SKIN 101: Basic Things Everyone Should Know About SKIN


Skin is one of the most important organs of your fact it is the body's BIGGEST organ. Getting to know the basics of your skin can help you understand its functions and help you realize why skin-care is so important to your overall health, beauty, and wellbeing.


SKIN 101

/ the basics /



  • The skin covers the external surface of the body and protects the interior of the body.

  • It is the largest organ in both surface area and weight

  • the skin is a sensory organ (sense of touch)

  • It is a temperature-sensing thermo-regulator

  • It synthesizes vitamin D

  • It's p.H. - 4 -to 5.6

  • Average thickness: 1-2 mm; thinnest on the eyelids: 0.5mm; thickest on the soles and palms: 6mm

  • Skin renewal takes ~ 28 - 50 days

  • Skin changes according to age

Your skin is an extremely complex organ.

In fact it is the largest organ and is comprised of all four types of human tissue: epithelial, connective, muscular, and nervous tissue. It is a cutaneous membrane, or integument that, well obviously, covers the entire body. It is the main organ of the integumentary organ system. It includes the accessory organs of the hair, nails, sweat glands, oil glands, blood vessels, as well as the nerves which lead to sensory receptors and give the skin its vital sensory function. The skin and its organ system isn't isolated, but operates integrally with all of the body's other organ systems.

An organ (like the heart, stomach, lungs, liver, and of course, the skin) is a combination of two or more types of tissues (groups of similar cells) working together to perform certain functions. Groups of organs which cooperate to carry out a particular process make up an organ system. Organ systems of the body include the integumentary, cardiovascular, lymphatic, digestive, respiratory, urinary, skeletal, muscular, nervous, endocrine, and reproductive systems.  Again, the skin is the main organ of the integumentary system.


The skin is known mostly as a barrier that protects underlying tissues from physical trauma, shields organs from the outside elements, prevents the invasion of pathogens, and helps the body retain water. However, the skin has many functions beyond being a protective covering. Our skin helps us regulate our body temperature, thus it plays a major role in homeostasis, or the relative constancy and balance of our internal environment. The skin also synthesizes particular chemicals which affect the entire body, for example, vitamin D. The skin's sensory and temperature receptors communicate with the environment, objects and others, bringing awareness to our immediate surroundings. The skin then, is what brings us into direct, physical contact with the world. 

Skin Anatomy 101: WHAT YOU NEED TO KNOW

The skin is made up of two main regions: the epidermis and the dermis. Let's take a closer look:

THE EPIDERMIS - outermost 'barrier' layer about 0.4 - 0.5 mm thick, thinnest on the eyelids and thickest on the palms of the hands and soles of the feet. The epidermis protects us from the elements and creates skin tone. The epidermis is made up of sublayers, the deepest of which is the stratum basale which contains stem (basal) cells. The top layer of the epidermis is the stratum corneum, which is about 30% water and contains corneocyteslipids and keratinocytes. Let's talk about these structures in a little more detail:

STRATUM CORNEUM -  free amino acids, lactic acid, urea, salts, water present in this outermost layer make up the skin's natural moisturizing factors (NMF) and are also common ingredients found in moisturizing skin creams. (superficial layers of dead, keratin and lipid filled cells which shed continuously. This water-repellent layer is the body's first defense against light, heat, water, chemicals, and bacteria. It also protects us against rough surfaces by forming callus.)

  • NMF : maintains healthy, supple skin by attracting and retaining water absorbed both from the application of topical products as well as from moisture in the atmosphere.

  • corneocytes : flattened, dead skin cells

  • lipids : makes up a fatty matrix responsible for maintaining a well-hydrated, supple skin barrier which protects against harmful environmental toxins. Skin lipids tend to decline after age 40 leading to drying and aging of the skin.

STRATUM BASALE -  in this deep layer of the epidermis, stem (basal) cells create new epidermal cells as part of the skin renewal process. These newly generated skin cells flatten and harden as they push to the surface layers. The hardening of skin cells comes from the production of keratin, a waterproof protein. (metabolically active layer where cells are continuously dividing and working their way to the upper layers of skin)

  • keratinocytes : hardened protein keratin which gives skin a waterproof quality. These cells are metabolically active and give structure to hair, skin, and nails as push into the upper layers of skin to form the stratum corneum where they will lose water and shed as "dead skin" in the regenerative skin cell renewal process. Cells renew at a rate of about 4-5 weeks, slowing down as we age, taking 7-8 weeks after age 40. Dead skin cells can accumulate, causing clogged and dilated pores as well as dull skin.

