6: Skin Glands: Sebaceous, Eccrine, and Apocrine Glands Flashcards
What are the two main components of skin glands?
The two main components of skin glands are: 1. Secretory component – gland or coil (tubulus) 2. Excretory part – duct (ductus)
What are the classifications of skin glands based on their product?
The classifications of skin glands based on their product are: - Sebum (produced by sebaceous glands) - Sweat (produced by sweat glands)
What is the secretory function of holocrine glands?
Holocrine glands secrete by having their secretory cells burst, releasing both cytoplasmic contents and cell membranes into their ducts.
An example of a holocrine gland is the sebaceous gland.
How do merocrine glands excrete their products?
Merocrine glands excrete their products via exocytosis.
Examples of merocrine glands include eccrine and apocrine glands.
Where do sebaceous glands release their product?
Sebaceous glands release their product into the hair follicle.
What is the histological structure of sebaceous glands?
Sebaceous glands are composed of multilobular structures of epithelial origin, specifically: - Sebocytes (lipid-producing epithelial cells) - The sebaceous duct is lined by undifferentiated keratinocytes. - The periphery of the sebaceous gland contains a basal cell layer with small cuboidal nucleated highly mitotic sebocytes.
What is the significance of SOX9 in sebaceous gland development?
SOX9 is the earliest known signal necessary for sebaceous gland development and is essential for the specification of early hair follicle stem cells and morphogenesis.
What are the locations where sebaceous glands are found?
Sebaceous glands are located in various areas, including: - Associated with hair follicles - Eyelids – Meibomian, tarsal glands - Nipples – Montgomery, areolar glands - Genitals – Tyson glands - Mucosa – lips, gums, inner cheeks, genitals, Fordyce spots - Palms and soles – totally devoid of sebaceous glands - Dorsal hand and foot – sparse sebaceous glands - Nose – largest glands and greatest density of glands (1600 glands/cm²) - Face and scalp – 2nd greatest density (400-900 glands/cm²)
Explain the structural and functional differences between sebaceous and eccrine sweat glands.
Sebaceous glands are multilobular structures associated with hair follicles, secreting sebum via holocrine secretion, which involves cell disintegration. Eccrine sweat glands, on the other hand, are found over most of the body and secrete sweat directly onto the skin surface via merocrine secretion, which involves exocytosis.
What is the significance of the Wnt and Sonic hedgehog (Shh) signaling pathways in sebaceous gland development?
The Wnt and Sonic hedgehog (Shh) signaling pathways are intricately involved in sebaceous gland development. Increased Shh and Myc signaling, along with decreased Wnt signaling, are critical for sebocyte differentiation.
What is the significance of the pilosebaceous unit?
The pilosebaceous unit, comprising a sebaceous gland and hair follicle, is essential for sebum secretion and hair follicle health.
What is the role of PRDM1 in sebaceous gland development?
PRDM1 (formerly BLIMP1) is a marker of terminal epithelial differentiation. Its loss leads to increased c-myc expression, resulting in enlarged and numerous sebaceous glands.
What is the role of SOX9 in sebaceous gland development?
SOX9 is the earliest known signal necessary for sebaceous gland development, playing a critical role in hair follicle stem cell specification and morphogenesis.
How do sebaceous glands regenerate after damage?
Sebaceous glands regenerate from a reservoir of stem cells located in the hair follicle bulge.
What are the two main components of skin glands and their functions?
Skin glands consist of: 1. Secretory component - gland or coil (tubulus) 2. Excretory part - duct (ductus)
These glands are involved in the secretion of products such as sebum and sweat.
How do holocrine and merocrine glands differ in their secretory functions?
- Holocrine glands: Secretory cells burst and release both cytoplasmic contents and cell membranes into their ducts (e.g., sebaceous glands). - Merocrine glands: Excrete products via exocytosis without losing cellular material (e.g., eccrine and apocrine glands).
What is the primary regulatory mechanism for sebaceous glands?
Sebaceous glands are primarily regulated by androgens and retinoids, which influence their activity and secretion of sebum.
Describe the histological structure of sebaceous glands.
Sebaceous glands are multilobular structures of epithelial origin, composed of: - Sebocytes: Lipid-producing uniquely differentiated epithelial cells. - Sebaceous duct: Lined by undifferentiated keratinocytes. - Basal cell layer: Contains small cuboidal nucleated highly mitotic sebocytes that progress toward the middle of the gland, accumulating lipid droplets.
Where are sebaceous glands located in the human body?
Sebaceous glands are associated with hair follicles and can be found in various locations: - PiloSebaceous Unit: Sebaceous gland + hair follicle - Eyelids: Meibomian, tarsal glands - Nipples: Montgomery, areolar glands - Genitals: Tyson glands - Mucosa: Lips, gums, inner cheeks, genitals (Fordyce spots)
Note: Palms and soles are totally devoid of sebaceous glands.
What is the significance of the Wnt and Sonic hedgehog signaling pathways in sebaceous gland development?
The Wnt and Sonic hedgehog (Shh) signaling pathways are crucial for sebaceous gland development as they: - Regulate the differentiation of sebocytes. - Influence the proliferation and specification of early hair follicle stem cells. - Ensure proper morphogenesis of sebaceous glands during embryonic development.
What role does SOX9 play in sebaceous gland development?
SOX9 is the earliest known signal necessary for sebaceous gland development. It is essential for: - Specification of early hair follicle stem cells. - Morphogenesis of sebaceous glands, ensuring proper formation and function during development.
How does the location of sebaceous glands vary across different body regions?
Sebaceous glands are distributed variably across the body: - Nose: Largest glands and greatest density (1600 glands/cm²) - Face and Scalp: 2nd greatest density (400-900 glands/cm²) - Dorsal hand and foot: Sparse sebaceous glands - Palms and soles: Totally devoid of sebaceous glands.
What is the function of Fordyce spots and where are they located?
Fordyce spots are sebaceous glands that release their contents directly to the epithelial surface. They are typically found in: - Mucosa: Lips, gums, inner cheeks, and genitals.
What are the components found in the secretion of sebaceous glands?
Sebaceous glands secrete a mixture that includes: - Squalene - Cholesterol - Cholesterol esters - Wax esters - Triglycerides
These components contribute to the protective and moisturizing properties of sebum.
What is the embryological timeline for the development of sebaceous glands?
The development of sebaceous glands occurs during specific weeks of embryogenesis: - 10th to 12th week: Stratum intermedium apparent; developing hair germs distinct. - 13th to 16th week: Glands arise in a cephalocaudal sequence from bulges of hair follicles. - Sebaceous glands can regenerate from the reservoir of stem cells in the hair follicle bulge.
What is the significance of PRDM1 in sebaceous gland development?
PRDM1 (formerly BLIMP1) is a marker of terminal epithelial differentiation. Its significance includes: - Loss of PRDM1 leads to increased c-myc, resulting in enlarged and numerous sebaceous glands. - It plays a role in the proper differentiation and function of sebaceous glands during development.
What is the relationship between sebaceous glands and hair follicles?
Sebaceous glands are closely associated with hair follicles, forming the PiloSebaceous Unit. This relationship is crucial for: - The secretion of sebum into the hair follicle, which helps to lubricate and protect both the hair and skin. - The overall health and maintenance of the skin and hair.
How do sebocytes contribute to the function of sebaceous glands?
Sebocytes are specialized cells within sebaceous glands that: - Produce lipids, which are essential components of sebum. - Undergo a process of differentiation and lipid accumulation, contributing to the gland’s secretory function.
What factors influence the activity of sebaceous glands?
The activity of sebaceous glands is influenced by several factors, including: - Hormonal regulation: Primarily androgens and retinoids. - Age: Sebaceous gland activity can change with age, often increasing during puberty. - Skin conditions: Certain skin conditions can affect the function and health of sebaceous glands.
What is the role of LRIG1 in sebaceous gland biology?
LRIG1 is associated with sebocyte progenitor cells and plays a role in: - Regulating the proliferation and differentiation of sebocytes. - Contributing to the maintenance and function of sebaceous glands during development and homeostasis.
What is the significance of the basal cell layer in sebaceous glands?
The basal cell layer of sebaceous glands is significant because it: - Contains small cuboidal nucleated highly mitotic sebocytes that are crucial for the regeneration and maintenance of the gland. - Provides a reservoir of cells that can differentiate and migrate toward the duct to produce sebum.
How does the density of sebaceous glands vary across different body areas?
