A histochemical study of human fetal skin.

Glycogen and alkaline phosphatase have been studied in human fetal epidermis between the 28th and 182nd days of gestation. Early on, bladder cells rich in glycogen and alkaline phosphatase are present in the periderm. After 140 days, however, keratin appears in the superficial layers of the periderm; the bladder cells degenerate and become 'rosette' cells, and glycogen and alkaline phosphatase begin to disappear. It is suggested from this evidence that, in early fetal life, before the onset of keratinization, glucose is absorbed from the amniotic fluid and stored as glycogen in the periderm.