The skin is the largest organ of the body. It covers the entire external surface and has important protective, sensory, and metabolic functions. The skin is composed of two main layers, the epidermis and dermis. The epidermis contains keratinocytes, melanocytes, Merkel cells, and Langerhans cells. The dermis lies underneath and contains collagen, elastic fibers, nerves, blood vessels, and skin appendages. The skin regulates body temperature, provides immune protection and sensation, and plays a role in vitamin D synthesis and hormone reception.

1. Skin and its
Appendages

2. Introduction
• The skin covers the entire external surface of the body,
including the external auditory meatus, the lateral aspect of
the tympanic membrane and the vestibule of the nose.
• It is continuous with the mucosae of the alimentary,
respiratory and urogenital tracts at their respective orifices,
where the specialized skin of mucocutaneous junctions is
present.
• It also fuses with the conjunctiva at the margins of the eyelids,
and with the lining of the lacrimal canaliculi at the lacrimal
puncta.

3. Functions
• Skin forms 15% of the total body mass.
• Its surface area varies with height and weight
• Its thickness ranges from 1.5–4.0 mm, according to its state of
maturation, ageing and regional specializations.
• Self-renewing interface between the body and its
environment
• Immune surveillance
• Many biochemical synthetic processes.
• Skin is the target of a variety of hormones.
• Control of body temperature
• Major sense organ
• Assisting locomotion and manipulation by its texture.

4. • Melanin has a protective role against ultraviolet radiation, and
acts as a scavenger of harmful free radicals.

5. Classification of Skin

6. Microstructure of Skin

7. Epidermis

9. Cell types in Epidermis

10. Interfollicular Epidermis

11. Basal Keratinocytes

12. Upper layers

14. Keratin

16. Epidermal Lipids
• A variety of lipids are present and synthesized in the
epidermis, including triglycerides and fatty acids,
phospholipids, cholesterol, cholesterol esters,
glycosphingolipids and ceramides.
• An intermediate in the synthesis of cholesterol, 7-
dehydrocholesterol, is the precursor of vitamin D, which is also
synthesized in the skin.
• The lamellar arrangement of the extracellular lipids is a major
factor in their barrier function.

17. Melanocytes Merkel Cells

18. Langerhans
Cells

19. Dermis

20. Dermis
• It has a matrix composed of an interwoven
collagenous and elastic network in an
amorphous ground substance of
glycosaminoglycans, glycoproteins
and bound water, which accommodates
nerves, blood vessels, lymphatics,
epidermal appendages and a changing
population of cells.
• Collagen fibres: give it tensile strength
• Elastic fibres: elastic recoil

21. Dermal Collagens

23. Layers of Dermis

24. Thick vs Thin Skin

26. Appendages of the Skin
•Pilosebaceous unit
•Sweat glands
•Nails

27. Pilosebaceous Unit

28. Hair

31. Apocrine Glands

33. Sweat Glands
Sweat glands are absent from the tympanic membrane, margins of
the lips, nail bed, nipple, inner preputial surface, labia minora,
penis and clitoris, where apocrine glands are located.

35. Nail Apparatus

38. Skin Vasculature

40. Skin Innervation

44. Embryology

46. Natural Skin Creases and Wrinkles

47. Wrinkle Lines

48. Flexure (joint) lines

49. Papillary Ridges

51. Relaxed skin tension lines
Kraissl’s Lines
Blaschko lines

52. Age related changes
Intrinsic Ageing
• Third decade onwards
• Epidermal and dermal atrophy
• Wrinkling, dryness, loss of elasticity,
thinning and a tendency towards
purpura on minor injury.
• Loss of the basal rete pegs with
flattening of the dermo-epidermal
junction.
• Rate of cell replacement decline with
age.
• Dermal changes are mainly
responsible for the appearance of
aged skin, its stiffness, flaccidity and
wrinkling, and loss of extensibility
and elasticity. Its general thickness
diminishes as a result of the decline
in collagen synthesis by a reduced
population of fibroblasts
Photoageing
• Association with
epidermal cancer.
• The effects of chronic
sun exposure on
melanocytes
(stimulatory) and
langerhans cells
(destructive) are thought
to be connected with the
increasing incidence of
malignant melanoma.

53. Cutaneous Wound Healing
• The end-point of healing of mammalian skin wounds is usually
scar formation.
• Cutaneous scars result from injury to both the epidermis and
underlying dermis; while the epidermis largely regenerates,
dermal architecture is abnormal after repair and the
undulating pattern of rete ridges at the dermo-epidermal
junction is not reproduced.

57. Skin Grafts and Flaps

58. A graft taken from skin adjacent
to the surgical defect, known as
Burrow’s graft often provides an
ideal match with respect to both
color and texture.
The anterior thigh provides a
large expanse of skin for larger
skin grafts. Split-thickness skin
graft donor sites are more
numerous than those for full-
thickness skin grafts, because
the former heal spontaneously,
mainly by reepithelialization
from epidermal appendages
found in the residual dermis.

59. Skin Flaps
• Flaps are named according to the type of tissue transferred
• Fasciocutaneous flap
• Musculocutaneous flap
• Skin flap
• Fascial flap
• Muscle flap
• Free tissue transfer

60. • Self-renewing interface between the body and its
environment
• Immune surveillance
• Many biochemical synthetic processes.
• Skin is the target of a variety of hormones.
• Control of body temperature
• Major sense organ
• Assisting locomotion and manipulation by its texture.