Human Cell Energy Production Quiz
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Questions and Answers

What is the primary source of energy utilized by human cells?

  • Glucose (correct)
  • Nucleic acids
  • Fat
  • Protein
  • Which process is responsible for the generation of ATP from ADP?

  • Lipid metabolism
  • Oxidative phosphorylation (correct)
  • Glycolysis
  • Protein synthesis
  • Where does glycolysis occur in human cells?

  • Mitochondria
  • Nucleus
  • Cytoplasm (correct)
  • Endoplasmic reticulum
  • Which enzyme is NOT classified as an endogenous antioxidant?

    <p>Lipoxygenase</p> Signup and view all the answers

    What can result from the deficiency of superoxide dismutase (SOD)?

    <p>Premature aging</p> Signup and view all the answers

    Which of the following statements about reactive oxygen species (ROS) is true?

    <p>ROS can cause irreversible modification to cellular components.</p> Signup and view all the answers

    What happens during lipid peroxidation caused by ROS?

    <p>It generates harmful downstream products.</p> Signup and view all the answers

    What role does ATP play in the cell?

    <p>It functions as the universal energy currency.</p> Signup and view all the answers

    What is the primary reason lipid peroxyl radicals are considered more dangerous than reactive oxygen species (ROS)?

    <p>They remain reactive far from their origin.</p> Signup and view all the answers

    What percentage of ATP production is attributed to oxidative phosphorylation within the mitochondrion?

    <p>90%</p> Signup and view all the answers

    Why is the ROS theory of ageing important in understanding cellular biology?

    <p>It suggests ageing results from oxidative stress due to aerobic metabolism.</p> Signup and view all the answers

    What role do antioxidants play in cellular protection?

    <p>They inhibit or reverse oxidation by donating electrons.</p> Signup and view all the answers

    Which of the following vitamins is an example of a lipophilic antioxidant?

    <p>Vitamin E</p> Signup and view all the answers

    What happens to antioxidants after they donate electrons?

    <p>They are no longer active and need to be regenerated.</p> Signup and view all the answers

    What is recommended for the effectiveness of antioxidants in cosmetic products?

    <p>Employing mixtures of different antioxidants.</p> Signup and view all the answers

    What is a characteristic of oxidized forms of antioxidants?

    <p>They are permanently oxidized and cannot regenerate.</p> Signup and view all the answers

    What defines oxidative stress?

    <p>There is an imbalance between free radical production and the neutralization by antioxidants.</p> Signup and view all the answers

    Which of the following is an example of a reactive oxygen species (ROS)?

    <p>Hydrogen peroxide (H2O2)</p> Signup and view all the answers

    What is a pro-oxidant?

    <p>Any substance that promotes the production of free radicals.</p> Signup and view all the answers

    Which of the following statements about free radicals is incorrect?

    <p>Free radicals have all their electrons paired in their outer orbital.</p> Signup and view all the answers

    Which factor is most directly responsible for oxidative damage in cells?

    <p>An imbalance of free radicals due to oxidative stress.</p> Signup and view all the answers

    Which of the following represent types of oxygen free radicals?

    <p>Hydroxyl radical (OH) and superoxide (O2-)</p> Signup and view all the answers

    What causes free radicals to stabilize?

    <p>Pairing their unpaired electrons with other atoms or molecules.</p> Signup and view all the answers

    What characterizes reactive oxygen species (ROS)?

    <p>They contain at least one oxygen atom and can be free radicals or non-free radical intermediates.</p> Signup and view all the answers

    What is the primary component of the skin's lipid profile in relation to dry skin?

    <p>Ceramides</p> Signup and view all the answers

    Which lipids make up approximately 20% of the stratum corneum volume?

    <p>Lipids</p> Signup and view all the answers

    How much lipid must the skin generate daily to replace what is lost through desquamation?

    <p>100-150 mg</p> Signup and view all the answers

    What mechanism is suggested for the induction and propagation of dry skin conditions?

    <p>Cyclical model</p> Signup and view all the answers

    Which statement about the role of sebum in xerosis is accurate?

