WordNet

one of several parallel layers of material arranged one on top of another (such as a layer of tissue or cells in an organism or a layer of sedimentary rock)

PrepTutorEJDIC

地層,岩層 / (社会的な)階層

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2019/10/06 21:07:11」(JST)

wiki en

Sampling of human stratum corneum using a tape-stripping method^[1]

The stratum corneum (Latin for 'horny layer') is the outermost layer of the epidermis. There has been a long-standing belief in dermatology that the stratum corneum consisted of dead cells (corneocytes), devoid of biological activity and function. The stratum corneum is now understood to be live tissue that performs protective and adaptive physiological functions including mechanical shear, impact resistance, water flux and hydration regulation, microbial proliferation and invasion regulation, initiation of inflammation through cytokine activation and dendritic cell activity, and selective permeability to exclude toxins, irritants, and allergens.^[2] This layer is composed of 15–20 layers of flattened cells with no nuclei and cell organelles. Their cytoplasm shows filamentous keratin. These corneocytes are embedded in a lipid matrix composed of ceramides, cholesterol, and fatty acids.^[3] Their properties depend on the component ratio of the three major components.^[4]

The stratum corneum functions to form a barrier to protect underlying tissue from infection, dehydration, chemicals and mechanical stress. Desquamation, the process of cell shedding from the surface of the stratum corneum, balances proliferating keratinocytes that form in the stratum basale. These cells migrate through the epidermis towards the surface in a journey that takes approximately fourteen days.^[5]

Function

During cornification, the process whereby living keratinocytes are transformed into non-living corneocytes, the cell membrane is replaced by a layer of ceramides which become covalently linked to an envelope of structural proteins (the cornified envelope).^[5]^[6] This complex surrounds cells in the stratum corneum and contributes to the skin's barrier function. Corneodesmosomes (modified desmosomes) facilitate cellular adhesion by linking adjacent cells within this epidermal layer. These complexes are degraded by proteases, eventually permitting cells to be shed at the surface. Desquamation and formation of the cornified envelope are both required for the maintenance of skin homeostasis. A failure to correctly regulate these processes leads to the development of skin disorders.^[5]

Cells of the stratum corneum contain a dense network of keratin, a protein that helps keep the skin hydrated by preventing water evaporation. These cells can also absorb water, further aiding in hydration. In addition, this layer is responsible for the "spring back" or stretchy properties of skin. A weak glutenous protein bond pulls the skin back to its natural shape.

The thickness of the stratum corneum varies throughout the body. In the palms of the hands and the soles of the feet (sometimes knees, elbows,^[7] knuckles,) this layer is stabilized and built by the stratum lucidum (clear phase) which allows the cells to concentrate keratin and toughen them before they rise into a typically thicker, more cohesive SC. The mechanical stress of heavy structural strain causes this SL phase in these regions which require additional protection in order to grasp objects, resist abrasion or impact, and avoid injury. In general, the stratum corneum contains 15 to 20 layers of dead cells. The stratum corneum has a thickness between 10 and 40 μm.

In reptiles, the stratum corneum is permanent, and is replaced only during times of rapid growth, in a process called ecdysis or moulting. This is conferred by the presence of beta-keratin, which provides a much more rigid skin layer.

In the human forearm, about 1300 cells per cm² per hour are shed.^{[citation needed]}

Stratum corneum protects the internal structures of the body from external injury and bacterial invasion.

Skin disease

An inability to correctly maintain the skin barrier function due to the dysregulation of epidermal components can lead to skin disorders. For example, a failure to modulate the activity of kallikreins via the disruption of the protease inhibitor LEKTI causes the debilitating disorder Netherton syndrome.^[8]

References

^ Sadowski T, Klose C, Gerl MJ, Wójcik-Maciejewicz A, Herzog R, Simons K, Reich A, Surma MA (2017). "Large-scale human skin lipidomics by quantitative, high-throughput shotgun mass spectrometry". Scientific Reports. 7: 43761. doi:10.1038/srep43761. PMC 5339821. PMID 28266621.
^ Del Rosso, James Q.; Levin, Jacqueline (2011). "The Clinical Relevance of Maintaining the Functional Integrity of the Stratum Corneum in both Healthy and Disease-affected Skin". The Journal of Clinical and Aesthetic Dermatology. 4 (9): 22–42. ISSN 1941-2789. PMC 3175800. PMID 21938268.
^ Mitra, Ashim K.; Kwatra, Deep; Vadlapudi, Aswani Dutt (2015). Drug Delivery. Burlington, MA: Jones & Bartlett Learning. pp. 285–286. ISBN 978-1-284-02568-2.
^ Podewitz, Maren; Wang, Yin; Gkeka, Paraskevi; von Grafenstein, Susanne; Liedl, Klaus R.; Cournia, Zoe (11 October 2018). "Phase Diagram of a Stratum Corneum Lipid Mixture". The Journal of Physical Chemistry B. 122 (46): 10505–10521. doi:10.1021/acs.jpcb.8b07200. PMID 30351111.
^ ^a ^b ^c Ovaere P; Lippens S; Vandenabeele P; Declercq W. (2009). "The emerging roles of serine protease cascades in the epidermis". Trends in Biochemical Sciences. 34 (9): 453–463. doi:10.1016/j.tibs.2009.08.001. PMID 19726197.
^ Haftek M; Callejon S; Sandjeu Y; Padois K; Falson F; Pirot F; Portes P; Demarne F; Jannin V. (2011). "Compartmentalization of the human stratum corneum by persistent tight junction-like structures". Exp Dermatol. 20 (8): 617–21. doi:10.1111/j.1600-0625.2011.01315.x. PMID 21672033.
^ Dr. Raelene V. Shippee-Rice. "Gerioperative Nursing Care: Principles and Practices of Surgical Care". p. 322.
^ Descargues P, Deraison C, Bonnart C, Kreft M, Kishibe M, Ishida-Yamamoto A, Elias P, Barrandon Y, Zambruno G, Sonnenberg A, Hovnanian A (Jan 2005). "Spink5-deficient mice mimic Netherton syndrome through degradation of desmoglein 1 by epidermal protease hyperactivity". Nat Genet. 37 (1): 56–65. doi:10.1038/ng1493. PMID 15619623.

