DOCSLIB.ORG

The Human Epidermal Basement Membrane -A Shaped and Cell Instructive Platform That Aging Slowly Alters Eva Roig-Rosello, Patricia Rousselle

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Human Epidermal Basement Membrane -A Shaped and Cell Instructive Platform That Aging Slowly Alters Eva Roig-Rosello, Patricia Rousselle The human epidermal basement membrane -a shaped and cell instructive platform that aging slowly alters Eva Roig-Rosello, Patricia Rousselle To cite this version: Eva Roig-Rosello, Patricia Rousselle. The human epidermal basement membrane -a shaped and cell instructive platform that aging slowly alters. Biomolecules, MDPI, 2020, 10 (12), pp.1607. 10.3390/biom10121607. hal-03037856 HAL Id: hal-03037856 https://hal.archives-ouvertes.fr/hal-03037856 Submitted on 3 Dec 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. 1 Review 2 The human epidermal basement membrane – a 3 shaped and cell instructive platform that aging 4 slowly alters 5 Eva Roig-Rosello 1,2 and Patricia Rousselle 1,* 6 1 Laboratoire de Biologie Tissulaire et Ingénierie Thérapeutique, UMR 5305, CNRS - Université Lyon 1, 7 Institut de Biologie et Chimie des Protéines, SFR BioSciences Gerland-Lyon Sud, 7 passage du Vercors, 8 Lyon, 69367, France 9 2 Roger Gallet SAS, 4 rue Euler, 75 008 Paris, France 10 * Correspondence: [email protected] 11 Received: date; Accepted: date; Published: date 12 Abstract: One of the most important functions of skin is to act as a protective barrier. To fulfill this 13 role, the structural integrity of the skin depends on the dermal–epidermal junction, a complex 14 network of extracellular matrix macromolecules that connect the outer epidermal layer to the 15 underlying dermis. This junction provides both a structural support to keratinocytes and a specific 16 niche that mediates signals influencing their behavior. It displays a distinctive microarchitecture 17 characterized by an undulating pattern, strengthening dermal–epidermal connectivity and cross- 18 talk. The optimal stiffness arising from the overall molecular organization together with 19 characteristic anchoring complexes keeps the dermis and epidermis layers extremely well connected 20 and capable of proper epidermal renewal and regeneration. Because of intrinsic and extrinsic 21 factors, a large number of structural and biological changes accompany skin aging. These changes 22 progressively weaken the dermal–epidermal junction substructure and affect its functions, 23 contributing to the gradual decline in overall skin physiology. Most changes involve reduced 24 turnover or altered enzymatic or nonenzymatic posttranslational modifications, compromising the 25 mechanical properties of matrix components and cells. This review combines recent and older data 26 on organization of the dermal–epidermal junction, its mechanical properties and role in 27 mechanotransduction, its involvement in regeneration, and its fate during the aging process. 28 Keywords: extracellular matrix; basement membrane; dermal-epidermal junction, skin, epidermal 29 rete-ridge, dermal papilla, aging, mechanical properties 30 31 1. Introduction 32 One of the most important functions of skin is to act as a protective barrier. To fulfil this role, 33 the structural integrity of the skin depends on the basement membrane, a complex network of 34 extracellular matrix (ECM) macromolecules that connect the outer epidermal layer to the 35 underlying dermis. The epidermis, which consists primarily of keratinocytes, is continuously 36 renewed by the proliferation of stem cells and the differentiation of their progeny. These cells 37 undergo terminal differentiation as they exit the basal layer and move toward the surface, where 38 they die and slough off [1]. Basal keratinocytes adjoin the dermal–epidermal junction (DEJ), a cell 39 surface–associated ECM that acts in concerted action by both epidermal and dermal cells [2]. The 40 DEJ provides both structural support to keratinocytes and a specific niche that mediates signals 41 influencing their behavior. Biomolecules 2020, 10, x; doi: FOR PEER REVIEW www.mdpi.com/journal/biomolecules Biomolecules 2020, 10, x FOR PEER REVIEW 2 of 32 42 Much progress has been made in understanding the molecular structure and functions of 43 extracellular macromolecules at the DEJ. Similar to all archetypal thin