Sebaceous and Sweat Glands

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SEBACEOUS GLANDS AND SWEAT GLANDS: 

S EBACEOUS GLANDS AND SWEAT GLANDS DR. Ahmed Essop DERMATOLOGY DEPARTMENT

SEBACEOUS GLANDS: 

SEBACEOUS GLANDS Definition: Lipid-producing structures that are unilobular or multi-lobular and are usually associated with a hair follicle

EMBRYOLOGY: 

EMBRYOLOGY Derived from the epidermis as bulge from developing hair follicle root sheath and grow downward into the dermis

EMBRYOLOGY: 

EMBRYOLOGY Develops around 13 th to 16 th week of gestation Present at birth ( vernix caseousa ) Declines and remains low until puberty where it increases Androgens (5 α - dihydrotestosterone ) –sebum production Decreases in females (menopause) and in males (6 th to 7 th decade)

LOCATION: 

LOCATION Associated with hair follicles all over the body - pilosebaceous unit Non-hairy sites – eyelids ( Meibomian gland) – nipple (Montgomery’s turbecles ) – internal fold of prepuce (Tyson’s gland) Palms and soles are devoid of sebaceous glands Largest on face and scalp Buccal mucosa and vermillion of lip (Fordyce’s spots)

ANATOMY: 

ANATOMY Consists of one or more lobules leading into a common excretory duct composed of stratified squamous epithelium

PowerPoint Presentation: 

ANATOMY Glands are composed of sebocytes and keratinocytes lining the sebaceous gland Peripheral layer composed of cuboidal , basophilic cells with an inner lipid-laden zone Immunohistochemistry – sebaceous gland label strongly for EMA (Epithelial membrane antigen)

ANATOMY: 

ANATOMY No CEA ( Carcinoembryonic antigen) or low molecular weight keratin and no S-100 protein expression As cells mature before disintegration, lipid droplets completely fill the cytoplasm and compress the centrally located nucleus. Disintegrate into amorphous mass of lipids and cellular debris – sebum

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PHYSIOLOGY Holocrine glands – during sebum secretion whole cell disintegrates Life span of sebocytes – 21-25 days Sebum contains: squalene, cholesterol esters, wax esters and triglycerides Triglycerides are hydrolyzed by bacterial enzymes – free fatty acids Free fatty acid and other sebum substances – acne vulgaris

FUNCTION OF SEBACEOUS GLANDS: 

FUNCTION OF SEBACEOUS GLANDS Role in causing acne Control moisture loss from the epidermis Protects skin from bacterial and fungal infections ( Ig A) Scent production Thermoregulation – hot and cold conditions Allows vit E to function on the skin surface

FACTORS REGULATING SEBACEOUS GLAND SIZE AND PRODUCTION: 

FACTORS REGULATING SEBACEOUS GLAND SIZE AND PRODUCTION Androgens and retinoids Other factors include – melanocortins , peroxisome proliferator activated receptor (PPAR) and fibroblast growth factor receptor (FGFR)

ECCRINE SWEAT GLANDS: 

ECCRINE SWEAT GLANDS

ECCRINE SWEAT GLANDS: 

ECCRINE SWEAT GLANDS Definition: Simple coiled glands that regulate body temperature

EMBRYOLOGY: 

EMBRYOLOGY 3 months gestation – cord of epithelial cells from epidermal ridge palms and soles 5 months – axillae 5 - 6 months – remainder of the body At birth morphologically normal and functional React to thermal and emotional stimuli No association with hair follicle

ANATOMY: 

ANATOMY Sweat gland distribution over the entire body surface: 1.6 – 4 million, excludes External ear canal, lips, clitoris and labia minora . High density on palms and soles Each gland weighs 30 – 40 µ g, total mass eccrine gland 100g (kidney size) A well acclimatized person can perspire as much as 10L per day

ANATOMY: 

ANATOMY Gland consists of a secretory coil in lower dermis and subcutaneous tissues Drains into the long thin duct with apical portion ( acrosyringium ) opening to the skin surface

PowerPoint Presentation: 

Types of secretory cells: Larger clear cells (main secretory cells) Small darker cells (resembling mucus-secreting cells), borders all apical surfaces Myoepithelial cells (spindle shaped masses of myofilaments ) Broader base than lumen Broader lumen supports gland and propels sweat to the surface PAS-positive, diastase-labile glycogen granules PAS positive glycoproteins Secretes aqueous material and glycogen Secretes sialomucin positive (PAS and alcian blue stain)

ANATOMY: 

ANATOMY Intercellular canaliculi are formed where clear cells adjoin and allows the secretion to reach the lumen Duct is composed of 2 or more layers of cuboidal cells (basal and luminal cells) no myoepithelium Basal cells rich in mitochondria and membrane rich in sodium potassium – ATPASE (sodium absorption)

ANATOMY: 

ANATOMY Luminal cells dense layer of tonofilaments – cuticular border gives structural resilience to ductal lumen and absorptive surface NaCl Intraepidermal portion ( acrosyringium ) twisted like corkscrew – similar coils of stratum corneum . Innervation – postsynaptic sympathetic fibers – Ach responds to thermal, osmotic, mental and gustatory stimuli

FUNCTION OF ECCRINE GLANDS: 

FUNCTION OF ECCRINE GLANDS Secretory and excretory organ Thermoregulation – sweat Maintains electrolyte balance Keeps the skin moist Excretes systemically administered drugs E.g. griseofulvin , ketoconazole , chemotherapy agents.

