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

EpidermisIncredibly 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)

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

Dermis Dermis is 20 to 40 times thicker than the epidermis

Provides a flexible support structure

Encloses the blood vessels, nerve and glands

Dermis

• 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

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

Skin Lesions

Small solid, elevated skin lesion, usually 1 cm or less in diameter.

Seen in many skin diseases like Acne

Papule

Elevated, flat-topped lesion

Usually greater than 1cm in diameter;

Described as being shaped like plateau

e. g.:

- psoriasis

Plaque

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

Transient, solid, itchy, raised area of cutaneous edema with irregular shape, different diameter and erythema.

e. g.:

- urticaria

- insect bites

Wheal

Elevated, thin-walled lesion; filled with serous fluid, less than 1 cm in diameter.

Ex.:

- Herpes simplex

- Varicella

- Herpes Zoster

Vesicle

Thickened and rough epidermis

Skin looks dry and leathery

e .g.:

- Atopic dermatitis

Lichenification

Change in skin’s appearance following repair after skin injury.

e. g.:

- healed wound

Scar

A linear and small split or crack in the epidermis and dermis.e. g.:

- Cracked feet

Fissure

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

Erosion

Deep erosion in which all of epidermis and part of dermis are eaten away

e. g.:

-wound ulcer-Bed sore

Ulcers

Reduction of skin thickness occurring at any skin layer.

e. g.:

- aged skin

Atrophy