6 - Skin Glands Flashcards
Excrete their products into the hair follicle
Sebaceous glands
Apocrine sweat glands
Excrete directly into the skin surface
Eccrine glands
Holocrine secretion
Sebaceous glands
Merocrine secretion
Apocrine and eccrine sweat glands
Totally devoid of sebaceous glands
Palms and soles
Largest and greater density of sebaceous glands
Nose
Face
Scalp
Sebaceous glands arise in a _____ sequence
Cephalocaudal
Earliest known signal necessary for sebaceous gland development
SOX9
Subpopulation of stem cells expressing _____ is established near the entrance of the sebaceous gland; marker of terminal epithelial cell differentiation
PRDM1 (formerly known as BLIMP-1)
Advanced differentiated vs undifferentiated sebocytes
Advanced differentiated:
increased size
Decreased nucleocytoplasmic ratio
Sebocyte stem cell signaling pathway
Increased Shh
Increased Myc
Decreased Wnt
Hair cell stem cell signaling pathway
Increased Wnt
Decreased Lef1
Basal cells of the peripheral zone from about _____% of the sebaceous gland
40
Maturation zone represents about _____% of the sebaceous gland
40
Distinguish sebum from lipids of human internal organs
Wax esters
Squalene
Form 40-60% of total skin surface lipids
Triglycerides
Diglycerides
Free fatty acids
“Normal” mammalian pathway of desaturation
Inserting a double bond between the 9th and 10th carbons of stearic acid to from oleic acid
Sebaceous gland pathway of desaturation
Insertion of a delta 6 double bond into palmitic acid resulting to sapienic acid
Major fatty acid of adult human sebum
Sapienic acid
Elongation of sapienic acid by two carbons and insertion of another double bond gives
Sebaleic acid
Fatty acid thought to be unique to human sebum
Sebaleic acid
Function of sebum
Maintaining stratum corneum hydration
Mild antibacterial action
Transit mechanism for vitamin E
Mild antibacterial action of sebum due to
Antiinflammatory lipids and immunoglobulin A
Cathelicidin in sebum has direct antimicrobial activity against
Propionibacterium acnes
Free fatty acids in sebum are bactericidal against
Gram-positive organisms
Skin stem cells can be found in
Follicle bulge
Base of sebaceous gland
Basal layer of epidermis
Average transit time of sebaceous gland cells from formation to discharge
7.4 days
Size of sebaceous glands (increases/decreases) with age
Increases
Number of sebaceous glands (increases/decreases) with age
Remains the same
Turnover of the sebaceous glands in older adults is (faster/slower) compared with young adults
Slower
Y/N: Levels of testosterone parallel the patterns of sebaceous gland activity
No - do not parallel
Most powerful androgens
Testosterone
5-DHT
Probably a significant regulator of sebaceous gland activity through its conversion to testosterone and DHT
Dehydroepiandrosterone sulfate (DHEAS)
Levels of DHEAS (high/low)
- Newborns
- 2-4 year old children
- Newborns - high
2. 2-4 year old children - very low
Decline in DHEAS starts in
Early adulthood
Most potent pharmacologic inhibitor of sebum secretion
Isotretinoin
Significant reductions in sebum production can be observed as early as _____ weeks of isotretinoin use
2
PPAR-alpha ligand for hyperlipidemia
Fibrates
PPAR-gamma ligand for diabetes
Thiazolidinediones
PPAR-_____ agonists may be beneficial in aging skin
PPAR-_____ may bee involved in sebaceous tumorigenesis
Gamma
Delta
In patients receiving PPAR agonists, sebum secretion rates are (increased/decreased)
Increased
Expressed in most lipid-metabolizing cells including the prostate, liver, fat tissue and skin
FoxO1
Acne and increased sebaceous lipogenesis are associated with relative nuclear (excess/deficiency) of FoxO1
Deficiency
Total number of sweat glands
2-4 million (200-400/cm2)
Amount of sweat produced per day by acclimatized individuals
10 liters
Strongest stimulus for sweating
Hypothalamic temperature
Marker of ductal cells of eccrine but not apocrine sweat glands
Stage-specific embryonic antigen-4 (SSEA-4)
Eccrine sweat glands are absent at
Margins of the lips
Eardrums
Nailbeds of fingers and toenails
Anlagen of eccrine sweat glands first appear in _____-old fetuses on the _____
3.5
Palms and soles
Eccrine sweat glands develop in the axillary skin in the _____ fetal month
