Introduction To Skin

Introduction to skin

  • The human skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system that protects the body from various kinds of damage, such as loss of water or abrasion from outside.
  • The system comprises the skin and its appendages(including hair, scales, feathers, hooves, and nails)
  • The skin has up to seven layers of Ectoderm tissue and guards the underlying    muscles, bones, ligaments and  internal organs.
  • Ectoderm is one of the three primary germ layers in the very early embryo
  • There are two general types of skin, hairy and glabrous skin
  • As the skin interfaces with the environment, it plays an important immunity role in protecting the body against pathogens and excessive water loss.
  • Its other functions are insulation, temperature regulation, sensation, synthesis of vitamin D, and the protection of vitamin B Severely damaged skin will try to heal by forming scar tissue. This is often discolored and pigmented.


Skin performs the following functions

  • Protection: An anatomical barrier from pathogens and damage between the internal and external environment in bodily defense; Langerhans cells in the skin are part of the adaptive immune system.
  • Sensation: Contains a variety of nerve endings that react to heat and cold, touch, pressure, vibration, and tissue injury.
  • Heat regulation: Contains a blood supply far greater than its requirements which allows precise control of energy loss by radiation, convection and conduction. Dilated blood vessels increase perfusion and heat loss, while constricted vessels greatly reduce cutaneous blood flow and conserve heat.


  • Control of evaporation: The skin provides a relatively dry and semi-impermeable barrier to fluid loss. Loss of this function contributes to the massive fluid loss in burns.

Aesthetics and communication: Others see our skin and can access our mood, physical state and attractiveness.

  • Storage and synthesis: Acts as a storage center for lipids and water, as well as a means of synthesis of vitamin D by action of UV on certain parts of the skin.
  • Excretion: Sweat contains urea, however its concentration is 1/130  that of urine , hence excretion by sweating is at most a secondary function to temperature regulation.
  • Absorption: The cells comprising the outermost 0.25–0.40 mm of the skin are “almost exclusively supplied by external oxygen”, although the “contribution to total respiration is negligible. In addition, medicine can be administered through the skin, by ointments or by means of adhesive patch, such as the nicotine patch or . The skin is an important site of transport in many other organisms.

Water resistance: The skin acts as a water-resistant barrier so essential nutrients are not washed out of the body.

Hygiene and skin care

The skin supports its own ecosystems of microorganisms, including yeasts and bacteria, which cannot be removed by any amount of cleaning. Estimates place the number of individual bacteria on the surface of one square inch (6.5 square cm) of human skin at 50 million, though this figure varies greatly over the average 20 square feet (1.9 m) of human skin. Oily surfaces, such as the face, may contain over 500 million bacteria per square inch (6.5 cm²). Despite these vast quantities, all of the bacteria found on the skin’s surface would fit into a volume the size of a pea. In general, the microorganisms keep one another in check and are part of a healthy skin. When the balance is disturbed, there may be an overgrowth and infection, such as when antibiotics kill microbes, resulting in an overgrowth of yeast. The skin is continuous with the inner epithelial lining of the body at the orifices, each of which supports its own complement of microbes.

Cosmetics should be used carefully on the skin because these may cause allergic reactions. Each season quires suitable clothing in order to facilitate the evaporation of the sweat. Sunlight, water and air play an important role in keeping the skin healthy.

Oily skin

  • Oily skin is caused by over-active sebaceous glands, that produce a substance called serum, a naturally healthy skin lubricant. When the skin produces excessive serum, it becomes heavy and thick in texture.. The oily skin type is less prone to wrinkling, or other signs of aging, because the oil helps to keep needed moisture locked into the epidermis
  • The negative aspect of the oily skin type is that oily complexions are especially susceptible to clogged pores, blackheads, and buildup of dead skin cells on the surface of the skin. Oily skin can be sallow and rough in texture and tends to have large, clearly visible pores everywhere, except around the eyes and neck.


Human skin has a low permeability ; that is, most foreign substances are unable to penetrate and diffuse through the skin. Skin’s outermost layer, the stratum corner, is an effective barrier to most inorganic anodized particles. This protects the body from external particles such as toxins by not allowing them to come into contact with iternal tissues. However, in some cases it is desirable to allow particles entry to the body through the skin.

solid lipid nano particles 

Solid lipid nano particles  are aqueous colloidal dispersion, the matrix of which comprises of solid biodegradable lipids.

It combine the advantages and avoid the drawbacks of several colloidal carriers of its class such as physical stability, protection of incorporated labile drugs from degradation and controlled release.

SLN formulations for various application routes (parental, oral, dermal, ocular, pulmonary, rectal) have been developed and thoroughly characterized in vitro.

Advantage of solid lipid nano particles

  • Use of biodegradable physiological lipids which decreases the danger of acute and chronic toxicity and avoidance of organic solvents in production methods.

Site specific delivery of drugs, enhanced drug.

penetration into the skin via dermal application

  • Possibility of scaling up.
  • Protection of chemically labile agents from degradation
  • In the gut and sensitive molecules from outer environment
  • SLNs have better stability compared to liposomes
  • Enhance the bio-availability of entrapped bio-active and chemical production of labile incorporated compound.
  • High concentration of functional compound achieved.


  • Disadvantages of SLN

  • Poor drug loading capacity,
  • Drug expulsion after polymeric transition during storage
  • Relatively high water content of the dispersions (70-99.9%)

The Use of Nanotechnology in Cosmetics

Nanotechnology is frequently used in many cosmetic product hair care products, make up and sunscreen.

There are two primary uses for nanotechnology in cosmetics.

First, nano-particles are used as UV filters. Titanium dioxide and zinc oxide are the main ingredients as organic alternatives have not been developed yes.

Secondly, nanotechnology is used for delivery particular components. Solid lipid nano-particles and nano-structured lipid carriers, which are used in cosmetic industry for delivery, can replace liposomes and niosomes.

With the help of encapsulation techniques, newer structures can provide better hydration of skin, stability of the agent, bio-availability and controlled occlusion.

Personal care products, which apply nanotechnology

Penetration enhancer Increases penetration of key ingredients into the skin, using so-called nano-emulsions or nano-spheres: anti-wrinkle cream , to avoid uneven skin pigmentation, wrinkles and lines in six weeks using nanotechnology.

Hair products –Carry active ingredients deeper into hair shafts with the help of nano-emulsions.

Sunscreens – “micronizing” of zinc and titanium in sunscreens made them transparent, less smelly, less greasy and boosted their ability to be absorbed into the skin.




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