what is the name and function of the thicker layer of cells next to the epidermis

Introduction

Skin is the largest organ in the body and covers the trunk's entire external surface. It is made up of iii layers, the epidermis, dermis, and the hypodermis, all iii of which vary significantly in their beefcake and function. The skin'southward structure is fabricated up of an intricate network which serves equally the body's initial bulwark against pathogens, UV light, and chemicals, and mechanical injury. It also regulates temperature and the amount of h2o released into the surroundings. This article discusses the relevant anatomical structures of the skin'due south epidermal layer, its construction, function, embryology, vascular supply, innervation, surgical considerations, and clinical relevance.

Skin Thickness

The thickness of each layer of the peel varies depending on body region and categorized based on the thickness of the epidermal and dermal layers. Hairless skin plant in the palms of the hands and soles of the feet is thickest considering the epidermis contains an extra layer, the stratum lucidum. The upper back is considered thickest based on the thickness of the dermis, but it is considered "thin peel" histologically because the epidermal thickness lacks the stratum lucidum layer and is thinner than hairless skin.

Layers of Epidermis

The layers of the epidermis include the stratum basale (the deepest portion of the epidermis), stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum (the most superficial portion of the epidermis).

Stratum basale, also known every bit stratum germinativum, is the deepest layer, separated from the dermis past the basement membrane (basal lamina) and fastened to the basement membrane past hemidesmosomes. The cells constitute in this layer are cuboidal to columnar mitotically active stalk cells that are constantly producing keratinocytes. This layer also contains melanocytes.

Stratum spinosum, 8-10 cell layers,too known as the prickle cell layer contains irregular, polyhedral cells with cytoplasmic processes, sometimes called "spines", that extend outward and contact neighboring cells by desmosomes. Dendritic cells can be found in this layer.

Stratum granulosum, 3-5 jail cell layers, contains diamond shaped cells with keratohyalin granules and lamellar granules. Keratohyalin granules contain keratin precursors that eventually aggregate, crosslink, and class bundles. The lamellar granules contain the glycolipids that become secreted to the surface of the cells and role equally a glue, keeping the cells stuck together.

Stratum lucidum, ii-3 cell layers,present in thicker pare constitute in the palms and soles, is a thin clear layer consisting of eleidin which is a transformation product of keratohyalin.

Stratum corneum, 20-xxx prison cell layers,is the uppermost layer, made up of keratin and horny scales fabricated up of dead keratinocytes, known as anucleate squamous cells. This is the layer which varies most in thickness, especially in callused skin. Within this layer, the dead keratinocytes secrete defensins which are part of our start immune defense.

Cells of the Epidermis

• Keratinocytes

• Melanocytes

• Langerhans' cells

• Merkel's cell

Keratinocytes

Keratinocytes are the predominant cell type of epidermis and originate in the basal layer, produce keratin, and are responsible for the formation of the epidermal h2o bulwark by making and secreting lipids. Keratinocytes also regulate calcium absorption by the activation of cholesterol precursors by UVB lite to form vitamin D.

Melanocytes

Melanocytes are derived from neural crest cells and primarily produce melanin, which is responsible for the paint of the skin. They are found between cells of stratum basale and produce melanin. UVB lite stimulates melanin secretion which is protective confronting UV radiation, interim equally a built-in sunscreen. Melanin is produced during the conversion of tyrosine to DOPA by the enzyme tyrosinase. Melanin and then travels from cell to jail cell by a process that relies on the long processes extending from the melanocytes to the neighboring epidermal cells. Melanin granules from melanocytes are transferred via the long processes to the cytoplasm of basal keratinocyte. Melanin transferred to neighboring keratinocytes by "paint donation"; involves phagocytosis of tips of melanocyte processes by keratinocytes.

