14: Skin Barrier Flashcards
What is the primary function of the skin as a barrier?
The primary function of the skin is to form a barrier between the organism and the external environment, protecting the body from physical damage, excessive water loss, and harmful substances.
What are the components of the stratum corneum?
The stratum corneum is composed of corneocytes and intercorneocyte water-impermeable lipid lamellae, which are wrapped with a cornified cell envelope and contain keratin filaments associated with filaggrin.
How do tight junctions contribute to the skin barrier?
Tight junctions seal the intercellular space between neighboring cells in the stratum granulosum, forming a liquid-liquid interface barrier that limits molecular movement through the paracellular pathway.
What role do Langerhans cells play in the skin barrier?
Langerhans cells are located in the epidermis and extend their dendrites to capture external antigens, contributing to the immunologic barrier of the skin.
What is transepidermal water loss and its significance?
Transepidermal water loss is the loss of water that passes from inside to outside the body through the epidermis, and it is useful for evaluating the stratum corneum barrier as its elevation rates are proportional to the level of barrier damage or formation.
What are the layers of the epidermis?
The epidermis consists of several layers: stratum corneum (uppermost), stratum granulosum, stratum spinosum, and stratum basale.
What is the thickness and composition of the stratum corneum?
The stratum corneum is 10 to 20 μm thick and contains about 10 to 25 layers of cornified cells, comprising protein-based bricks (corneocytes) and lipid-based mortar (intercellular lipid lamellae).
How does the stratum corneum act as a two-way barrier, and what are its structural components?
The stratum corneum prevents inward penetration of external molecules and microorganisms and outward leakage of water and solutes. It consists of protein-based corneocytes and lipid-based intercorneocyte lipid lamellae.
How does the skin microbiota interact with the epidermal barrier to prevent infections?
The skin microbiota is controlled by antimicrobial peptides, lipids, acidic pH, and desquamation, which prevent colonization by harmful microorganisms.
How does the stratum corneum prevent the penetration of external molecules?
The stratum corneum acts as a barrier with corneocytes and intercorneocyte lipid lamellae, limiting molecular penetration.
What is the function of Langerhans cells in the epidermis?
Langerhans cells capture external antigens by extending dendrites through tight junctions and activate immune responses.
How does the stratum corneum regulate water permeability?
The stratum corneum uses intercorneocyte lipid lamellae and natural moisturizing factors to limit water permeability and prevent desiccation.
What are the key functions of the skin in relation to external environmental protection?
The skin serves to:
- Form a barrier between the organism and the external environment.
- Protect against physical damage from desiccation, infection, overheating, and UV irradiation.
- Prevent excessive water loss (inside-outside barrier) and entry of harmful substances (outside-inside barrier).
How do tight junctions contribute to the skin barrier’s function?
Tight junctions seal the intercellular spaces between neighboring cells in the stratum granulosum, forming a liquid-liquid interface barrier that limits molecular movement through the paracellular pathway, thus preventing leakage of water and solutes.
What role do Langerhans cells play in the skin barrier?
Langerhans cells are located in the epidermis and extend their dendrites to capture external antigens. They are activated upon exposure to external stimuli, contributing to the immunologic barrier of the skin.
What is transepidermal water loss and its significance in evaluating the skin barrier?
Transepidermal water loss (TEWL) is the loss of water that passes from inside to outside the body through the epidermis. It is useful for evaluating the stratum corneum barrier, as higher rates of TEWL indicate greater levels of barrier damage or formation.
Describe the composition and structure of the stratum corneum and its role in skin barrier function.
The stratum corneum is 10 to 20 μm thick and contains 10 to 25 layers of cornified cells. It acts as a two-way barrier, preventing inward penetration of external molecules and microorganisms, as well as outward leakage of water and solutes. It comprises protein-based bricks (corneocytes) and lipid-based mortar (intercellular lipid lamellae).
