Transcript Microstructure of the skin

Structure and Function
of Human Skin
Lianjun Chen
Huashan Hospital
Importance of the study of
skin diseases
Common and prevalent diseases
 Skin beauty and health care
 reflection of the body health
（paraneoplastic skin diseases)
 Sex Transmitted Disease(STD), AIDS,
other contagious diseases
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OUTLINE
 Introduction
of the Skin
 Microstructure of the skin
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Epidermis
The basement membrane zone
Dermis
Subcutis
Appendageal Structure
 The
function of the skin
Introduction
The single biggest organ in the body
 Cover an average area of 1.5 m2
 Varying thickness (0.4-4mm)
 Different color by the race, age, gender &
location
 Perform many vital roles
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Microstructure of the skin
Epidermis
 Dermis
 Subcutis

The basement membrane zone
 Appendageal Structure
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Epidermis
 Derived
from ectoderm
 The celluar external layer
– Keratinocyte
– non-keratinocyte
 Melanocyte
 Langerhans’
 Merkel
cell
cell
Keratinocytes
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stratum basalum, basal cell layer
stratum spinosum, prickle cell layer
stratum granulosum, granular layer
stratum lucidum
stratum corneum, horny layer
keratinocyte
non-keratinocyte
keratin
+
─
tonofilament
+
─
desmosome
+
─
dendritic-shaped
─
+
Function of the keratinocytes
Continuously producing keratin and
forming horny layer to protect against
various chemical and physical factors
 Participating immune response in the
skin
 Secreting cytokines and helping to
activate T lymphocytes
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Desmosome
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Attachment plates between adjacent
keratinocytes in basal layer and prickle layer
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Desmosome transmembrane protein
– desmoglein,DG
– desmocollin,DC
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Desmosome cytoplasm plakin
– desmoplakin,DP
– plakoglobulin,PG
Non-keratinocytes
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Melanocyte
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Langerhans cell
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Merkel cell
Melanocytes

Epidermal melanin unit
– melanocytes are derived from the nerual
crest and reside in the basal layer
– Melanocytes are dendritic cells and contain
large number of melanosomes
– Any one melanocyte is contact with 30-40
keratinocytes through its dendrites, form
the so-called epidermal melanin unit.
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Protective barrier against UV
Langerhans’ cells
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Langerhans’ cells are originate in bone marrow.
They exist in the epidermis above the basal layer .
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They are characterized by a folded nucleus and
distinct intracytoplasmic organelles called Birbeck
granules，resembling a tennis racquet.
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Recognition, uptake, processing, and presentation
of antigens to sensitized T lymphocytes.
Langerhans’
Granules
Birbeck granules
Merkel cells
a kind of neurosecretory cell
 located directly above the basement
membrane and closely associated with
neurites, so called Merkel cell-axon
complex.
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Basement membrane zone
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The base of basal cell
containing hemidesmosome
The lamina lucida
– A clear zone crossed by a fine network of anchoring
filaments, largely composed of the structural protein
laminin
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The lamina densa
– An electron dense band, largely composed of type IV
collagen
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The reticular lamina(collagen VII)
Dermis
Derived from mesoderm
 Papillary dermis & reticular dermis
 Connective tissue

– Collagen, elastic fiber, reticulum fiber
matrix (mucopolysaccharides)
 blood vessel, lymphatics, nerve ending
 Appendageal sructure

