Skin Anatomy

Human Skin

The skin is the largest organ of the body, with a total area of approximately 20 square feet.

Skin provides the following functions:

  • Protection – an anatomical barrier from pathogens and damage from the external environment
  • Sensation – contains a variety of nerve endings that react to heat and cold, touch, pressure, vibration and tissue injury
  • Heat regulation – the skin contains a blood supply far greater than its requirements which allows precise temperature control through dilation and constriction of the vessels
  • Control of evaporation – a relatively dry and semi-impermeable barrier to fluid loss
  • Storage and synthesis – storage center for lipids and water and a means to synthesize vitamin D
  • Excretion of urea – a secondary function to temperature regulation
  • Absorption – outermost skin supported by external oxygen. Medication can be administered through the skin
  • Water resistance – a water resistant barrier to preserve essential nutrients

Skin is composed of 3 primary layers:

  • Epidermis
  • Dermis
  • Hypodermis


Epidermis is the outermost layer of the skin. It forms the waterproof, protective wrap over the body’s surface which also serves as a barrier to infection. The epidermis contains no blood vessels and is nourished by diffusion from the dermis. The epidermis helps the skin to regulate body temperature. The outer most layer of the epidermis consists of 25 to 30 layers of dead cells forming the keratinized layer of the skin, which continually turns over, and provides the protective barrier to infection and is responsible for keeping water in the body.

Dermis is the layer of skin beneath the epidermis that consists of epithelial tissue and cushions the body from stress and strain. It contains many nerve endings that provide the sense of touch and heat, hair follicles, sweat glands, lymphatic vessels and blood vessels. The dermis is divided into two areas, the papillary region and a deep thicker reticular region.

  • Papillary region – interdigitates with the epidermis, strengthening the connection between the two layers of skin
  • Reticular region – composed of dense connecting tissue with a high concentration of collagenous, elastic and reticular fibers which give the dermis its properties of strength, extensibility and elasticity. Surrounding the components of the dermis is a gel-like substance composed of mucopolysaccharides (primarily hyaluronic acid), chondroitin sulphate and glycoproteins. Collagen makes up 70% of the weight of the dermis, elastic fibers constitute less than 1% but play a vital role maintaining skin shape.


Hypodermis is not part of the skin, lying below the dermis. Attaches the skin to underlying bone and muscle. It consists of loose connective tissue, fat and elastin.

As skin ages, it becomes thinner and more easily damaged due to an decreased ability to heal itself. Skin aging is noted by a decrease in volume and elasticity.

Skin Conditions

Rash – a change in skin appearance caused by simple skin irritation or results from medical conditions

Dermatitis – general term for inflammation of the skin. Atopic dermatitis (a type of eczema) is the most common form

Eczema – skin inflammation (dermatitis), normally due to an over active immune system causing an itchy rash

Psoriasis – an autoimmune condition that can cause a variety of skin rashes principally scaly plaques

Dandruff – a scaly condition of the scalp, may be caused by dermatitis, psoriasis or eczema

Acne - the most common skin condition. Occurs when hair follicles are clogged with dead skin cells and oil from the skin

Cellulitis – inflammation of the dermis and subcutaneous tissues, usually due to an infection

Skin abscess (boil) – a localized skin infection creates a collection of pus under the skin

Rosacea – a chronic skin condition causing a red rash on the face

Warts – a virus infects the skin and causes the skin to grow excessively

Melanoma – the most dangerous type of skin cancer, melanoma results from sun damage and other causes

Basel cell carcinoma – the most common type of skin cancer which grows and spreads slower than melanoma

Squamous cell carcinoma – a common form of skin cancer which may begin as an ulcer that will not heal or an abnormal growth. Usually develops in sun exposed areas

Seborrheic keratosis – a benign, often itchy growth that appears like a wart

Actinic keratosis – a crusty or scaly bump that forms on sun exposed skin that sometimes progresses to cancer

Herpes – HSV-1 and HSV-2 viruses that can cause periodic blisters and skin irritation around the lips or the genitals

Hives – raised red itchy patches that arise suddenly usually due to an allergic reaction

Tinea versicolor – a benign fungal skin infection creates pale areas of skin pigmentation

Viral exanthem – viral infections can cause red rash affecting large areas of the skin

Shingles (herpes zoster) – caused by the chicken pox virus, is a painful rash on one side of the body (an adult vaccine can prevent shingles in most people)

Scabies – tiny mites that burrow into the skin cause an intensely itchy rash in the webs of fingers, wrists, elbows and buttock

Ringworm – a fungal skin infection forming a characteristic ring (not due to worms)

Impetigo – a highly contagious skin infection that usually attacks exposed areas

Skin Treatments

Corticosteroids (steroids) – medications that reduce inflammation and reduce immune system activity that may improve dermatitis

Antibiotics – medications used to kill bacteria causing cellulitis and other skin infections

Antiviral drugs – medications that can suppress the activity of the herpes virus, reducing symptoms

Antifungal drugs – topical creams can cure most fungal infections. Occasionally, oral medications may be needed

Antihistamines – oral or topical medication, can block histamine, a substance that causes itching

Immune modulators – medications that can modify the activity of the immune system, improving psoriasis or other forms of dermatitis

