皮膚科學基礎概論 皮膚科學基礎概論
Overview of the Skin Overview of the Skin
• The skin is one of the largest organs in the body:
surface area ≒ 1.8 m2
weight: approximately 16% of our body weight
• Four main functional areas:
1. Epidermis: the major protective layer derived from ectoderm 2. Dermis: the major support layer derived from mesoderm
3. Skin Appendages: derived from both ectoderm and mesoderm
Eccrine Sweat Gland Apocrine Sweat Gland Sebaceous Gland
Hair Follicle Nails
Arrector Pili muscle
4. Subcutis: this layer consists of loose connective tissue and fat
SKIN SKIN
Functions of the Skin Functions of the Skin
1. barrier to physical agents
2. protects against mechanical injury
3. prevents dehydration of body through fluid loss 4. reduces the penetration of UV Radiation
5. helps regulate body temperature 6. acts as a sensory organ
7. acts as an outpost for immune surveillance 8. plays a role in Vitamin D production
9. has a cosmetic association
Epidermis
Epidermis
Epidermis I.
Epidermis I.
• a continually renewing, stratified, squa mous epithelium that keratinizes and giv es rise to derivative structures (pilose baceous units, nails & sweat glands) cal led appendages
• about 0.4 to 1.5 mm in thickness (thicke st --- palms & soles)
• full-thickness skin:1.5-4 mm
Epidermis II.
Epidermis II.
• keratinocytes
• Melanocytes
• Langerhans cells
• Merkel cells
*basement membrane: separates epidermis &
dermis, mediates their attachment
Keratinocyte Keratinocyte
• ectodermally derived
• > 80 percent of the epidermal cells
• cytoplasmic keratin filaments:
1. ＞ 30 different keratins
2.a hallmark of the keratinocyte and other epithelial cells
3.structural (cytoskeletal) role
* desmosomes
# modified desmosomal junctions
Layers of the epidermis
Layers of the epidermis
1.Basal Cell Layer (stratum basale) I 1.Basal Cell Layer (stratum basale) I
• Mitotically active, columnar-shaped keratinocytes. att ach to the basement membrane zone by hemidesmosomes.
• The normal transit time for a basal cell,
from the time it detaches from the basal layer to th e
time it enters the stratum corneum, is at least 14 days.
• Transit through the stratum corneum and desquamation require another 14 days.
1. Basal Cell Layer (stratum basale) II 1. Basal Cell Layer (stratum basale) II
• Melanocytes:
5-10% of the layer and make melanin wh ich is transferred to neighboring keratinocytes via d endritic processes– neural crest origin
– most numerous on the face and other exposed areas of skin
• Epidermal melanin unit
: Approximately 36 basal an d suprabasal keratinocytes are thought to coexist fun ctionally with each melanocyte• Merkel cells:
among basal keratinocytes in particu lar regions of the body (in hairy skin and in the gla brous skin of the digits, lips, regions of the oral c avity, and the outer root sheath of the hair follicl e) and join with them by desmosomal junctions2. Spinous Cell Layer (stratum spinosum) 2. Spinous Cell Layer (stratum spinosum)
• Suprabasal spinous cells are polyhedral in shape (spin e-like appearance of the cell margins)
• The “spines” of spinous cells:abundant desmosomes, c alcium-dependent cell surface modifications that promo te adhesion of epidermal cells and resistance to mecha nical stresses
• Desmosomes:a mechanical coupling between epidermal cel ls, gap junctions between keratinocytes are sites of p hysiologic communication (regulation of cell metabolis m, growth, and differentiation)
• Langerhans cells: from bone marrow, mostly found in t his layer. dendritic, immunologically active cells th at play a role in antigen presentation.
3. Granular Cell Layer (stratum granulosum) 3. Granular Cell Layer (stratum granulosum)
• Flattened cells and lose their nuclei. In cytoplasm, keratohyalin granules as well as membrane-coating gr anules which expel their lipid contents into the inte rcellular spaces.
• The most apparent structures within these cells: baso philic, keratohyalin granules
• Keratohyalin granules are membrane-coating granules w hich expel their lipid contents into the intercellula r spaces.