What are corneocytes and how do they adhere to one another?
Corneocytes are terminally differentiated dead keratinocytes that adhere to one another via proteinaceous cell-cell adhesion complexes called corneodesmosomes and the adhesive force of intercellular lipid lamellae.
What is the role of ABCA12 in the skin?
ABCA12 functions in cellular lipid trafficking on the limiting membrane of lamellar bodies, with severe defects causing Harlequin ichthyosis.
What are the major classes of lipids found in the stratum corneum?
The major classes of lipids in the stratum corneum are cholesterol, free fatty acids, and ceramides, with ceramides accounting for 30% to 40% of lipids by weight.
How does cholesterol biosynthesis in the epidermis contribute to vitamin D production?
Cholesterol biosynthesis in the epidermis is important for the production of vitamin D, as 7-dehydrocholesterol is converted to previtamin D in a photolytic reaction by UVB radiation, followed by thermal isomerization to form vitamin D3.
What is the significance of ceramides in the stratum corneum?
Ceramides are a major lipid component in the stratum corneum, essential for maintaining the skin barrier function and are synthesized by serine palmitoyltransferase and hydrolysis of glucosylceramide and sphingomyelin.
What are corneodesmosomes and their role in the skin?
Corneodesmosomes are formed by the secretion of corneodesmosin by lamellar bodies into the extracellular spaces surrounding SG1 cells, integrating into desmosomes and playing a crucial role in the adhesion of corneocytes.
A patient with congenital ichthyosis has a defect in transglutaminase 1. What is the role of this enzyme in skin barrier formation?
Transglutaminase 1 cross-links scaffold proteins to form the cornified envelope, which is essential for the structural integrity of the stratum corneum. Defects in this enzyme disrupt the skin barrier.
What is the role of ceramides in the stratum corneum, and what happens if their biosynthesis is impaired?
Ceramides are essential for the formation of the corneocyte lipid envelope and intercorneocyte lipid lamellae, crucial for barrier function. Impaired biosynthesis causes congenital ichthyosis and barrier defects.
A patient has a mutation in ABCA12. What skin condition might they develop, and why?
Mutations in ABCA12 cause Harlequin ichthyosis due to defects in lipid trafficking and lamellar body function, disrupting the lipid barrier of the stratum corneum.
What is the role of lamellar bodies in the stratum corneum, and what happens if they are defective?
Lamellar bodies secrete lipids and proteins essential for barrier formation. Defects in lamellar bodies disrupt lipid organization, leading to barrier dysfunction and ichthyosis.
A patient has a defect in serine palmitoyltransferase. What skin condition might they develop, and why?
Defects in serine palmitoyltransferase impair ceramide biosynthesis, leading to barrier defects and conditions like congenital ichthyosis.
What is the role of transglutaminase 1 in forming the cornified envelope?
Transglutaminase 1 cross-links scaffold proteins to form the cornified envelope, providing structural integrity to the stratum corneum.
What is the significance of the basket-weave structure in the stratum corneum?
The basket-weave structure, seen in H&E stains, reflects stable lateral adhesions between corneocytes, maintaining barrier integrity.
What is the function of involucrin in the cornified envelope?
Involucrin forms a scaffold for the cornified envelope, which is reinforced during later stages of cornification.
How does the stratum corneum’s lipid composition contribute to its barrier function?
The stratum corneum’s lipids, including ceramides, cholesterol, and fatty acids, form intercorneocyte lipid lamellae, essential for barrier integrity.
What is the role of acylceramide in the stratum corneum?
Acylceramide is essential for forming the corneocyte lipid envelope and organizing intercorneocyte lipid lamellae, crucial for barrier function.
What is the role of corneodesmosomes in the stability of corneocyte layers, and how do they differ from apicobasal adhesions?
Corneodesmosomes provide lateral adhesions between corneocytes, making these connections more stable than apicobasal adhesions. This stability allows corneocyte layers to detach from one another while maintaining their lateral connections, which is crucial for the integrity of the skin barrier.