Langerhans' Cells

Langerhans cells, dendritic cells, are the skins first line defenders and play a significant office in antigen presentation. These cells need special stains to visualize, primarily found in the stratum spinosum. These cells are the mesenchymal origin, derived from CD34 positive stem cells of bone marrow and are part of the mononuclear phagocytic organisation. They incorporate Birbeck granules, tennis dissonance shaped cytoplasmic organelles. These cells express both MHC I and MHC II molecules, uptake antigens in skin and transport to the lymph node.

Merkel Cells

Merkel cells are oval-shaped modified epidermal cells institute in stratum basale, direct above the basement membrane. These cells serve a sensory function as mechanoreceptors for light touch on, and are almost populous in fingertips, though too found in the palms, soles, oral, and genital mucosa. They are leap to bordering keratinocytes past desmosomes and contain intermediate keratin filaments and their membranes interact with free nerve endings in the pare.

Dermis

The dermis is continued to the epidermis at the level of the basement membrane and consists of two layers, of connective tissue, the papillary and reticular layers which merge together without clear demarcation. The papillary layer is the upper layer, thinner, composed of loose connective tissue and contacts epidermis. The reticular layer is the deeper layer, thicker, less cellular, and consists of dense connective tissue/ bundles of collagen fibers. The dermis houses the sweat glands, pilus, pilus follicles, muscles, sensory neurons, and blood vessels.

Hypodermis

The hypodermis is deep to the dermis and is also called subcutaneous fascia. It is the deepest layer of skin and contains adipose lobules along with some skin appendages similar the pilus follicles, sensory neurons, and blood vessels.

Construction and Office

The skin has many functions. Information technology serves as a barrier to water, invasion by microorganisms, mechanical and chemic trauma, and damage from UV low-cal. The epidermal h2o barrier established past the cell envelop, a layer of insoluble proteins on the inner surface of the plasma membrane. Information technology is formed past cantankerous-linking of small proline-rich proteins and larger proteins similar cystatin, desmoplakin, filaggrin and contributes to potent mechanics of bulwark. And the lipid envelope, a lipid/hydrophobic layer fastened to the outer surface of the plasma membrane. As keratinocytes in stratum spinosum produce keratohyalin granules, they also produce lamellar bodies (containing a mixture of glycosphingolipids, phospholipids, and ceramides) assembled within Golgi.  Lamellar bodies' contents are so secreted by exocytosis into extracellular spaces between the stratum granulosum and corneum. Skin is the first site of immunologicaldefense by the action of the Langerhans cells in the epidermis which are dendritic epidermal T lymphocytes and function of the adaptive immune system. The skin preserves the bodies homeostasis by regulating temperature and water loss, while besides serving both endocrine and exocrine functions. The endocrine functions include the production of vitamin D in the keratinocytes which are responsible for converting vii-dehydrocholesterol in the epidermis to vitamin D, with the aid of UV calorie-free from the sun. The keratinocytes express the vitamin D receptor (VDR) and also contain the enzymes needed to convert vitamin D to its active form of 1, 25 dihydroxy vitamin D. The significance of the VDR is that stimulation of it plays a role in the proliferation of the stratum basale and differentiation of keratinocytes as they move up in the epidermis. The exocrine functions of the peel are by way of the sweat and sebaceous glands. Another important role of the skin is aawareness to bear upon, estrus, common cold, and pain by the deportment of the nociceptors. The full general advent, turgor, and other qualities also give insight into the general health of the torso. [7][eight][nine][10]

Embryology

The epidermis is derived from ectodermal tissue. The dermis and hypodermis are derived from mesodermal tissue from somites. The mesoderm is also responsible for the germination of Langerhans cells. Neural crest cells, responsible for specialized sensory nerve endings and melanocyte germination migrate into the epidermis during epidermal development. [11][12]