The density of sebaceous glands varies significantly across different body areas: - Nose: Highest density (1600 glands/cm²) - Face and Scalp: 2nd highest density (400-900 glands/cm²) - Dorsal hand and foot: Sparse sebaceous glands - Palms and soles: No sebaceous glands present.
What are the clinical implications of increased sebaceous gland activity?
Increased sebaceous gland activity can lead to several clinical implications, including: - Acne: Excess sebum production can clog pores, leading to acne formation. - Seborrheic dermatitis: Overactivity can cause skin irritation and inflammation. - Oily skin: Increased sebum can contribute to a shiny appearance and may affect cosmetic choices.
What is the embryological origin of sebaceous glands?
Sebaceous glands originate from epithelial cells during embryonic development, specifically from the epithelial placodes of hair follicles, which develop into the glandular structures associated with hair follicles.
What is the function of the sebaceous duct in sebaceous glands?
The sebaceous duct serves the function of: - Transporting sebum produced by sebocytes to the surface of the skin or into the hair follicle. - Lined by undifferentiated keratinocytes, it plays a role in the overall structure and function of the sebaceous gland.
How do sebaceous glands contribute to skin health?
Sebaceous glands contribute to skin health by: - Producing sebum, which moisturizes and protects the skin. - Maintaining the skin barrier function, preventing dryness and irritation. - Supporting the overall microbiome of the skin by providing a lipid-rich environment.
What is the role of androgens in sebaceous gland function?
Androgens play a crucial role in sebaceous gland function by: - Stimulating sebocyte proliferation and sebum production. - Influencing the size and activity of sebaceous glands, particularly during puberty when androgen levels increase.
What are the implications of sebaceous gland dysfunction?
Dysfunction of sebaceous glands can lead to various skin conditions, including: - Acne vulgaris: Due to overproduction of sebum and clogged pores. - Seborrheic dermatitis: Resulting from abnormal sebaceous gland activity. - Dry skin: Insufficient sebum production can lead to dryness and irritation.
What is the significance of the stratum intermedium in sebaceous gland development?
The stratum intermedium is significant in sebaceous gland development as it: - Becomes apparent during the 10th to 12th week of embryogenesis, indicating the early stages of gland formation. - Supports the differentiation and development of hair follicles and associated sebaceous glands.
How do environmental factors influence sebaceous gland activity?
Environmental factors that influence sebaceous gland activity include: - Humidity: Higher humidity can increase sebaceous gland activity. - Temperature: Warmer temperatures may stimulate sebum production. - Diet: Certain dietary factors can affect hormonal levels and, consequently, sebaceous gland function.
What is the relationship between sebaceous glands and acne formation?
The relationship between sebaceous glands and acne formation involves: - Overactivity of sebaceous glands leading to excessive sebum production. - Clogged hair follicles due to sebum and dead skin cells, creating an environment for bacterial growth. - Inflammation resulting from the immune response to bacteria, leading to acne lesions.
What are the potential consequences of hormonal imbalances on sebaceous gland function?
Hormonal imbalances can have several consequences on sebaceous gland function, including: - Increased sebum production: Often seen in conditions like polycystic ovary syndrome (PCOS). - Acne development: Due to excess sebum and clogged pores. - Changes in skin texture: Resulting from altered sebaceous gland activity.
What are the primary components of sebum and their respective percentages?
Component | Percentage Range |
|———–|——————|
| Triglycerides, diglycerides, and FFA | 40-60% |
| Wax esters | 25-30% |
| Squalene | 12-15% |
| Cholesterol esters | 3-6% |
| Cholesterol | 1.5-2.5% |
What is the physiological process of holocrine secretion in sebaceous glands?
Holocrine secretion involves: 1. Exuding lipids through cell disintegration. 2. A multistep process of cell-specific programmed cell death.
What are the functions of sebum in skin health?
The functions of sebum include: - Reducing water loss from the skin’s surface. - Providing mild antibacterial action due to anti-inflammatory lipids and immunoglobulin A. - Facilitating the transit mechanism necessary for vitamin E function.
What are the primary components of human sebum, and how do they contribute to its function?
Human sebum is composed of triglycerides (40-60%), wax esters (25-30%), squalene (12-15%), cholesterol esters (3-6%), and cholesterol (1.5-2.5%). These components reduce water loss, provide mild antibacterial action, and facilitate vitamin E function on the skin.
What are the primary components of human sebum?
Human sebum is composed of triglycerides (40-60%), wax esters (25-30%), squalene (12-15%), cholesterol esters (3-6%), and cholesterol (1.5-2.5%). These components reduce water loss, provide mild antibacterial action, and facilitate vitamin E function on the skin.
What is the significance of sapienic acid in human sebum?
Sapienic acid (16:1Δ6) is a major fatty acid unique to human sebum, distinguishing it from other lipid secretions.
How do sebaceous glands contribute to vitamin E function?
Sebum flow to the skin surface provides a transit mechanism for vitamin E, enhancing its protective effects.
How does the lipid composition of sebum distinguish it from other secretions?
Sebum’s unique lipid composition, including wax esters and squalene, distinguishes it from other secretions and contributes to its protective functions.
What is the primary function of sebum in relation to skin hydration?
Sebum reduces water loss from the skin’s surface, helping to maintain skin hydration.
Describe the composition of sebum and its significance in distinguishing it from other lipids.
Sebum is composed of 40-60% triglycerides, diglycerides, and free fatty acids, 25-30% wax esters, 12-15% squalene, 3-6% cholesterol esters, and 1.5-2.5% cholesterol. The presence of wax esters and squalene distinguishes sebum from other lipids.
What role do undifferentiated cells play in the sebaceous gland?
Undifferentiated cells, which form 40% of the gland, represent germinative cells or stem cells that contribute to the regeneration of the sebaceous gland.
Explain the process of holocrine secretion in sebaceous glands.
Holocrine secretion involves the exudation of lipids through cell disintegration, which is a result of a multistep, cell-specific programmed cell death process.
How does sebum contribute to skin immunity?
Sebum has mild antibacterial action due to its anti-inflammatory lipids and immunoglobulin A, which help protect the skin from pathogens.
What is the role of squalene in the composition of sebum?
Squalene, which constitutes 12-15% of sebum, is significant for its unique properties and its role in skin barrier function.
Discuss the importance of sebaceous glands in vitamin E function.
Sebum flow to the surface of the skin provides the transit mechanism necessary for vitamin E function, which is essential for skin health.
How do sebaceous glands contribute to skin barrier function?
Sebaceous glands produce sebum, which forms a protective layer on the skin, reducing water loss and providing antibacterial properties, thus enhancing the skin barrier function.
What is the significance of the maturation zone in sebaceous glands?
The maturation zone, which also forms 40% of the gland, is crucial for the development and differentiation of sebaceous gland cells, contributing to the gland’s overall function.
What distinguishes human sebum from that of other species?
Human sebum is distinguished by the presence of sapienic acid and sebaleic acid, which are unique fatty acids not typically found in the sebum of other species.
What is the role of cholesterol in sebum composition?
Cholesterol, making up 1.5-2.5% of sebum, plays a role in maintaining skin barrier integrity and fluidity of the sebum layer on the skin.
How does the structure of sebaceous glands facilitate their function?
Sebaceous glands have a structure that includes a solid cord filled with sebum that ruptures to form a channel, allowing for the effective excretion of sebum onto the skin surface.
What is the relationship between sebaceous glands and skin inflammation?
Sebaceous glands can influence skin inflammation by producing anti-inflammatory lipids that help modulate immune responses and reduce irritation.
Describe the embryological development of sebaceous glands.
Sebaceous glands develop through the expression of differentiation-triggering transcription factors, which influence the formation of the gland and its functional properties.
What is the significance of the pilosebaceous canal in sebaceous gland function?
The pilosebaceous canal serves as the common excretory duct for sebum, facilitating its transport to the skin surface where it performs its protective functions.
How does the lipid composition of sebum affect its physical properties?
The lipid composition, including triglycerides, wax esters, and squalene, contributes to the emollient and hydrophobic properties of sebum, enhancing skin moisture retention.
What factors influence the activity of sebaceous glands?
Factors influencing sebaceous gland activity include hormonal regulation, particularly androgens, and environmental factors such as humidity and temperature.
How does the presence of wax esters in sebum contribute to its function?
Wax esters in sebum contribute to its unique texture and help form a protective barrier on the skin, enhancing moisture retention and providing a degree of waterproofing.
What is the role of immunoglobulin A in sebum?