Describe the process of forming a cornified cell envelope and the significance of transglutaminase 1 in this process.
The formation of a cornified cell envelope involves several steps:
- Formation of lamellar body from Golgi
- Secretion of the lamellar body contents
- Conversion from peripheral cell membrane to corneocyte
- Lipid lamellar formation
- Conversion from desmosome to corneodesmosome
- Formation of cornified envelope by cross-linking scaffold proteins via transglutaminase 1 (TG1).
Transglutaminase 1 is essential for cross-linking proteins in the cornified envelope, and defects in this enzyme can lead to congenital ichthyosis.
What are the major classes of lipids found in the stratum corneum, and what is their significance in skin health?
The major classes of lipids in the stratum corneum include:
- Cholesterol
- Free fatty acids
- Ceramides
These lipids play a crucial role in maintaining the skin barrier function, hydration, and overall skin health. Ceramides, in particular, account for 30% to 40% of the lipids by weight and are vital for the barrier function of the stratum corneum.
How does a deficiency in the biosynthesis pathway of acylceramide affect skin health?
A deficiency in the biosynthesis pathway of acylceramide can lead to several types of congenital ichthyosis. Acylceramide is essential for the formation of the corneocyte lipid envelope and the proper organization of intercorneocyte lipid lamellae, which are critical for maintaining the barrier function of the stratum corneum.
Explain the significance of ABCA12 in the context of lamellar bodies and skin health.
ABCA12 functions in cellular lipid trafficking on the limiting membrane of lamellar bodies. Severe defects in ABCA12 can lead to Harlequin ichthyosis, a severe skin condition characterized by a disrupted skin barrier and abnormal lipid composition, highlighting the importance of lipid transport in maintaining skin health.
What role do Kallikrein proteases play in the stratum corneum?
Kallikrein proteases (Kallikreins 5, 7, and 14) are major proteases involved in the degradation of corneodesmosomes, facilitating the detachment of corneocytes from the stratum corneum during desquamation. They are activated by lower pH and can be autoactivated or activated by matriptase, a transmembrane serine protease.
What are the consequences of filaggrin mutations in the stratum corneum?
Mutations in filaggrin can lead to a decrease in natural moisturizing factors, disturb the lattice structure of keratin filaments, and increase the incidence of barrier breakage in the stratum corneum. This can result in conditions such as ichthyosis vulgaris and contribute to the development of allergic diseases.
Describe the three parts of the stratum corneum and their functions.
The stratum corneum consists of three parts:
- Upper part - Contains water-soluble small molecules that can soak in and out; the protein-based structure of corneocytes is proteolytically degraded.
- Middle part - Acts as a permeation barrier, limiting the absorption of water-soluble small molecules while having a high potential to absorb and hold water, enriched with natural moisturizing factors.
- Lower part - Composed of an intracellular lattice structure of keratin filaments, integrated by mature filaggrin monomers.
What is the significance of tight junctions in the stratum corneum?
Tight junctions are specialized intercellular adhesion complexes located at the apical-most part of the apical junctional complex. They are crucial for limiting molecular movement through the paracellular pathway, thereby contributing to the integrity and barrier function of the stratum corneum.
How does the degradation of filaggrin contribute to the natural moisturizing factors in the stratum corneum?
As corneocytes move upward, intracellular filaggrin is degraded into free amino acids and their derivatives by proteases like caspase 14. These amino acids, along with lactic acid, urea, citrate, and sugars, form the natural moisturizing factors that help maintain skin hydration and barrier function.
A patient presents with ichthyosis vulgaris. What molecular defect is most likely responsible, and how does it affect the skin barrier?
Ichthyosis vulgaris is caused by haploinsufficiency of filaggrin. This leads to a decrease in natural moisturizing factors, disturbance of the keratin filament lattice structure, and increased barrier breakage in the stratum corneum.