5th
Eccrine glands develop all over the body by the _____ fetal month
6th
By the _____ fetal month, eccrine secretory cells resemble those of an adult
8th
By the _____ fetal month, myoepithelial cells form around the secretory coil and excretory duct
9th
Eccrine gland secretory coil primary components
Bicarbonate
Potassium
Sodium chloride
Relative to the plasma and extracellular fluid, the concentration of Na ions is much (higher/lower) in sweat
Lower
Eccrine secretory coil contains _____ distinct cell types
Clear (secretory)
Dark (mucoid)
Myoepithelial
_____ cells contain abundant mitochondria and an autofluorescent antibody called the lipofucsin granule
Clear
Clear vs dark cell surface
Clear - forms villi
Dark - smooth
Y/N: Proximal (coiled) eccrine duct is more active than the distal straight portion
Yes
_____ activity and the number of _____ are higher in the proximal (coiled) eccrine duct vs the luminal ductal cells
Na-K-adenosine triphosphatase
Mitochondria
Dense layer of tonofilaments near the luminal membrane of eccrine ducts
Cuticular border
Provides the strongest stimulus for thermoregulatory sweating responses
Elevation of hypothalamic temperature associated with an increase in body temperature
Increase in internal temperature is about _____ times more efficient than an increase in mean skin temperatures in stimulating the sweat center
9
Menopausal hot flashes seem to be caused by
Hypersensitive brain response
Decreased norepinephrine release is postulated as the mechanism by which _____ relieves hot flashes in symptomatic women
Clonidine
Decreased _____ may be the reason that women with decreased body madd index tend to have fewer symptoms of hot flashes
Core temperature
Y/N: Levels of estrogen, luteinizing hormone, and beta-endorphins influence hot flashes
No
Major neurotransmitter released from periglandular nerve endings of sweat glands
Acetylcholine
Major stimulant of sweat secretion; periglandular concentration determines the sweat rate
Acetylcholine
Y/N: Males perspire more profusely than females
Yes
Sweat rate in a given area of the skin is determined by (2)
Number of active glands
Average sweat rate per gland
Y/N: Cholinergic stimulation yields a 5-10 times higher sweating rate than does beta-adrenergic stimulation
Yes
Myoepithelial contraction occurs with _____ stimulation
Cholinergic
Endogenous glycogen stored in the clear cells can sustain sweat secretion for
Less than 10 minutes
Major route of ATP formation for sweat secretory activity
Oxidative metabolism of glucose
Steps in sweat formation (2)
- Secretion of isotonic NaCl concentrations by the secretory coil
- Reabsorption of NaCl by the duct
Has the most important influence on final sweat NaCl concentration
Sweat rate
Sweat NaCl (increases/decreases) with increasing sweat rate
Increases
Sweat NaCl concentration is (increased/decreased) in individuals with cystic fibrosis
Increased
Seen more frequently in carriers and patients with cystic fibrosis
Aquagenic wrinkling of the palms
ACh-induced sweating appears to be mediated by _____ vs adrenergic-induced sweating which appears to be mediated by _____
Intercellular calcium
Intercellular cAMP
Final sweat product
Hypotonic and acidic
Mutation in cystic fibrosis
Cystic fibrosis transmembrane regulator (CFTR) chloride channels
In atopic dermatitis, lesional skin presents a decreased _____ expression in sweat glands, which is accompanied by sweat leakage
Claudin-3
When aldosterone is injected systemically or locally, the Na/K ratio is sweat begins to (increase/decrease)
Decrease
More potent carbonic anhydrase inhibitors, such as _____, have been reported to induce oligohidrosis
Topiramate
Apocrine sweat glands do not become functional until
Just before puberty
There are high levels of _____ in the secretory cells of the apocrine gland
15-lipoxygenase-2
Apocrine sweat contains three types of precursors
- Fatty acids
- Sulfanyl alkanols
- Odiferous steroids
Axillary odor is significantly reduced in Asian populations that carry a single nucleotide polymorphism in this gene
ABCC11
Secretion of apocrine glands
Merocrine
Apocrine glands are controlled mainly by
Adrenergic agonists