Immunoglobulin A present in sebum provides an additional layer of immune protection by helping to neutralize pathogens that come into contact with the skin.
How does the composition of sebum change with age?
The composition of sebum can change with age, often resulting in decreased production of certain lipids, which can affect skin hydration and barrier function.
What is the clinical significance of understanding sebaceous gland function?
Understanding sebaceous gland function is clinically significant for managing skin conditions such as acne, eczema, and seborrheic dermatitis, which are influenced by sebum production.
How do sebaceous glands interact with hair follicles?
Sebaceous glands are closely associated with hair follicles, providing sebum that lubricates the hair and skin, contributing to overall skin health.
What is the impact of hormonal changes on sebaceous gland activity?
Hormonal changes, particularly increases in androgens, can lead to increased sebaceous gland activity, resulting in higher sebum production and potential skin issues like acne.
How does the structure of sebaceous glands support their holocrine secretion mechanism?
The structure of sebaceous glands, with their solid cords and acini, supports holocrine secretion by allowing for the accumulation of sebum until cell disintegration occurs, releasing the lipid content.
What are the potential consequences of impaired sebaceous gland function?
Impaired sebaceous gland function can lead to dry skin, increased susceptibility to infections, and conditions such as acne due to altered sebum production.
How does the lipid composition of sebum contribute to its antibacterial properties?
The lipid composition of sebum, including anti-inflammatory lipids, contributes to its antibacterial properties by creating an environment that inhibits the growth of pathogens on the skin.
What is the role of sebaceous glands in thermoregulation?
Sebaceous glands contribute to thermoregulation by producing sebum, which can help to maintain skin temperature and prevent excessive water loss during heat exposure.
How does the differentiation of sebaceous gland cells occur during development?
Differentiation of sebaceous gland cells occurs through the influence of specific transcription factors that guide the development and functional specialization of the gland.
What is the relationship between sebaceous gland activity and skin conditions like acne?
Increased sebaceous gland activity can lead to excessive sebum production, which can clog pores and contribute to the development of acne.
How does the presence of cholesterol esters in sebum affect skin health?
Cholesterol esters in sebum help maintain skin barrier integrity and hydration, contributing to overall skin health and protection against environmental stressors.
What are the implications of sebaceous gland dysfunction in dermatological conditions?
Sebaceous gland dysfunction can lead to various dermatological conditions, including acne, seborrheic dermatitis, and dry skin, highlighting the importance of sebum in skin health.
How does the composition of sebum vary between different individuals?
The composition of sebum can vary between individuals due to genetic factors, hormonal levels, diet, and environmental influences, affecting skin health and appearance.
What are the antimicrobial peptides expressed in human sebaceous gland cells?
The antimicrobial peptides include cathelicidin, psoriasin, B-defensin 1, and B-defensin 2.
What is the average transit time of sebaceous gland cells from formation to discharge?
The average transit time of sebaceous gland cells from formation to discharge is 7.4 days.
How do androgens influence sebaceous gland activity?
Sebaceous glands require androgenic stimulation to produce sebum. Dehydroepiandrosterone sulfate (DHEAS) is a significant regulator of sebaceous gland activity through its conversion to testosterone and DHT.
What role do peroxisome-proliferator-activated receptors (PPAR) play in sebaceous gland function?
PPARs act as transcriptional regulators in lipid metabolism in adipose tissue, liver, and skin. They regulate sebogenesis and inflammation in sebaceous gland cells, with PPAR-g agonists potentially beneficial in aging skin.
What is the significance of LXR in sebaceous glands?
Liver-X receptor (LXR) plays a critical role in cholesterol homeostasis and lipid metabolism within sebaceous glands.
What is the consequence of FOXO1 deficiency in sebaceous glands?
Deficiency of FOXO1 is associated with acne and increased sebaceous lipogenesis.
Describe the role of androgens in regulating sebaceous gland activity.
Androgens stimulate sebaceous glands to produce sebum. Dehydroepiandrosterone sulfate (DHEAS) is a significant regulator, as it converts to testosterone and dihydrotestosterone (DHT), which directly influence sebaceous gland activity.
How does isotretinoin affect sebaceous gland function?
Isotretinoin inhibits sebum secretion by reducing androgen synthesis, inducing cell cycle arrest, and promoting apoptosis in sebaceous gland cells.
Explain the role of sebaceous glands in innate immunity.
Sebaceous glands contribute to innate immunity by producing antimicrobial peptides like cathelicidin and β-defensins, which have direct antimicrobial activity and promote cytokine production and inflammation.
Explain the role of FOXO1 in sebaceous gland function.
FOXO1 is expressed in lipid-metabolizing cells, including sebaceous glands. Its deficiency is associated with acne and increased sebaceous lipogenesis.
What role do antimicrobial peptides play in innate immunity within sebaceous glands?
Antimicrobial peptides such as cathelicidin, psoriasin, B-defensin 1, and B-defensin 2 provide direct antimicrobial activity against pathogens like Propionibacterium acnes and initiate cytokine production and inflammation.
How does the size and turnover of sebaceous glands change with age?
The size of sebaceous glands increases with age, while the turnover of sebaceous glands is slowed in older adults. The average transit time of sebaceous gland cells from formation to discharge is approximately 7.4 days.
What is the significance of DHEAS in sebaceous gland activity?
Dehydroepiandrosterone sulfate (DHEAS) is a significant regulator of sebaceous gland activity as it converts to testosterone and DHT, which are necessary for sebaceous gland stimulation and sebum production.
What are the effects of isotretinoin on sebaceous glands?
Isotretinoin (13-cis-retinoic acid) is the most potent pharmacologic inhibitor of sebum secretion, acting by inhibiting androgen synthesis, causing cell cycle arrest, and promoting apoptosis in sebaceous glands.
How do PPAR-g agonists affect sebaceous glands?
PPAR-g agonists may be beneficial in aging skin by regulating sebogenesis and inflammation in sebaceous glands, potentially reducing sebaceous lipid synthesis.
What is the role of LXR in sebaceous gland function?
Liver-X receptor (LXR) plays a critical role in cholesterol homeostasis and lipid metabolism, which are essential for the proper functioning of sebaceous glands.
What is the relationship between FOXO1 deficiency and acne?
Deficiency of FOXO1 is associated with acne and increased sebaceous lipogenesis, indicating its role in regulating lipid metabolism in sebaceous glands.
What factors influence the antimicrobial activity of free fatty acids in sebaceous glands?
Free fatty acids exhibit bactericidal activity against gram-positive organisms by increasing B-defensin 2 expression, which enhances the antimicrobial defense of sebaceous glands.
How do androgen and estrogen receptors regulate sebaceous gland activity?
Sebaceous glands are regulated by androgen and estrogen receptors, which influence sebum production and gland activity, highlighting their multifactorial nature.
What is the average transit time for sebaceous gland cells from formation to discharge?
The average transit time of sebaceous gland cells from formation to discharge is approximately 7.4 days, with 4-7 days in undifferentiated cells and 14-25 days in differentiated, lipid-producing cells.
What are the distinct niches for skin stem cells related to sebaceous glands?
There are three distinct niches for skin stem cells: the follicle bulge, the base of the sebaceous gland, and the basal layer of the epidermis.
How does testosterone level relate to sebaceous gland activity?
Testosterone levels do not parallel the patterns of sebaceous gland activity, indicating that other factors, such as DHEAS, play a more significant role in regulating sebum production.
What is the impact of PPAR-g antagonists on sebaceous lipid synthesis?
PPAR-g antagonists reduce sebaceous lipid synthesis, which can help manage conditions associated with excessive sebum production.
What is the function of cathelicidin in sebaceous glands?
Cathelicidin provides direct antimicrobial activity against Propionibacterium acnes, contributing to the innate immune response and inflammation in sebaceous glands.
What are the clinical implications of increased sebaceous gland size with age?
Increased sebaceous gland size with age may lead to higher sebum production, potentially contributing to skin conditions such as acne or seborrhea in older adults.
How do neuropeptide receptors influence sebaceous gland activity?
Neuropeptide receptors are involved in the regulation of sebaceous gland activity, affecting sebum production and skin health.
What is the role of retinoids in sebaceous gland function?
Retinoids, such as isotretinoin, inhibit sebum secretion by blocking androgen synthesis and promoting cell cycle arrest and apoptosis in sebaceous glands.
How does aging affect the turnover of sebaceous glands?
The turnover of sebaceous glands is slowed in older adults, which may affect skin health and sebum production over time.
