UNDERSTANDING SKIN ANATOMY

Skin or Twacha is the longest organ of our body and is a seat of “sparshanendriya”. Giving external covering to the whole body, the senses of touch, pain, temperature, pressure are also felt by it.


Skin is one of the important presentable organ of the body. It has a definite role in ones personality. Skin issues (twacharogas) affect not only on somatic level but also on a psychological level.


According to Ayurveda, skin is the mirror to an individual’s health. Normal healthy skin is necessary in a healthy individual in order to combat the various challenges faced by a healthy skin as the skin also performs various excretory and metabolic functions. The skin is constantly in flux, either from season to season or thanks to bodily and hormonal changes.



To get a proper idea of skin ailment, one must know the normal echo texture. Everybody’s skin is different. Hence the approach to care and nurture the face and body has be customized. This means there is a need to analyze your skin and treat it according to its current condition, not overall type.


Skin Anatomy

The skin is the organ of integumentary system that is covering system of the body. It is formed by about:


8% of the total body mass.

2.2 square meter covering area.

16% of total body weight.


Thickness of the skin is different according to maturation, aging and regional specialization. It may be 0.5 mm on the eyelid and 4 mm on heal. Most of the body skin is average 1:2cm thick. Skin is a fascinating organ as it forms a self renewing and self repairing interface between the body and its environment. Within limit, it forms an effective barrier against microbial invasion and has properties which can protect against mechanical, chemical, cosmetic, thermal and photonic damage.


1. Epidermis:

The epidermis, the outermost layer of skin, provides a waterproof barrier and creates our skin tone. It is a compound tissue consisting mainly of the continuously self replacing keratinized stratified squamous epithelium. It varies in thickness 0.04 mm on the eyelid and 0.16 mm on palms, 0.1 mm is average thickness. Epidermis contains five layers (Strata). Stratum basale Stratum spinosum Stratum granulosum Stratum corneum Stratum lucidum

  • Stratum Basale: It is deepest layer of the epidermis and formed by a single row of columnar keratinocytes. Four types of cells are germinated through these layers which are keratinocytes, melanocytes, langerhans cells and merkels cells.

  • Stratum spinosum: It lies super ficial to basal and it consists of 5 to 12 layers of polyhedral keratinocytes cells are joined tightly to other cells by bundles of intermediate filaments of the cytoskeleton. This arrangement provides both strength and flexibility.

  • Stratum granulosum: It is 3 to 5 layers of flattened keratinocytes that contains darkly staining granules of proteins called keratohyalin. The lipid rich secretion produced by the lamellar granules work as a water repellent sealant that retards loss of body fluid and entry of foreign materials.

  • Stratum lucidum: It is present only in the skin of fingertips, palms and soles. It consists of 3:5 layers of clear, flat, dead keratinocytes

  • Stratum corneum: This is the most superficial layer consisting of anucleated flattened confirmed 25:30 layers of dead keratinocytes. These cells are continuously shed and replaced by cells from the deeper strata. It serves as an effective water repellant barrier and also protects against injury and microbes.


Adnexa of epidermis: It contains the eccrine glands, apocrine glands and the pilosebaceous apparatus.

  • Eccrine sweat glands: These are distributed all over body except the venillion borders of the lips nailbeds, labia minora, glans penis etc. There density is maximum on the palms, sales and axillae. These glands initiate the sweat formation which dissipate heat by evaporation.

  • Apocrine glands: These are located in the axillar, areolae, periumbilical, perianal, external ear etc. areas. These are small and nonfunctional till puberty, after which they enlarge.

  • Hair follicles: They presents all over body except some parts like palm, sole etc and they protects scalp from injury and sunrays and decrease heat loss.

  • Sebaceous gland: They are lipid producing structures disturbed all over body except palms and soles.

  • Nail unit: The nail unit helps in the appreciation of the fine and tactile stimulation, protect the terminal phalanges from trauma.



Dermis:

The dermis rests upon the subcutaneous fat and is 15:40 time thicker than the epidermis. The dermis is composed mainly of noncellular connective tissue containing collagen, elastic tissue and ground substances within which are embedded the nerves, blood vessels, lymphatics, muscles, and pilosebaceous apocrine and eccrine sweat unit. Dermis can be divided into following:

  • Superficial: Papillary region: It consists of areolar connective tissue containing fine elastic fibers. Elastic fibers play a role in maintaining the elasticity of the skin.

  • Deeper: Reticular region: It consists of dense irregular connective tissue containing bundle of collagen and some elastic fibers. Both these provides strength elasticity to skin.

Pigmentation of Skin: Melanin, carotene and hemoglobin: these three pigments give skin a wide variety of color. Melanin located in epidermis, carotene is mostly in the stratum corneum and dermis and hemoglobin is in red blood cells within capillaries in the dermis.


Hypodermis

The deeper subcutaneous tissue -hypodermis (also called the subcutaneous layer or superficial fascia) is a layer directly below the dermis and serves to connect the skin to the underlying fascia (fibrous tissue) of the bones and muscles. It is not strictly a part of the skin, although the border between the hypodermis and dermis can be difficult to distinguish. The hypodermis consists of well-vascularized, loose, areolar connective tissue and adipose tissue, which functions as a mode of fat storage and provides insulation and cushioning for the integument.

Ayurveda Take on Skin Anatomy :

Sushruta had further divided these layers into 7 layers.