planar basement membranes, 44 the DEJ consists primarily of laminins, collagen IV, nidogens, and the heparan sulfate (HS) 45 proteoglycan perlecan, all of which are necessary for tissue organization and structural integrity 46 [3,4,5]. Electron microscopy evaluation of the DEJ following conventional fixation protocols has 47 revealed a lamina densa and lamina lucida much like those of other basement membranes. In 48 addition, the DEJ contains numerous regular structures known as anchoring complexes [6,7]. These 49 anchoring complexes consist of electron-dense thickenings of the basolateral plasma membrane, 50 which are called hemidesmosomes because of their resemblance to half of the desmosome plaques 51 present on the plasma membranes at sites of cell–cell contact. Cytoskeletal keratin filaments insert 52 into the hemidesmosomes, bridging the plasma membranes and providing a continuous 53 intercellular network throughout the entire epidermis. Thin filaments known as anchoring 54 filaments appear to traverse the lamina lucida and insert into the lamina densa, tethering the 55 hemidesmosomes to the basement membrane [8,9]. Other structures, the anchoring fibrils, originate 56 within the lamina densa and project into the upper regions of the papillary dermis. They either loop 57 back and reinsert into the lamina densa or extend perpendicularly from the basement membrane 58 and insert into anchoring plaques. Anchoring plaques are electron-dense condensations of the ends 59 of anchoring fibrils together with other intrinsic constituents of the basal lamina [10,11]. Additional 60 anchoring fibrils originate in the plaques and extend further into the papillary dermis. The 61 complexity of these structures probably serves to increase the frictional resistance of external 62 epithelia to applied forces [12]. 63 In addition, the DEJ provides a highly dynamic microenvironment to the keratinocytes by 64 participating in epidermal renewal under physiological conditions and taking part in repair 65 processes during skin healing [13,14,15,16]. In both scenarios, the DEJ serves as an adhesive 66 scaffold, and its constituents may be part of signaling events that vary depending on maturation 67 processes driven by ECM-modifying enzymes [17,18]. Basement membranes can function as 68 signaling platforms by sequestering growth factors and other ligands. Perlecan, agrin, and collagen 69 XVIII bind to many growth factors via HS glycosaminoglycan chains [19,20]. Through binding and 70 sequestering of soluble growth factors in the presence of appropriate cell-mediated forces or 71 proteolytic degradation, basement membranes can also enable spatial-temporal regulation of 72 receptor–ligand interactions. Furthermore, these ECMs can generate and transduce mechanical 73 signals. Through interactions with cell surface receptors, these ECMs modulate a remarkably wide 74 range of signaling processes. 75 2. General organization of the interfollicular DEJ 76 The originally inferred thickness of the DEJ, around 100 nm, was based on measurements made 77 on transmission electron microscopy images taken of human skin cross-sections. The development 78 of imaging approaches that require less or no chemical treatment of samples, such as atomic force 79 microscopy (AFM) and super-resolution light microscopy, consistently have allowed re-evaluation 80 of basement membrane thickness values, yielding results that double those obtained by transmission 81 electron microscopy [5,21]. 82 2.1. The DEJ undulating pattern and the rete ridges 83 84 The DEJ displays a distinctive microarchitecture characterized by an undulating pattern arising 85 from epidermal rete ridges that are downgrowths of the epidermis within the papillary dermis, 86 leading to the characteristic varying number of strata along the epidermis [22] (Figure 1). These 87 nipple-like elevations indent the epidermis layer and substantially increase the surface area of the 88 DEJ, strengthening dermal–epidermal connectivity and keeping the dermis and the epidermis layer 89 well connected. In addition, they increase the overall number of hemidesmosomes at the DEJ and 90 subsequently improve the strength of the interface and of the mechanical properties of skin [23,24]. Biomolecules 2020, 10, x FOR PEER REVIEW 3 of 32 A Epidermis Rete-ridges Dermal papillae Dermis B Micro-vessels 