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Skin
Jun Zhou
School of Medicine, Zhejiang University
20150407
Overview
the largest organ of the body
constitutes about 16% of body weight
total surface area is about 1.2-2.2 m2
function: protection, sensory reception,
excretion and thermoregulation
skin
epidermis
附属器官：
(dermis)
hypodermis
毛
皮脂腺
汗腺
指（趾）甲
Structure of skin
Epidermis (表皮)
Dermis (真皮)
Epidermis
---consist of
keratinised cell
（角质形成细胞）
non-keratinised cell
（非角质形成细胞）
---keratinised stratified
squamous epithelium
Keratinised cell


from
basal
surface
five layers
to
Epidermis
stratum corneum （C）
stratum lucidum （L）
stratum granulosum （G）
stratum spinosum（S）
stratum basale （B）
Thin skin

1.
2.
3.
4.
Dermis
Only has four layers:
Stratum corneum
Stratum granulosum
Stratum spinosum
Stratum basalis
stratum basale （基底层）
---structure:
LM:

one layer, cuboidal or low
columnar,

basophilic cytoplasm
EM:

free ribosome

keratin filament 角蛋白丝
( tonofilament 张力丝)

desmosome
---function:

mitotic activity and proliferation
stratum spinosum（棘层）
LM:
 4-10 layers, polygonal cell
 spinous processes
 slight basophilic cytoplasm
 Tonofibrils（张力原纤维）
EM:
 Keratin filament （角蛋白丝）
 lamellated granules:
/100-300nm membrane-coated
/contain phospholipid and steroid
 intercellular bridges- Desmosome
stratum granulosum（颗粒层）
LM:



3-5 layers, flattened cell
nuclei begin to degenerate
keratohyalin granules
（透明角质颗粒）

basophilic
EM:

keratohyalin granules:
with tonofilament insert into them

lamellated granules:
fused with cell membrane

* keratohyalin + tonofilament =
keratin （角质）
stratum lucidum （ 透 明 层 ）
LM:
 3-4 layers
 homogeneous and
transparent
 no nucleus and organella
 eosinophilic-keratohyalin
 tonofilament embedded in
homogeneous matrix
lucidum
stratum corneum（角质层）
LM:





several layers horny cell
died cell- no nucleus and
organella
eosinophilic
keratin
* desquamation: surface
keratin will shed from outer
surface
corneum
lucidum
Non-keratinised cell
A. Melanocyte （黑色素细胞）:
LM:
 located among stratum basale cells
 large cell with long branches
EM:
 ribosome
 RER
 Golgi complexes
tyrosine
-melanosome(tyrosinase)
→ ↓
↓
melanin
melanin granules
Melanocytes黑素細胞
Melanocytes
Dermis
Basal cells contain
brown pigment
Function:

responsible for skin color

absorb ultraviolet light

protect deep tissue
B. Langerhans cell
---structure:
LM:



Among the spinous cell
deep nucleus, light cytoplasms
dendritic-typed processes
EM:
 lysosome
 Birbeck granule:
/membrane-coated
/15-30 nm long, 4 nm in D
---function:
 antigen presenting cell in skin
 involve in immune reaction
C. Merkel cell



located in basal layer
with short processes
contain many dense-core
granules
Function:

not very clear

may be sensory epithelial
cell

neuroendocrine cell
Dermis
DCT
---Papillary layer（乳头层）
junction between epi. and
underlying CT
papillary layer
---Reticular layer（网状层）


DCT, BV, LV
lamellar corpuscle
skin appendages
sweat gland, sebaceous
gland and hair
reticular layer
Papillary layer 乳头层
Spiraling duct of
sweat gland
through thick
epidermis
Papillary layer
(dermal papilla),
contains fine collagen
fibres, capillary
network and nerves
Dermal ridge
Dermal ridges determine the patterns of fingerprints;
scientific basis of dermatoglyphics
Epidermal ridge
Hypodermis（皮下组织）
LCT and fat tissue
skin appendages
Hair
A
B
C
D
Schematic
diagram to
show
various
parts and
associated
structures of
hair follicle
Hair follicle
Hair
Hair follicle
Sebaceous gland
Dermis
Sebaceous gland
Sweat glands
Types of nerve endings in skin
Free ending
Meissner’s corpuscle
Merkel’s ending
Paccinian
corpuscle
Krause’s end organ
Meissner’s
corpuscle
Paccinian corpuscle
•Located deep in
dermis
•Sensation of
pressure
•Characterized
by nerve
terminal
(arrowhead)
surrounded by
concentric layers
of connective
tissue cells
THE END!