    <p>Sebum contributes but does not play a significant role.</p> Signup and view all the answers

    Which class of skin diseases is categorized as non-infectious?

    <p>Psoriasis</p> Signup and view all the answers

    What is the composition of epidermal ceramides primarily based on?

    <p>Sphingoid base linked to a fatty acid</p> Signup and view all the answers

    Which microorganism is NOT typically part of the normal skin flora?

    <p>Streptococci</p> Signup and view all the answers

    What percentage of the dry weight of the dermis is accounted for by Type 1 collagen?

    <p>80%</p> Signup and view all the answers

    Which cofactors are necessary for the enzyme activity of lysyl and prolyl hydroxylase?

    <p>Fe(II), 2-oxoglutarate, and ascorbate</p> Signup and view all the answers

    What happens to collagen production in chronologically aged skin?

    <p>Type 1 and type 3 collagen production is reduced.</p> Signup and view all the answers

    What are matrix-metalloproteinases (MMP) responsible for?

    <p>Degrading existing collagen in the extracellular matrix.</p> Signup and view all the answers

    What are advanced glycation end products (AGEs) primarily formed from?

    <p>Covalent attachment of free-sugar molecules to collagen.</p> Signup and view all the answers

    How do matrikines influence collagen production?

    <p>As signal peptides for enhanced collagen production.</p> Signup and view all the answers

    What is the role of the alkyl chain (C 16) in Palmitoyl tripeptide?

    <p>Enhances stability and penetration of the peptide.</p> Signup and view all the answers

    What is a common consequence of collagen glycation over time?

    <p>Formation of cross-links between collagen molecules.</p> Signup and view all the answers

    What is a characteristic feature of psoriasis?

    <p>It is an autoimmune condition involving T lymphocytes.</p> Signup and view all the answers

    Which of the following is a precipitating factor for psoriasis?

    <p>Genetic influences</p> Signup and view all the answers

    What percentage of the population in Europe and North America is affected by psoriasis?

    <p>2%</p> Signup and view all the answers

    How does the cell proliferation rate in psoriatic skin compare to normal skin?

    <p>It is 20 times higher or more.</p> Signup and view all the answers

    Which type of eczema is associated with a personal or family history of asthma?

    <p>Atopic eczema</p> Signup and view all the answers

    What primary immune factor is elevated in atopic eczema?

    <p>IgE</p> Signup and view all the answers

    Which is not classified as an endogenous type of eczema?

    <p>Irritant dermatitis</p> Signup and view all the answers

    In psoriatic skin, how long does it typically take for a cell to reach the surface compared to normal skin?

    <p>6-8 days in psoriatic skin, 40-56 days in normal</p> Signup and view all the answers

    What term describes the inflammation of the skin that can be caused by both internal and external factors?

    <p>Dermatitis</p> Signup and view all the answers

    Which of the following is a common trigger for atopic eczema?

    <p>Animal dander</p> Signup and view all the answers

    Study Notes

    Introduction to Healthy, Distressed, and Diseased Skin

    • The study examines healthy, distressed, and diseased skin.
    • The presenter outlines topics like biochemical processes affecting skin appearance, cosmetics' impact, skin conditions, and common skin diseases.

    Content Outline

    • Biochemical processes: Keratinisation, melanin production, sebum and sweat production, blood supply, wound healing, immune function, and inflammatory responses are discussed.
    • Cosmetics: The role of cosmetics in relation to skin conditions is explored.
    • Skin conditions: Examples such as jaundice, palmar erythema, and acanthosis nigricans are presented.
    • Skin diseases: Some common skin diseases, both infectious and non-infectious, are introduced for self-study.

    Skin – a Window to Health

    • Skin reflects the inner workings of the body.
    • Biochemical imbalances can manifest as visible changes on the skin (e.g., jaundice, redness).