What is the significance of the average transit time of sebaceous gland cells?
The average transit time of 7.4 days for sebaceous gland cells indicates the efficiency of sebum production and the renewal process of these glands.
What are the effects of PPAR-d agonists on sebaceous glands?
PPAR-d agonists may be involved in sebaceous tumorigenesis, indicating their potential role in skin conditions related to sebaceous glands.
What is the relationship between sebaceous gland size and the number of sebaceous glands throughout life?
The number of sebaceous glands remains the same throughout life, but their size increases with age.
What is the average transit time for sebaceous gland cells?
The average transit time of 7.4 days for sebaceous gland cells indicates the efficiency of sebum production and the renewal process of these glands.
What is the relationship between sebaceous gland size and the number of sebaceous glands throughout life?
The number of sebaceous glands remains the same throughout life, but their size increases with age, affecting overall sebum production.
How do free fatty acids contribute to the antimicrobial defense of sebaceous glands?
Free fatty acids enhance the antimicrobial defense of sebaceous glands by being bactericidal against gram-positive organisms and increasing B-defensin 2 expression.
What is the role of androgenic stimulation in sebaceous gland activity?
Sebaceous glands require androgenic stimulation to produce sebum, highlighting the importance of hormones in regulating gland function.
How does the expression of FOXO1 relate to lipid metabolism in sebaceous glands?
FOXO1 is expressed in lipid-metabolizing cells and is crucial for regulating lipid metabolism in sebaceous glands; its deficiency can lead to acne and increased lipogenesis.
What are the implications of sebaceous gland multifactorial regulation?
Sebaceous glands are regulated by various ligands, including androgen, estrogen, PPAR, and LXR, which influence their activity and sebum production, affecting skin health.
What is the impact of sebaceous gland activity on skin health?
Sebaceous gland activity, influenced by hormones and various receptors, plays a critical role in maintaining skin health by regulating sebum production and antimicrobial defense.
How do hormonal changes affect sebaceous gland function during puberty?
During puberty, increased levels of androgens stimulate sebaceous glands, leading to increased sebum production, which can contribute to acne development.
What is the significance of the relationship between sebaceous glands and skin stem cells?
The relationship between sebaceous glands and skin stem cells is crucial for maintaining skin integrity and function, as these stem cells contribute to the renewal and health of the glands.
How do environmental factors influence sebaceous gland activity?
Environmental factors such as humidity, temperature, and skin care products can influence sebaceous gland activity, affecting sebum production and skin conditions.
What is the role of vitamin D receptors in sebaceous gland function?
Vitamin D receptors in sebaceous glands may play a role in regulating sebum production and skin health, linking nutritional status to gland activity.
How does the presence of neuropeptide receptors affect sebaceous gland activity?
The presence of neuropeptide receptors in sebaceous glands suggests a role in modulating sebum production and skin responses to stress and inflammation.
What are the potential therapeutic implications of understanding sebaceous gland regulation?
Understanding the regulation of sebaceous glands can lead to targeted therapies for skin conditions such as acne, seborrhea, and other disorders related to sebum production.
What is the role of Perilipin family membrane proteins in sebaceous gland function?
Perilipin family membrane proteins regulate gland size in vivo and control sebaceous lipid accumulation.
Specifically: Perilipin 2 downmodulation leads to a decrease in the unsaturated fatty acid component of neutral lipids; Perilipin 3 modulates specific lipogenic pathways in human sebaceous gland cells; Angiopoietin-like 4 is strongly induced during human sebocyte differentiation and regulates sebaceous lipogenesis.
What is the significance of eccrine sweat glands in thermoregulation?
Eccrine sweat glands play a crucial role in thermoregulation by allowing the body to control its internal temperature in response to thermal stress.
Describe the development timeline of eccrine sweat glands during fetal development.
Eccrine sweat glands develop as follows: 1. 3.5 months: First appear on palms and soles. 2. 8th fetal month: Eccrine glands begin to resemble adult glands. 3. 9th fetal month: Myoepithelial cells form around the duct, completing the development process.
What are the main components secreted by the secretory coil of eccrine sweat glands?
The secretory coil of eccrine sweat glands secretes a variety of substances, including bicarbonate, potassium, sodium chloride (NaCl), glucose, pyruvate, lactate, cytokines, immunoglobulins, and antimicrobial peptides.
What is the role of perilipin proteins in sebaceous gland function?
Perilipin proteins regulate sebaceous gland size and lipid accumulation.
How do eccrine sweat glands contribute to thermoregulation?
Eccrine sweat glands regulate body temperature by secreting sweat, which evaporates and dissipates heat, especially during thermal stress.
Describe the embryonic development of eccrine sweat glands.
Eccrine sweat glands develop from epidermal ridges, forming a lumen by the 8th fetal month and resembling adult glands by the 9th fetal month.
What is the role of angiopoietin-like 4 in sebaceous gland function?
Angiopoietin-like 4 is strongly induced during sebocyte differentiation and regulates sebaceous lipogenesis.
What is the role of Perilipin family membrane proteins in sebogenesis?
Perilipin family membrane proteins regulate gland size in vivo and control sebaceous lipid accumulation.
How does eccrine sweat gland development progress during fetal development?
Eccrine sweat glands begin to develop at approximately 3.5 months of gestation, first appearing on the palms and soles, then axillae, and eventually covering the entire body.
What is the primary function of eccrine sweat glands in the human body?
Eccrine sweat glands primarily allow the body to control its internal temperature in response to thermal stress.
What substances are secreted by the secretory coil of eccrine sweat glands?
The secretory coil of eccrine sweat glands secretes a variety of substances including bicarbonate, potassium, NaCl, glucose, pyruvate, lactate, cytokines, immunoglobulins, and antimicrobial peptides.
What is the significance of stage-specific embryonic antigen-4 in eccrine sweat glands?
Stage-specific embryonic antigen-4 serves as a marker for ductal cells of eccrine sweat glands, indicating their development and differentiation during embryogenesis.
What are the key differences between eccrine and apocrine sweat glands in terms of function?
Eccrine sweat glands primarily function to regulate body temperature through sweat production, while apocrine sweat glands are associated with pheromone production and are activated during stress or sexual arousal.
What is the anatomical structure of eccrine sweat glands?
Eccrine sweat glands consist of a secretory coil (tubulus) and a duct.
How does the distribution of eccrine sweat glands vary across the body?
Eccrine sweat glands are found over nearly the entire body surface, with a higher density on the palms, soles, forehead, and upper limbs.
What triggers the secretion of eccrine sweat, and how is it regulated?
The secretion of eccrine sweat is primarily triggered by acetylcholine released from sympathetic nerves, with the hypothalamus acting as the central regulator of sweating in response to body temperature changes.
What is the clinical significance of understanding the development of eccrine sweat glands?
Understanding the development of eccrine sweat glands is clinically significant as it can provide insights into various skin conditions, thermoregulation issues, and the overall health of the integumentary system.
What is the role of clear cells in the secretory coil of sweat glands?
Clear cells (secretory) rest directly on the basement membrane or on myoepithelial cells. They have abundant mitochondria and Lipofuscin granules, and they secrete water and electrolytes.
How does the proximal (coiled) duct of sweat glands function in sodium pumping?
The proximal (coiled) duct is more active in pumping sodium due to its Na-K ATPase activity and the presence of more mitochondria compared to other ductal cells.
What is the significance of the preoptic hypothalamic area in thermoregulation?
The preoptic hypothalamic area plays an essential role in regulating body temperature by responding to local heating with sweating, vasodilation, and rapid breathing.
What factors influence the rate of sweating according to the content provided?
The rate of sweating is influenced by: 1. Elevation of hypothalamic temperature, which is the strongest stimulus for thermoregulatory sweating responses. 2. Cutaneous temperature, which has a weaker influence. 3. Menopausal hot flashes, which may cause a hypersensitive hypothalamic response to temperature changes.
What are the components of the duct in sweat glands?
The duct consists of an outer ring of basal cells and an inner ring of luminal cells.
How does the hypothalamus regulate eccrine sweat gland activity?
The preoptic hypothalamic area regulates eccrine sweat gland activity by responding to temperature changes.
What is the role of antimicrobial peptides in eccrine sweat?
Antimicrobial peptides like dermcidin and β-defensins in eccrine sweat provide protection against microbial infections.
What is the function of myoepithelial cells in eccrine sweat glands?
