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 spinosum statum granulosum stratum corneum Melanocytes Keratinocyte Ⅰ. Epidermis Nonkeratinocytes

Stratum Basale Stratum Spinosum Stratum Granulosum stratum corneum

Stratum Spinosum Stratum Granulosum stratum corneum Strstum basale

⑴ stratum basale: Stratum Germinativum The stratum basale consists of a single layer of basophilic columnar or cuboidal cells resting on the basement 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 filaments about 10nm in diameter.

（ 2 ） stratum spinosum The stratum spinosum consists of polygonal,or slightly flattened cells with a central nucleus and a cytoplasm whose processes are filled with bundles of keratin filaments. These cell bear many spines and there are some desmosome between the spines. Cohesion.

（ 3 ） Stratum granulosum The strstratum granulosum consists of layers of flattened spindle cells whose cytoplasm is filled with coarse basophilic granules called keratohyalin granules. The proteins of these granules contain a phosphorylated histidine-rich protein as well as proteins containing 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 eosinophilic epidermal cells. The organelles and nuclei are no longer evident and the cytoplasm consists primarily of densely packed keratin filaments embedded in an electron-dense matrix. Desmomes are still evident between adjacent cells.

Stratum Lucidum

（ 5 ） stratum corneum The stratum corneum consists of layers nonnueleated keratinized cells whose cytoplasm is filled with birefringent filamentous scleroprotein, keratin. These cell have not the exact limit and acidophilic 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 melanocyte.

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 layer is composed of loose connective tissue. fibroblasts and other connective tissue cells such as mast cells and macrophages are present. The papillary layer is so because it constitutes the major part of the dermal papillae. Capillary, Tactile Corpuscles

表皮 乳头层 网状层

2 、 reticular layer ： The reticular layer is thicker, composed of irregular dense connective 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 hair Epithelium follicle Connective tissue:dermis Epidermal invagination, hair follicle hair shaft hair root hair follicle

Termical dilation of hair follicle are called hair bulb, the invagination is called hair papilla. The epithelium cells covering this dermal papilla referred to germinal matrix of hair. In the hair papilla there are rich in capillaries and nerving ending.

Hair shaft Hair root Arrector pili muscle Hair follicle

Hair follicle

hair bulb 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