Blood Supply and Lymphatics

Blood vessels and lymphatic vessels are establish in the dermal layer of the pare. Blood supply to the skin is an arrangement of two plexuses, the starting time lies between the papillary and reticular layers of the dermis and the 2nd lie between the dermis and subcutaneous tissues. Supply to the epidermis is past style of the superficial arteriovenous plexus (subepidermal/papillary plexus). These vessels are important for temperature regulation. The mechanism past which the body regulates temperature through the skin is very effective and works by increased claret catamenia to the peel, transferring oestrus from the body to the environment. The changes in blood flow are controlled by the autonomic nervous organisation, sympathetic stimulation resulting in vasoconstriction (heat retention) and while vasodilation results in rut loss. Vasodilation of the claret vessels is the response to increased body temperature and is the result of inhibition of the sympathetic centers in the posterior hypothalamus whereas decreased body temperature will cause vasoconstriction of skin blood vessels. [13] [14]

Nerves

Nerves of the peel include both somatic and autonomic nerves. The somatic sensory system is responsible for pain (nociceptors), temperature, light bear on, discriminative bear on, vibration, pressure, and proprioception medicated primarily by specialized cutaneous receptors/end organs including Merkel disks, Pacinian corpuscles, Meissner'due south corpuscles, and Ruffini corpuscles. The autonomic innervation is responsible for the control of the tone of the vasculature, pilomotor stimulation at the hair root, and sweating. The costless nervus endings extend into the epidermis and sense pain, heat, and cold. They are nigh numerous in the stratum granulosum layer and surround virtually hair follicles. Merkel disks sense calorie-free touch and attain the stratum basale layer. The other nervus endings are establish in the deeper portions of the skin and include the Pacinian corpuscle which senses deep pressure level, Meissner's corpuscle which senses low-frequency stimulation at the level of the dermal papillae, and Ruffini corpuscles which sense pressure. [15][sixteen][17]

Muscles

The arrector pili muscles are bundles of smooth muscle fibers that attach to the connective tissue sheath of hair follicles. When the muscles contract, they pull the pilus follicle outward resulting in the hair erecting up but also compresses the sebaceous glands, resulting in the secretion of their contents. Hair does not exit perpendicularly, but instead at an angle. This erection of pilus also produces goosebumps, the bumpy appearance of the skin. [18]

Physiologic Variants

Pare is continuously shedding and desquamating and varies slightly depending on the torso region. There are more layers of cells in thicker hairless peel with an additional layer, known as the stratum lucidum. Overall, the procedure of jail cell sectionalisation, desquamation, and shedding get as follows:

1. Cell division occurs in stratum basale/germinativum. One prison cell remains, another cell is pushed toward the surface. Basal cells brainstorm synthesis of tonofilaments (composed of keratin) which are grouped into bundles (tonofibrils).

2. Cells are pushed into stratum spinosum. In the upper part of the spinous layer, cells begin to produce keratohyalin granules having intermediate-associated proteins, filaggrin, and trichohyalin; helps amass keratin filaments and conversion of granular cells to cornified cells, i.e. keratinization. Cells also produce lamellar bodies.

3. Cells are pushed into stratum granulosum and become flattened and diamond shaped. The cells accumulate keratohyalin granules mixed betwixt tonofibrils.

4. Cells continue to stratum corneum where they flatten and lose organelles and nuclei.  The keratohyalin granules turn tonofibrils into a homogenous keratin matrix.

5. Finally, cornified cells achieve the surface and are desquamated via a pause-down of desmosomes. Proteinase activity of KLK (kallikrein-related serine peptidase) is triggered by lowered pH near the surface.[19][20]

Surgical Considerations

Langer's Lines, as well known equally cleavage lines, are topological lines used to define the tension of the skin, corresponding to the alignment of collagen and elastic fibers in the reticular dermis. Surgical incisions made along these lines, less scarring will occur. [21]

Clinical Significance

There are numerous clinically significant aspects of the skin, including the dermatomes of the peel, skin segments divided based on the afferent nerves they are supplied by which are numbered co-ordinate to the level of spinal vertebral from which they arise. There are vii cervical, twelve thoracic, 5 lumbar, and v sacral. Certain diseases like shingles, caused past varicella-zoster infection, have hurting sensation and eruptive rashes that involve a dermatomal distribution. Dermatomes are useful in the diagnosis of vertebral spinal injury levels. Aside from the dermatomes, the cells of the epidermis are susceptible to neoplastic changes resulting in various cancer types. Some autoimmune and immunological diseases target the desmosomes and hemidesmosomes founds in the epidermis. Sure infections tin can also disrupt the integrity of the epidermis forth with drug reactions that present variably too.