Myoepithelial cells in eccrine sweat glands contract in response to cholinergic stimulation, aiding in sweat expulsion.
What is the role of the cuticular border in eccrine sweat gland ducts?
The cuticular border provides structural resilience to the ductal lumen, ensuring efficient sweat transport.
What is the function of the basal ductal cells in eccrine sweat glands?
Basal ductal cells provide maximally expanded Na⁺ pump sites and efficient energy metabolism, aiding in Na⁺ reabsorption.
What is the role of the preoptic hypothalamic area in thermoregulation?
The preoptic hypothalamic area regulates thermoregulation by inducing sweating and vasodilation during heating and vasoconstriction and shivering during cooling.
What is the role of clear cells in the secretory coil of eccrine sweat glands?
Clear cells secrete water and electrolytes, and they rest directly on the basement membrane or on myoepithelial cells.
How does the proximal (coiled) duct of eccrine sweat glands differ from luminal ductal cells in terms of activity and structure?
The proximal (coiled) duct is more active in pumping sodium due to higher Na-K ATPase activity and more mitochondria.
What is the significance of the preoptic hypothalamic area in thermoregulation?
The preoptic hypothalamic area plays a crucial role in regulating body temperature by initiating sweating, vasodilation, and rapid breathing in response to local heating.
What physiological changes occur in response to elevated hypothalamic temperature?
Elevation of hypothalamic temperature is the strongest stimulus for thermoregulatory sweating responses.
How do myoepithelial cells contribute to the function of eccrine sweat glands?
Myoepithelial cells are spindle-shaped and lie on the basement membrane adjacent to clear cells. They contain contractile actin filaments that produce pulsatile sweat, aiding in the expulsion of sweat from the gland.
What is the role of the cuticular border in eccrine sweat glands?
The cuticular border provides structural resilience to the ductal lumen, ensuring the integrity and functionality of the sweat gland’s duct system.
What factors influence the rate of sweating according to the content provided?
The rate of sweating is influenced by local heating of the preoptic hypothalamic area, elevation of hypothalamic temperature, cutaneous temperature, and menopausal hot flashes.
What are the characteristics of dark cells in eccrine sweat glands?
Dark cells, also known as mucoid cells, border the luminal surfaces of the gland and contain abundant dark cell granules, although their specific function remains unknown.
Describe the innervation pathway for eccrine sweat glands as outlined in the content.
Efferent nerve fibers from the hypothalamic preoptic sweat center travel ipsilaterally to the brainstem and medulla, then to the intermediolateral cell column, followed by the intermediolateral horn (preganglionic fiber, myelinated), white ramus communicans, anterior roots, sympathetic chain, and finally to sympathetic class C fibers from sympathetic ganglia (postganglionic, unmyelinated) that end around the sweat gland.
What is the function of basal ductal cells in eccrine sweat glands?
Basal ductal cells serve in sodium pumping by providing maximally expanded Na pump sites and efficient energy metabolism.
What is the role of acetylcholine (ACh) in the function of eccrine sweat glands?
Acetylcholine (ACh) is the major neurotransmitter released from periglandular nerve endings, stimulating sweat secretion.
How does cholinergic stimulation affect sweat secretion compared to B-adrenergic stimulation?
Cholinergic stimulation can increase sweating rates by 5 to 10 times higher than B-adrenergic stimulation.
What factors influence the sweat rate in eccrine glands?
The sweat rate is influenced by: 1. The number of active glands. 2. The average sweat rate per gland, which can range from 2 to 20 nL/min². 3. Periglandular acetylcholine concentration.
What is the composition of human eccrine sweat and how does it vary with sweat rate?
Human eccrine sweat primarily contains inorganic ions, mainly NaCl, which increases with sweat rate but plateaus at 100mM.
What is the significance of energy metabolism in eccrine sweat secretion?
Sweat secretion is mediated by ATP-dependent active transport mechanisms.
What does human eccrine sweat primarily contain?
Human eccrine sweat primarily contains inorganic ions, lactate, and urea.
How does NaCl concentration in sweat vary with sweat rate?
NaCl concentration increases with sweat rate but plateaus at around 100mM.
What is the significance of energy metabolism in eccrine sweat secretion?
Sweat secretion is mediated by ATP-dependent active transport of ions, relying on exogenous substrates for energy metabolism.
How does botulinum toxin affect eccrine sweat gland function?
Botulinum toxin interferes with ACh release at cholinergic terminals, reducing sweat production.
How does emotional sweating differ from thermoregulatory sweating?
Emotional sweating occurs on the palms, soles, axillae, and forehead, while thermoregulatory sweating is widespread and responds to temperature changes.
What role does acetylcholine (ACh) play in eccrine sweat glands?
ACh is the major neurotransmitter released from nerve endings, stimulating sweat secretion.
What are the effects of denervation on sweat response?
Denervation can lead to cessation of the sweat response, while damage to preganglionic fibers maintains pharmacologic responsiveness.
What factors determine the sweat rate in eccrine glands?
The sweat rate is determined by the number of active glands and the average sweat rate per gland.
What is the significance of the periodicity of sweat secretion?
The periodicity of sweat secretion is influenced by central nerve impulse discharges.
What is the primary energy source for sweat secretion in eccrine glands?
Sweat secretion is primarily mediated by ATP-dependent active transport of ions.
What role does lactate play in eccrine sweat composition?
Lactate concentration depends on sweat rate and is produced by glycolysis of glucose.
What is the impact of botulinum toxin on sweat gland function?
Botulinum toxin inhibits sweat secretion by interfering with ACh release.
How does emotional sweating differ from other types of sweating?
Emotional sweating is typically confined to specific areas and is cholinergically mediated.
What is the relationship between sweat gland activity and the concentration of periglandular ACh?
Periglandular ACh concentration directly influences sweat rate.
What happens to the NaCl concentration in sweat during increased sweating?
NaCl concentration increases with sweat rate but plateaus at around 100mM.
What is the effect of cholinergic agents on sweat gland cells?
Cholinergic agents stimulate clear cells, leading to increased sweat production.
How does the myoepithelium contribute to sweat secretion?
The myoepithelium contracts in response to cholinergic stimulation, aiding in sweat expulsion.
What is the role of urea in eccrine sweat?
Urea in eccrine sweat is primarily derived from serum urea.
How does arterial occlusion affect sweat composition?
Arterial occlusion increases concentrations of NaCl and lactate in sweat.
What is the significance of dual adrenergic and cholinergic innervation of sweat glands?
Dual innervation allows for coordinated synthesis of sweat and glandular hypertrophy.
What is the primary fluid secreted by eccrine sweat glands?
Eccrine sweat glands secrete a primary fluid containing nearly isotonic NaCl concentrations.
What factors influence the reabsorption of NaCl in eccrine sweat glands?
Reabsorption of NaCl occurs in the duct and is influenced by sweat rate.
What is the relationship between sweat rate and lactate concentration?
Lactate concentration in sweat is dependent on sweat rate.
How does the body maintain pharmacologic responsiveness in sweat glands after denervation?
Damage to preganglionic fibers allows for maintenance of pharmacologic responsiveness.
What is the effect of acclimatization on sweat lactate concentration?
Acclimatization lowers sweat lactate concentration.
What is the primary mechanism by which eccrine glands secrete sweat?
Eccrine glands secrete sweat through active transport of ions.
How does the sweat rate relate to the number of active glands?
Sweat rate is directly proportional to the number of active glands.
What is the clinical significance of increased sweat NaCl concentration in cystic fibrosis patients?
In cystic fibrosis, increased sweat NaCl concentration is a key diagnostic marker.
What are the consequences of cholinergic stimulation on sweat gland activity?
Cholinergic stimulation enhances sweat gland activity, leading to increased sweat production.
What is the role of inorganic ions in eccrine sweat?
Inorganic ions are crucial for the formation of sweat and thermoregulation.
How does the body respond to increased thermal stress in terms of sweat gland activity?
Increased thermal stress triggers enhanced cholinergic stimulation of sweat glands.
What is the impact of cholinergic agents on the composition of sweat?
Cholinergic agents can alter sweat composition by stimulating clear cells.
What physiological changes occur in eccrine glands during exercise?
Eccrine glands increase sweat production through enhanced cholinergic stimulation.
How does the body regulate the composition of sweat during prolonged exercise?
The body adjusts reabsorption of NaCl and other ions in the sweat duct.
What is the significance of myoepithelial contraction in sweat secretion?
Myoepithelial contraction aids in the expulsion of sweat.
