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Fig. 230. The development of the human nail


A, 10 weeks (X 20); B, 14 weeks (X 1,3); C, longitudinal section at 14 weeks (X 24).

Nails are modifications of the epidermis that correspond to the claws and hoofs of lower mammals. The nail anlage is recognizable in fetuses of 10 weeks as an epidermal, pouch-like fold that soon extends from the proximal border of the future exposed plate almost to the articulation of the terminal phalanx (Fig. 230 C) this proximal nail fold also continues laterally on either side as the lateral nail folds (Fig. 230 A, B).

The material of the nail is developed in the lower lamina of the proximal nail fold (Fig. 230 C). Certain of the epidermal cells, which, according to Bowen, represent a modified stratum lucidum, develop keratin fibrils during the fifth fetal month. These appear without the preliminary keratohyalin stage, as is the case in ordinary epidermis. The cells flatten and form the compact mass of which the nail plate is composed. Thus, the nail substance differentiates in the proximal nail fold as far distad as the outer edge of the Iunula (the whitish crescent at the base of the adult nail). Beyond the lunule, the underlying epidermis takes no active part in development. The stratum corneum and periderm of the epidermis for a time cover completely the free nail and are termed the eponychium (Fig. 230 C).

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   Developmental Anatomy 1924: 1 The Germ Cells and Fertilization | 2 Cleavage and the Origin of the Germ Layers | 3 Implantation and Fetal Membranes | 4 Age, Body Form and Growth Changes | 5 The Digestive System | 6 The Respiratory System | 7 The Mesenteries and Coelom | 8 The Urogenital System | 9 The Vascular System | 10 The Skeletal System | 11 The Muscular System | 12 The Integumentary System | 13 The Central Nervous System | 14 The Peripheral Nervous System | 15 The Sense Organs | C16 The Study of Chick Embryos | 17 The Study of Pig Embryos | Figures Leslie Arey.jpg


Arey LB. Developmental Anatomy. (1924) W.B. Saunders Company, Philadelphia.

Cite this page: Hill, M.A. (2024, February 29) Embryology Arey1924 fig230.jpg. Retrieved from

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