    Biochemical Processes Affecting Skin Appearance

    • Keratinisation: The process of keratin formation in the skin.
    • Melanin production: The production of pigment in the skin.
    • Sebum and Sweat Production: The functions and effects of sebum and sweat on the skin.
    • Blood supply to skin: The importance of blood flow in skin health.
    • Wound healing: Aspects of wound healing and repair.
    • Immune Function: Role of the immune system within the skin.
    • Inflammatory responses: How the skin responds to inflammation.
    • Oxidative stress: A key factor impacting skin health, impacting oxidative stress, desquamation, stratum corneum regeneration, and the integrity of the dermis

    Biochemical Events Negatively Affecting Skin Health

    • Extrinsic factors: Factors such as sun exposure, temperature, humidity, and pH changes affecting skin biochemical processes.
    • Intrinsic factors: Factors like skin microflora, nutrition (including proteins, carbohydrates, fats, vitamins, and minerals), hydration, gene and protein expression, and hormone changes affecting skin biochemical processes.
    • Oxidative stress: The imbalance between free radical production and antioxidant capacity, damaging cells and contributing to aging.
    • Irregular desquamation: Problems in skin shedding linked to moisture, pH, and bacteria.
    • Impaired SC regeneration: The reduced ability of the stratum corneum to regenerate, associated with the loss of collagen, elastin, and hyaluronic acid
    • Loss of dermal integrity: Reduced structural support due to diminished collagen, elastin, and hyaluronic acid.
    • Inflammation (not covered today): Inflammatory processes affecting skin health.
    • UV damage: Damage caused by ultraviolet radiation (not covered today).

    Oxidation: Oxidative Stress

    • Oxidative stress occurs when free radical production exceeds the body's antioxidant capacity.
    • This causes damage to cells and tissues.
    • Oxidative damage is directly linked to harm sustained by excessive free radicals.

    Terminology: Radical/Free Radical

    • A molecule or atom with an unpaired electron and can be neutral, positively or negatively charged.
    • Chlorine (Cl) is an example where the outer electron shell is not completely filled, forming a Cl free radical
    • Oxygen free radicals (such as alkoxyl, peroxyl, and hydroperoxyl) are further examples and have a high impact on human health

    Terminology: ROS (Reactive Oxygen Species)

    • Highly reactive oxygen molecules or ions containing at least one oxygen atom.
    • Examples include hydrogen peroxide (H₂O₂), superoxide (O₂⁻), and hydroxyl radical (OH⁻).
    • N-based ROS, such as nitric oxide (NO) and nitrogen dioxide (NO₂), are also presented.
    • Pro-oxidants induce oxidative stress either by generating ROS or inhibiting antioxidant systems.

    Cellular Energy Production

    • Glucose is the primary energy source in human cells.
    • Glycolysis is the initial process, breaking down glucose to release energy.
    • The process ultimately aims to create ATP from ADP.
    • Oxidative phosphorylation occurs in mitochondria to create ATP.
    • ATP is the universal energy currency for cellular functions.

    Cellular Damage and Removal of ROS

    • Free radicals from ROS cause uncontrolled damage to proteins, lipids, and DNA, which can lead to broader damage within cells linked to aging.
    • Endogenous antioxidants, such as superoxide dismutase (SOD), glutathione peroxidase, and catalase, eliminate ROS by converting them into water.
    • SOD deficiency impacts aging due to the accumulation of oxidative stress.

    Example of Oxidative Damage: Lipid Peroxidation

    • ROS damages lipids and generates downstream products like lipid peroxidation radicals.
    • Lipid peroxyl radicals have a high impact on cells through the skin's membrane and can induce widespread cellular damage.

    ROS Theory of Aging

    • The electron transport chain is crucial for ATP production.
    • An impaired chain can increase reactive oxygen species leading to oxidative stress contributing to skin aging.
    • Oxidative damage to cells and tissues linked to aerobic metabolism initiates the aging process.

    Oxidative Damage Pathway

    • ROS damage lipids, proteins, and nucleic acids.
    • Antioxidants help repair these damages.

    Antioxidant & Electron Donation

    • Antioxidants donate electrons to free radicals to stabilize them.

    Protection from ROS: Small Molecule, Non-enzymatic Antioxidants

    • Antioxidants inhibit or reverse the oxidation of molecules by becoming oxidised themselves.
    • Examples of antioxidants, such as vitamin E (lipophilic) and vitamin C(hydrophilic), can enhance skin penetration.
    • Stability and functionality of antioxidants vary.
    • Mixtures of antioxidants are beneficial compared to single ones in skin care products.