91 92 93 Figure 1. Histological section of human skin showing the undulated structure of the dermal-epidermal 94 junction with epidermal rete-ridges and dermal papillae. Section of a paraffin‐embedded skin biopsy from the 95 abdomen of a 30 years old donor was processed for HES staining. (A) Epidermis, dermis, rete-ridges and dermal 96 papillae are shown. (B) Micro-vessels are shown within dermal papillae. Scale bars = 100 μm. 97 98 Rete ridges surround the dermal papillae, which can be seen as small extensions protruding 99 from the papillary dermis within the epidermis. These two structures are perfectly embedded; the 100 alternation of a rete ridge with a dermal papilla creates
Load more

Recommended publications
  • Te2, Part Iii
    TERMINOLOGIA EMBRYOLOGICA Second Edition International Embryological Terminology FIPAT The Federative International Programme for Anatomical Terminology A programme of the International Federation of Associations of Anatomists (IFAA) TE2, PART III Contents Caput V: Organogenesis Chapter 5: Organogenesis (continued) Systema respiratorium Respiratory system Systema urinarium Urinary system Systemata genitalia Genital systems Coeloma Coelom Glandulae endocrinae Endocrine glands Systema cardiovasculare Cardiovascular system Systema lymphoideum Lymphoid system Bibliographic Reference Citation: FIPAT. Terminologia Embryologica. 2nd ed. FIPAT.library.dal.ca. Federative International Programme for Anatomical Terminology, February 2017 Published pending approval by the General Assembly at the next Congress of IFAA (2019) Creative Commons License: The publication of Terminologia Embryologica is under a Creative Commons Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0) license The individual terms in this terminology are within the public domain. Statements about terms being part of this international standard terminology should use the above bibliographic reference to cite this terminology. The unaltered PDF files of this terminology may be freely copied and distributed by users. IFAA member societies are authorized to publish translations of this terminology. Authors of other works that might be considered derivative should write to the Chair of FIPAT for permission to publish a derivative work. Caput V: ORGANOGENESIS Chapter 5: ORGANOGENESIS
    [Show full text]
  • Expression of Integrins and Basement Membrane Components by Wound Keratinocytes
    Expression of integrins and basement membrane components by wound keratinocytes. H Larjava, … , R H Kramer, J Heino J Clin Invest. 1993;92(3):1425-1435. https://doi.org/10.1172/JCI116719. Research Article Extracellular matrix proteins and their cellular receptors, integrins, play a fundamental role in keratinocyte adhesion and migration. During wound healing, keratinocytes detach, migrate until the two epithelial sheets confront, and then regenerate the basement membrane. We examined the expression of different integrins and their putative ligands in keratinocytes during human mucosal wound healing. Migrating keratinocytes continuously expressed kalinin but not the other typical components of the basement membrane zone: type IV collagen, laminin, and type VII collagen. When the epithelial sheets confronted each other, these missing basement membrane components started to appear gradually through the entire wound area. The expression of integrin beta 1 subunit was increased in keratinocytes during migration. The beta 1-associated alpha 2 and alpha 3 subunits were expressed constantly by wound keratinocytes whereas the alpha 5 subunit was present only in keratinocytes during reepithelialization. Furthermore, migrating cells started to express alpha v-integrins which were not present in the nonaffected epithelium. All keratinocytes also expressed the alpha 6 beta 4 integrin during migration. In the migrating cells, the distribution of integrins was altered. In normal mucosa, beta 1-integrins were located mainly on the lateral plasma membrane and alpha 6 beta 4 at the basal surface of basal keratinocytes in the nonaffected tissue. In wounds, integrins were found in filopodia of migrating keratinocytes, and also surrounding cells in […] Find the latest version: https://jci.me/116719/pdf Expression of Integrins and Basement Membrane Components by Wound Keratinocytes Hannu Lariava, * Tuula Salo,t Kirsi Haapasalmi, * Randall H.
