The skin is the body's largest organ, making up 16% of total body weight with a surface area of 1.2 to 2.3 square meters. It has two main layers - the epidermis and dermis. The epidermis is the thin outer layer made of five distinct cell layers that undergoes a process of keratinization to form a protective barrier. The dermis lies below the epidermis and is 20 to 40 times thicker, providing structure and housing blood vessels, nerves, and glands. The skin serves several important functions like protection, temperature regulation, sensation, and vitamin D synthesis.

2. Skin
Body's largest organ: ~ 16% total body weight
1.2 to 2.3 m2
surface area
Described as body’s “Cutaneous envelop”
Protects us from the outside world

7. Epidermis
Incredibly thin…..as thin as a piece of paper
Total skin thickness is 1.5 to 4 mm
Thickness of epidermis is between 0.06 – 0.1 mm ( except on
palms and soles)
Epidermis is made of 5 distinct cell layers
- stratum corneum (Horny cell layer)
- stratum lucidum (Clear cell layer)
- stratum granulosum (Granular cell layer)
- stratum spinosum (Prickle cell layer)
- stratum Germinativum (Basal cell layer)

9. Process of Keratinization
The skin is in continuous process of self-
renewal
Keratinization is the series of events
through which the epidermis forms its
protective outer sheath – the stratum
corneum

11. Dermis
Dermis is 20 to 40 times thicker than the epidermis
Provides a flexible support structure
Encloses the blood vessels, nerve and glands
Dermis

15. • Apocrine sweat glands
Large specialized sweat glands localized in axilla,
areola, bearded regions of the face in adult males.
Begin to function in puberty and respond to hormones
Secrete oily colorless substance
Sweat decomposed by bacteria…… Body Odour
Sweat Glands

20. Protection: Physical trauma, micro-organism and
Harmful UV light
Regulation of body temperature
Maintenance of fluid and electrolyte balance
Transmission of sensations of pain, touch,
pressure, warmth and cold
Synthesis of vitamin D
Functions of the Skin

21. Skin Lesions

23. Small solid, elevated skin lesion,
usually 1 cm or less in diameter.
Seen in many skin diseases like
Acne
Papule

24. Elevated, flat-topped lesion
Usually greater than 1cm in diameter;
Described as being shaped like plateau
e. g.:
- psoriasis
Plaque

25. Solid deep seated mass in the dermis or
subcutaneous tissue
Produces elevation on the skin surface
Can be seen in gross inspection or only
on palpation.
Ex.:
- Nodulocystic acne
Nodule

26. Transient, solid, itchy, raised area of
cutaneous edema with irregular
shape, different diameter and
erythema.
e. g.:
- urticaria
- insect bites
Wheal

27. Elevated, thin-walled lesion;
filled with serous fluid, less than
1 cm in diameter.
Ex.:
- Herpes simplex
- Varicella
- Herpes Zoster
Vesicle

33. Thickened and rough
epidermis
Skin looks dry and leathery
e .g.:
- Atopic dermatitis
Lichenification

34. Change in skin’s appearance
following repair after skin
injury.
e. g.:
- healed wound
Scar

36. A linear and small split or
crack in the epidermis and
dermis.
e. g.:
- Cracked feet
Fissure

37. Depressed lesion that is wider
than a fissure but not as deep
Erosion

38. Deep erosion in which all
of epidermis and part of
dermis are eaten away
e. g.:
-wound ulcer
-Bed sore
Ulcers

39. Reduction of skin thickness occurring
at any skin layer.
e. g.:
- aged skin
Atrophy