    Oxidized Forms of Antioxidants

    • Donating electrons makes antioxidants inactive.
    • Oxidized forms become stable due to electron resonance.
    • Regenerative processes are required for antioxidants to regain activity.

    Antioxidant Regeneration

    • Antioxidants can be regenerated by other antioxidants.
    • Vitamins C and E can regenerate each other synergistically.
    • Glutathione can reduce vitamins C and E.
    • Enzymes, such as glutathione reductase, regenerate oxidized glutathione.

    Phytochemicals - Antioxidants

    • Plants utilize various antioxidants for protection from UV exposure, which help maintain membrane fluidity.
    • Several notable examples include beta-carotene, carotenoids, ascorbic acid, tocopherols, polyphenols, and melatonin.
    • These compounds often are brightly colored.

    Abnormal Levels of Oxidative Stress

    • Basal oxidative stress is necessary for cell survival.
    • Excessive oxidative stress (above basal levels) causes cell damage and premature aging.
    • Oxidative stress can be triggered by factors including physical exercise, increased calorie consumption, UV light, smoking, and ozone exposure.
    • Air pollution is another source.

    Extrinsic Oxidative Stress - Air Pollution

    • Ozone exposure depletes skin's tocopherol and vitamin C levels and causes lipid peroxidation.
    • Particulate matter increases metalloproteinases, degrading collagen and causing inflammation.
    • Topical application of antioxidants like vitamin C, E, and ferulic acid offers protection against this environmental stress.

    ROS & Other Factors Affecting Stem Cells

    • Impaired DNA and protein repair mechanisms in aging stem cells can be caused by ROS.
    • Existing mechanisms for stem cell aging are due to the exhaustion of supporting cells, chronic inflammation, circulating factors, and the aggregation of damaged proteins and mitochondrial dysfunction.
    • Methods to improve stem cell proteostasis and enhance mitochondrial function have been suggested.

    Desquamation: Facts

    • Stratum corneum sheds regularly at a rate of 0.7 kg per year in an average person.
    • Exfoliation, both chemical and physical, can assist in the desquamation process.
    • Hydration, pH, skin microflora, and inflammation affect the rate of desquamation.

    Desquamation: Mechanism

    • Corneocytes are interconnected through corneodesmosomes.
    • Desquamation follows by the elimination of corneocytes at the skin surface.

    Desquamation: Proteases Involved

    • The enzyme family kallikreins (KLKs) plays a major role in desquamation, alongside other proteases.
    • They are secreted by granular keratinocytes and cleave amino-terminal peptides for activation.
    • Activated KLKs cleave corneodemosomes to enable desquamation.
    • The enzyme family LEKTI inhibits KLK activity to maintain balance and prevent uncontrolled desquamation.
    • KLK activity is higher in more acidic conditions.

    Kallikreins

    • A family of serine proteases, essential in protein cleavage.
    • Function as a cascade to amplify their effects.
    • Activity is influenced by skin hydration.
    • Increased levels can lead to increased desquamation, observed in conditions like psoriasis and atopic eczema.

    Stratum Corneum Regeneration: Facts

    • Corneocytes turnover every 28 days, on average.
    • Stem cells continually divide to maintain the cell pool and compensate for cell loss.
    • Cells are limited in the number of divisions they can undergo.
    • A decline in active stem cells can affect skin regeneration, particularly in older age.

    The Integrity of Dermis: Facts

    • Older skin shows deeper wrinkles in the dermis.
    • Younger dermis shows consistent collagen and elastin fibers and a higher hydrated state.
    • The integrity of the dermis is affected by decreased collagen and elastin fibers and a lower amount of hydration.

    Collagen

    • Collagen is made up of three polypeptide alpha chains.
    • Type 1 collagen accounts for about 80% of the total collagen in the skin.
    • Certain enzymes (lysl and prolyl hydroxylase) modify collagen by forming 4-hydroxyproline making it more stable, and require certain essential micronutrients like iron (Fe), 2-oxoglutarate, and ascorbate (vit C).

