normal histology of the skin

1. Dr PrennieVidiera
Fr Muller Homoeopathic
Medical College & Hospital

2. Superficial Layer
• EPIDERMIS
• Stratified Squamous Epithelium
Deeper Layer
• DERMIS
• Connective Tissue

3. Dermis
Rests on
Subcutaneous tissue/ Subcutis
Third layer

5. The line of junction between the 2 layers is
wavy
because of
The presence of numerous finger like
projections of
Dermis upwards into the epidermis
Dermal papillae

6. The downward projections of the epidermis
Epidermal papillae

7. The surface of the epidermis is marked by
elevations & depressions
Prominent on the palms & ventral surface of
the fingers & feet
These elevation form EPIDERMAL RIDGES
Essential for finger prints

10. • Has stratified epithelium

11. 5 layers
Basal layer
Stratum basale
Stratum spinosum
(Malpighian layer)
Stratum
Granulosum
Stratum Lucidum Stratum Corneum

13. Stratum Basale
• Deepest
• Single layer of columnar cells
• Undergo mitosis & give off cells called
Keratinocytes
also known as
Germinal layer/ Stratum Germinativum

14. Stratum spinosum
• Several layers of polygonal keratinocytes
• Cells are attached to one another by
numerous Desmosomes
• Some mitosis may occur in the deeper cells
• Germinative zone

16. Stratum Granulosum
• Overlies the stratum spinosa
• Few (1-5) layers of flattened cells (deeply
staining)
• The granules consists of a protein called
keratohyalin.

17. Stratum Lucidum
• Lucid=Clear
• Appears homogenous
• Cell boundaries extremely indistinct
• Traces of flattened nuclei

18. Stratum Corneum
• Superficial layer
• Acellular
• Made up of flattened scale like elements
containing keratin filaments embedded in
protein
• held together by a glue like material
containing lipids & carbohydrates
• Resistant to permeability

19. • The thickness of this layer is greatest where
the skin is exposed to maximal friction
• Eg:- Soles and palms
• The superficial layer constantly sheds off &
replaced by proliferation of cells in deeper
layers

20. Zone of Keratinization
(Cornified Zone)
• Stratum Corneum
• Stratum Lucidum
• Stratum Granulosum

22. • Made up of connective tissue

23. Papillary
Layer
Connective Tissue
is dense
Thick skin of
palms and soles
Reticular
Layer
Thick fibre
bundles & elastic
fibres
Interval between
the fibre bundles
are occupied by
adipose tissue.

24. Appendages of the skin

25. • Hairs
• Nails
• Sebaceous Glands
• Sweat Glands

27. • Present almost the whole body
• Not present : Palms, Soles, Ventral surface &
sides of the digits & some parts of the male &
female external genitalia

28. Parts
• The visible part – shaft
• Embedded part – root
• Expanded lower end of the root – bulb
• The bulb is generated invaginated from below
by part of the dermis – hair papilla
• Root is surrounded by a tubular sheath – hair
follicle

30. Structure of hair shaft
Hair – Modified part of stratum corneum
Has outer cortex and inner medulla in large hairs,
no medulla in thin hairs
Cortex is acellular & is made up of keratin
Medulla consists of cornified cells of irregular
shapes

31. Surface is covered by a thin membrane
Cuticle
formed by
flattened cornified cells
contains
melanin
responsible for colour

32. Both in medulla & cortex minute air bubbles are
present

33. Structure of Hair Follicle
• Part of the epidermis that has been
invaginated into the dermis around the hair
root
• Its innermost layer continues with the surface
of the skin & outermost layer continues with
the dermis

34. Arrector Pili Muscles
• These are bands of smooth muscles attached
at one end to the dermis, just below the
dermal papilla &
• at the other end to the connective tissue
sheath of the hair follicle

35. • Contraction of arector pilorum muscle results
in erection of hair shaft

37. • Found in dermis of the skin
• Ducts open into the hair follicle
• Holocrine gland
• Secretes sebum: antifungal & anti bacterial.
Contains lipids & cholesterol
– Oily in nature
– Prevents dryness
– Resistant to moisture

38. • The secretary acinus has,
– flattened epithelial cells
– Centrally placed rounded cells / sebocytes

41. Sweat Glands
• Found in deeper parts of the dermis

42. The part of the duct present in the dermis is
straight
Stratified cuboidal epithelium
the part passing through the dermis is coiled
epidermal cells

44. 2 Types
Eccrine Glands
Apocrine Glands

46. ECCRINE GLANDS
• Widely distributed
• Numerous on forehead, scalp, palms & soles
• Absent on
– Tympanic Membrane
– Margins of lips
– Labia minora
– Glans penis

47. • Each gland is long, unbranched tubular
structure
• Presents a highly coiled secretory portion
called as body within the dermis & a narrower
ductal portion, which opens on skin surface
• Secretions of sweat glands are clear,
colourless and hypotonic

48. APOCRINE GLANDS
• Found in
– Axilla
– Areola
– Perianal region
– Prepuce scrotum
– Mons pubis
– External acoustic meatus

49. • These glands secrete a protein rich, milky fluid
which is initially odourless but acquires a
distinct odour due to bacterial decomposition

51. Nails

52. • Nails are plates of keratinised epithelial cells
on dorsal surface of distal phalynx
• Consists of 3 parts
– Proximal part or root
– Exposed part or body
– Free distal border

53. • Consists of dead anucleate keratin
• Body rests on nail bed which is composed of
stratum basale & stratum spinosum