  • melanocytes : cells which produce melanin, a pigment that gives skin its color,(skin color varies depending on the amount of melanin produced.) Melanin also protects us from damaging UV radiation by absorbing UV light. The sun's UV rays are beneficial in the small mounts needed to convert a cholesterol related steroid into calcium absorbing "bone vitamin" vitamin D.

  • langerhans cells : specialized macrophages (white blood cells) found deep in the epidermis (stratum spinosum). They phagocytize, or ingest infectious agents before traveling into the organs of the {lymphatic system} where the immune system reacts to pathogens. ... basically they are skin immune system cells which help keep us healthy.

THE DERMIS - lies beneath the dermis and contains tough connective tissue (elastin and collagen), hair follicles, and sweat glands. It is responsible for sensory reception, skin color, and maintenance of body temperature by sensing pressure, vibrations, and sensations of heat and cold.

  • collagen and elastic fibers : help maintain skin youthfulness by providing suppleness, flexibility and structure. These fibers can tear and cause "stretch marks." Age and sun expose decrease the amount of collagen and elastic fibers causing sagging and wrinkling of the skin.

  • blood vessels : blood vessels are responsible for the skin's rosy hue. They regulate temperature by constricting when we are cold to keep the body warm or dilating to increase blood flow and signaling a sweat response. Supply oxygen and nutrients to the skin as well as remove waste products. As we age, collagen in blood vessels tend to break down, weakening the vessels and leading to bruising or "broken capillaries" visible from the surface of the skin.

  • sensory receptors : receptors are the key players of our central nervous system (CNS). Nerves are present all over the body. There are countless number of nerve endings that cover the entire surface of the skin. They help the body recognize pain and pleasure and help us perceive sensations of temperature, touch, and pressure.

SUBCUTANEOUS LAYER - also called the hypodermis, it lies between the dermis layer of skin and the body's underlying structures of bone and muscle.  It is a layer of fat (adipose tissue) and connective tissue. This layer stores fat which insulates, gives smoothness and contour to the body, provides energy, and absorbs shock for vital organs. It also allows for blood vessel passage where nutrients and oxygen diffuse and nourish skin. How skin is nourished?  Blood and lymph supply nourishment to the skin by contributing essential materials for growth and repair. Circulation is maintained by a network of arteries and lymphatics which send smaller branches to hair follicles, skin glands, and hair papilae and remove bacteria and produce infection fighting antibodies. The skin breathes by taking in oxygen through the blood cells and discharging carbon dioxide.

subcutaneous fat -  gives skin its shape and structure, acts as a shock absorber and heat insulator. As we age, there is a breakdown in subcutaneous fat tissue which results in hollowness, sagging of the skin and loss of contour and volume. 


Skin as a mirror to inner health. How? remember when I mentioned that the skin's organ system works with all of the organ systems of the body? Since the skin is the largest and most visible organ of the human body, it is not surprising that some of the tell tale signs of complications and disorders of internal organs can occur to the skin. It is generally agreed upon by modern day medical practitioners that the skin reflects the health of our internal organs. Even subtle symptoms and signs of the skin are not overlooked when looking for health complications. Skin, as an organ of touch is very connected to the nervous system. Thus, we can start to understand the possibility of skin disorders to be affected by stress. 

Aside from sensations of burning, itching, pain, swelling, and other discomforts, there are psychological implications. Whether skin complications are medical (like burns or skin cancers) or cosmetic (hyper-pigmentation and discoloration for example), in an appearance driven world, disorders and dis-ease can lead to social embarrassment, taking a toll on a person's confidence and self-esteem thus leading to damaging psychological effects on a person's state of mind.

It takes more than just superficial application of products to maintain the skin health necessary to keep it "looking beautiful..." And a healthy human does not need to be on products or pills all of the time. Troubled skin, however, should be treated.

True beauty, however, is the reflection of optimum health. Beautiful skin is skin that appears glowing and smooth. In Sanskrit literature, it is often said that a beautiful face is one that appears "bright like the moon." 

Human Biology by S. Mader and M. Winderlspecht
Skin Talks by Dr. Jaishree Sharad