The skin is the largest organ of the body, with a total area of about 20 square feet. The skin protects us from microbes and the elements, helps regulate body temperature, and permits the sensations of touch, heat, and cold.
Skin has three layers:
The epidermis, the outermost layer of skin, provides a waterproof barrier and creates our skin tone.
The dermis, beneath the epidermis, contains tough connective tissue, hair follicles, and sweat glands.
The deeper subcutaneous tissue (hypodermis) is made of fat and connective tissue.
The first, topmost, or superficial, layer of the skin the sun’s rays hit is called the epidermis. Again, the epidermis is the outermost layer of the skin. The epidermis is itself made up of several layers. From outer to innermost, they are the:
1- Stratum corneum (horny layer)
– layer has many rows of dead cells filled with keratin
– continuously shed and replaced (desquamation)
– effective barrier against light, heat and bacteria
– 20-30 cell layers thick
– excess exfoliation of corneocytes cells formed dandruff and flakes
2- Stratum lucidum
– seen in thick skin of the palms and soles of feet.
– 3-5 rows of clear flat dead cells
3- Stratum granulosum
– 3-5 rows of flattened dead cells.
– keratohyalin granules (darkly stained) accumulate
– lamellated granules secrete glycolipids into extracellular spaces to slow water loss in the epidermis.
4- Stratum spinosum: “spiny layer”
– 8-10 rows of polyhedral (many sided) cells
– appearance of prickly spines
– melanin granules and Langerhans’ cell predominate
5- Stratum basale: deepest epidermal layer
– attached to dermis (Forms a strong bond between epidermis and dermis)
– single row of cells,Forms epidermal ridges (e.g., fingerprints)
– mostly columnar keratinocytes
– with rapid mitotic division
– contain merkel cells and melanocytes
The skin’s color is created by special cells called melanocytes, which produce the pigment melanin. Melanocytes are located in the epidermis.
** The Dermis
This layer of skin is called the dermis, and it is the middle layer of the skin, right below the epidermis.
The dermis makes up the bulk of the skin and provides physical protection. It is composed of an association of fibres, mainly collagen, with materials known as glycosaminoglycans, which are capable of holding a large amount of water, thus maintaining the turgidity of the skin. A network of extendable elastic fibres keeps the skin taut and restores it after it has been stretched.
The hair follicles and skin glands are derived from the epidermis but are deeply embedded in the dermis. The dermis is richly supplied with blood vessels, although none penetrates the living epidermis. The epidermis receives materials only by diffusion from below. The dermis also contains nerves and sense organs at various levels.
** Hypodermis (Subcutaneous tissue):-
The subcutaneous tissue is a layer of fat that lies beneath the dermis, and acts as an insulator and shock absorber.
These are specialized structures that are located in the dermis and subcutaneous fat.
Cutaneous appendages include the eccrine gland, apocrine gland, hair, and sebaceous gland.
*** Skin aging:
Loss of structural integrity and physiological function of skin. It is caused by both intrinsic and extrinsic factors.
Intrinsic factors is characterized by fine lines, wrinkles, skin thinning, decreased skin ability in wound healing. For exa:
1) Genetics: DNA damage
2) Hormones: Decline of hormones (estrogen, testosterone etc.) and growth hormone
3) Oxidative Stress
4) Elevated Blood Sugar Levels.
Extrinsic factor is characterized by skin thickening, rough texture, coarse wrinkles and age spots.
1) UV Radiation and “Photoaging“
2) Environmental Toxins.
*** What causes our skin to age?
One thing that we cannot change is the natural aging process. It plays a key role. With time, we all get visible lines on our face. It is natural for our face to lose some of its youthful fullness. We notice our skin becoming thinner and drier. Our genes largely control when these changes occur. The medical term for this type of aging is “intrinsic aging.”
We can influence another type of aging that affects our skin. Our environment and lifestyle choices can cause our skin to age prematurely. The medical term for this type of aging is “extrinsic aging.” By taking some preventive actions, we can slow the effects that this type of aging has on our skin.