External links

MedEd at Loyola medicine/dermatology/melton/skinlsn/stcorn.htm
Histology image: 08422loa – Histology Learning System at Boston University - "Integument: thick skin"

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. アトピー性皮膚炎（湿疹）：発症機序、臨床症状、診断atopic dermatitis eczema pathogenesis clinical manifestations and diagnosis [show details]
… release of proinflammatory cytokines . The tight junctions are located in the stratum granulosum below the stratum corneum and are thought to seal the intercellular space to prevent the free diffusion …
2. 顆粒性不全角化granular parakeratosis [show details]
…the stratum granulosum as the keratinocytes mature and flatten to become the stratum corneum . Increased epidermal turnover may lead to epidermal hypertrophy and thickening of the stratum corneum . …
3. 点状角質融解症pitted keratolysis [show details]
…erosions confined to the stratum corneum . The pits and erosions have sharply inclined walls and a flat base consisting of a thin layer or localized absence of stratum corneum. Microorganisms with coccoid …
4. 皮膚剥脱症候群peeling skin syndrome [show details]
…adhesion in the stratum corneum . Type A PSS is characterized by slight hyperkeratosis, thinning of the granular layer, and separation of the stratum corneum from the underlying stratum granulosum or intracorneal …
5. 外傷性水疱friction blisters [show details]
…on the thickness of the overlying stratum corneum. Compared with blisters on skin sites with a thinner stratum corneum, blisters in sites with a thick stratum corneum, such as the palms or soles, tend …

English Journal

Polyphenol-hydrogen peroxide reactions in skin: In vitro model relevant to study ROS reactions at inflammation.

Eskandari M, Rembiesa J, Startaitė L, Holefors A, Valančiūtė A, Faridbod F, Ganjali MR, Engblom J, Ruzgas T.
Analytica chimica acta. 2019 Oct;1075()91-97.
Antioxidants are important to protect and maintain biological barriers, such as the skin. Antioxidant effects are often assessed using clinical trials, however these tests are costly and time consuming. In this work we introduce a skin membrane-covered oxygen electrode (SCOE) as an in vitro tool fo
PMID 31196427

Selectivity in cornified envelop binding of ceramides in human skin and the role of LXR inactivation on ceramide binding.

Boiten W, Helder R, van Smeden J, Bouwstra J.
Biochimica et biophysica acta. Molecular and cell biology of lipids. 2019 Sep;1864(9)1206-1213.
The cornified lipid envelope (CLE) is a lipid monolayer covalently bound to the outside of corneocytes and is part of the stratum corneum (SC). The CLE is suggested to act as a scaffold for the unbound SC lipids. By profiling the bound CLE ceramides, a new subclass was discovered and identified as a
PMID 31112754

The consequences of overcoming the human skin barrier by siloxanes (silicones) Part 1. Penetration and permeation depth study of cyclic methyl siloxanes.

Krenczkowska D, Mojsiewicz-Pieńkowska K, Wielgomas B, Cal K, Bartoszewski R, Bartoszewska S, Jankowski Z.
Chemosphere. 2019 Sep;231()607-623.
Dynamic production of cyclic siloxanes: octamethylcyclotetrasiloxane D4, decamethylcyclopentasiloxane D5 and dodecamethylcyclohexasiloxane D6 increases their concentrations in environment. It is considered that both environmental pollution and the usage of personal care products and cosmetics contai
PMID 30292575

Japanese Journal

周辺空気の絶対温度変化に対する皮膚含水率の経時変化の測定

開原典子,高田暁
人間と生活環境 = Journal of human and living environment 21(2), 67-74, 2014-11
NAID 40020282761

Keratinization induced by air exposure in the reconstructed human epidermal model : An in vitro model of a cultured epithelial autograft

Hanada Takao,Itahara Yuichi,Katoh Masakazu [他]
Journal of bioscience and bioengineering 118(3), 323–326, 2014-09
NAID 40020209157

Keratinization induced by air exposure in the reconstructed human epidermal model : An in vitro model of a cultured epithelial autograft(CELL AND TISSUE ENGINEERING)

Hanada Takao,Itahara Yuichi,Katoh Masakazu,Inoie Masukazu,Hata Ken-ichiro
Journal of bioscience and bioengineering 118(3), 323-326, 2014-09
… A reconstructed human epidermis, an in vitro model of a cultured epithelial autograft, was used to examine the formation of a stratum corneum induced by exposure to air. … A prolonged wet condition and excess application of petrolatum on the dressing reduced efficient production of the stratum corneum. …
NAID 110009857365

Related Pictures

★リンクテーブル★

リンク元	「点状角質融解症」「角質層」
拡張検索	「stratum corneum epidermidis」
関連記事	「corneum」「stratum」

「点状角質融解症」

Stratum corneum
	Histologic image of human epidermis in thick skin.
Details
Identifiers
Latin	stratum corneum epidermidis
	Anatomical terminology [edit on Wikidata]