm. The underlying mesenchymal cells produce a thick layer of loose tissue that separates the ectoderm from the deeper muscle masses.

MAMMARY GLAND

The major part of the mammary ridge disappears. Only a small circular area remains in the thoracic region at the level of the T-4 intercostal space. It represents the mammary gland primordium and begins to penetrate the underlying tissue (Fig. 7–1A).

TEETH

The oral epithelium thickens on the maxillary and mandibular processes forming the labiodental laminae that are arranged in a U-shaped manner on the surface of each process. The laminae follow the configuration of the primordial jaws.

Source: Atlas of Human Embryos.