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Anatomy, physiology, and histology of the skin
Published in Michael Parker, Charlie James, Fundamentals for Cosmetic Practice, 2022
The cells in this grainy layer are flatter and produce far more keratin than cells deeper within the epidermis. Upon migrating to the stratum granulosum, cellular components start to disintegrate, leaving only keratin, keratohylin and cell membranes. It also contains a high concentration of lipid molecules, which along with desmosomal connections between the skin cells affords a waterproof barrier to prevent the loss of fluid from the body.
Exploring the Plant Kingdom for Sources of Skincare Cosmeceuticals
Published in Mahendra Rai, Shandesh Bhattarai, Chistiane M. Feitosa, Wild Plants, 2020
Mayuri Napagoda, Sanjeeva Witharana
The skin is the outer covering of the human body and is considered as the largest organ in a human. It is comprised of three major structural layers viz., epidermis, dermis, and hypodermis (Tabassum and Hamdani 2014). The epidermis is the outermost layer of the skin which encompasses five sub-layers/strata; stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale. The dermis lies beneath the epidermis and is attached to an underlying hypodermis or subcutaneous connective tissue (Tabassum and Hamdani 2014).
The Flaky Skin (fsn) Mutation, Chromosome ?
Published in John P. Sundberg, Handbook of Mouse Mutations with Skin and Hair Abnormalities, 2020
John P. Sundberg, Dawnalyn Boggess, Leonard D. Shultz, Wesley G. Beamer
Keratinocyte markers specific for mouse epidermis verify changes in protein expression compatible with hyperplasia. The mouse-specific keratin, K6 is normally restricted to the inner layer of the outer root sheath of the hair follicle. During hyperplastic responses in fsn/fsn, K6.5 is expressed in the suprabasilar epidermis. Concurrently, K1 and K10, the normal terminal differentiation markers for suprabasilar epidermal keratinocytes, decrease in expression as hyperplasia increases.12 In normal mouse epidermis, filaggrin is first associated with keratohyalin granules in the stratum granulosum, and later with larger keratohyalin granules in transitional cells, at the junction of the stratum corneum. In lower cornified cells, filaggrin disperses and becomes evenly distributed in the cytoplasm. In the upper cornified cells, filaggrin becomes undetectable. The disappearance of filaggrin in upper cornified cells correlates well with the dispersion of keratin filament bundles, thus providing strong evidence that filaggrin may be involved in keratin filament aggregation in vivo. The dispersion step of filaggrin in the fsn/fsn epidermis appears to be defective, resulting in the accumulation of a large number of superficial cell layers with a filaggrin pattern characteristic of transition cells.13
Exposure to the anti-microbial chemical triclosan disrupts keratinocyte function and skin integrity in a model of reconstructed human epidermis
Published in Journal of Immunotoxicology, 2023
Rachel Baur, Michael Kashon, Ewa Lukomska, Lisa M. Weatherly, Hillary L. Shane, Stacey E. Anderson
The skin, comprised of the epidermis and dermis, is the first line of defense against environmental exposures and influences immune responses. Distinct features of the physical skin barrier, such as lipids, cornified envelopes in the stratum corneum, and tight junctions in the stratum granulosum, limit or prevent the passage of certain molecules, such as high molecular weight proteins, through the skin (Goleva et al. 2019). When barrier integrity or permeability are disrupted, chemicals and/or proteins are more likely to be absorbed through the skin (Rietz Liljedahl et al. 2021), and may lead to increased allergic sensitization. Additionally, in children, elevated levels of transepidermal water loss or mutations in the skin barrier gene filaggrin are a risk factor for development of atopic dermatitis or food allergy (Kelleher et al. 2015, 2016). Due to the use of triclosan in skin products, the skin is a primary route of exposure through which triclosan can be absorbed (MacIsaac et al. 2014). Thus, investigating the skin barrier integrity and response of keratinocytes, the most abundant cell type in the epidermis, to triclosan exposure is critical to understanding the effects on the immune system and associations with increased sensitization potential.
Higher degree of keratinization correlated with severe bone destruction in acquired Cholesteatoma
Published in Acta Oto-Laryngologica, 2023
Yisi Feng, Zhuohao Li, Wuhui He, Ying Xiong, Yu Si, Zhigang Zhang
NIS element software (Nikon) was used to examine cathepsin K-positive osteoclasts, which were counted via Image-Pro Plus 6.0 software (Media Cybernetics, USA). Measurement of the area ratio (the bone resorption area divided by the grafted skin area) was performed according to the procedures previously put forward by Jiang et al. [9]. The stratum corneum thickness of mouse skin and human cholesteatoma samples was measured by ImageJ software according to McCoombe et al. [10]. Two experienced microscopists performed the examinations of stratum corneumthickness on HE-stained slides. The distance from the outermost surface to the start of the stratum granulosum was used to define the stratum corneum thickness. ImageJ was used to measure such distance. Three microscopic fields of each sample were randomly selected and the maximum thickness was recorded and the average SC thickness was calculated.
Transcriptional control and transcriptomic analysis of lipid metabolism in skin barrier formation and atopic dermatitis (AD)
Published in Expert Review of Proteomics, 2019
Nilika Bhattacharya, Gitali Ganguli-Indra, Arup K. Indra
Thus, a comprehensive transcriptomic study to detect how alteration in the expression of skin lipid biosynthesis enzymes resulting in corresponding changes in SC lipid composition can lead to impaired barrier function and AD development is the need of the hour. Cells comprising the stratum corneum are shed periodically and are replaced by cells migrating upwards from the stratum granulosum. Replacement of this entire layer takes about 4 weeks in humans. This raised the question about the appropriateness of the transcriptomic data to get a complete view of the long-term process since it could provide only a momentary reflection of the present condition. Even though the transcriptomic data indeed provide view over a short time interval, it necessarily detects the expression level of the genes whose pool has already been created and therefore may not alter with periodic replenishment of the stratum corneum that occurs essentially every 4 weeks accompanied by renewed lipid biosynthesis. Moreover, given the chronic and the complex nature of the AD, the altered expression level of the genes involved in lipid biosynthesis is likely to be stably maintained in a person harboring AD possibly avoiding the need of a study over a longer time frame. Nonetheless, given the dynamicity of the barrier formation events, transcriptomic analysis at multiple time points might serve useful in gaining additional knowledge about the intricacies of the process.