Squamous cell carcinoma is cancer that arises from mutated keratinocytes, unremarkably due to UV harm in individuals with Blazon I or II skin types (light pare, blue or green eyes, red or blonde pilus, burn and never tan) and often appear equally scaly, flaky, thick ruby patches that may bleed or even announced wart-like. This type of peel cancer can metastasize. Squamous prison cell carcinoma may arise from actinic keratosis, which is also caused past sun damage to the epidermal layer of skin and may accept cutaneous horns. Basal jail cell carcinoma is a cancer of the basal layers of the epidermis and is much less likely to metastasize. This type of skin cancer is more than common in sun-exposed areas and ofttimes announced are pearly papules on the face, with telangiectasias and ulcerate easily. Melanomas are cancers of the melanocytes and have a high metastatic potential, significantly mediated by the depth of the lesion. Melanomas tin be institute anywhere on the body, are unremarkably irregularly pigmented but tin be amelanotic. Langerhans Cell Histiocytosis is a blazon of cancer where Langerhans cells accumulate in the torso and result in the formation of granulomas, often in the basic, resulting in bone pain. These granulomas tin can also appear in the peel similar rashes, erythematous papules or blisters. An interesting association with this status is the effect of the pituitary gland, which can exist affected and individuals may present with diabetes insipidus, infertility, or other endocrine diseases due to insufficient hormones. Other serious and deadly complications are due to pancytopenia (anemia, thrombocytopenia, leukocytopenia) as a direct response to overcrowding past the Langerhans cells. Merkel cell carcinoma is an uncommon cancer of the Merkel cells and is categorized every bit neuroendocrine small jail cell carcinoma

Pemphigus vulgaris is an autoimmune disease that targets the intercellular proteins, desmosomes, that connect the keratinocytes to each other. Blisters form within the epidermis and are easily ruptured, resulting in acantholysis histologically. This disease is associated with a positive nikolsky sign, peeling away from the epidermis with rubbing of that area. Bullous Pemphigoid is some other blistering disease that results in tense subepidermal blisters in older populations, that are due to antibodies that target the hemidesmosomes that connect the epidermis at the level of the basement membrane to the extracellular matrix of the dermis. This condition is not acantholytic and is not associated with a positive nikolsky sign.

Infections that affect the integrity of the skin include scalded skin syndrome caused by the exfoliative toxin released by staphylococcal aureus bacteria infection. This infection results in peeling away of the peel, positive nikolsky, an advent of a astringent burn down (very ruby-red), and fever. Drug reactions like Wearing apparel syndrome, erythema multiforme, Stevens-Johnsons syndrome, and Toxic Epidermal Necrolysis syndrome are ofttimes associated with sure medications that include sulfa-containing drugs, NSAIDs, and anti-seizure medications. [22][23][24][25][26][27][28][29]

Other Problems

The epidermal layer of peel contains much of our normal flora and the microbiome of the epidermis varies based on the torso region. The microorganisms that inhabit our peel surface is nonpathogenic and can be commensal or mutualistic in nature. The leaner that tend to predominate are staphylococci epidermidis, aureus, cutibacterium acnes, Corynebacterium, Streptococcus, candida and clostridium perfringens. When the protective skin barrier is altered, an infection can occur.  [30]

Review Questions

Figure

Histology, Trichodysplasia spinulosa, Trichodysplasia spinulosa polyomavirus, Good for you control on pinnacle, TS skin on the bottom, Skin over view, Epidermis, Pilus follicle, Acanthosis, Eosinophilic protein granules, trichohyalin, HE Stain. Contributed past Kazem (more than...)