    Collagen: Role, Synthesis, and Aging

    • Collagen provides structure, strength, and firmness to the dermis.
    • Collagen is important in skin healing.
    • Collagen production declines with age, leading to disorganisation and reduced collagen integrity.

    Collagen Degradation: MMP

    • Matrix metalloproteinases (MMPs) break down damaged proteins in the extracellular matrix.
    • Increased MMP activity leads to collagen degradation and reduced skin elasticity, especially in aged or photoaged skin.

    Collagen: Glycation and AGEs

    • Collagen can attach to free sugars via glycation, a non-enzymatic action.
    • This process creates advanced glycation end products (AGEs).
    • AGEs cause cross-linking and loss in skin elasticity.

    Matrikines

    • Matrikines are oligopeptides derived from extracellular matrix degradation.
    • They can act as signaling peptides to enhance collagen and elastin production.
    • Examples like palmitoyl tripeptide include a specific sequence of amino acids that act as a messenger peptide to promote collagen renewal.

    Elastin and Aging

    • Elastin fibers provide elasticity and flexibility in the dermis.
    • Elastin biosynthesis is relatively stable in younger individuals (0-30-40 years) and subsequently declines.
    • Capacity to regenerate elastin decreases with age.

    Hyaluronic Acid

    • Crucial component in dermis that accounts for only 1-3% of the total weight of the dermis.
    • Effectively binds to water and provides hydration support.
    • Its large size prevents its penetration through the stratum corneum when applied externally.

    What Can Cosmetics Do?

    • Cosmetics are substances for external application to human parts including body and face to clean, perfume, improve appearance, and or protect.
    • They can treat skin conditions but not diseases.

    Skin Disorder: Dry Skin (Xerosis)

    • Dry skin is a common condition, congenital or acquired.
    • It varies from mild to severe.
    • It affects people across demographics and presents a significant interest area of research for cosmetics scientists to understand the underlying causes and develop treatment options.

    The Role of Water in the Stratum Corneum

    • Water is essential in hydrating the stratum corneum to maintain flexibility.
    • Water content is important in the processes of SC maturation and desquamation

    What is Dry Skin?

    • Dry skin is characterized by decreased water content in the stratum corneum (approximated at 10% of typical water content in the skin).
    • Dry skin results from increased transepidermal water loss (TEWL) due to barrier dysfunction.
    • Factors like low sebum production and age can exacerbate dry skin.
    • Dry skin is usually not considered a disease, and most instances are not pathological.

    Critical Steps in the Formation of the Stratum Corneum

    • Progressive degradation and desquamation of corneodesmosomes
    • Transglutaminase-mediated corneocyte strengthening
    • Dehydration triggers and conversion of filaggrin to Natural Moisturizing Factor (NMF)
    • Acidification and lipid lamellar bilayer formation.
    • Lamellar granule formation and lipid precursors
    • Keratohyalin formation and Natural Moisturizing Factor (NMF) precursor profilaggrin
    • Transglutaminase-mediated corneocyte envelope formation
    • Cells linking through desmosomes.

    Natural Moisturizing Factor (NMF)

    • Water-retaining substances in the epidermis.
    • Filaggrin hydrolysis is the source of NMF in the skin.
    • Key components include free amino acids, lactic acid, PCA, urea, urocanic acids, sugars, and various ions (sodium, potassium, calcium, magnesium, chloride, citrate, phosphate, and formate).
    • NMF constitutes a substantial component of the stratum corneum, contributing to the water content.

    SC Lipids

    • Lipids in the stratum corneum make up approximately 20% of its volume.
    • Lipids are arranged in intercellular lamellar sheets.
    • The main lipid components are ceramides (50%), cholesterol (25%), and fatty acids (10-20%).
    • Skin must produce about 100-150mg of lipids daily to compensate for the lipids lost from desquamation.
    • Sebum levels are not a significant factor in dry skin.

    Structure of Ceramides

    • Ceramides are composed of a sphingolipid base (e.g., sphingosine), a fatty acid, and an amide linkage.
    • Different classes of ceramides exist, varying in hydroxylation patterns in the head group region.
    • These 'two-tail lipids' are an essential component of the stratum corneum.

