Skin 皮肤

Department of Histology and Embryology Medical college in Three Gorges University

hair

sebaceous gland

sweat gland

Nails

Ⅰ.Skin： Epidermis

Dermis

Ⅱ.Skin Appendages

Skin

Epidermis

Dermis

Keratinocytes

Nonkeratinocytes

Papillary Layer

Reticular Layer

Function of skin

1 、 Protect organism from impact

and friction injuries

2 、 receptor organ

3 、 participate in thermoregulation

4 、 secreting the sweat

5 、 Absorption

stratum lucidum

Langerhans Cells

Merkels Cells

strstum basale

stratum spinosumstatum granulosum

stratum corneum

Melanocytes

Keratinocyte

Ⅰ. Epidermis

Nonkeratinocytes

Stratum Basale

Stratum Spinosum

Stratum Granulosum

stratum corneum

Stratum Spinosum

Stratum Granulosum

stratum corneum

Strstum basale

⑴stratum basale: Stratum Germinativum

The stratum basale consists of a single layer of baso

philic columnar or cuboidal cells resting on the ba

sement membrane at the dermal-epidermal junction.

Hemidesmosomes ,found in the basal plasmalemma ,

help bind these cells to the basal lamina.

Mitotic activity

EM ： RER,ribosome, etc, organlles.

the cells contain the intermediate keratin fil

aments about 10nm in diameter.

（ 2 ） stratum spinosum

The stratum spinosum consists of polygonal,or

slightly flattened cells with a central nucleus a

nd a cytoplasm whose processes are filled wit

h bundles of keratin filaments.

These cell bear many spines and there are s

ome desmosome between the spines. Cohesi

on.

（ 3 ） Stratum granulosum

The strstratum granulosum consists of 3---5

layers of flattened spindle cells whose cytop

lasm is filled with coarse basophilic granule

s called keratohyalin granules. The proteins

of these granules contain a phosphorylated

histidine-rich protein as well as proteins co

ntaining cystine.

Stratum Spinosum

Stratum Granulosum

stratum corneum

strstum basale

（ 4 ） Stratum Lucidum

More apparent in thick skin ,the stratum lucidum is

a translucent ,thin layer of extremely flattened eosi

nophilic epidermal cells. The organelles and nucl

ei are no longer evident and the cytoplasm consist

s primarily of densely packed keratin filaments em

bedded in an electron-dense matrix. Desmomes are

still evident between adjacent cells.

Stratum Lucidum

（ 5 ） stratum corneum

The stratum corneum consists of 15-20 layers

nonnueleated keratinized cells whose cytopla

sm is filled with birefringent filamentous scle

roprotein, keratin.

These cell have not the exact limit and a

cidophilic cytoplasm.

Stratum Spinosum

Stratum Granulosum

stratum corneum

strstum basale

keratin

2 、 Nonkeratinocytes

（ 1 ） melannocyte

（ 2 ） Langerhans cell

（ 3 ） Merkel cell

（ 1 ） melannocyte Melanin is synthesized in the melanocyt

e.

Melanocytes

（ 2 ） Langerhans cell

Langerhans cells are derived from bone-marrow. They are Star-shaped cells found mainly in the stratum spinosum of the epidermis. H-E: Dark stained nuclei with light cytoplasm.

（ 3 ） Merkel cell Merkel cell generally present in the thick

skin of palms and soles

真皮

Ⅱ.Dermis 1 、 papillary layer ： The thin papillary l

ayer is composed of loose connective tissue.

fibroblasts and other connective tissue cells s

uch as mast cells and macrophages are presen

t. The papillary layer is so because it constitu

tes the major part of the dermal papillae. Cap

illary, Tactile Corpuscles

表皮

乳头层

网状层

真皮

2 、 reticular layer ： The reticular layer

is thicker, composed of irregular dense conn

ective tissue and therefore has more fibers

and fewer cells than does the papillary layer.

The dermis contains a network of fibers of

the elastic system.

epidermis

Papillary layer

Reticular layer

dermis

sweat gland

hypodermis

Ⅲ.Skin Appendages

hair

sebaceous gland

sweat gland

nail

(1) 、 hair 1 、 structure of hai

r

Epithelium follicle

Connective tissue:dermis

Epidermal invagination, hair follicle

hair shaft

ha

ir roothair follicle

Termical dilation of hair follicle are called hair

bulb, the invagination is called hair papilla. T

he epithelium cells covering this dermal papill

a referred to germinal matrix of hair. In the h

air papilla there are rich in capillaries and ner

ving ending.

Hair shaft

Hair root

Arrector pili muscle

Hair

follicle

Hair follicle

hair bulbhair papilla

hair papilla

（ 2） sebaceous gland

Acini

duct

Secreting unit

sebum

The acini consist of a basal layer of undifferentiated flattened epithelial cells that rest on the basal lamina.These cells proliferate and differentiate filling the acini with rounded cells containing increasing amounts of fat droplets in their cytoplasm. The product of this process is sebum, the secretion of the sebaceous gland which is gradually moved to the surface of the skin

（ 3） Sweat gland Secreting portion: simple cuboid cells or pyramidal cells, myoepithelial cell which help to discharge the secretion.

Duct: present in the dermis. They are lined by stratified cuboidal epithelium