6 - Skin Glands Flashcards by dvojnd rivera

Excrete their products into the hair follicle

Sebaceous glands

Apocrine sweat glands

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Excrete directly into the skin surface

Eccrine glands

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Holocrine secretion

Sebaceous glands

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Merocrine secretion

Apocrine and eccrine sweat glands

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Totally devoid of sebaceous glands

Palms and soles

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Largest and greater density of sebaceous glands

Nose
Face
Scalp

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Sebaceous glands arise in a _____ sequence

Cephalocaudal

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Earliest known signal necessary for sebaceous gland development

SOX9

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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)

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Advanced differentiated vs undifferentiated sebocytes

Advanced differentiated:
increased size
Decreased nucleocytoplasmic ratio

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Sebocyte stem cell signaling pathway

Increased Shh
Increased Myc
Decreased Wnt

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Hair cell stem cell signaling pathway

Increased Wnt

Decreased Lef1

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Basal cells of the peripheral zone from about _____% of the sebaceous gland

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Maturation zone represents about _____% of the sebaceous gland

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Distinguish sebum from lipids of human internal organs

Wax esters

Squalene

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Form 40-60% of total skin surface lipids

Triglycerides
Diglycerides
Free fatty acids

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“Normal” mammalian pathway of desaturation

Inserting a double bond between the 9th and 10th carbons of stearic acid to from oleic acid

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Sebaceous gland pathway of desaturation

Insertion of a delta 6 double bond into palmitic acid resulting to sapienic acid

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Major fatty acid of adult human sebum

Sapienic acid

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Elongation of sapienic acid by two carbons and insertion of another double bond gives

Sebaleic acid

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Fatty acid thought to be unique to human sebum

Sebaleic acid

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Function of sebum

Maintaining stratum corneum hydration
Mild antibacterial action
Transit mechanism for vitamin E

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Mild antibacterial action of sebum due to

Antiinflammatory lipids and immunoglobulin A

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Cathelicidin in sebum has direct antimicrobial activity against

Propionibacterium acnes

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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) 1. Newborns 2. 2-4 year old children

1. 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

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

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

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

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)

1. Secretion of isotonic NaCl concentrations by the secretory coil 2. 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

1. Fatty acids 2. Sulfanyl alkanols 3. 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

Total number of sweat glands

2-4 million (200-400/cm2)