• At the interface between the granular and cornified c ell layers, “barrier” lipids (e.g., sphingolipids) are formed
4. Horny Layer (stratum corneum) 4. Horny Layer (stratum corneum)
• Complete transition from a granular to a cornified cell is accomp anied by a 45 to 86 percent loss in dry weight
• The layers of resultant cornified cells provide mechanical protec tion to the skin and a barrier to water loss and permeation of so luble substances from the environment
• The stratum corneum barrier is formed by a two-compartment system of lipid-depleted protein-enriched corneocytes surrounded by a co ntinuous extracellular lipid matrix
• Horny cell:
1. the flattened, polyhedral-shaped, horny cell is the largest c ell
of the epidermis
2. Its shape and surface features are adapted to maintain the integrity of the stratum corneum yet allow for desquamation 3. the cell contain keratins and filaggrin
• Three key lipid types—cholesterol, ceramides, and free fatty aci ds—form the lamellar bilayers
Regulation of Epidermal Regulation of Epidermal
Proliferation and Differentiation Proliferation and Differentiation
1. Integrins: Keratinocytes express several integ rins and important to skin homeostasis
2. Growth Factors: epidermal growth factor (EGF), transforming growth factor (TGF)-α, TGF-ß, ke ratinocyte growth factor (KGF)...
3. Cytokines: keratinocyte-derived cytokines (int erleukin (IL)-1α, IL-6, IL-8) and granulocyt e-macrophage colony-stimulating factor (GM-CS F)
4. Retinoids 5. Vitamin D
36. Calcium
The dermal–epidermal The dermal–epidermal
junction (DEJ) junction (DEJ)
• The DEJ is a basement membrane zone that forms the inte rface between the epidermis and dermis
• Function:
1. attach the epidermis and dermis to each other
2. provide resistance against external shearing force s
3. serves as a support for the epidermis 4. determines the polarity of growth
5. directs the organization of the cytoskeleton in basal cells
6. provides developmental signals
7. serves as a semipenetrable barrier
Three supramolecular network Three supramolecular network
s of DEJ s of DEJ
1. Hemidesmosome-anchoring filament comp lex
2. Basement membrane
3. Anchoring fibrils
Overview of the Dermis Overview of the Dermis
• a supportive connective tissue matrix containing numerous specialized structures.
• The dermal thickness varies being thinnest
(0.6 mm) on the eyelids and thickest (3 mm or more) on the back,
palms, and soles.
Contains of the dermis I Contains of the dermis I
1. Collagen fibers
• Make up 70% of the dermis and give structural toughness and strength.
• Type I, III, and V account for the greatest proportion of the collagen in adult dermis
2. Elastic fibers
• Account for 4% of the dermal matrix protein
• loosely arranged in all directions and give elasticity to the skin
• Elastic fibers are also present in the walls of cutaneo us blood vessels and lymphatics and in the sheaths of h air follicles
Contains of the dermis II Contains of the dermis II
3. Ground substance
• consists of a semi-solid matrix of Proteoglycans ( hyaluronic acid, chondroitin sulfate, heparan sulf ate…)
4. Cells
• Fibroblasts
• Macrophages
• Mast cells
Organization of the Dermis Organization of the Dermis
1. Papillary Dermis
• Beneath the epidermis ex tending to vascular boun dary of subpapillary ple xus
2. Rticular Dermis
• The dominant region of t he dermis
• Composed of large-diamet er collagen fibers and m ature elastic fibers
Cutaneous vasculature I Cutaneous vasculature I
Function:
• provide nutrition
• regulation of temperature
• blood pressure
• wound repair
• immunologic events
Cutaneous vasculature II Cutaneous vasculature II
1. Arteries
• Musculocutaneous arteries in the subcutaneous fat migrate upwards to give rise to a subpapillary ple xus at the papillary/reticular dermal boundary.
• Subpapillary plexus gives off branches of its own that branch upwards to the dermal papillae.
• Each dermal papillae has a single loop of capillar y vessels, one arterial and one venous.
Cutaneous vasculature III Cutaneous vasculature III
2. Veins
• Veins drain from the venous side of t
he loop and branch downward to form t
he venous return network of the mid-d
ermis and subcutaneous layer.
Cutaneous vasculature IV Cutaneous vasculature IV
3. Lymphatic Vessels
• Function: regulating pressure of the interstitial fluid, clearing the tiss ue of cells, proteins, lipids, bacter ia, and degraded substances
• The lymphatics originate in the papil
lae then drain into increasingly larg
er vessels that ultimately reach the
regional lymph nodes.
Nerves and Receptors I Nerves and Receptors I
• The nerve networks of the skin – somatic sensory
– sympathetic autonomic fibers
• Nerve fibers of the skin
– myelinated or non-myelinated
– contain neuropeptides such as
substance P.