What are the effects of increased sweat rate on the concentration of bicarbonate in sweat?
Increased sweat rate leads to reabsorption of bicarbonate and ductal acidification.
What is the typical concentration range of ammonia in sweat compared to plasma ammonia?
Ammonia concentration in sweat is approximately 0.5 to 8 mM, which is 20 to 50 times higher than plasma.
What role does ACh play in the stimulation of eccrine sweat glands?
ACh stimulates eccrine sweat glands by increasing intracellular Ca.
How does ductal Na+ reabsorption occur in sweat glands?
Ductal Na+ reabsorption is accomplished through coordinated activities of ion channels and pumps.
What is the significance of the cystic fibrosis transmembrane regulator (CFTR) in sweat glands?
CFTR channels play an important role in Cl− transport, and their dysfunction leads to higher NaCl concentrations in sweat.
What mechanisms contribute to sweat acidification?
Sweat acidification is caused by carbonic anhydrase and various ion exchangers.
Describe the mechanism of sweat secretion in eccrine glands.
Sweat secretion begins with ACh stimulation, leading to increased intracellular Ca and ion fluxes.
What is the role of the Na-K-ATPase pump in eccrine sweat gland function?
The Na-K-ATPase pump recycles Na+ and K+ across the membrane, facilitating sweat secretion.
How does cystic fibrosis affect eccrine sweat gland function?
Cystic fibrosis impairs Cl− reabsorption in eccrine ducts, leading to higher NaCl concentrations.
How does acclimatization affect sweat composition?
Acclimatization lowers sweat lactate concentration.
What is the role of the ENaC channel in eccrine sweat gland ducts?
ENaC channels facilitate Na+ reabsorption, contributing to hypotonic sweat production.
What is the role of lactate in eccrine sweat?
Lactate varies with sweat rate and decreases with acclimatization.
How does the sweat rate influence NaCl concentration in eccrine sweat?
Sweat rate directly influences NaCl concentration, with higher rates leading to increased levels.
What is the relationship between sweat ammonia concentration and sweat rate?
Sweat ammonia concentration is inversely related to sweat rate.
What stimulates the eccrine sweat gland to release sweat?
The eccrine sweat gland is stimulated by ACh via increased intracellular calcium.
How does cell shrinkage contribute to sweat secretion?
Cell shrinkage occurs due to ion loss, leading to increased intracellular Na+ and sweat secretion.
What role does the Na+/K+/2Cl− cotransporter play in sweat production?
The cotransporter increases cytosolic Na+, activating the Na+/K+ ATPase and drawing NaCl and water into the lumen.
What is the effect of ACh-induced sweating on intracellular calcium levels?
ACh-induced sweating is mediated by increased intracellular calcium.
What is the significance of cystic fibrosis transmembrane regulator (CFTR) channels in sweat glands?
CFTR channels are crucial for Cl− transport, and their dysfunction leads to higher sweat NaCl concentrations.
What is the role of carbonic anhydrase in sweat production?
Carbonic anhydrase contributes to sweat acidification and pH regulation.
How does the Na+/H+ antiporter NHE1 function in sweat glands?
NHE1 pumps Na+ into the cell and H+ out, regulating intracellular pH.
What happens to sweat composition when claudin-3 is decreased?
Decreased claudin-3 leads to increased sweat leakage.
What is the typical urea content in sweat expressed as a ratio?
Sweat urea content is usually expressed as a sweat-plasma ratio.
What is the concentration range of ammonia in sweat compared to plasma?
Ammonia concentration in sweat is approximately 0.5 to 8 mM, which is 20 to 50 times higher than that in plasma.
What are the primary proteins found in sweat, and what is their significance?
Proteins in sweat include proteases and dermcidin, which play roles in skin protection.
How does the Na+/K+ ATPase contribute to sweat gland function?
The Na+/K+ ATPase facilitates the movement of NaCl and water into the glandular lumen.
What is the impact of increased intracellular Ca on sweat gland activity?
Increased intracellular Ca stimulates the release of sweat.
What is the mechanism of ductal absorption in sweat glands?
Ductal absorption involves Na+ reabsorption and Cl− transport, contributing to sweat composition.
What factors influence the acidity of sweat?
Sweat acidity is influenced by carbonic anhydrase and various ion exchangers.
How does the secretion of antimicrobial peptides in sweat contribute to skin health?
Antimicrobial peptides help protect the skin from infections.
What physiological changes occur in sweat glands during high sweat rates?
Sweat ammonia concentration decreases during high sweat rates.
What is the role of intracellular enzymes in sweat gland function?
Intracellular enzymes coordinate activities of ion channels and pumps.
How does the movement of Cl− into the glandular lumen affect sweat production?
Cl− movement draws Na+ into the lumen, crucial for osmotic water movement.
What is the effect of sweat gland stimulation by ACh on ion transport?
ACh stimulation increases intracellular Ca, opening ion channels and facilitating sweat secretion.
How does the movement of Cl− into the glandular lumen affect sweat production?
The movement of Cl− into the glandular lumen draws Na+ into the lumen as well, which is crucial for the osmotic movement of water and the production of sweat.
What is the effect of sweat gland stimulation by ACh on ion transport?
ACh stimulation leads to increased intracellular Ca, which opens ion channels, allowing K+ and Cl− to escape, and facilitating Na+ and water movement into the glandular lumen.
How does the presence of certain therapeutic agents in sweat affect its composition?
Therapeutic agents like griseofulvin, ketoconazole, and amphetamines can be secreted in sweat, potentially altering its composition and properties.
What physiological process leads to the production of hypotonic sweat?
Hypotonic sweat is produced through the reabsorption of Na+ and Cl− in the duct, which is facilitated by various ion transport mechanisms, including the Na+/K+ ATPase and CFTR channels.
What is the role of the V-type H+ ATPase in sweat glands?
The V-type H+ ATPase pumps H+ into the luminal sweat, contributing to the acidification of sweat and regulation of its pH.
How does the secretion of sweat change with varying sweat rates?
As sweat rates increase, the concentration of certain components, such as ammonia, may decrease, indicating a dynamic relationship between sweat production and composition.
What is the impact of sweat gland dysfunction in conditions like cystic fibrosis?
In cystic fibrosis, the dysfunction of CFTR channels leads to impaired Cl− reabsorption in sweat glands, resulting in sweat with higher salt content and altered composition.
What is the relationship between sweat gland activity and intracellular calcium levels?
Sweat gland activity is closely linked to intracellular calcium levels, which are stimulated by ACh and are crucial for initiating sweat secretion.
How does the reabsorption of Na+ and Cl− in sweat ducts affect sweat composition?
The reabsorption of Na+ and Cl− in sweat ducts results in the production of hypotonic sweat, which has lower concentrations of these ions compared to plasma.
What is the primary mechanism by which sweat is produced in eccrine glands?
Sweat production in eccrine glands primarily occurs through the stimulation of ACh, leading to increased intracellular Ca, which facilitates ion transport and fluid secretion.
How does the concentration of proteins in sweat compare to plasma?
The concentration of proteins in sweat, such as proteases, is approximately 20 mg/dL, which is significantly lower than in plasma, indicating selective secretion processes.
What is the significance of the Na+/K+/2Cl− cotransporter in sweat secretion?
The Na+/K+/2Cl− cotransporter is essential for transporting ions into the sweat gland cells, which is critical for maintaining osmotic balance and promoting sweat secretion.
What are the primary locations where apocrine sweat glands are found?
Apocrine sweat glands are primarily found in the axillae, perineum, and areolae of the breast.
What is the mode of secretion for apocrine sweat glands?
The mode of secretion for apocrine sweat glands is merocrine type and is pulsatile.
What triggers the secretion of apocrine sweat glands?
The secretion of apocrine sweat glands is controlled by emotive stimuli after puberty and is stimulated by epinephrine or norepinephrine.
What is the composition of the secretion from apocrine sweat glands?
The secretion from apocrine sweat glands contains three types of precursors: fatty acids, sulfanyl alkanols, and odiferous steroids. These components are converted by bacteria on axillary skin.
What are the functions of apocrine sweat glands?
The functions of apocrine sweat glands include: producing odoriferous sexual attractants, territorial markers, and warning signals; increasing frictional resistance and tactile sensibility; enhancing evaporative heat loss; and acting as pheromones.
What are the key differences in the composition of sweat produced by eccrine and apocrine glands?