A patient with Netherton syndrome has congenital defects in LEKTI. How does this affect desquamation?
LEKTI inhibits kallikrein proteases. Defects in LEKTI lead to uncontrolled kallikrein activity, causing excessive degradation of corneodesmosomes and peeling of the stratum corneum.
What is the significance of natural moisturizing factors (NMFs) in the stratum corneum?
NMFs, derived from filaggrin degradation, maintain hydration, enhance barrier function, and prevent desiccation. Deficiency in NMFs leads to dry, scaly skin and barrier defects.
A patient with atopic eczema has a filaggrin mutation. How does this mutation predispose them to allergic diseases?
Filaggrin mutations reduce natural moisturizing factors and weaken the stratum corneum barrier, increasing allergen penetration and susceptibility to allergic diseases.
How does the stratum corneum adapt to prevent water loss in low-humidity environments?
The stratum corneum increases natural moisturizing factors and lipid content to enhance water retention and maintain barrier function in low-humidity environments.
What is the role of urocanic acid in the stratum corneum?
Urocanic acid plays a role in absorbing UV radiation and contributes to the skin’s protective barrier.
How does a filaggrin mutation predispose individuals with atopic eczema to allergic diseases?
Filaggrin mutations reduce natural moisturizing factors and weaken the stratum corneum barrier, increasing allergen penetration and susceptibility to allergic diseases.
What is the role of urocanic acid in the stratum corneum?
Urocanic acid, derived from filaggrin degradation, absorbs UV radiation and contributes to the skin’s photoprotective barrier.
How do occlusive patches affect the stratum corneum during patch testing?
Occlusive patches disrupt intercorneocyte lipid lamellae, increasing solute and solvent permeation through the stratum corneum.
What is the role of kallikrein proteases in desquamation?
Kallikrein proteases degrade corneodesmosomes in the outer stratum corneum, facilitating the detachment of corneocytes.
How does the stratum corneum’s multilayered structure enhance its barrier function?
The stratum corneum’s upper, middle, and lower layers provide distinct functions, from water absorption to structural integrity.
What role do kallikrein proteases play in the stratum corneum, and how are they activated?
Kallikrein proteases are major proteases involved in the degradation of corneodesmosomes in the stratum corneum. They are produced as inactive precursors and activated via proteolytic conversion by themselves (autoactivation) or by matriptase, particularly in response to lower pH conditions.
How does filaggrin deficiency affect the skin barrier and what conditions can it lead to?
Filaggrin deficiency leads to a decrease in natural moisturizing factors and disrupts the lattice structure of keratin filaments in the innermost layers of the stratum corneum. This can result in increased barrier breakage and is associated with conditions such as ichthyosis vulgaris, atopic eczema, and other allergic diseases.
Describe the three parts of the stratum corneum and their functions.
The stratum corneum consists of three parts:
1. Upper part - Contains water-soluble small molecules that can soak in and out; the protein-based structure of corneocytes is proteolytically degraded.
2. Middle part - Acts as a permeation barrier where the absorption of water-soluble small molecules is limited, but it has a high potential to absorb and hold water, enriched with natural moisturizing factors.
3. Lower part - Composed of an intracellular lattice structure of keratin filaments, integrated by mature filaggrin monomers, providing structural integrity.
What is the significance of tight junctions in the stratum corneum?
Tight junctions are specialized intercellular adhesion complexes located at the apical-most part of the apical junctional complex. They are crucial for limiting molecular movement through the paracellular pathway, thereby contributing to the integrity and function of the skin barrier.
What are the implications of defective stratum corneum barriers in early childhood?
Defective stratum corneum barriers in early childhood are associated with the development of various allergic diseases, influenced by genetic differences in immune reactions, skin microbiota, and environmental factors.
What are the main components of tight junctions in the skin?