Figure

Cross section of layers of the pare. Hair follicles, hair roots and hair shafts, sweat glands, pores, epidermis, dermis, hypodermis. Papillary and reticular layer. Eccrine sweat gland. Arrector pili muscles, sebaceous oil glands. Contributed by Chelsea (more...)

Effigy

Illustration of cells of the epidermis. Stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale, dermis. Contributed by Chelsea Rowe

References

1.

Bonifant H, Holloway S. A review of the effects of ageing on peel integrity and wound healing. Br J Customs Nurs. 2019 Mar 01;24(Sup3):S28-S33. [PubMed: 30817191]

2.

Herskovitz I, Macquhae F, Play a joke on JD, Kirsner RS. Skin movement, wound repair and development of engineered skin. Exp Dermatol. 2016 February;25(2):99-100. [PubMed: 26660718]

iii.

Ravara B, Hofer C, Kern H, Guidolin D, Porzionato A, De Caro R, Albertin G. Dermal papillae flattening of thigh skin in Conus Cauda Syndrome. Eur J Transl Myol. 2018 Nov 02;28(4):7914. [PMC free article: PMC6317141] [PubMed: 30662702]

4.

Rzepka K, Schaarschmidt G, Nagler Thou, Wohlrab J. [Epidermal stem cells]. J Dtsch Dermatol Ges. 2005 Dec;iii(12):962-73. [PubMed: 16405712]

5.

Karim N, Phinney BS, Salemi M, Wu PW, Naeem Yard, Rice RH. Man stratum corneum proteomics reveals cantankerous-linking of a broad spectrum of proteins in cornified envelopes. Exp Dermatol. 2019 May;28(5):618-622. [PubMed: 30916809]

6.

Brownish TM, Krishnamurthy K. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): May 10, 2021. Histology, Dermis. [PubMed: 30570967]

7.

O'Connell RL, Rusby JE. Anatomy relevant to bourgeois mastectomy. Gland Surg. 2015 December;four(half dozen):476-83. [PMC costless article: PMC4646999] [PubMed: 26645002]

8.

Andersson T, Ertürk Bergdahl M, Saleh Chiliad, Magnúsdóttir H, Stødkilde Thou, Andersen CBF, Lundqvist K, Jensen A, Brüggemann H, Lood R. Common skin leaner protect their host from oxidative stress through secreted antioxidant RoxP. Sci Rep. 2019 Mar 05;9(1):3596. [PMC free article: PMC6401081] [PubMed: 30837648]

9.

Losquadro WD. Anatomy of the Skin and the Pathogenesis of Nonmelanoma Skin Cancer. Facial Plast Surg Clin North Am. 2017 Aug;25(3):283-289. [PubMed: 28676156]

10.

Slominski AT, Manna PR, Tuckey RC. On the role of pare in the regulation of local and systemic steroidogenic activities. Steroids. 2015 Nov;103:72-88. [PMC free article: PMC4631694] [PubMed: 25988614]

11.

Fenner J, Silverberg NB. Pare diseases associated with atopic dermatitis. Clin Dermatol. 2018 Sep - October;36(5):631-640. [PubMed: 30217275]

12.

Hall BK. Germ layers, the neural crest and emergent organization in evolution and evolution. Genesis. 2018 Jun;56(6-7):e23103. [PubMed: 29637683]

13.

Denkler KA, Denkler C. The Management of Optimal Pare Incisions Derived from Striae Distensae. Plast Reconstr Surg. 2015 Jul;136(1):120e-121e. [PubMed: 26111326]

xiv.

Schlader ZJ, Vargas NT. Regulation of Body Temperature by Autonomic and Behavioral Thermoeffectors. Exerc Sport Sci Rev. 2019 Apr;47(2):116-126. [PubMed: 30632999]

15.

Iizaka S. Peel hydration and lifestyle-related factors in customs-dwelling older people. Arch Gerontol Geriatr. 2017 Sep;72:121-126. [PubMed: 28624752]

sixteen.