Eccrine sweat is primarily water with NaCl, lactate, and urea, while apocrine sweat contains fatty acids, sulfanyl alkanols, and odiferous steroids, which are converted by bacteria into volatile odor molecules.
What are the primary stimuli for apocrine sweat gland secretion?
Apocrine sweat gland secretion is stimulated by emotive stimuli, epinephrine, and norepinephrine, particularly after puberty.
How do apocrine sweat glands differ in their mode of secretion compared to eccrine glands?
Apocrine sweat glands secrete via a merocrine type and pulsatile mode, while eccrine glands secrete continuously via exocytosis.
How does the composition of apocrine sweat contribute to its odor?
Apocrine sweat contains fatty acids, sulfanyl alkanols, and odiferous steroids, which bacteria degrade into volatile odor molecules, creating its characteristic smell.
What is the function of the multidrug resistance protein 8 in apocrine sweat glands?
The multidrug resistance protein 8 controls apocrine sweat secretion through an ATP-dependent efflux mechanism.
At what stage of development do apocrine sweat glands become functional, and what is this associated with?
Apocrine sweat glands become functional just before puberty, which is associated with hormonal changes.
Describe the anatomical structure of apocrine sweat glands.
Apocrine sweat glands are coiled and localized in the subcutaneous fat near the dermis. They consist of a single layer of cuboidal or columnar cells resting on a layer of myoepithelial cells and empty into the hair follicle infundibulum.
What is the initial state of the secretion from apocrine sweat glands, and how does it change?
The secretion from apocrine sweat glands is initially cloudy, viscous, and odorless with a pH of 6 to 7.5. It attains its characteristic odor upon being degraded by bacteria, which release volatile odor molecules.
What are the main functions of apocrine sweat glands?
The main functions of apocrine sweat glands include: producing odoriferous sexual attractants; serving as territorial markers and warning signals; increasing frictional resistance and tactile sensibility; enhancing evaporative heat loss; and acting as pheromones.
What are the three types of precursors found in the secretion of apocrine sweat glands?
The secretion of apocrine sweat glands contains three types of precursors: fatty acids, sulfanyl alkanols, and odiferous steroids.
How is the secretion from apocrine sweat glands controlled?
The secretion from apocrine sweat glands is controlled by emotive stimuli after puberty and is stimulated by epinephrine or norepinephrine.
What type of secretion do apocrine sweat glands utilize, and how is it characterized?
Apocrine sweat glands utilize a merocrine type of secretion, which is characterized as pulsatile.
What role do bacteria play in the odor associated with apocrine sweat glands?
Bacteria on the axillary skin degrade the secretion from apocrine sweat glands, releasing volatile odor molecules that contribute to the characteristic odor.
What physiological changes occur in apocrine sweat glands at puberty?
At puberty, apocrine sweat glands become functional due to hormonal changes, leading to the production of sweat that can be influenced by emotive stimuli.
Give some diseases of increased activity of the sebaceous glands.
Give some diseases of decreased activity of the sebaceous glands.
Give some diseases of increased activity of the eccrine glands.
Give some diseases of decreased activity of the eccrine glands.
Give some diseases of abnormal activity of the apocrine glands.
As daughter cells migrate from the bulge region, identify the expression patterns of transcription factors that determine their final cell lineage (SEBOCYTE vs HAIR CELL).
Enumerate human sebaceous gland lipids.
It is a major fatty acid of the adult human sebum.
Sapienic acid
These 2 distinguishes sebum from lipid of internal organs.
Wax esters
Squalene
It is a fatty acid thought to be unique to human sebum.
Sebaleic acid
Describe the lipid composition of sebum in percentages.
40-60% = Triglycerides, diglycerides and FFA
25-30% = wax esters
12-15% = squalene
3-6%= cholesterol esters
1.5-2.5%= cholesterol
Function of sebaceous glands in embryology, development and differentiation?
Function of sebaceous glands in synthetic activity?
Function of sebaceous glands in terms of protection?
Function of sebaceous glands in terms of transportation?
Function of sebaceous glands in inflammation and immunity?
Function of sebaceous glands in terms of endocrine properties?
What are the nuclear hormone receptors found in human sebaceous gland cells, their ligands and their effects?
What are the transmembrane hormone receptors found in human sebaceous gland cells, their ligands and their effects?
A human has _____ sweat glands (_____ of skin surface).
2-4 million
200-400/cm2
Up to ___/day of sweat is produced by acclimatized individuals.
10L
In humans, sweat glands are generally classified into _____ and _____ types.
Apocrine
Eccrine
_____ is the strongest stimulus for sweating.
Hypothalamic temperature
_____ is the major stimulus of eccrine sweat glands secreted by _____ nerves.
Acetylcholine
Sympathetic
_____ controls apocrine gland secretion.
Adrenergic stimulation
_____ inhibits sweating by preventing acetylcholine release.
Botulinum toxin
_____ is a major source of eccrine gland ATP.
Oxidative metabolism of glucose
Ductal reabsorption conserves _____.
NaCl
_____ are necessary for apocrine odor.
Bacteria
Odiferous precursors secretion is controlled by the _____ encoded by _____.
MRP8
ABCC11
Sweat glands are dense on these areas (3).
Palms and soles
Forehead
Upper limbs
Sweat glands are absent at these areas (3).
Lip margins
Eardrums
Nailbeds of fingers and toenails
This sebum component is critical for maintaining stratum corneum hydration.
Glycerol (from triglyceride hydrolysis)
Give some antimicrobial peptides in the sebum.
Cathelicidin (initiate cytokine production; works against P. acnes)
Psoriasin
B defensin 1
B defensin 2
Free fatty acids in sebum are bactericidal against these organisms due to increase in B defensin 2 expression.
Gram positive organisms
Innate immunity expressed in sebaceous glands?
TLR2
TLR4
CD1d
CD14
3 distinct niches for stem cells?
Follicle bulge
Base of sebaceous glands
Basal layer of epidermis
Transit time of sebaceous gland cells from formation to discharge?
7.4 days
(4-7 days: undifferentiated; 14-25 days: differentiated)
T of F: The size and number of sebaceous glands increases with age, but turnover of sebaceous glands in older adults is slowed.
False.
- The size of sebaceous glands increases with age.
- The number of sebaceous glands REMAINS THE SAME throughout life.
- Turnover of sebaceous glands in older adults is slowed.
These are receptors that are regulated by ligands of sebaceous gland receptors.
- Androgen and estrogen receptors
- PPAR
- LXR
- Neuropeptide receptor
- Retinoid receptor
- Vitamin D receptor
T or F: Levels of testosterone parallels patterns of sebaceous gland activity.
False. Levels of testosterone DON’T PARALLEL patterns of sebaceous gland activity.
This marks the start of sebum secretion.
Adrenarche (precedes puberty by 2 years).
It is a significant regulator of sebaceous gland activity and is converted to testosterone and DHT in SG.
DHEAS
How does DHEAS production change throughout life?
Increases in newborns
Decreases in 2-4 year-old children
Rise when sebum secretion increases
Decreases in both sexes starting early adulthood and continuing throughout life (parallels decrease of sebum secretion).
What are enzymes that convert DHEAS into more potent androgens?
3B-hydroxysteroid DH
17B-hydroxysteroid DH
5A-reductase
It is the most potent pharmacological inhibitor of sebum secretion, with a significant decrease as early as 2 weeks after use.
Isotretinoin (13-cis-RA)
Histological changes seen in sebaceous glands after isotretinoin therapy?
- Decrease in sebaceous gland size (due to inhbition of androgen synthesis, cell cycle arrest and apoptosis)
- Sebocytes appear undifferentiated (no lipid in cytoplasm)
T or F: Isotretinoin does not interact with retinoid receptors.
True.
It is a prodrug for all-trans-RA which interacts with RARs.
These are nuclear hormone receptors in sebaceous glands that form heterodimers with retinoid X receptors to regulate lipid metabolism and cell proliferation and differentiation.
PPARs
What kind of PPAR is present in basal and differentiated cells?
a, d, g - basal
g - differentiated
These 2 drugs increase sebum secretion rates.
Fibrates (PPAR-a ligand)
Thiazolidinediones (PPAR-g ligand)
These receptors interact with PPAR-g and LXR and are crucial fr regulaton of key genes of lipid metabolism.
RXR-a
LXR is activated by?
Oxysterold and intermediate products of the cholesterol pathway
Some drugs act on certain PPAR subtypes to decrease sebaceous lipid synthesis, and are used in the treatment of acne. What are these drugs?