COMPOSITION OF ECCRINE GLAND: 

COMPOSITION OF ECCRINE GLAND Sterile dilute electrolyte solution: Sodium chloride Cytokines Amino acids Potassium Bicarbonate Proteolytic enzymes Pyruvate Antimicrobial peptides Cytokines Immunoglobulins Lactate Ammonia Calcium Urea Epidermal growth factor

PowerPoint Presentation: 

Hyperhidrosis Neurological – peripheral neuropathy, brain diseases Infections – tuberculosis and malaria Neoplasms – lymphomas Endocrine diseases – low oestrogen (menopause) Hypohidrosis / Anhidrosis Acquired – autonomic disorders (Ross syndrome) Congenital – Congenital ectodermal dysplasia – Icthyosis – Incontinentia pigmenti DISORDERS OF ECCRINE GLANDS

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Disorders of Eccrine Glands Hypohidrosis / Anhidrosis continues Neurological disorders – CNS lesions (stroke, tumours) – Degenerative disorders (Parkinson’s disease) – Peripheral nerve lesions ( Guillian Barre syndrome, leprosy, alcohol neuropathy) Toxins and pharmacological agents – botulism, anticholinergics , opiods Disorders of skin – burns, trauma, radiation therapy Disorders affecting sweat ducts – miliaria , palmoplantar psoriasis, atopic dermatitis Disorders of sweat composition – Cystic fibrosis

APOCRINE SWEAT GLANDS: 

APOCRINE SWEAT GLANDS

PowerPoint Presentation: 

Definition : Large lumen glands associated with hair follicles. Name derived from way of secretion – pinching off parts of their cytoplasm into the lumen APOCRINE SWEAT GLANDS

EMBRYOLOGY: 

EMBRYOLOGY Develops from an epithelial germ layer which gives rise to the sebaceous gland and hair follicle Begins in the 4th month of gestation until in late embryonic life Solid epithelial cord projects into the perifollicular mesenchyme Grows downwards past the developing sebaceous glands and arrector pili bulge

PowerPoint Presentation: 

Predominantly found in the anogenital and axillary regions, periumbilical Modified apocrine glands – external auditory meatus ( cerumious glands ) – Eyelids (Moll’s gland) – Areolar (Montgomery turbecles ) – Breast (Mammary glands) Occasionally on the face, scalp, abdomen usually small and non functional LOCATION

PowerPoint Presentation: 

Apocrine glands are short tubular glands, composed of: Intra epidermal duct Intra dermal duct Secretory portion Ductal portion leads to a pilosebaceous follicle entering the infundibulum above the sebaceous gland opening Occasionally opens directly to the skin surface ANATOMY

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Ductal portion shows a double layer of basophilic cells and periluminal eosinophilic cuticle Secretory portion shows a single layer of columnar or cuboidal cells Peripheral layer consist of myoepithelial cells which supports the ducts and propels the secretion to the surface ANATOMY

PowerPoint Presentation: 

Cytoplasm is eosinophilic except the apical portion containing PAS-positive, diastase-resistant granules. Lumen of the secretory portion is large -200 μ m in diameter Type of secretion consists of releasing portions of cytoplasm into the lumen (decapitation) Secretion visible on hematoxylin-eosinophil (H+E)stain ANATOMY

PowerPoint Presentation: 

Decapitation secretion

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Secretion contains an armophous PAS-positive, diastase-resistant material from granules that dissolved in the apical portion of secretory cells. PAS-positive material consists of sialomucin . ANATOMY

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Apocrine glands secrete an oily fluid, milky coloured, odourless with Ph 5.0 - 6.5 Characteristic odour – due to bacteria decomposition Stimulated by sympathetic nerve fibers – adrenergic PHYSIOLOGY OF APOCRINE GLANDS

PowerPoint Presentation: 

Function of apocrine sweat glands is not entirely clear but has been attributed to the following: Role as odoriferous sexual attractants Increase frictional resistance and tactile sensibility Production of pheromones FUNCTION OF APOCRINE GLANDS

PowerPoint Presentation: 

DIFFERENCES IN ECCRINE AND APOCRINE GLANDS Apocrine Eccrine Development Present at birth, associated with hair follicle Present at birth, no relation to pilosebaceous unit Localization Axilla , anogenital , periumbilical and nipples Entire body surface, high density on soles and palms Morphology Short, thick duct, opens into the upper part of follicular canal Secretory coil with wide lumen Long thin duct, opens to skin surface Secretory coil with narrow lumen Cell types Epithelial and myoepithelial Large secretory clear cells, dark cell and myoepithelium cells Innervation Sympathetic fibers Sympathetic fibers Function Production of pheromones Thermoregulation

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Bromhidrosis – sweaty body odour Hidradinitis suppurativa Psychological – paranoia Chromhidrosis Fox–Fordyce disease Disorders associated with apocrine glands

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Found in an adult axilla having morphology of both eccrine and apocrine epithelium Duct opens directly to the skin surface Secretory component – dilated apocrine segment and nondilated eccrine segment Innervated by sympathetic fibers APOECCRINE GLANDS

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REFERENCES Bolognia JL, Jorizzo JL, Rapini RP. Volume1: Dermatology 2nd Edition. 2008. Mosby. Ross MH, Romrell LJ, Kaye GI, Histology: A Text and Atlas. 3rd Edition. 1995. Williams & Wilkins. Wolff K, Goldsmith LA, Katz SI, Gilchrest BA, Paller AS, Leffell DJ. Volume1: Fitzpatrick’s Dermatology in General Medicine. 7th Edition. 2008. McGraw-Hill. Lever WF, Schaumburg-Lever G. Histopathology of the Skin. 7th Edition. 1990. J.B. Lippincott Company. McKee PH, Calonje E, Granter SR. Volume1: Pathology of the Skin with Clinical Correlations. 3rd Edition. 2005. Elsevier Limited.