Skin moisturizers – moisturizers can reduce symptoms of many skin conditions

Specialty skin cream – products containing elastin, D-panthenol, vitamin E and hyaluronic acid. Can help improve fine lines, UV radiation skin damage, skin elasticity and support the regenerative metabolic processes of the skin

Skin surgery – most skin cancers must be removed by surgery

Cosmetic treatments – to improve skin appearance numerous treatments are available including laser therapy, radiofrequency treatments, chemical peels, tissue fillers and botox


Dry Skin

Dry skin is not usually serious. Dry skin can be inherited. However, most dry skin is caused by environmental factors that can be partially controlled. Dry skin is often temporary and signs and symptoms depend on your age, your health, where you live and time spent outdoors. Dry skin is likely to cause one of the following:

- Skin tightness, especially after bathing

- Rough skin

- Itching

- Slight to severe flaking or scaling

- Fine lines or cracks

- Redness


Dry skin often has an environmental cause. Potential causes of dry skin include:

  • Weather – skin tends to be driest in winter when temperatures and humidity levels plummet
  • Heat – central heating reduces humidity and dries the skin
  • Hot baths and showers – long hot showers or baths can dry skin
  • Swimming – particularly in heavily chlorinated pools
  • Harsh soaps and detergents – formulated to remove oil from the skin

Dry skin increases with age as your skin naturally produce less components that contribute to hydrating your skin including oils and hyaluronic acid.

Treatments and Prevention

Treatments are dependent on the cause of dry skin and include:

  • Life style changes – avoiding long hot baths and showers
  • Moisturizing soap – when bathing or showering
  • Moisturizing cream – apply immediately after bathing or showering
  • Specialty creams – those that contain ingredients such as elastin, vitamin E, D-panthenol and hyaluronic acid to support skin elasticity and repair
  • Prescription medications – including hydrocortisone for more serious dermatitis conditions

Fine Lines and Wrinkles

Fine lines and wrinkles are often linked together. However, dermatologists differentiate between the two. Most dermatologists characterize fine lines as less than 2 millimeters in depth, with wrinkles being greater than 2 millimeters. Fine lines are shallow folds caused by lax, sagging skin and are associated with the earliest signs of aging or photo damage. Wrinkles are predominantly caused by muscle contractions under the skin, which is why they show up where you make the most facial expressions, like squinting, frowning and smiling. Repeated facial muscle movements, contracting and releasing in the same way, over the years create folds along those habitual lines.

Fine lines and wrinkles are caused by the breakdown of collagen and elastin in the skin, and by skin dryness. Collagen and elastin provide the support structure for skin, helping to keep it smooth and resilient. As these fibers breakdown, the skin begins to lose its strength and elasticity.

The major causes of fine lines and wrinkles are:

  • The natural aging process – reduced production of components such as collagen and elastin
  • Heredity – certain skin conditions
  • Dry skin – environmental and lifestyle
  • UV rays – excessive exposure to the sun’s damaging rays
  • Facial expressions – responsible for deeper wrinkles

Collagen fibers strengthen the skin, while elastin helps skin stretch and return to its original shape and hyaluronic acid is the principal component to maintain skin moisture.

Both collagen and elastin break down as you get older. Skin becomes less firm and loses its flexibility, which causes fine lines and wrinkles to appear.

Treatments and Preventions

  • Avoid the sun – clinical studies document this is the primary cause of fine lines and wrinkles
  • Wear sunscreen – use to prevent fine lines and wrinkles
  • Adequate sleep – reduced sleep increases cortisol production, a hormone that breaks down important skin cells
  • Reduce squinting – repetitive facial movements overwork facial muscles, forming a groove beneath the skin’s surface
  • Diet – increase consumption of foods containing important skin components:
    • Salmon is a great source of protein (a skin building block) and a source of an essential fatty acid, omega-3
    • Soy – improves skin’s structure and firmness
    • Cocoa – protects skin from sun damage and improves hydration
    • Fruit and vegetables – contain antioxidants that protect cells from damage caused by free radicals
  • Use moisturizer – gives skin the necessary hydration
  • Alpha-hydroxy acids (AHAs) – natural fruit acids lift away the top layer of dead skin cells and may help stimulate collagen production
  • Retinoids (including RetinA) – reduces fine lines and wrinkles and repairs sun damage (Retinol is a natural form of vitamin A found in numerous OTC products)
  • Topical vitamin C (L-ascorbic acid) – may increase collagen production, protect against UVA and UVB rays, and improve inflammatory conditions and pigmentation
  • Idebenone – related to coenzyme Q10 (CoQ10) a powerful antioxidant, reduces dryness and improves sun damage
  • Botox – relaxes the muscle underneath the wrinkle, smoothing the skin
  • Dermal fillers – inject substances including collagen, hyaluronic acid and other synthetic compounds to fill wrinkles
  • Laser/light resurfacing – removes the top layer of skin which promotes the skin’s natural collagen production system
  • Chemical peels – chemicals used to eliminate the top layer of skin to promote collagen production
  • Dermabrasion – vacuum suction device used in tandem with a mild chemical to remove the top layer of skin cells