– apocrine gland, eccrine gland, sebaceous
gland, hair follicle, nail, et al
Subcutis
It consist largely of fat tranversed by
nerves and blood vessels.
 The name implies that it is not properly
the part of the skin, however, it could be
an integrated whole as for the function.
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Appendages
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Hair follicles
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Sebaceous glands
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Sweat glands
– Eccine glands
– Apocrine glands
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Nails
Pilosebaceous units
Hair follicles
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Classification
– Terminal hair
Scalp,axillae, pubic,beard
eyebrow,eyelash,vibrissa
– Vellus
– lanugo
Hair Anatomy
Infundibulum – surface to entrance of
sebaceous duct
 Isthmus – sebaceous duct to pilar
muscle insertion
 Lower segment
– Stem,Bulb (matrix and papilla)
 Perifollicular sheath (mesenchyme)
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Infundibulum
Isthmus
Arrector pili muscle
Stem
Bulb
anagen
catagen
telogen
Sebaceous glands
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Distribute throughout all skin sites except
palms and soles，greatest abundant on scalp,
face,middle part of the body and vulvae.
Always associated with upper portion of the
hair follicles
Reach skin surface,such as
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vermilion border of the lip(Fordyce’s spots）
areolas(Montgomery’s tubercles)
prepuce(Tyson’s glands)
eyelids(Meibomian’s glands)
Production of sebum
Eccrine glands
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Distribution: almost all skin site
– Exclude the vermilion border of the lip,
nympha, phallus, glans, flexion side of
prepuce and nail beds
– most abundant on the palms, soles and axillae
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Reach to skin surface directly
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Under psychological and thermal control
Eccrine glands
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Composition of the eccrine gland
– Coil gland is composed of a single layer
of cells with two types: pale cell and
darker-staining cell and regulated by
cholinergic nerve
– The duct is composed of a double layer
of basophilic epithelial cells and divided
into intraepidermal component and
intradermal component
Function of the eccrine gland
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Dissipate excessive body heat
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Soften horniness
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Acidify sweat
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Take place of partial renal
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Emulsify lipid
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Secrete immunoglobulin
function
Apocrine glands
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Distribution: generally confined to axillae,
areolae and the anogenital region.
reach to the hair follicle instead of skin
surface
Becoming active at puberty
Producing a protein-rich secretion ,
sometimes gives out a characteristic odour.
Nails
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Consist of a dense plate of hardened keratin
between 0.3 and 0.5mm thick
The nail is made up of a nail bed, nail matrix
and a nail plate.
The thickened epidermis which underlies the
free margin of the nail at the proximal end is
called the hyponychium.
Fingernails grow at 0.1 mm per day; the
toenails more slowly.
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Skin is the largest organ in the body by weight
and surface area.
Skin is composed by three layers : epidermis ,
dermis and subcutis.
Epidermis is the outer layer composed mainly
of keratinocytes but also melannocytes and
Langerhan’s cells.
Dermis is a supportive connective tissue layer
comprised mainly of collogen but also
containing elastin embbed in a matrix of
mucopolysaccharides.
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Hairs are ketatinized tubes emerging from
invaginations of the epidermis called follicles.
Sebaceous glands deliver sebum into follicle
lubricating the hair surface.
Eccrine sweat glands are found almost over the
entire skin surface and innervated by the
sympathetic nervous system,responding to
temperature/psychological changes.
Apocrine sweat glands are localized (axillae,
nipples,perineum,scalp) and androgen-sensitive.
Nails, like hair, are made largely of keratin.
Function of the skin
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As a barrier
– Provides a protective barrier to:
 mechanical,thermal,and other physical injury
 the ingress of noxious agents
 the excessive loss of moisture and protein(if the
skin absent or seriously compromised)
 The harmful effect of ionizing radiation
especially ultraviolet radiatio
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Sensation
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Rich in nerve ending and specialized sensory receptor
Function of the skin
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Thermoregulation
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Skin is the principle organ of heat control
Immunological surveillance
– Contains immunologically component cells
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Biochemical reaction
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Vitamin D synthesis
Involved in androgen degradation and others
Social and sexcial communication
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Disorders of the skin such as dicoloration may cause
tremendous stress of human, impair the individual’s
sense of well-being and self-worth.
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Some pictures are from Mosby’s Color Atlas and
Textbook of Dermatology. These cannot be
copied without the pemission of the publisher,
only used in self-learning.
Web address of this curriculum
http://jpkc.fudan.edu.cn/s/283/main.jspy
 From 12th .Oct, practice time
– Place of Assembly: dermatopathology Unit,
floor 3, building 6, Huashan Hospital
– Time of Assembly: 1:30 p.m.
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Tel: 13817311071
Lianjun Chen