Tight junctions in the skin are composed of four-transmembrane proteins of claudins, along with proteins such as occludin, junctional adhesion molecule A (JAM-A), tricellulin, and angulins. Additionally, intracellular scaffold proteins like ZO-1, ZO-2, and ZO-3 are involved.
How do Langerhans cells interact with tight junctions in the skin?
Langerhans cells have dendrites located beneath the tight junctions (TJ) in a steady state. Upon activation, these dendrites can penetrate through the TJ barrier to access the outside, leading to the formation of new tight junctions.
What is the significance of the shape of keratinocytes in skin barrier homeostasis?
The shape of keratinocytes is characterized by a regular stacking structure with zigzag interdigitation patterns between adjacent cell columns, contributing to skin barrier homeostasis.
What are the characteristics of the antimicrobial barrier of the skin?
The antimicrobial barrier of the skin includes:
1. Desquamation that prevents colonization of microorganisms.
2. Low carbohydrate and water content.
3. A weakly acidic pH ranging from 5.6 to 6.4.
4. An active antimicrobial defense system comprising various antimicrobial proteins.
What types of antimicrobial proteins are found on the skin surface and their functions?
The skin surface contains various antimicrobial proteins, including:
- Beta-defensins: Antimicrobial activity against gram-negative bacteria.
- Cathelicidin (LL-37): Involved in keratinocyte differentiation and has antibacterial activity.
- Psoriasin (5100A7): Attracts mast cells and neutrophils, and has antibacterial properties.
- RNase 7: Exhibits broad spectrum antimicrobial activity against various bacteria.
How do tight junctions contribute to the skin barrier, and what proteins are involved?
Tight junctions seal intercellular spaces to limit molecular movement through the paracellular pathway. Key proteins include claudins, occludin, JAM-A, tricellulin, and ZO-1, 2, and 3.
What structural feature of keratinocytes contributes to skin barrier homeostasis?
Keratinocytes have a regular zigzag interdigitation pattern, forming a stable stacking structure that maintains barrier integrity.
How does the acidic pH of the stratum corneum contribute to its antimicrobial barrier?
The acidic pH (5.6-6.4) inhibits microbial growth and activates proteases like kallikreins for controlled desquamation.
What is the role of claudins in tight junctions, and what happens if they are defective?
Claudins are crucial for tight junction integrity. Defects, such as in claudin-1, cause conditions like neonatal ichthyosis sclerosing cholangitis syndrome.
How does the stratum corneum adapt to prevent microbial colonization?
The stratum corneum uses desquamation, low water content, acidic pH, and antimicrobial proteins to inhibit microbial colonization.
What is the role of tight junctions in the interaction between Langerhans cells and keratinocytes during immune activation?
During immune activation, Langerhans cell dendrites penetrate through the tight junction (TJ) barrier to access the outside, forming new tight junctions with keratinocytes.
How does the structure of keratinocytes contribute to skin barrier homeostasis?
Keratinocytes have a regular stacking structure with zigzag interdigitation patterns, essential for maintaining skin barrier integrity and function.
What are the key components of the antimicrobial barrier of the skin?
The antimicrobial barrier of the skin includes:
1. Desquamation - prevents colonization of microorganisms.
2. Low carbohydrate and water content - limits microbial growth.
3. Weakly acidic pH (5.6 to 6.4) - due to free fatty acids, lactic acid, urocanic acid, and microbial metabolites.
4. Active antimicrobial defense system - comprising various antimicrobial proteins.
What is the significance of antimicrobial proteins on the skin surface?
Antimicrobial proteins on the skin surface exhibit broad antibacterial activity against both gram-positive and gram-negative bacteria, some have antifungal or antiviral properties, and they act as ‘alarmins’ to alert host cells to injuries and microbial invasions.
What are the two major antimicrobial proteins of the skin?
Cathelicidins and Beta-defensins are the two major antimicrobial proteins of the skin.
What cells produce antimicrobial proteins in the skin?