    [Show full text]
  • Nomina Histologica Veterinaria, First Edition
    NOMINA HISTOLOGICA VETERINARIA Submitted by the International Committee on Veterinary Histological Nomenclature (ICVHN) to the World Association of Veterinary Anatomists Published on the website of the World Association of Veterinary Anatomists www.wava-amav.org 2017 CONTENTS Introduction i Principles of term construction in N.H.V. iii Cytologia – Cytology 1 Textus epithelialis – Epithelial tissue 10 Textus connectivus – Connective tissue 13 Sanguis et Lympha – Blood and Lymph 17 Textus muscularis – Muscle tissue 19 Textus nervosus – Nerve tissue 20 Splanchnologia – Viscera 23 Systema digestorium – Digestive system 24 Systema respiratorium – Respiratory system 32 Systema urinarium – Urinary system 35 Organa genitalia masculina – Male genital system 38 Organa genitalia feminina – Female genital system 42 Systema endocrinum – Endocrine system 45 Systema cardiovasculare et lymphaticum [Angiologia] – Cardiovascular and lymphatic system 47 Systema nervosum – Nervous system 52 Receptores sensorii et Organa sensuum – Sensory receptors and Sense organs 58 Integumentum – Integument 64 INTRODUCTION The preparations leading to the publication of the present first edition of the Nomina Histologica Veterinaria has a long history spanning more than 50 years. Under the auspices of the World Association of Veterinary Anatomists (W.A.V.A.), the International Committee on Veterinary Anatomical Nomenclature (I.C.V.A.N.) appointed in Giessen, 1965, a Subcommittee on Histology and Embryology which started a working relation with the Subcommittee on Histology of the former International Anatomical Nomenclature Committee. In Mexico City, 1971, this Subcommittee presented a document entitled Nomina Histologica Veterinaria: A Working Draft as a basis for the continued work of the newly-appointed Subcommittee on Histological Nomenclature. This resulted in the editing of the Nomina Histologica Veterinaria: A Working Draft II (Toulouse, 1974), followed by preparations for publication of a Nomina Histologica Veterinaria.
    [Show full text]
  • Nails Develop from Thickened Areas of Epidermis at the Tips of Each Digit Called Nail Fields
    Nail Biology: The Nail Apparatus Nail plate Proximal nail fold Nail matrix Nail bed Hyponychium Nail Biology: The Nail Apparatus Lies immediately above the periosteum of the distal phalanx The shape of the distal phalanx determines the shape and transverse curvature of the nail The intimate anatomic relationship between nail and bone accounts for the bone alterations in nail disorders and vice versa Nail Apparatus: Embryology Nail field develops during week 9 from the epidermis of the dorsal tip of the digit Proximal border of the nail field extends downward and proximally into the dermis to create the nail matrix primordium By week 15, the nail matrix is fully developed and starts to produce the nail plate Nails develop from thickened areas of epidermis at the tips of each digit called nail fields. Later these nail fields migrate onto the dorsal surface surrounded laterally and proximally by folds of epidermis called nail folds. Nail Func7on Protect the distal phalanx Enhance tactile discrimination Enhance ability to grasp small objects Scratching and grooming Natural weapon Aesthetic enhancement Pedal biomechanics The Nail Plate Fully keratinized structure produced throughout life Results from maturation and keratinization of the nail matrix epithelium Attachments: Lateral: lateral nail folds Proximal: proximal nail fold (covers 1/3 of the plate) Inferior: nail bed Distal: separates from underlying tissue at the hyponychium The Nail Plate Rectangular and curved in 2 axes Transverse and horizontal Smooth, although
    [Show full text]
  • Basement Membrane
    J Clin Pathol: first published as 10.1136/jcp.s3-12.1.59 on 1 January 1978. Downloaded from J. clin. Path., 31, Suppl. (Roy. Coll. Path.), 12, 59-66 Basement membrane JOHN T. IRELAND From the Southern General Hospital, Glasgow, and the University of Glasgow Basement membrane has attracted less attention will be reviewed with the aim of providing new than the other components of connective tissue. But, insight into the function of basement membrane in like the other extracellular fibres and matrix health and disease. materials, it can profoundly influence both the structure and function of advanced life forms. Basement membrane turnover Usually taking the shape of thin, structureless cementing material between epithelial and con- Much evidence has accumulated from various nective tissue, basement membranes are widely sources (Farquhar et al., 1961; Andres et al., 1962; distributed throughout the body. They are found Kurtz and Feldman, 1962; Vernier, 1964; Pierce, as extracellular components of blood capillaries, 1966; Thoenes, 1967; Lee et al., 1969; Walker, 1973) renal glomeruli and tubules, alveoli, retina, lens to show that visceral epithelium is responsible for capsule, muscle parasarcolemma, sweat glands, basement membrane synthesis (Fig. 2). Until recently, Schwann cells, and breast ducts. Although sharing however, its rate of turnover had been less clear. The similar morphological, biochemical, and antigenic elegant, long-termsequentialstudiesof Walker (1973), properties, basement membrane can be developed using the argyric technique, confirmed the view that for different functions in special situations. In the turnover is slow. Clearance of silver from the rat lens capsule of the eye, for example, it provides glomerulus is exclusively undirectional from the copyright.
