Asthi Dhatu (अस्थी धातु)
The term 'Asthi' in samskrit refers to a 'Bone'. Thus Asthi dhatu mentioned in Ayurveda is similar to bony tissue in human body. In a literal sense, the word Asthi means that entity which doesn't get destroyed easily and stays longer as compared to all other counterparts. It is well known that even after years of burial of human bodies, the remnant tissue which one can find is bone. Thus bone or asthi is that body component which is not easily destroyed naturally very rapidly. In human beings Asthi dhatu performs the vital function of forming the skeleton, providing stability and shape.
Characteristic feature of Asthi dhatu
Asthi dhatu is identified by Ayurveda acharyas by its peculiar feature of strength. Acharya sushruta has beautifully explained the properties, role and importance of Asthi dhatu with example as follows,
अभ्यन्तरगतैः सारैर्यथा तिष्ठन्ति भूरुहाः | अस्थिसारैस्तथा देहा ध्रियन्ते देहिनां ध्रुवम् ||२१||
तस्माच्चिरविनष्टेषु त्वङ्मांसेषु शरीरिणाम् | अस्थीनि न विनश्यन्ति साराण्येतानि देहिनाम् |
मांसान्यत्र निबद्धानि सिराभिः स्नायुभिस्तथा | अस्थीन्यालम्बनं कृत्वा न शीर्यन्ते पतन्ति वा ||२३||
Meaning: Physical bodies of the humans are held stable by the strong asthi like the trees are held strong rooted to the ground due to their strong stem (heartwood). Since asthi are like the essence of the body those never decay and get destroyed long after decaying of mansa and twak (Muscular tissue and skin). Various sira (vessels, nerves) and snayu (tendons, ligaments) are attached to asthi and those are held in place because of asthi which themselves never decay or fall.
Thus Asthi dhatu is also termed as the extract (sara) of the body (Su.sha 5/21-22]
Panchabhautika constitution
Asthi dhatu is that tissue which is called as essence or extract of body. It is strong, hard and stable. Therefore it is clear that it has Prithvi mahabhuta dominance in it. At the same time it is also khara (dry and rough) in texture. (Cha chi 15/24,25) This property of Asthi is developed during its generation from meda dhatu by the action of Teja and Vayu along with Pruthvi. Also Asthi is one of the chief sites of vata residence. Thus Along with Pruthvi, Asthi dhatu has dominant vayu and teja mahabhuta as well.
Metabolism and Development
The asthi dhatu is formed from its predecessor adipose tissue (meda dhatu). The nourishing portion of adipose tissue (meda dhatu) and constituents of nutrient fluid (ahara rasa) are transformed into asthi dhatu by action of factors responsible for its metabolism (asthi dhatvagni). Agni mahabhuta and vayu mahabhuta play a major role in the solidification and roughness of asthi by acting upon prithvi mahabhuta components of adipose tissue (meda dhatu).[Cha. Sa. Chikitsa Sthana 15/30]
Porosity in bones are due to actions of vayu and akasha mahabhuta. [Cha. Sa. Chikitsa Sthana 15/30]
Metabolic byproducts and waste products (Upadhatu and mala)
During the process of metabolism and development of asthi dhatu, nails (nakha) are formed as the metabolic byproducts (upadhatu). [Su. Sa. Sutra Sthana 46/529] Sharangadhara considered teeth (danta) only as metabolic byproduct.[Sha. Sa. Purva khanda chapter 5]
Scalp hair (kesha) and body hair(loma) are waste products of metabolism of asthi dhatu. [Cha.Sa. Sutra Sthana 15/18]
Utpatti of Asthi dhatu
The asthi dhatu is formed from its predecessor meda dhatu. When meda dhatu is subjected to the process of micro-transformation (सूक्ष्मपचनम्), one processed part of it is specifically utilized to provide nourishment to the next dhatu in order i.e. Asthi Dhatu (धातु). This part is responsible for development and nourishment of asthi dhatu in body. Transformation of this fluid and unctuous form of meda dhatu into solid and tough (cha chi 15 24, 30) form of asthi dhatu happens due to action of Pruthvi, Teja and Vayu mahabhutas and generation of excess dryness in the processed part. Excess dryness and hardness are thus the distinguishing features of asthi dhatu from all other dhatus.
Characteristics of best quality or essence (asthisara)
The persons with essence of asthi dhatu have prominent heels (parshni), ankles (gulpha), knee joint (janu), elbows (aratni), collarbones (jatru), chin (chibuka), head (shira), flanks (parshva) and joints and also bones and teeth. Such persons are highly enthusiastic, active, enduring, having strong and firm body as well as longevity.[Cha.Sa. Vimana Sthana 8/107]
Anatomical and physiological structures
The asthi dhatu is present in various forms as below.
Channels for transportation and transformation of asthi dhatu (asthivaha srotas)
The channels originate from predecessor meda dhatu and buttocks (jaghana). [Cha. Sa. Vimana Sthana 5/8] There are various other anatomical structures related to asthi dhatu. These can be included in the system. The structures are as described below.
Functions
The important function of asthi dhatu is providing structure and support to the body. It also nourishes the successor bone marrow tissue (majja dhatu).[Su. Sa. Sutra Sthana 15/5]
Causes of vitiation
The following are causative factors for the vitiation of channels for transport and transformation of asthi dhatu (asthivahasrotasa). [Cha. Sa. Vimana Sthana 5/17]
Dietary causes
- Excessive consumption of food that aggravates vatadosha in body. This includes the dietary items which possess properties like light to digest (laghu), dry(ruksha), cold(sheeta), rough(khara), highly penetrating or subtle (sukshma), mobile(chala).
Lifestyle causes
- Excessive physical exercise
- Excessive jerks to the body or jerky movements
- Excessive pressure on bones.
Signs of decrease
- loss of scalp and body-hair, beard, nails and teeth
- fatigue
- loose joints
- pain in bones
- dryness
- breaking of teeth and nails
[Cha. Sa. Sutra Sthana 17/67], [Su. Sa. Sutra Sthana 15/9]
Signs of increase
- extra tooth and bony growth [Su. Sa. Sutra Sthana 15/14]
Importance in preservation of health and prevention
Bone tissue (asthi dhatu) is considered as the essence of body tissue which remains even after destruction of all other tissues. [Su. Sa. Sharira Sthana 5/21-22]
The enthusiasm, endurance, strength, body structure, firmness, and longevity depend upon quality of asthi dhatu. [Cha. Sa. Vimana Sthana 8/107]