Antimicrobial proteins in the skin are produced by:
1. Keratinocytes - produce cathelicidins and Beta-defensins.
2. Eccrine, apocrine, and sebaceous glands.
3. Mast cells - produce cathelicidins.
4. Commensal bacteria (e.g., Staphylococcus epidermidis).
How do defensins and cathelicidins function as antimicrobial proteins?
Defensins and cathelicidins function by:
- Being cationic and interacting with the bacterial membrane surface through electrostatic interactions.
- Stimulating chemokine and cytokine secretion from various cell types.
- Using chemotactic activity to recruit leukocytes, modifying the inflammatory response.
What are the characteristics of the epidermal barrier in newborn skin?
The epidermal barrier in newborn skin is characterized by:
- A well-developed and functional skin barrier at birth.
- A thinner stratum corneum and low levels of natural moisturizing factors.
- Greater transepidermal water loss compared to adults.
What is the significance of vernix caseosa for newborn skin?
Vernix caseosa is significant for newborn skin because it:
- Provides greater skin hydration and a lower skin surface pH.
- Contains antimicrobial agents and exhibits antifungal and antibacterial activities.
What are the barriers against ultraviolet stresses in the skin?
The barriers against ultraviolet stresses in the skin include:
1. Reflection at the air-skin interface.
2. Absorption by trans-urocanic acid.
3. Diffraction via keratin filaments.
4. Melanin - absorbs UV irradiation and protects genomic DNA from UV-induced damage.
How does the skin respond to heat stresses?
The skin responds to heat stresses through:
- Cooling: Evaporation of water secreted from eccrine sweat glands.
- Vasodilation: Superficial veins dilate to enhance cooling.
What are the barriers against physical stresses in the skin?
The barriers against physical stresses in the skin include:
1. Rigid stratum corneum.
2. Soft layers of keratinocytes.
3. Rigid collagenous tissue of the dermis.
4. Soft cushion of the hypodermis.
A newborn lacks vernix caseosa at birth. What are the potential consequences for the skin barrier, and why?
The absence of vernix caseosa can lead to a weaker epidermal barrier, increased transepidermal water loss, and reduced antimicrobial protection.
How does the epidermis protect genomic DNA from UV-induced damage?
The epidermis reflects UV light at the air-skin interface, absorbs it via trans-urocanic acid and melanin, and repairs DNA damage using DNA repair enzymes.
How does the epidermis respond to heat stress through sweating and blood flow control?
Eccrine sweat glands secrete water for evaporative cooling, while superficial veins dilate to enhance heat dissipation.
A premature infant has high transepidermal water loss. What factors contribute to this condition?
Premature infants have a thin stratum corneum, low natural moisturizing factors, and lack vernix caseosa, leading to increased water loss.
How do antimicrobial proteins like cathelicidins and beta-defensins function in the skin?
Cathelicidins and beta-defensins interact with bacterial membranes, stimulate cytokine secretion, and recruit leukocytes to modulate inflammation.
How does melanin protect the skin from UV-induced damage?
Melanin absorbs UV radiation, preventing DNA damage in the basal layer of the epidermis.
How does the epidermis maintain a nonproliferative state in the upper layers?
The upper epidermis eliminates cells continuously, preventing tumorigenesis and maintaining a nonproliferative state.
What is the role of En1 in determining eccrine gland density?
En1 transcription factor inversely determines the density of eccrine glands and hair follicles, affecting thermoregulation.
How does the stratum corneum protect against physical stresses?
The stratum corneum’s rigid structure, combined with keratinocytes and dermal collagen, absorbs and distributes physical stresses.
What are the two major antimicrobial proteins of the skin and their primary functions?
The two major antimicrobial proteins of the skin are cathelicidins and Beta-defensins. Their primary functions include:
- Interacting with bacterial membranes through electrostatic interactions.
- Stimulating chemokine and cytokine secretion from various cell types.