Nerves and Receptors II Nerves and Receptors II
1. Sensory fibers
• The sensory fibers are receptors of touch, pain, temperature , itch, and mechanical stimuli
• Rceptors are particularly dense in hairless areas such as th e palms, face areola, labia, and glanspenis
• Free sensory nerve endings can be seen in both the dermis an d the epidermis ； In the epidermis, they may end on Merkel c ells which detect pain, itch and temperature.
• In the dermis, there are specialized corpuscular receptors s uch as:
– Pacinian corpuscle: detects pressure and vibration
– Meissner's corpuscle: touch sensitive and mainly located in the dermal papillae of the hands and feet.
Nerves and Receptors III Nerves and Receptors III
2. Motor fibers
• Sympathetic motor fibers are codistri
buted with the sensory nerves in the
dermis until they branch to innervate
the sweat glands, vascular smooth mus
cle, the arrector pili muscle of hair
follicles, and sebaceous glands
Nerves and Receptors
Nerves and Receptors
Appendages of the Skin
Appendages of the Skin
Hair Follicle Hair Follicle
• Functions
1. prevent heat loss
2. as a “first line of defense”
3. as a “touch organ”
4. a conduit in the delivery of scents secreted by the sebaceous and
apocrine glands
5. an important component of the body image
• Hair follicles are distributed through out the integument with the exception of the palms, soles, and portion of th e genitalia (so-called glabrous skin)
• The highest density of follicles is on the scalp (about 100000 hair follicle s), growth rate is about 1 cm/month
Compartments of hair shaft and hair follicle
Compartments of hair shaft and hair follicle
The Hair Cycle The Hair Cycle
1. Anagen: 2-6 years, 85-90%
2. Catagen: 2-3 weeks, less than 1%
3. Telogen: 2-3 months, about 13%
• Each follicle goes through the hair cycle 10 to 20 times in a lifetime
Sebaceous glands Sebaceous glands
• The sebaceous glands go hand in hand wit h hair follicles.
• They are especially prominent with the h air follicles of the face, scalp, chest, and back ； they are absent on non-hairy glabrous skin.
• Sebaceous glands, being holocrine glands , form their secretion by decomposition of their cells.
• As a child, these glands are small, but they enlarge and become active during pu berty due to their androgen sensitivity.
Sweat Glands I Sweat Glands I
• Sweat glands reside in the dermis and produce a watery secretion.
• There are two types of sweat glands: eccrine and apocri ne.
1. Eccrine Sweat Glands
• Anatomy: Coiled secretory portion is located in the ret icular dermis. Excretory ducts spirals upwards and open s onto the skin surface.
• Distribution: all over our body, most dense on our axil lae, palms, soles, and forehead.
• Nervous control: The eccrine glands are under sympathet ic cholinergic control.
• Composition: Inorganic ions (NaCl, K, HCO3-), Lactate, U rea, Ammonia and Amino acids, Proteins and proteases, P H between 4-6.8
Sweat Glands II Sweat Glands II
2. Apocrine
• Anatomy: apocrine sweat glands open into hair folli cles and are larger glands.
• Distribution: They densely populate the axillae, pe rineum, and areolae. They are not functional until just before puberty.
• Nervous control: The apocrine sweat glands are inne rvated by sympathetic adrenergic nerve fibers.
• Composition: The sweat is generated by "decapitatio n" secretion of the gland's cells.
• The apocrine sweat is milky and viscid without orde r when it is first secreted. It is only after ski
n's bacteria has acted upon the apocrine sweat that
Eccrine Apocrine
Eccrine Apocrine
Nails Nails
• A plate of hardened
and densely packed keratin.
• Nail matrix is full of dividing cells which age, keratinize
and progress forward to form
Nails Nails
• Nail plate is what we consider our "nail" a nd has a thickness of 0.3-0.5 mm and grows an average of 0.1 mm/day. (fingernails do g row faster than toenails)
• Nail bed is just below the nail plate.
• Hyponychium is the thickened epidermis whic h is below the free edge of the nail.
• The pink color of the nail can be accounted for by dermal capillaries that are adjacent to the nail bed.
• The distal white lunula is basically the vi
sible part of the nail matrix.
Primary skin lesions
Primary skin lesions
Macules Macules
• A macule is a circumscribed, flat lesion that differs fro m
surrounding skin because of its color.
• They may be the result of hy perpigmentation, hypopigment ation, vascular
abnormalities, capillary dil atation (erythema), or purpu ra (extravasated red
blood cells).
Papule Papule
• A papule is a small, solid, elevated lesion.
• Papules are generally smaller than 0.5 cm in diameter.