    [Show full text]
  • The Nail Bed, Part I. the Normal Nail Bed Matrix, Stem Cells, Distal Motion and Anatomy
    Central Journal of Dermatology and Clinical Research Review Article *Corresponding author Nardo Zaias, Department of Dermatology Mount Sinai Medical Center, Miami Beach, FL. 33140, 4308 The Nail Bed, Part I. The Normal Alton rd. Suite 750, USA, Email: [email protected] Submitted: 25 November 2013 Nail Bed Matrix, Stem Cells, Distal Accepted: 28 December 2013 Published: 31 December 2013 Copyright Motion and Anatomy © 2014 Zaias Nardo Zaias* OPEN ACCESS Department of Dermatology Mount Sinai Medical Center, USA Abstract The nail bed (NB) has its own matrix that originates from distinctive stem cells. The nail bed matrix stem cells (NBMSC) lie immediately distal to the nail plate (NP) matrix cells and are covered by the keratogenous zone of the most distal NPM (LUNULA). The undivided NBMS cells move distally along the NB basement membrane toward the hyponychium; differentiating and keratinizing at various locations, acting as transit amplifying cells and forming a thin layer of NB corneocytes that contact the overlying onychocytes of the NP, homologous to the inner hair root sheath. At the contact point, the NB corneocytes express CarcinoEmbryonic Antigen (CEA), a glycoprotein-modulating adherence which is also found in hair follicles and tumors. Only when both the NP and the NB are normal do they synchronously move distally. The normal NB keratinizes, expressing keratin K-5 and K-17 without keratohyaline granules. However, during trauma or disease states, it reverts to keratinization with orthokeratosis and expresses K-10, as seen in developmental times. Psoriasis is the only exception. Nail Bed epidermis can express hyperplasia and giant cells in some diseases.
    [Show full text]
  • Science of the Nail Apparatus David A.R
    1 CHAPTER 1 Science of the Nail Apparatus David A.R. de Berker 1 and Robert Baran 2 1 Bristol Dermatology Centre , Bristol Royal Infi rmary , Bristol , UK 2 Nail Disease Center, Cannes; Gustave Roussy Cancer Institute , Villejuif , France Gross anatomy and terminology, 1 Venous drainage, 19 Physical properties of nails, 35 Embryology, 3 Effects of altered vascular supply, 19 Strength, 35 Morphogenesis, 3 Nail fold vessels, 19 Permeability, 35 Tissue differentiation, 4 Glomus bodies, 20 Radiation penetration, 37 Factors in embryogenesis, 4 Nerve supply, 21 Imaging of the nail apparatus, 37 Regional anatomy, 5 Comparative anatomy and function, 21 Radiology, 37 Histological preparation, 5 The nail and other appendages, 22 Ultrasound, 37 Nail matrix and lunula, 7 Phylogenetic comparisons, 23 Profi lometry, 38 Nail bed and hyponychium, 9 Physiology, 25 Dermoscopy (epiluminescence), 38 Nail folds, 11 Nail production, 25 Photography, 38 Nail plate, 15 Normal nail morphology, 27 Light, 40 Vascular supply, 18 Nail growth, 28 Other techniques, 41 Arterial supply, 18 Nail plate biochemical analysis, 31 Gross anatomy and terminology with the ventral aspect of the proximal nail fold. The intermediate matrix (germinative matrix) is the epithe- Knowledge of nail unit anatomy and terms is important for lial structure starting at the point where the dorsal clinical and scientific work [1]. The nail is an opalescent win- matrix folds back on itself to underlie the proximal nail. dow through to the vascular nail bed. It is held in place by The ventral matrix is synonymous with the nail bed the nail folds, origin at the matrix and attachment to the nail and starts at the border of the lunula, where the inter- bed.