The sun plays a major role in prematurely aging our skin. Other things that we do also can age our skin more quickly than it naturally would.
*** Prevention of skin aging:
To help their patients prevent premature skin aging, dermatologists offer their patients the following tips.
1- Protect your skin from the sun every day. Whether spending a day at the beach or running errands, sun protection is essential. You can protect your skin by seeking shade, covering up with clothing, and using sunscreen that is broad-spectrum, SPF 25 (or higher), and water-resistant. You should apply sunscreen every day to all skin that is not covered by clothing.
2- If you smoke, stop. Smoking greatly speeds up how quickly skin ages. It causes wrinkles and a dull, sallow complexion.
3- Eat a healthy, well-balanced diet. Findings from a few studies suggest that eating plenty of fresh fruits and vegetables may help prevent damage that leads to premature skin aging. Findings from research studies also suggest that a diet containing lots of sugar or other refined carbohydrates can accelerate aging.
4- Cleanse your skin gently. Scrubbing your skin clean can irritate your skin. Irritating your skin accelerates skin aging. Gentle washing helps to remove pollution, makeup, and other substances without irritating your skin.
5- Wash your face twice a day and after sweating heavily. Perspiration, especially when wearing a hat or helmet, irritates the skin, so you want to wash your skin as soon as possible after sweating.
6- Apply a facial moisturizer every day. Moisturizer traps water in our skin, giving it a more youthful appearance.
7- Stop using chemical based skin care products that sting or burn. When your skin burns or stings, it means your skin is irritated. Irritating your skin can make it look older.
Note: Some anti-aging products prescribed by a dermatologist may burn or sting. When using a prescription anti-aging product, this can be okay. Just be sure to let your dermatologist know.
*** Sun burn: Sunburn is a form of radiation burn that affects living tissue, such as skin, that results from an overexposure to ultraviolet (UV) radiation, commonly from the sun. Common symptoms in humans and other animals include red or reddish skin that is hot to the touch, pain, general fatigue, and mild dizziness. An excess of UV radiation can be life-threatening in extreme cases. Exposure of the skin to lesser amounts of UV radiation will often produce a suntan.
The primary measure is avoiding further exposure to the sun. The best treatment for most sunburns is time. Applying soothing lotions that contain aloe vera, to the sunburn areas.
*** What is dry skin
Lack of the appropriate amount of water in the most superficial layer of the skin (Transepidermal water loss -TEWL) and the condition known as dry skin.
The epidermis is normally composed of fat (lipid) and protein.The lipid portion of the epidermis helps prevent skin dehydration. When the skin’s fatty oils are removed, the skin loses its protection and loses moisture more easily.
Rough dry skin
Moisturisers : Increase the water content of the stratum corneum. Moisturizers work by using ingredients that are occlusive and/or humectant agents.
Ingredients may improve the skin’s softness by lubricating and filling in the spaces between dry skin cells. An ingredient list on a moisturizer will list these agents as the “active” ingredients.
hair can be defined as a slender, thread-like outgrowth from a follicle in the skin of mammals. Composed mainly of keratin protein.
Hair consists of broadly:
Shaft above the surface of skin.
Root that penetrates below the skin.
Hair Shaft : composed of three principal parts.
The cuticle varies in Scales.
Regulates the amount of water in the hair structure, which keeps its physical properties.
The damage to the cuticle can be caused by Weather or mechanical friction such as combing, brushing & the excessive use of Chemical based hair products.
The cortex varies in: Thickness, Texture, Color.
Keratin: provides mechanical properties to the fibers.
The matrix comprises the major structure of the hair and contains a high concentration of disulfide bonds.
Matrix swells when in contact with water and forms a lightly cross linked gel structure. It exhibits keratin & melanin in the direction of the hair strand which are responsible for the hair color and its photo protection.
The medulla can be empty or filled with sponge keratin, can serve as a pigment reservoir, and can contribute to the brightness of the hair.