1. Structure and Function of Human Skin
Lianjun Chen
Huashan Hospital

2. 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

4. OUTLINE Introduction of the Skin Microstructure of the skin
Epidermis
The basement membrane zone
Dermis
Subcutis
Appendageal Structure
The function of the skin

5. 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

6. Microstructure of the skin
Epidermis
Dermis
Subcutis
The basement membrane zone
Appendageal Structure

8. Epidermis Derived from ectoderm The celluar external layer
Keratinocyte
non-keratinocyte
Melanocyte
Langerhans’ cell
Merkel cell

9. Keratinocytes stratum basale, basal cell layer
stratum spinosum, prickle cell layer
stratum granulosum, granular layer
stratum lucidum
stratum corneum, horny layer

11. Keratohyaline Granules
Epidermal keratinocytes-differentiation involve four phase to produce the cells of statum corneum;
The time take from differentiation of the basal cell to shedding of the horny cell is approximately 28 days

12. keratin + ─ tonofilament + ─ desmosome + ─ dendritic-shaped ─ +
keratinocyte non-keratinocyte
keratin ─
tonofilament ─
desmosome ─
dendritic-shaped ─

13. 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

14. Desmosome
Attachment plates between adjacent keratinocytes in basal layer and prickle layer
Desmosome transmembrane protein
desmoglein,DG
desmocollin,DC
Desmosome cytoplasm plakin
desmoplakin,DP
plakoglobulin,PG

17. Non-keratinocytes
Melanocyte
Langerhans cell
Merkel cell

18. Melanocytes Epidermal melanin unit Protective barrier against UV
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 keratinocytes through its dendrites, form the so-called epidermal melanin unit.
Protective barrier against UV

20. Langerhans’ cells
Langerhans’ cells are originate in bone marrow. They exist in the epidermis above the basal layer .
They are characterized by a folded nucleus and distinct intracytoplasmic organelles called Birbeck granules，resembling a tennis racquet.
Recognition, uptake, processing, and presentation of antigens to sensitized T lymphocytes.
without keratin filament or desmosomes.

21. Langerhans’
Granules

22. Birbeck granules

23. Merkel cells a kind of neurosecretory cell
located directly above the basement membrane and closely associated with neurites, so called Merkel cell-axon complex.

26. Basement membrane zone
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
The lamina densa
An electron dense band, largely composed of type IV collagen
The reticular lamina(collagen VII)

29. 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

31. 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.

32. Appendages Hair follicles Sebaceous glands Pilosebaceous units
Sweat glands
Eccine glands
Apocrine glands
Nails
Pilosebaceous units

33. Hair follicles Classification Terminal hair
Scalp,axillae, pubic,beard eyebrow,eyelash,vibrissa
Vellus
lanugo

34. 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)

35. Infundibulum
Isthmus
Arrector pili muscle
Stem
Bulb

37. anagen
catagen
telogen

38. Sebaceous glands
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
vermilion border of the lip(Fordyce’s spots）
areolas(Montgomery’s tubercles)
prepuce(Tyson’s glands)
eyelids(Meibomian’s glands)
Production of sebum

40. Eccrine glands 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
Reach to skin surface directly
Under psychological and thermal control

41. Eccrine glands 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

42. Function of the eccrine gland
Dissipate excessive body heat
Soften horniness
Acidify sweat
Take place of partial renal function
Emulsify lipid
Secrete immunoglobulin ： ⑴

43. Apocrine glands
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.

45. Nails
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.

48. 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.

49. 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.

50. Function of the skin As a barrier Sensation
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 radiation
Sensation
Rich in nerve ending and specialized sensory receptor

51. Function of the skin Thermoregulation Immunological surveillance
Skin is the principle organ of heat control
Immunological surveillance
Contains immunologically component cells
Biochemical reaction
Vitamin D synthesis
Involved in androgen degradation and others
Social and sexcial communication
Disorders of the skin such as dicoloration may cause tremendous stress of human, impair the individual’s sense of well-being and self-worth.

52. From 12th .Oct, practice time
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
From 12th .Oct, practice time
Place of Assembly: dermatopathology Unit, floor 3, building 6, Huashan Hospital
Time of Assembly: 1:30 p.m.
Tel: Lianjun Chen

53. Thanks
for your attention!