Plaque Plaque
• A plaque is a mesalike elevation that occupie
s a relatively large surface area in comparis
on with its height above skin level
Patch Patch
• A patch is a portion of any surface markedly different in appearance or character from what is around it.
• Dermatologists have used this
term in different ways: some restrict
its use to the description of very la
rge macules; others use it to refer t
o relatively thin but large plaques.
Nodule Nodule
• A nodule is a palpable, solid, round or ellipsoidal lesion.
• Depth of involvement rather than diameter, differentiate a nodule from a papule.
Wheals Wheals
• A wheal is a rounded or flat-topped papule or plaque that is characteristically evanescent, disappearing within hours.
• The epidermis is not affected: there is no scaling.
Vesicles and Bullae Vesicles and Bullae
• A vesicle is a circumscribed, elevated lesion that contains fluid.
• A bullae is a vesicle larger than 0.5 cm
Pustule Pustule
• A pustule is a circumscribed , raised lesion that contain s a purulent exudate.
• Pus, composed of leukocytes with or without cellular deb ris,
may contain bacteria or may be sterile,
Erosion and Ulcer Erosion and Ulcer
• An erosion is a moist, circumscribed, usually depressed lesion that results from loss of all or a portion of the viable epidermis.
• An ulcer is a “hole in the skin” in which there has been destruction of the epidermis and at least the upper dermis.
Clinical signs
Clinical signs
Dimple sign Dimple sign
• Useful maneuver in differentiating dermatofib roma from melanoma.
• Application of lateral pressure with the thum
b and index finger results in the formation o
f depression (dimple) in a dermatofibroma.
Nikolsky’s sign Nikolsky’s sign
• It refers to the sheetlike removal of epidermis by gentle traction.
• Pemphigus vulgaris, Toxic epidermal necrolysis
Darier’s sign Darier’s sign
• It refers to the development of an ur
ticarial wheal in the lesions of urti
caria pigmentosa afer they are rubbed
.
Auspitz’s sign Auspitz’s sign
• It refers to the appearance of
pinpoint dots of blood at the tops of ruptured capillaries when scale is
forcibly removed from psoriatic
plaques.
Examinations
Examinations
1. KOH Smear 1. KOH Smear
• KOH digest the proteins, lipids, and m ost of the other epithelial debris pre sent in the samples.
• Diagnosis:
1. Fungual infection (dermatophyte, candidiasis, tinea versicolor…) 2. Scabies
3. Pediculosis…
2. Wood’s light examination 2. Wood’s light examination
• 原理 : Longwave ultraviolet light (320-400nm) 照射病灶 產生 fluorescence
• Diagnosis:
1. Fungual infection (ex. Tinea capitis, Tinea versicolor)
2. Bacteria infection (ex. Erythrasma) 3. Porphyria
4. Pigmentation (ex. Vitiligo and melasma)
Wood’s light: results Wood’s light: results
• Microsporum : bright blue
• Malassezia furfur : golden green
• Corynebacterium minutissimun: coral red
• Pseudomonas : yellowish green
• Porphyria : pinkish-red
• Localize site of melanin ( 加深位於表皮層 的黑色素 , 但真皮層黑色素反而變不明顯 ) freckle and melasma darker
Mongolian sacral spot lightening
3. Tzanck Smear 3. Tzanck Smear
• Diagnosis:
1. Herpes virus infection: Chickenpox, Herpes simplex, Herpes zoster
2. Bullous disease: Pemphigus, Pemphigoid
• Procedure:
1. 以刀片輕刮水泡 base , 在均勻塗抹於載玻片上 2. Liu’s stain
• Results:
1. Herpes virus infection: Multinucleated giant cells
2. Bullous disease: 表淺的 kerationcyte 較為扁平，
較深的 keratinocyte 較立方形，故可由水泡底部表 皮細胞的形狀來判斷水泡位置之深淺
Multinucleated giant cells
Multinucleated giant cells
4. Patch test 4. Patch test
• 原理 : To elicit an immune response by challenging
already sensitized persons to define allergens &
assessing the degree of response
• Diagnosis: allergic contact dermatitis
• Procedure: 將 allergens 置於圓形凹槽中，再貼於上背部，
於 48hr 後判讀
• Results:
+? (Doubtful reaction): faint erythema only
+ (Weak positive reaction): erythema, infiltration, possibly papules ++ (Strong positive reaction): erythema, infiltration,
papules, vesicle s
+++ (Extreme positive reaction): intense erythema
and infiltrati on and
coalescing ves