Stecco C, Pirri C, Fede C, Fan C, Giordani F, Stecco L, Foti C, De Caro R. Dermatome and fasciatome. Clin Anat. 2019 Oct;32(7):896-902. [PubMed: 31087420]

17.

Iheanacho F, Vellipuram AR. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Sep 12, 2021. Physiology, Mechanoreceptors. [PubMed: 31082112]

xviii.

Murphrey MB, Agarwal S, Zito PM. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Aug 11, 2021. Anatomy, Hair. [PubMed: 30020684]

19.

Sanz-Gómez N, Freije A, Gandarillas A. Keratinocyte Differentiation by Flow Cytometry. Methods Mol Biol. 2020;2109:83-92. [PubMed: 31123997]

xx.

Wagner T, Beer L, Gschwandtner M, Eckhart L, Kalinina P, Laggner M, Ellinger A, Gruber R, Kuchler U, Golabi B, Tschachler Due east, Mildner Chiliad. The Differentiation-Associated Keratinocyte Protein Cornifelin Contributes to Jail cell-Cell Adhesion of Epidermal and Mucosal Keratinocytes. J Invest Dermatol. 2019 Nov;139(xi):2292-2301.e9. [PubMed: 31129056]

21.

Lemperle G, Knapp D, Tenenhaus Chiliad. Minimal Scar Formation After Orthopaedic Peel Incisions Along Principal Folding Lines. J Os Articulation Surg Am. 2019 Mar 06;101(5):392-399. [PubMed: 30845033]

22.

Tenea D, Dinkel J, Becker JC, van der Walt E. Merkel Cell Carcinoma of the Head in a Young African Albino Adult female with HIV/HTLV-one Coinfection Associated with Multiple Squamous Cell Carcinomas. Case Rep Dermatol. 2019 Jan-April;xi(1):113-122. [PMC free article: PMC6528093] [PubMed: 31143109]

23.

PDQ Developed Treatment Editorial Board. PDQ Cancer Data Summaries [Cyberspace]. National Cancer Institute (Us); Bethesda (MD): Sep 3, 2021. Melanoma Treatment (PDQ®): Patient Version. [PubMed: 26389388]

24.

Cribier B. Ann Dermatol Venereol. 2019 May;146 Suppl 2:IIS10-IIS15. [PubMed: 31133224]

25.

PDQ Cancer Genetics Editorial Board. PDQ Cancer Information Summaries [Cyberspace]. National Cancer Institute (US); Bethesda (MD): Jul 6, 2021. Genetics of Peel Cancer (PDQ®): Wellness Professional Version. [PubMed: 26389333]

26.

Izumi G, Bieber 1000, Ludwig RJ. Current Clinical Trials in Pemphigus and Pemphigoid. Front Immunol. 2019;10:978. [PMC free article: PMC6509547] [PubMed: 31130959]

27.

Jordan KS. Staphylococcal Scalded Skin Syndrome: A Pediatric Dermatological Emergency. Adv Emerg Nurs J. 2019 April/Jun;41(two):129-134. [PubMed: 31033660]

28.

Vern-Gross TZ, Kowal-Vern A. Erythema multiforme, Stevens Johnson syndrome, and toxic epidermal necrolysis syndrome in patients undergoing radiation therapy: a literature review. Am J Clin Oncol. 2014 October;37(5):506-thirteen. [PubMed: 22892429]

29.

PDQ Pediatric Treatment Editorial Board. PDQ Cancer Information Summaries [Internet]. National Cancer Institute (US); Bethesda (Physician): Aug 27, 2021. Langerhans Cell Histiocytosis Treatment (PDQ®): Patient Version. [PubMed: 26389196]

30.

Sander MA, Sander MS, Isaac-Renton JL, Croxen MA. The Cutaneous Microbiome: Implications for Dermatology Exercise. J Cutan Med Surg. 2019 Jul/Aug;23(iv):436-441. [PubMed: 30938174]

parksthervicarl.blogspot.com

Source: https://www.ncbi.nlm.nih.gov/books/NBK470464/

Share this post