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Microneedles and Transdermal Transport
Published in Boris Stoeber, Raja K Sivamani, Howard I. Maibach, Microneedling in Clinical Practice, 2020
The epidermis is the outermost layer of the skin and can range from 0.04 mm to 1.5 mm in thickness (Table 1.1), based on age, gender, ethnicity, and location on the body.2 It is composed of self-regenerating stratified squamous epithelium, and serves as a protective barrier to the structures underneath. It is further separated into four layers: stratum corneum, stratum granulosum, stratum spinosum, and stratum germinativum. The stratum corneum consists of dead keratinocytes that form a relatively impermeable barrier to transdermal movement.
The Many Faces of Neoplasia
Published in Jeremy R. Jass, Understanding Pathology, 2020
The term ‘stratified’ means that the cells are piled up like the bricks of a wall. Those nearest the top become flattened like slates and are shed. Stratified squamous epithelium occurs in the skin, mourn, oesophagus, vagina and ectocervix. The most common type of cancer occurring in all these sites is a squamous cell carcinoma. In the skin, the flattened cells accumulate a protein within their cytoplasm called keratin. The cells in all squamous epithelia are tightly held together by patches of adhesion molecules forming junctions called desmosomes. These specialised characteristics ensure the squamous epithelium is relatively tough and waterproof. Keratin production and desmosomes may be seen in squamous cell carcinomas of all sites, even those in which their normal counterpart does not produce abundant keratin (e.g. in sites such as the oesophagus and cervix).
The gastrointestinal system
Published in C. Simon Herrington, Muir's Textbook of Pathology, 2020
Sharon J. White, Francis A. Carey
The oral cavity extends from the lips anteriorly to the oropharynx posteriorly and contains the buccal mucosae, floor of mouth, anterior two-thirds of the tongue, hard palate, teeth, and gingivae (gums). Stratified squamous epithelium lines the oral mucosa and has a high rate of cell turnover. It is keratinized in areas such as the hard palate, the dorsum of the tongue and attached gingivae, which are subject to functional trauma. Specialized structures such as taste buds and papillae are present in areas of the lingual mucosa, and numerous minor salivary glands are located throughout the oral mucosa. The functions of the mouth include mastication, speech, taste, and swallowing.
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
In this study, we identified highly keratinized ectopic epidermis in cholesteatoma matrix as a potential inducer of bone erosion. Keratinization is known to be a process involving keratinocyte differentiation, during which proliferative basal cells expressing K5 and K14 are keratinized and transit to the postmitotic suprabasal layer with upregulated K1 and K10. In stratified squamous epithelium, epithelial cells are gradually cornified and die as they move to the superficial cell layer, forming the stratum corneum [13]. Therefore, the expression levels of K1 and K10, as well as the thickness of the stratum corneum, can be regarded as markers of epidermal keratinization. K1 and K10 were also detected in clinical samples of cholesteatoma [14,15]. In the present study, high K10 expression and a thicker stratum corneum in the cholesteatoma matrix correlated with more severe bone resorption induced by cholesteatoma. Animal experiments also supported these findings. The implantation of highly keratinized skin from mouse tails resulted in more damage to mice calvaria. It was suggested that in cholesteatoma, these highly differentiated keratinocytes were induced by fibroblasts from the perimatrix [16]. Furthermore, K1, the ligand of K10, can maintain the integrity and mechanical stress of the epidermis and is involved in decreasing the release of IL-18, which is known to synergize with IL-12 and IFN-γ and inhibit osteoclast formation [17]. Therefore, it was implied that K1 could promote the process of osteoclastogenesis, which suggested that bone destruction tended to be caused by the epidermis that was more keratinized.
Development and machine-learning optimization of mucoadhesive nanostructured lipid carriers loaded with fluconazole for treatment of oral candidiasis
Published in Drug Development and Industrial Pharmacy, 2021
Mohammed H. Elkomy, Mohammed Elmowafy, Khaled Shalaby, Ahmed F. Azmy, Naveed Ahmad, Ameeduzzafar Zafar, Hussein M. Eid
Figure 10 provides the histological photomicrographs of the buccal mucosal tissue (lip) of rabbits isolated from the control group (A), the group received FLZ-NLC (B), and the group received FLZ-CTS-NLC (C). The images are very similar. The structure of the stratified squamous epithelium is normal. Also, the stratum basalis columnar cells are within normal size without any shrinkage. All epithelial cells are tightly packed without intercellular bridge disruption. No nuclear changes are present. The submucosa of all groups shows no histopathological changes. The treated group (Figure 10(B,C)) shows little vacuolation in the stratified squamous epithelium and some epithelial cells show karyolysis which is insignificant. Consequently, the FLZ-NLC and FLZ-CTS-NLC are considered highly biocompatible.
Therapy for prevention and treatment of skin ionizing radiation damage: a review
Published in International Journal of Radiation Biology, 2019
José L. Soriano, Ana C. Calpena, Eliana B. Souto, Beatriz Clares
Figure 3 schematizes the main layers of skin. Dermis and epidermis are the two main layers of skin, which are separated by a dermal-epidermal junction protein thin layer called basement membrane. The epidermis is the outer region of human skin, which comes from the embryotic ectoderm and contains no blood vessels. It consists of stratified squamous epithelium primarily composed of keratinocytes and other types of cells such as melanocytes, Langerhans cells, and Merkel cells. The lowest portion of the epidermis is the basal layer, which is in contact with the basement membrane (Larcher et al. 2007). The basal layer contains proliferating cells undergoing continuous division and provides a source of cells that move up through suprabasal layers of the epidermis. Beneath the basement membrane is the dermis. The dermis, which is derived from mesoderm, is an underlying connective tissue that contains nerve and vascular networks, lymphatics, as well as epidermal appendages such as glands (sebaceous, endocrine and apocrine), hair follicles and nails. In both cases, in sebaceous glands and hair follicles, proliferation takes place. The former is in the basal layer of the sebaceous gland, and the latter is in the matrix cells of the hair bulb. Other types of cells in the dermis are fibroblasts, macrophages, and mast cells. Finally, the hypodermis is the connective and adipose tissue underlying the skin and located below the dermis. However, it is not actually considered as a part of skin.