In Ayurveda the word “TWACHA” or “CHARMA‟ is used for skin
– (Ch. Sha.7/16)
.The term twacha is derived from samvarana or covering.
FORMATION OF SKIN ACCORDING TO AYURVEDA
According to Charaka:
After the union of shukra, sonita and jeeva in the garbhasaya, the garbha comes
into existence. In the 3rd month all indriyas are made and skin being an indriya takes its
form in the 3rd month.- (Ch.Sha.3/6)
According to Sushruta-
The growth of skin follows after the fertilization of shukra and sonita. The
progress of twacha is initiated by tridosha chiefly pitta. The development and further
growth of twacha is identical to the formation of santanika (cream) when milk is boiled.
Just as the santanika forms layers and gradually increase in thickness; likewise all sheets
are formed in the growing stages of the embryo and join together to turn into the skin on
the exterior surface of fully matured child. -(Su.Sha.4/4)
.
According to Vagbhatta:
Skin is made due to paka of rakta dhatu by its dhatwagni in the foetus, after
paka, it become dry to form twacha, just like the deposition of cream over the surface of
boiled milk. (A. H.Sa. 3/8)
Panchabhautikatva of Tvacha:
- Prithvi Twacha has been considered as the Upadhatu of Mamsa Dhatu that shows it is sthira.
- Jala Due to the presence of Jala Maha bhuta, Twacha is moist.
- Agni Twacha has the specific colour and lusture.
- Vayu Twacha is the Adhisthana of Sparshanendirya.
- Akasha Presence of some micro channels for elimination of Sweda.
RACHANA OF TWAK
The structure of twacha describes that twacha has numerous layers.
DESCRIPTION OF TWACHA ACCORDING TO CHARAKA:(Ch. Sha. 7/4)
- The outermost layer of skin is known as Udaka Dhara.
- The second layer holds up blood.
- The third is site of Sidhma and Kilasa.
- The fourth layer is for Dadru and Kustha.
- The fifth one is the site for origin of Alaji and Vidradhi.
- The sixth layer is that which if cut, causes loss of sense.
DESCRIPTION OF TWACHA ACCORDING TO SUSHRUTA:(Su.Sha 4/4)
According to Sushruta there are seven layers of Skin . They are described as follows-
AVABHASINI:
This is the first layer having a thickness of 1/18th of a Vrihi. This layer is the seat
of disease like sidhma, Padmakantaka.
LOHITA:
This layer is reddish and 1/16th of a Vrihi in thickness, diseases like Tilakantaka,
Nyaccha andVyanga take their origin in this layer.
SWETA:
This layer is 1/12th of a Vrihi in thickness and diseases like Charmadala,
Ajagalli, Masaka, take their origin in this layer.
TAMRA:
This is the fourth layer which is copper coloured 1/8th of a Vrihi in thickness and
is the site of diseases like Kilasa, Kustha rogas.
VEDINI:
This is the fifth layer, it is 1/6th of a Vrihi in thickness. Kusth and Visarpa take
their origin in this layer.
ROHINI:
This is the sixth layer of the skin; it is one Vrihi in thickness. It is thicker than
the previous layers and is the seat of Roma. This layer gives origin to diseases like
Granthi, Apachi, Arbuda, Sleepada and Galaganda Vyadhi.
MAMSADHARA:
This is the seventh innermost layer having thickness of Two Vrihi. This is the
layer in which Bhagandara, Vidradhi and Arshas occurs.
COMPARATIVE TABLE OF SUSHRUTA (ANCIENT) AND MODERN LAYERS OF SKIN
- Avabhasini -Stratum corneum
- Lohita -Stratum lucidum
- Shweta -Stratum Granulosum
- Tamra -Stratum Spinosum
- Vedini -Stratum basale
- Rohini -Papillary layer
- Mamsadhara -Reticular layer
EPIDERMIS
The stratum corneum is the outermost layer of the epidermis. The stratum corneum functions to form a barrier to protect underlying tissue from infection, dehydration, chemicals and mechanical stress. Desquamation, the process of cell shedding from the surface of the stratum corneum, balances proliferating keratinocytes that form in the stratum basale. These cells migrate through the epidermis towards the surface in a journey that takes approximately fourteen days.