Epidermis :-

1) Avabhasini (Horne layer)

2) Lohita (Stratum lucidum)

3) Shweta (Stratum Granulosum )


Dermis:-

4) Tamra (Malphagian Layer)

5) Vedini (Papillary Layer)

6) Rohini (Reticular Layer)


Hypodermis:-

7) Mamsadhara- Sthula (Subcutaneous Tissue and Muscles)



The Seven Layers of the Skin

Ayurveda describes the said seven distinct layers of the skin, each with its own structure and function. The layers are designed so that each layer provides support to the layers above it. The skin as a whole is able to effectively perform its overall functions when all the layers are healthy and balanced.


  1. Avabhasini (Horne layer): This is the outermost layer. It reflects the complexion and the quality of the Rasa Dhatu (nutrient fluid, the first of the seven tissues of the body). It also acts as a mirror: it indicates whether the physiology as a whole is balanced or imbalanced, and whether there is inner health or disorder. The avabhasini layer also reflects the aura of the individual — if there is inner bliss, it shows on this layer. It does not have its own color: it reflects the colors of the inner layers. Internal and external re-hydration and regular massage supports the health and appearance of the avabhasini layer of the skin.

  2. Lohita (Stratum Lucidum): This layer supports the outermost layer. It indicates the quality of Rakta Dhatu (blood). If there is ama(impurities) in the blood, it impacts the aura of the outer layer and accentuates sensitivity to the sun. The color of this layer resembles molten iron.

  3. Shweta (Stratum Granulosum): This is a white layer, and it provides balance to skin color, lightening the darker colors of the inner layers.

  4. Tamra (Malphagian Layer): This layer nurtures the upper layers of the skin. It supports the immune system. This is the layer that helps the skin perform its function of being a "barrier." Skin infections reflect an imbalance in this layer. It is copper-colored.

  5. Vedini (Papillary Layer): This fifth layer sensually links the skin to the rest of the body. It is the center for transformation of sensation — feeling of pain, for example.

  6. Rohini (Reticular Layer): This layer supports healing and regeneration. Imbalance in this layer retards healing and the disappearance of scars over time. A balanced diet, rich in nutritional value, supports the Rohini Layer.

  7. Mamsadhar (Subcutaneous Tissue and Muscles): This innermost layer is the platform for the skin's stability and firmness. When this layer is in balance, the skin looks young and supple. A skin product that has a vayasthapana effect nourishes this layer to help retard the aging process.

The seven layers of skin get their nutrition from Mansa Dhatu {muscle tissue}. It is known as an Updhatu (secondary tissue product) of the Raktadhatu (blood) because it only mimics the Dhatu's in beholding the body. Hence it reflects the qualities of rakta (blood) and rasa dhatu (body’s plasma tissue). It does not do Poshan Karma i.e. do not give nutrition to the other Dhatus. Interestingly, computational modelling of the skin also describes seven layers, as were described in Ayurveda.


Western medical science suggests, simulated diffuse reflectance spectra were assumed by a wavelength independent scattering coefficient for the different skin tissues, using the known wavelength dependence of the absorption coefficient of oxy and deoxy Hb and water. This computational modelling resulted in a three dimensional media which has seven layers. The physical and structural parameters of internal tissues were comparable with results of in vivo measurements of skin reflectance spectra. According to the computational model, the first layer has desquamating cells containing keratin, and was called the stratum corneum (20µm thick). The second layer, called the ‘living epidermis’ (80 µm thick) contains columnar cells, cells with keratohyalin granules, and a fraction of dehydrated cells. 16 The remaining layers which were speculated to provide support and protection, as well as sensation and pigmentation, have been called the papillary dermis (150 µm thick), upper blood net dermis (80 µm thick), reticular dermis (1500 µm thick), and deep blood net dermis (100 µm thick). The deepest layer in this model is subcutaneous fat (6000 µm thick). These layers are approximate but illustrate that the spatial distribution of blood in heterogenous tissues is an important factor, which influences the transport of light in the tissue. It is interesting that computational modeling, conventional and ancient Ayurveda texts (of Sushruta Samhita, Chapter 4 Verse 3) describe the skin ascribing similar functions to the layers, even though the methods used are very different. These common features can be considered important as medical conditions, especially dermatological diseases often do not respond adequately to conventional medicine. It is increasingly apparent that an integrated approach, which combines conventional dermatology and complementary and alternative treatments would be a better alternative. This was proposed by Terence Ryan (1998), who as the Chairman of the International Foundation of Dermatology advocated Skin Care for All.


The Institute of Applied Dermatology (IAD) in Kerala, India under S.R. Narhari MD has already developed a unique integrated approach, combining allopathic treatment with Ayurveda to successfully manage lymphatic filariasis, lichen planus and vitiligo. The integrated approach has been successful, with a good response rate and no side effects. In order to promote an integrated approach to dermatology, common features between the two knowledge systems, i.e., allopathy and Ayurveda is essential. A good starting point would be to demonstrate common features in the anatomy and physiology of the skin layers in both systems.




Skin Health: The Ayurvedic Perspective

We have already read in previous blogs, Ayurveda is based on the principles of three doshas- Vata, Pitta and Kapha. Doshas are the energies that govern the activities of the mind and body and create physical, emotional and mental tendencies.


These three principles are combinations of the five elements — Vata, for example, is mostly air and space, Pitta is mainly fire and water and Kapha is primarily earth and water. A person's ayurvedic skin type, therefore, can be Vata, Pitta or Kapha, or sometimes a combination of two of these doshas.


  • Vata skin is in generally dry, thin, delicate and cool to the touch, easily gets dehydrated, and is very vulnerable to the influence of dry windy weather. Vata skin may age faster, and tends to be dry, rough and flaky when out of balance. Its color is black and smoky.