    Epidermal Ceramides

    • Presents structural variations and combinations of different fatty acids.

    Organisation of Lamellar Sheets

    • Ceramides, cholesterol, and fatty acids form lamellar sheets in the intercellular spaces of the stratum corneum.
    • The arrangement and ratios of these components are key to maintaining skin barrier function.

    Arrangement of SC Bilayers

    • Stratum corneum bilayers are composed of ceramides, cholesterol, and fatty acids.
    • Ceramides form the core of the lamellae, while cholesterol and fatty acids are situated on the periphery maintaining stability and integrity for water retention

    Dry Skin Cycle

    • Dry skin is a cyclical process where barrier impairment, scratching, infection, and eczema bouts lead to further dry skin.
    • Intervention must target different points of the vicious cycle to resolve.

    Infectious Skin Diseases: Self-Study

    • Infectious skin conditions are caused by bacteria, viruses, or fungi.
    • Bacterial, viral, fungal, and infestation-related skin diseases are topics for self-study.

    Normal Skin Flora

    • Normal skin flora (microbiome) includes bacteria, microorganisms, yeasts, and mites.
    • Bacteria are widespread in the various parts of the skin.

    Distribution of Normal Flora

    • Bacterial populations and ratios vary by location on the body (e.g., back, forehead, and palms).
    • Skin types and environments (oily vs. dry) can impact the presence and ratio of the various skin bacteria

    Bacterial Infections (Staphylococcal and Streptococcal)

    • Staphylococcal infections (like those caused by Staph. aureus): often found in the nose, axillae, and perineum, and can directly or secondarily (when barrier is broken) affect the skin .
    • Streptococcal infections (like those by Streptococcus pyogenes) are primary pathogens of skin and may colonise damaged skin, sometimes originating in the nose.

    Folliculitis

    • Staphylococcal infections can cause folliculitis, affecting hair follicles.
    • Follicular pustules, particularly in areas with increased hair density (e.g., beards in men, lower legs in women), or related to poor hygiene are common symptoms.
    • Furuncles (boils) and Carbuncles (deep abscesses) are more severe forms of localised infection.

    Impetigo

    • Staphylococcal or streptococcal infection can cause impetigo, characterised by superficial skin blisters, particularly on the face.

    Other Bacterial Infections (Lyme Disease)

    • Lyme disease, caused by Borrelia burgdorferi, often starts with a slowly expanding red ring (erythema chronicum migrans) at the site of the tick bite.
    • The classic "bull's eye" rash does not always develop.

    Viral Infections

    • Herpes simplex, warts (caused by HPV), herpes zoster (shingles), and molluscum contagiosum are viral infections affecting the skin.
    • Several different types of HPV have been identified (e.g., types that cause common warts, plantar warts, and genital warts)

    Viral Warts

    • Warts are benign tumors caused by human papilloma virus (HPV) infection.
    • Different HPV types cause various wart types, affecting different areas of the body.

    Herpes Simplex

    • Herpes simplex is an acute viral infection causing cold sores/fever blisters.
    • These sores typically appear around the mouth and nose.
    • The infection often remains within the body, making recurring symptoms possible.

    Herpes Zoster (Shingles)

    • Herpes zoster is an infection along nerve pathways often in the thoracic area (chest/back).
    • Blisters usually appear on one side of the body and develop from a previous chickenpox infection.
    • It is generally painful.

    Disorders Caused by Fungi (Dermaphytes and Yeasts)

    • Fungal infections primarily affect skin and some internal tissues caused by dermaphytes (multicellular fungi) or yeasts (single-celled fungi).
    • Specific fungal infections like tinea capitis (scalp), tinea corporis (body), tinea pedis (feet-athlete's foot), tinea cruris (groin), and tinea unguium (nails) can depend on infection location.

    Candida Albicans

    • Candida albicans is a common yeast found in the mouth and gastrointestinal tract (GI).
    • It can cause opportunistic infections of the genitals (thrush), skin folds (intertrigo), nails, and in rare cases, systemic infections.

    How Many Legs? Insects or Mites?