The stratum lucidum is a thin, clear layer of dead skin cells in the epidermis named for its translucent appearance under a microscope. It is readily visible by light microscopy only in areas of thick skin, which are found on the palms of the hands and the soles of the feet.
Located between the stratum granulosum and stratum corneum layers, it is composed of three to five layers of dead, flattened keratinocytes. The keratinocytes of the stratum lucidum do not feature distinct boundaries and are filled with eleidin, an intermediate form of keratin. They are surrounded by an oily substance that is the result of the exocytosis of lamellar bodies accumulated while the keratinocytes are moving through the stratum spinosum and stratum granulosum.[
The stratum granulosum is a thin layer of cells in the epidermisKeratinocytes migrating from the underlying stratum spinosum become known as granular cells in this layer. These cells contain keratohyalin granules, which are filled with histidine- and cysteine-rich proteins that appear to bind the keratin filaments together. Therefore, the main function of keratohyalin granules is to bind intermediate keratin filaments together.
At the transition between this layer and the stratum corneum, cells secrete lamellar bodies into the extracellular space. This results in the formation of the hydrophobic lipid envelope responsible for the skin's barrier properties. Concomitantly, cells lose their nuclei and organelles causing the granular cells to become non-viable corneocytes in the stratum corneum.
The stratum spinosum is a layer of the epidermis
found between the stratum granulosum
and stratum basale
.Their spiny (Latin, spinosum) appearance is due to shrinking of the microfilaments
between desmosomes
that occurs when stained with H&E
. Keratinization
begins in the stratum spinosum.[3] This layer is composed of polyhedral keratinocytes
. They have large pale-staining nuclei as they are active in synthesizing fibrilar proteins, known as cytokeratin
, which build up within the cells aggregating together forming tonofibrils
. The tonofibrils go on to form the desmosomes, which allow for strong connections to form between adjacent keratinocytes.
The stratum basale is the deepest layer of the five layers of the epidermis, the external covering of skin in mammals.The stratum basale is a single layer of columnar or cuboidal basal cells. The cells are attached to each other and to the overlying stratum spinosum cells by desmosomes and hemidesmosomes. The nucleus is large, ovoid and occupies most of the cell. Some basal cells can act like stem cells with the ability to divide and produce new cells, and these are sometimes called basal keratinocyte stem cells. Others serve to anchor the epidermis glabrous skin (hairless), and hyper-proliferative epidermis.
DERMIS
The papillary dermis is the uppermost layer of the dermis. It intertwines with the rete ridges of the epidermis and is composed of fine and loosely arranged collagen fibers.The papillary region is composed of loose areolar connective tissue. This is named for its finger like projections called papillae or Dermal papillae specifically , that extend toward the epidermis and contain either terminal networks of blood capillaries or tactile Meissner's corpuscles.
The reticular dermis is the lower layer of the dermis, found under the papillary dermis, composed of dense irregular connective tissue featuring densely packed collagen fibers. It is the primary location of dermal elastic fibers.The reticular region is usually much thicker than the overlying papillary dermis. It receives its name from the dense concentration of collagenous, elastic, and reticular fibers that weave throughout it. These protein fibers give the dermis its properties of strength, extensibility, and elasticity. Within the reticular region are the roots of the hair, sebaceous glands, sweat glands, receptors, nails, and blood vessels. The orientation of collagen fibers within the reticular dermis creates lines of tension called Langer's lines, which are of some relevance in surgery and wound healing.
Physiological concept of Twak:
- Skin is the base of tactile perception because of prevalence of vayu mahabhoota hence sparshanendriyaen circles the entire body.
- It also offers various varna and chhaya of the body. (A.H. Sha. 7/56).
- It is a seat of bhrajakapitta. Thus completes the function of absorption of drug like oils, lotions, ointments, poultices and other topical medicines applied in the form of massage, fomentation etc.
- Bhrajak pitta conveys lusture to the body and controls body temperature.
- Sweat is the excretory product of medo dhatu.
- The total quantity of sweda should be “10Anjali” in normal body and regulate
- evaporation of water.
