Skin Lesions | Skin Layers | Types of Lesions

Skin and Skin Lesions:

Human skin is outer covering of body and is largest organ of integumentary system skin have layers of ectodermal tissue and guards underlying muscles, bones, ligaments and internal organs. Human is similar to most of the mammalian’s skin. There are different kinds of skin lesions as well.

Hair Follicles:

Human skin is covered with hair follicles but might appear hairless.

Skin lesions
Skin lesions

Types of Skin:

There are two types of skin:

  • Hairy skin
  • hairless (Glabrous)

Structure of Skin:

Human skin shares anatomical, physiological, immunological, and biochemical properties with other mammalians.
thickness of skin on an average on forearm is 1.3mm in males and 1.26mm in female. The average square inch  (6.5sq. cm)of skin consist of 650 sweat glands ,20 blood vessels, 60,000 melanocytes and more than 1000 nerve endings. Depending on variety of factors.

Layers of Skin:

Skin is composed of three primary layers:

  • Epidermis
  • Dermis
  • Hypodermis

Skin is actually a layer of soft amd flexible outer tissue covering.


Epidermis forms a waterproof protective cover over body’s surface which serves as a barrier to infection and is made up of stratified squamous epithelium with an underlying basal lamina.

Layers of Epidermis:

Epidermis contain no blood vessels and cells are nourished by diffused oxygen epidermis helps skin in regulating human body temperature. Main cells that make up epidermis includes:

  1. Merkel cells 
  2. Keratinocytes
  3. Langerhans cells
  4. Epidermis may further be subdivided into:
  5. Stratum corneum
  6. Lucidum
  7. Stratum Granulosum
  8. Spinosum
  9. Stratum Basale


This skin lies beneath epidermis.


It consist of connective tissue that cushions body from stress and strain dermis is tightly bound to epidermis by basement membrane. This layer contains hair follicles, sweat glands, sebaceous glands, apocrine glands, lymphatic vessels and blood vessels.

Blood vessels:

Blood vessels in dermis provide nourishment and waste removal from its own cells and from stratum basale of epidermis.

Structural Division:

Dermis is structurally divided into two areas:
Papillary region: Superficial area adjacent to epidermis 
Reticular region: Deep thick area known as reticular region.


Hypodermis lies between dermis and underlying tissues and organs it consists of adipose tissue and is the storage site of most of the body fat.


It consists of vascularized, loose, aereolar connective tissue and adipose tissue provides insulation and cushioning of integuments.

Skin Lesions:

Skin lesions are part of skin that has an abnormal growth or appearance compared to skin around it. Two categories of skin lesion exist:

  • Primary lesion
  • Secondary lesion

Conditions that cause Skin lesions:

Conditions which may cause skin lesions are described below:


Commonly locates on face, neck. shoulders. It may leave scars or darken skin if untreated.

Cold Scars:

Red, Painful, fluid filled blister that appears near mouth and lips. Affected area will often burn or tingle before sore is visible.

Allergic eczema:

May resemble a burn. Skin is itchy, red, scaly or raw. Often found on hands blisters that ooze or become crusty.

Contact Dermatitis:

Skin is itchy, red, scaly or raw.


Scaly, silvery and sharply defined skin patches. Commonly located on scalp, elbows, knees. May be itchy or asymptomatic.


Clear, watery, fluid-filled blister that is greater than 1cm. in size.


Bacterial or fungal infection of hair follicle or oil gland. Red, Painful, raised bump with yellow or white center.

Types of Primary Skin Lesions:


Small blisters also called vesicles, filled with clear fluid less than 1/2cm. large vesicles are called bullae.


They are small spots that are typically brown, red about 1cm. in diameter eg: freckles.


This is solid, raised lesion about 2cm. in diameter.


Raised lesion a patch of papules called plaque that is common in patients with Psoriasis.


Pustules are small lesions filled with pus in result of acne, boils and impetigo.


This is skin lesion caused by allergic reaction. eg. hives

Types of Secondary Skin Lesions:


Crust or scab is created when dried blood forms over scratched lesion.


Scale is patch of skin cells that build and after that flake off the skin.


Some scratches leave scars which are not replaced with normal skin and skin returns as thick scar known as keloid.

Skin Atrophy:

It occurs when areas of skin become thin and wrinkled from overuse of topical steroids or poor circulation.

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