Microscopic Studies of Fetal and Mature Nail and Surrounding Soft Tissue

Lewis, Barton L.

doi:10.1001/archderm.1954.01540240038005

Cited by 145 publications

(37 citation statements)

References 6 publications

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“…6). The production of keratohyalin is a phenomenon that is rarely encountered in the nail bed [12,13]. Countless spherical keratino-somes were also distinguishable in the cells immediately subjacent to the keratohyalin-bearing cells.…”

Section: Resultsmentioning

confidence: 97%

Photo-Onycholysis Induced by 8-Methoxypsoralen

Zala¹,

Omar²,

Krebs³

1977

Dermatology

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Two patients, whom we had under surveillance since 1969, were found to develop photo-onycholysis from orally administered 8-methoxypsoralen and sunlight irradiation. Morphological examination of the nail bed revealed characteristics of a microtrauma. The photosensitizing effect of the drug induced the generation of numerous binucleate, tetranucleate and multinucleate epithelial cells as well as numerous binucleate and tetranucleate fibroblasts in the dermis.

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Section: Resultsmentioning

confidence: 97%

Photo-Onycholysis Induced by 8-Methoxypsoralen

Zala¹,

Omar²,

Krebs³

1977

Dermatology

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“…Each of the three layers in the nail plate consists of closely bonded but poorly defined lamellae. Each lamella is composed of one or more layers of flattened epithelial cells [206]. Fig.…”

Section: Nailsmentioning

confidence: 99%

Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration

Wang

Yang

McKittrick

et al. 2016

Progress in Materials Science

658

474

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a b s t r a c tA ubiquitous biological material, keratin represents a group of insoluble, usually high-sulfur content and filament-forming proteins, constituting the bulk of epidermal appendages such as hair, nails, claws, turtle scutes, horns, whale baleen, beaks, and feathers. These keratinous materials are formed by cells filled with keratin and are considered 'dead tissues'. Nevertheless, they are among the toughest biological materials, serving as a wide variety of interesting functions, e.g. scales to armor body, horns to combat aggressors, hagfish slime as defense against predators, nails and claws to increase prehension, hair and fur to protect against the environment. The vivid inspiring examples can offer useful solutions to design new structural and functional materials.Keratins can be classified as a-and b-types. Both show a characteristic filament-matrix structure: 7 nm diameter intermediate filaments for a-keratin, and 3 nm diameter filaments for b-keratin.Both are embedded in an amorphous keratin matrix. The molecular unit of intermediate filaments is a coiled-coil heterodimer and that of b-keratin filament is a pleated sheet. The mechanical response of a-keratin has been extensively studied and shows linear Hookean, yield and post-yield regions, and in some cases, a high reversible elastic deformation. Thus, they can be also be considered 'biopolymers'. On the other hand, b-keratin has not been investigated as comprehensively. Keratinous materials are strain-rate sensitive, and the effect of hydration is significant.Keratinous materials exhibit a complex hierarchical structure: polypeptide chains and filament-matrix structures at the nanoscale, Progress in Materials Science 76 (2016) 229-318 Contents lists available at ScienceDirect Progress in Materials Sciencej o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / p m a t s c i organization of keratinized cells into lamellar, tubular-intertubular, fiber or layered structures at the microscale, and solid, compact sheaths over porous core, sandwich or threads at the macroscale. These produce a wide range of mechanical properties: the Young's modulus ranges from 10 MPa in stratum corneum to about 2.5 GPa in feathers, and the tensile strength varies from 2 MPa in stratum corneum to 530 MPa in dry hagfish slime threads. Therefore, they are able to serve various functions including diffusion barrier, buffering external attack, energy-absorption, impact-resistance, piercing opponents, withstanding repeated stress and aerodynamic forces, and resisting buckling and penetration.A fascinating part of the new frontier of materials study is the development of bioinspired materials and designs. A comprehensive understanding of the biochemistry, structure and mechanical properties of keratins and keratinous materials is of great importance for keratin-based bioinspired materials and designs. Current bioinspired efforts including the manufacturing of quill-inspired aluminum composites, animal horn-inspired SiC composites, and feather-i...

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“…Although the structure of fingernails has been comprehensively reported in the literature by primatologists and clinicians (Achten, 1981;Ditre and Howe, 1992;Dykyj, 1989;Le Gros Clark, 1936;Lewin, 1965;Lewis, 1954;Soligo and Muller, 1999), little attempt has been made to understand how they perform mechanically under changing environmental conditions. The nail plate comprises three histological layers of keratinous tissue, which are deposited by the nail matrix at the base of the nail unit beneath the skin (Achten, 1981;Caputo et al, 1982).…”

Section: Introductionmentioning

confidence: 99%

The effect of humidity on the fracture properties of human fingernails

Farran

Ennos²,

Eichhorn

2008

Journal of Experimental Biology

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SUMMARYFingernails are a characteristic anatomical feature of primates and their function is dictated by the environment in which they are utilised. The present study examined the mechanical properties of human fingernails as a function of relative humidity (RH) and the subsequent moisture content of the nail material. Nail clippings were stored at a range of RH values and then weighed in order to determine their moisture content. There was a non-linear relationship between the moisture content of nails and the RH of their local environment. The in vivo moisture content of nails, measured from 55% to 80% RH, was between 14% and 30%, similar to other keratinous materials such as claws, hooves and feathers. Cutting tests on the nail samples showed that the work of fracture was between 11 and 22 kJ m -2 , rising to a peak at 55% RH and falling at higher and lower humidities. At all RH values there was anisotropy within the nail between the proximal and lateral directions, the work of fracture being greater proximally. This anisotropy was greatest at 55% RH, at which point the proximal work of fracture was double the lateral value. These results suggest that the mechanical behaviour of human fingernails is optimised at in vivo conditions; they resist tearing most strongly under these conditions and particularly resist tearing into the nail bed. At more extreme humidity levels the fracture properties of the nail deteriorate; they are brittle when fully dry and fracture and split when wet.

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Microscopic Studies of Fetal and Mature Nail and Surrounding Soft Tissue

Cited by 145 publications

References 6 publications

Photo-Onycholysis Induced by 8-Methoxypsoralen

Photo-Onycholysis Induced by 8-Methoxypsoralen

Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration

The effect of humidity on the fracture properties of human fingernails

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