    • Lice (head lice) and mites (scabies mites) cause skin infections and are identified by their multiple legs.

    Non-Infectious Conditions (Psoriasis)

    • Psoriasis is a common chronic skin condition leading to scaly skin patches.
    • It's immune-mediated and can affect the entire body.
    • Several types exist, with varying severity and locations. Environmental factors play a significant role in exacerbating or diminishing the affected condition.

    Epidermal Kinetics

    • The rate at which skin cells are produced.
    • Cell proliferation in psoriasis is significantly faster.

    Pathogenesis of Psoriasis

    • Factors that cause the condition, including environmental stress triggers, TNF-α, IL-1β, IL-6, TGFβ, and IL-23; along with dendritic cells and keratinocytes, all play key roles in initiating and sustaining psoriasis.

    Eczema/Dermatitis

    • Inflammation of the skin due to both internal and external factors.
    • Sometimes referred to as dermatitis.
    • Often mis-classified or mistakenly treated but has significant impact on affected individuals

    Atopic Eczema

    • A chronic inflammatory skin condition associated with a family history of allergic conditions or asthma.
    • Often caused by a cellular immunity deficiency and heightened IgE levels.
    • T-cell dysfunction can cause problems, with a prominent role in skin itching and uncontrolled scratching.

    Irritant Contact Dermatitis

    • Skin inflammation due to direct, negative effects of substances rather than an allergic reaction.
    • It can occur in 80% of occupational cases.
    • Irritants can be from chemicals, water, or abrassives.

    Severity of Dermatitis

    • Depends on irritant strength, duration of exposure, and individual susceptibility.
    • Environmental factors, like temperature and humidity, can also influence the severity.

    Allergic Contact Dermatitis

    • A form of delayed hypersensitivity reaction, characterized by a two-stage process: sensitization (the first exposure to the allergen) and elicitation (the subsequent exposure leading to a reaction).
    • The adaptive immune system is involved in this adverse reaction.

    Clinical features in Allergic Contact Dermatitis

    • Usually localised to the area of contact.
    • Allergens can spread.
    • Characteristic skin reactions like redness, swelling, blistering, and dry bumps are common.
    • Common allergens include nickel, fragrance, hair dye, plants, and certain preservatives or additives.

    Disorders of Pigmentation (Hyper and Hypo)

    • Hyperpigmentation (often hypermelanosis) is the darkening or increase in skin pigmentation.
    • Hypopgmentation is a decrease or loss of skin pigmentation.
    • Key causes of hyperpigmentation such as: drugs, endocrine disorders, genetic disorders, metabolic disorders, nutritional deficiencies, post-inflammatory effects, and various skin conditions.
    • Key causes of hypopigmentation such as albinism, hypopituitarism, vitiligo, chemical exposures, and infections.

    Lentigines and Freckles

    • Freckles are small, flat tan/brown spots on sun-exposed areas.
    • Lentigines are similar but remain consistent with exposure; often larger than freckles.
    • Both have an elevated number of melanocytes (pigment-forming cells).

    Melasma (Chloasma)

    • Melasma is hyperpigmentation that primarily affects women of reproductive age.
    • It mainly develops in the face, especially on the forehead, cheeks, and upper lips.
    • It's associated with pregnancy in many cases.

    Naevi

    • Moles are benign proliferations of one or more normal skin constituents.
    • They can be present at birth or develop later in life, often during childhood and adolescence.
    • They can increase in number due to sun exposure or pregnancy.

    Vitiligo

    • A condition characterised by the loss of skin pigment in patches.
    • It often presents between 10 and 30 years old.
    • It's associated with autoimmune disorders and affects about 0.5% of the population (with a male:female ratio of around 1:1).

    Hypopigmentation

    • Loss of skin pigment (blanching) can be generalized or specific to a region.
    • Causes include albinism, hypopituitarism, vitiligo, post-inflammatory hyperpigmentation, chemical exposures, and infections.

    Albinism

    • Characterized by a lack of melanin pigment in the skin, hair, and eyes due to a genetic mutation that impacts melanin production.
    • Sufferers usually inherit the trait from parents.

    References

    • Includes various research articles on skin and its related conditions.

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