How does the epidermal barrier of newborn skin differ from that of full-term infants?
The epidermal barrier of newborn skin is characterized by:
- A thinner stratum corneum.
- Low levels of natural moisturizing factors.
- Greater transepidermal water loss.
What mechanisms does the skin employ to protect against ultraviolet stresses?
The skin employs mechanisms such as:
- Reflection at the air-skin interface.
- Absorption by trans-urocanic acid.
- Diffraction via keratin filaments.
- Melanin absorbs UV irradiation and protects genomic DNA.
What physiological responses occur in the skin to protect against heat stresses?
To protect against heat stresses, the skin responds through:
1. Cooling: Evaporation of water secreted from eccrine sweat glands.
2. Vasodilation: In hot environments, superficial veins dilate.
What are some diseases associated with aberrant stratum corneum in animal models?
Some diseases include:
- CLID syndrome (Mouse, MIM Number: 601117)
- NCLD syndrome (Mouse, MIM Number: 608930)
- Ichthyosis (Mouse, MIM Number: 614177)
How is the skin cooled?
The skin is cooled via evaporation of eccrine sweat.
What happens during vasoconstriction in cold environments?
In cold environments, superficial veins contract, and countercurrent heat exchange precools blood in arteries before reaching superficial vessels.
What are some diseases associated with aberrant stratum corneum in animal models?
Some diseases include CLID syndrome (Mouse, MIM 601117), NCLD syndrome (Mouse, MIM 608930), Ichthyosis (Mouse, MIM 614177), Chari-van der Hoeven syndrome (Dog, MIM 73530), Nevoid basal cell carcinoma syndrome (Mouse, MIM 604833), Ectodermal dysplasia (Mouse, MIM 305100), and Nephrogenic systemic fibrosis (Mouse, MIM 273000).
What are the common features of diseases that show aberrant stratum corneum in animal models?
Common features include classification based on characteristics, impaired barrier function and lipid transport, involvement of specific proteins such as filaggrin, and mutations in genes associated with skin barrier function.
How do different animal models contribute to the understanding of diseases affecting the stratum corneum?
Different animal models, such as mice and dogs, provide insights into pathophysiology, genetic studies, and therapeutic approaches.
What role do specific proteins play in the maintenance of the stratum corneum?
Specific proteins such as filaggrin and ceramides are crucial for maintaining the integrity and hydration of the skin. Mutations or deficiencies in these proteins can lead to conditions like atopic dermatitis and ichthyosis.
What are the major physical assaults that the epidermis is subjected to?
The major physical assaults include desiccation, irritation, UV irradiation, heat, and cold shock.
What is the role of tight junctions in the epidermis?
Tight junctions play a crucial role in preventing the loss of water, solutes, and nutrients, and maintaining the integrity of the epidermal barrier.
What are the types of assaults that the epidermis faces?
The types of assaults include physical assaults (e.g., desiccation, UV irradiation), microbial assaults (e.g., bacteria, fungus, virus), and chemical assaults (e.g., irritants, allergens).
What is the significance of lamellar bodies in the epidermis?
Lamellar bodies are significant for desquamation, formation of the lipid barrier, and regulating the extracellular environment.
How does the epidermis prevent the loss of water and nutrients?
The epidermis prevents the loss of water and nutrients through tight junctions that create a barrier and lipid lamellae that form an interface barrier.
What are the major types of assaults that the epidermis is subjected to?
The major types of assaults include physical assaults, microbial assaults, and chemical assaults, which can compromise the skin’s protective barrier.
How do tight junctions contribute to the prevention of water and nutrient loss in the epidermis?
Tight junctions prevent paracellular permeability, regulate the extracellular environment, and facilitate cell signaling.
What is the significance of lamellar bodies in the epidermis?
Lamellar bodies store lipids, facilitate lipid secretion, and aid in desquamation, which is essential for maintaining a healthy skin surface.