    [Show full text]
  • 433 Dermatology Team Structure of Skin
    433 Dermatology Team structure of skin Lecture (4) Structure of skin [email protected] 1 | P a g e 433 Dermatology Team structure of skin Objectives: • To be familiar with the different structures of the skin. • To have basic knowledge of anatomy and function of the skin. • To be familiar with different tools to investigate skin disorders. • The relation between anatomy and diseases. • To have a general idea about different therapeutic options used in dermatology practice. Color index: slides, doctor notes, 432 notes 2 | P a g e 433 Dermatology Team structure of skin Functions of Skin: Prevent infections via innate and adaptive immunity Maintain a barrier Repair injury Provide circulation Communicate Provide nutrition Regulate temperature Attract attention Pathologies affecting functions of skin: Infections Autoimmunity Cancers Dehydration Eczema Ulcers Infarction Vasculitis Sensory neuropathy Pruritus Vitiligo Alopecia Hyperthermia Vitamin D deficiency The Skin as an organ: General structure and embryological origins Epidermis (ectoderm) Dermal- Epidermal junction is called basement membrane, Weakest part in the skin usual site of blisters Dermis (mesoderm) Subcutaneous fat and skin appendages (ectoderm and mesoderm Palms, soles, genitalia and scalp skin have slightly different structure 3 | P a g e 433 Dermatology Team structure of skin Epidermis: • Keratinocytes: 95% of the cells in epidermis. Division of these cells only occur in the basal layer where 10% of them are stem cells. • The normal transit time of a differentiating keratinocyte from basal layer to the outer surface of the stratum corneum is 28 days. (in psoriasis it is much shorter). • The epidermis doesn’t have blood vessels it obtains its nutrients from the blood vessel of dermis diffusing through the dermoeoidermal junction (papillary layer of dermis).
    [Show full text]
  • Fascia: a Morphological Description and Classification System Based on a Literature Review Myroslava Kumka, MD, Phd* Jason Bonar, Bsckin, DC
    0008-3194/2012/179–191/$2.00/©JCCA 2012 Fascia: a morphological description and classification system based on a literature review Myroslava Kumka, MD, PhD* Jason Bonar, BScKin, DC Fascia is virtually inseparable from all structures in Le fascia est pratiquement inséparable de toutes les the body and acts to create continuity amongst tissues structures du corps, et il sert à créer une continuité to enhance function and support. In the past fascia entre les tissus afin d’en améliorer la fonction et le has been difficult to study leading to ambiguities in soutien. Il a déjà été difficile d’étudier le fascia, ce qui nomenclature, which have only recently been addressed. a donné lieu à des ambiguïtés dans la nomenclature, Through review of the available literature, advances qui n’ont été abordées que récemment. Grâce à un in fascia research were compiled, and issues related examen de la documentation disponible, les avancées to terminology, descriptions, and clinical relevance of dans la recherche sur le fascia ont été compilées, fascia were addressed. Our multimodal search strategy et les problèmes relevant de la terminologie, des was conducted in Medline and PubMed databases, with descriptions et de la pertinence clinique du fascia ont été other targeted searches in Google Scholar and by hand, traités. Nous avons adopté une stratégie de recherche utilizing reference lists and conference proceedings. multimodale pour nos recherches dans les bases de In an effort to organize nomenclature for fascial données Medline et PubMed, avec des recherches ciblées structures provided by the Federative International dans Google Scholar et manuelles, au moyen de listes de Committee on Anatomical Terminology (FICAT), we références et de comptes rendus de congrès.