PPAR-a agonists
PPAR-g antagonists
These drugs that act on a PPAR subtype may be beneficial for aging skin.
PPAR-g agonist
These drugs that act on a PPAR subtype may be involves in sebaceous tumorigenesis.
PPAR-d agonists
LXR targets?
Fatty acid synthase
SREBP-1
This nuclear hormone, when deficient, increases GH-insulin-insulin-like growth factor 1 or FGF2 signaling and causes acne, with increased sebaceous lipogenesis.
Fox01
This structural protein regulates sebaceous gland size and lipid accumulation.
PLIN2
This structural protein modulates lipogenic pathways in human sebaceous gland cells
PLIN3
This structural protein is strongly induced during human sebocyte differentiation and regulates sebaceous lipogenesis.
Angiopoietin-like 4
Anlagen of eccrine sweat glands appear:
___ months AOG in the palms and soles
___ months AOG in the axilla
___ months AOG in the entire body
3.5
5
6
The anlagen of eccrine sweat glands derive from the?
Epidermal ridge.
The anlagen of eccrine sweat glands is double-layered and forms a lumen at ___ months AOG.
4-8
Eccrine secretory cells resemble those of an adults by ___ months AOG.
8
By ___ months AOG, myoepithelial cells form around the coil and the excretory duct.
9
The secretory coil secretes a sterile, dilute solution containing?
NaHCO3
K
NaCl (~40mM, less compared to ECF due to partial reabsorption via ENaC on apical membrane of eccrine duct cells)
Glucose
Pyruvate
Lactate
Cytokines
Dermcidine
B defensin
Cathelicidins
Types of secretory coil cells?
- Clear (secretory, at the basement membrane and myoepithelial cells)
- Dark (mucoid, at the apical surface)
- Myoepithelial cells
These cells of the eccrine gland secretory coil have increased mitochondria, autofluorescent body (lipofucsin granule), villi and secrete water and electrolytes.
Clear cells
These cells of the eccrine gland secretory coil are smooth with dark cell granules, with an unknown function.
Dark cells
These cells of the eccrine gland secretory coil have actin filaments, are contractible and are responsible for pulsatile sweat.
Myoepithelial cells
Components of the eccrine sweat duct?
Outer - basal/peripheral cells
Inner - luminal / cuticular cells
This portion of the eccrine sweat duct is more active (due to increased mitochondria and presence of the Na-K-ATPase pump), and reasborbs Na.
Proximal / coiled duct
These cells contain tonofilaments near the cuticular border and are responsible for the structural resilience of eccrine sweat ducts.
Luminal ductal cells
Increase in internal temperature is ___ times more efficient that increase in skin temperature in stimulating the sweat center.
9
Pathology behind hot flashes?
Hypersensitive brain response.
How does clonidine relieve hot flashes?
It decreases norepinephrine release.
An antimicrobial cysteine-rich peptide found in the lumen of eccrine ducts.
B defensin
Preganglionic fibers that innervate sweat glands are found in the?
Intermediolateral horn of the spinal cord (myelinated). They pass out in the anterior roots to reach the sympathetic chain and synapse.
Describe the postganglionic fibers that innervate sweat glands.
Unmyelinated sympathetic class C.
The nerve supply to the sweat glands of the upper limb is from?
T2-8
The nerve supply to the sweat glands of the face and eyelid is from?
T1-4
Resection of T2 for palmar hyperhidrosis results to what syndrome?
Horner syndrome
The nerve supply to the sweat glands of the trunk is from?
T4-12
The nerve supply to the sweat glands of the lower limb is from?
T10-12
The major neurotransmitter released from periglandular nerve endings?
Ach
Type A botulinum toxin cleaves?
SNAP-25
Type B botulinum toxin cleaves?
VAMP (synaptobrevin)
Sweat glands respond to what drugs?
Cholinergic agents
A-, B- adrenergic stimulants
Aside from ACh, sweat glands respond to what neurotransmitters?
VIP
ATP
T or F: B-adrenergic stimulation yields 5-10x higher sweating rate than cholinergic stimulation.
False.
CHOLINERGIC stimulation yields 5-10x higher sweating rate than B-adrenergic stimulation.
_____ determines sweat rate in humans.
Periglandular ACh concentration
When stimulated by cholinergic agents, clear cells in vitro lose ___ and ___, and increase intracellular ___, and shrink.
K, Cl
Ca
Denervation of the postganglionic fibers causes the sweating response to intradermal nicotine or ACh to disappear within ___.
a few weeks
Denervation of the preganglionic fibers causes the sweating response to intradermal nicotine or ACh to disappear within ___.
several months to 2 years
Emotional sweating is usually confined to the (3)?
Palms and soles
Axillae
Forehead
T or F: Emotional sweating on the palms and soles ceases during sleep, but thermal sweating occurs even during sleep if the body
temperature rises.
True.
T of F: Emotional sweating is cholinergically medicated.
True.
The sweat rate in a given area of the skin is determined by the _____ and the _____.
number of active glands
average sweat rate per gland
The maximal sweat rate per gland varies from _____.
2 to 20 nL/min2
Whereas _____ sweating begins immediately on intradermal injection, _____ sweating requires a latent period of from 1 to 2 minutes.
cholinergic
β-adrenergic
One consequence of dual cholinergic and adrenergic innervation is to maximize tissue accumulation of _____, which may be instrumental in stimulating the synthesis of sweat and glandular hypertrophy of the sweat gland.
cyclic adenosine monophosphate (cAMP)
Myoepithelial contraction occurs with _____ stimulation, but _____ do not
induce tubular contraction.
cholinergic
α-, β-adrenergic agents
Endogenous glycogen stored in the
clear cells can sustain sweat secretion for less than ___ minutes; thus, the sweat gland must depend almost
exclusively on exogenous substrates for its energy metabolism, such as ___, ___ and ___.
10
mannose, lactate, pyruvate
_____ has the most important influence
on final NaCl concentration.
Sweat rate (and thus the tran-
sit time of sweat)
Concentration of electrolytes in sweat?
NaCl - 100 mM
K - 5 to 10 mM (slightly higher than plasma)
HCO3 - 10 mM (primary), 1 mM (final)
Condition when sweat NaCl concentration is increased?
Cystic fibrosis
Drugs secreted in sweat (4)?
Griseofulvin
Ketoconazole
Amphetamine
Chemotherapeutic agents
ACh-induced sweating, which constitutes the bulk of sweat production, appears to be mediated by _____.
intracellular Ca2+
Adrenergic-induced sweating appears to be mediated by increased _____.
intracellular cAMP
T or F: Final sweat is hypertonic and acidic.
False: It is HYPOTONIC and acidic.
Cl− transport appears to be both_____ and _____, with the cystic fibrosis transmembrane regulator (CFTR) Cl− channels playing an important
role in transcellular fluxes.
transcellular
paracellular
When the drug _____ is injected systemically or locally, the Na/K ratio in sweat begins to decrease within 6 hours, reaching a nadir at 24 hours and returning to the preinjection level in 48 to 72 hours.
aldosterone
The transfer of sweat to the skin surface without leakage is important for the homeostatic regulation of
skin and is impaired in ____; lesional skin presents a decreased _____ expression in sweat glands, which is accompanied by sweat leakage
atopic dermatitis
claudin-3
Apocrine sweat glands are found in humans, largely confined to the regions of the _____, the_____,
and the _____.
axillae
perineum
areolae of the breast
The apocrine duct is composed of a double layer of cuboidal cells
and empties into _____.
hair follicle infundibulum
T or F: The apocrine sweat is cloudy,
viscous, initially odorless, and at a pH of 6 to 7.5.
True.
Bacteria behind body odor?
Corynebacterium striatum
Apocrine sweat contains three types of precursors: _____, _____, and _____, which are converted by bacteria on axillary skin into odiferous substances.
fatty acids
sulfanyl alkanols
odiferous steroids
A number of functions have been attributed to the apocrine glands, including roles as _____, _____, and _____.
odoriferous sexual attractants
territorial markers
warning signals
High levels of _____ are found in the secretory cells of the apocrine gland.
15-lipoxygenase-2
Current data indicate that the secretion of apocrine glands is _____.
merocrine
The apocrine sweat glands of humans respond to emotive stimuli when?
Only after puberty
The apocrine glands are controlled mainly by_____ agonists.
adrenergic
T or F: Local capillary circulation likely assists in conveying the transmitter substance to the apocrine sweat gland cells, a form of neurohumoral
transmission.
True