    [Show full text]
  • Dermis (Ectoderm), Basement Membrane, Dermis (Mesoderm), Subcutaneous Fat and Skin Appendages (Ectoderm and Mesoderm)
    Lecture (1) Structures and functions of the skin. (basic anatomy and physiology) [email protected] Color index: slides, doctor notes, 432 notes, Doctor’s notes (group F) Objectives To know the normal skin structure. To be able to take proper history. To be able to describe lesions by using proper dermatological terminology. To be able to formulate a differential diagnosis. To be able to diagnose and treat common skin disorders. To be familiar with dermatologic emergencies Color index: slides, doctor notes, 432 notes, Doctor’s notes (group F) Introduction The skin is a complex, dynamic organ. The skin is the largest organ of the human body (1.75 m2), and the weight about 15% of the body It consists of many cell types called Keratinocytes and Specialized structures like “the Basement Membrane” Dermal- Epidermal junction is called basement membrane, the weakest part in the skin and the usual site of blisters. It serves multiple functions that are crucial to health and survival. It is divided into epidermis (ectoderm), basement membrane, dermis (mesoderm), subcutaneous fat and skin appendages (ectoderm and mesoderm). Function Barrier to harmful exogenous substance & pathogens Prevents loss of water & proteins Sensory organ protects against physical injury Regulates body temperature Important component of immune system Vitamin D production by absorbing UVB Has psychological and cosmetic importance such as hair, nails Color index: slides, doctor notes, 432 notes, Doctor’s notes (group F) Epidermis Anchors it to the dermis (وتد) Epidermal peg The epidermis consists of several layers and many cells 95% are Keratinocytes, and other prominent cells are melanocytes, Langerhans cells, and markels cells.
    [Show full text]
  • The Significance of Reciprocal Induction Relations Between the Derivates of Nephrogenic Mesoderm
    Rom J Leg Med [22] 199-208 [2014] DOI: 10.4323/rjlm.2014.199 © 2014 Romanian Society of Legal Medicine The significance of reciprocal induction relations between the derivates of nephrogenic mesoderm. Implications in pathology and regeneration Gheorghe S. Dragoi1,*, Petru Razvan Melinte2, Ileana Dinca2, Elena Patrascu2, Serban A. Dragoi3 _________________________________________________________________________________________ Abstract: Functional capacity of renal excretory biosystem is assured by remarkable complex structures: glomerular basal membrane for ultrafiltration of blood plasma, tubular system of the nephron for resorption-secretion processes and juxtaglomerular complex for self-balancing.The purpose of the paper is to draw the attention of histopathologists over the phenotypic transformation of metanephrogen mesenchyme and over the relations between derivates of this mesenchyme in the ontogenesis process, with implications in pathology and regeneration. Authors conducted this study and, by classical microanatomic methods, they highlighted the structural heterogeneity of renal cortex, the phenotypic variability of glomerular capillary network, the spatial distribution and the relations of intraglomerular mesangial matrix Based on personal observations, authors notice the fact that only a proper acknowledgement of reciprocal induction relations consequences between ureteric bud emerged from mesonephros and metanephrogenic blastema allows the understanding of renal parenchyma structural particularities and the determinant factors
    [Show full text]
  • Structure and Function of the Skin
    2 Structure and Function of the Skin Skin disease illustrates structure and function. Loss of or Chapter Contents defects in skin structure impair skin function. Skin dis­ ease is discussed in more detail in the other chapters. ● Epidermis ● Structure ● Other Cellular Components EPIDERMIS ● Dermal–Epidermal Junction – The Basement Membrane Zone ● Dermis ● Skin Appendages Key Points ● Subcutaneous Fat 1. Keratinocytes are the principal cell of the epidermis 2. Layers in ascending order: basal cell, stratum spinosum, stratum granulosum, stratum corneum 3. Basal cells are undifferentiated, proliferating cells Key Points 4. Stratum spinosum contains keratinocytes connected by desmosomes 1. The major function of the skin is as a barrier to maintain 5. Keratohyalin granules are seen in the stratum granulosum internal homeostasis 6. Stratum corneum is the major physical barrier 2. The epidermis is the major barrier of the skin 7. The number and size of melanosomes, not melanocytes, determine skin color 8. Langerhans cells are derived from bone marrow and are the skin’s first line of immunologic defense ABSTRACT 9. The basement membrane zone is the substrate for attach- ment of the epidermis to the dermis The skin is a large organ, weighing an average of 4 kg and 10. The four major ultrastructural regions of the basement covering an area of 2 m2. Its major function is to act as membrane zone include the hemidesmosomal plaque of a barrier against an inhospitable environment – to pro­ the basal keratinocyte, lamina lucida, lamina densa, and tect the body from the influences of the outside world. anchoring fibrils located in the sublamina densa region of The importance of the skin is well illustrated by the high the papillary dermis mortality rate associated with extensive loss of skin from burns.
    [Show full text]