Shukra Dhatu (शुक्र धातुः)
Shukra Dhatu is one of the 7 body tissues as per Ayurveda. It is the 7th dhatu in Sharira according to Ayurveda. Since it is developed last i.e. at the end of dhatu development and nourishment pathway, it is called as 7th or the last dhatu. Shukra literally means semen, sperm, clear, lucid, white or spotless. Since Shukra dhatu passes through rigorous metabolic transformations occurring at every stage during development of all 7 dhatus and develops at the end of this pathway, it is more clear or spotless. Thus it is also called as purest dhatu from which ojas also develops.
The term shukra originates from the root word "शुच क्लेदे + “ऋज्रे न्द्राग्रवज्रेति ।”
In Ayurveda literature, 2 dimensions of shukra dhatu are be found to be mentioned. One form of it is Shukra dhatu which is ejaculated at the end of mating and is responsible for conception. The other form of shukra dhatu refers to the body tissue that is present in every part of shariram (physical body) and controls the rebuilding of body tissues, new cell/tissue generation and overall development. Thus the dhatu which controls the function of reproduction of any form in the body is called as shukra dhatu.
Location of Shukra Dhatu
Shukra dhatu is present all over the body as stated by Acharya Charaka.
सर्वदेहगतं शुक्रं प्रवदन्ति मनीषिणः| (Char. Samh. 15.26)
In spite of that, there are some body parts which are specifically mentioned to be the related to Shukra dhatu. Those are Vrishana (testicles), Medhra (Penis), Stana (Breasts). Also, vessels carrying shukra dhatu have also been mentioned to be associated with transportation of shukra.
Formation of shukra dhatu
Shukra dhatu is formed from 'Majja dhatu'(धातु). When Majja 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. Shukra Dhatu (रक्त धातु). This part is responsible for development and nourishment of Shukra dhatu in body. Transformation of unctuous part of predecessor majja into Shukra happens through a specific process. It is stated that, the asthi dhatu develops porosity due to action of vayu and akasha mahabhutas. The unctuous part of majja dhatu present inside this porous asthi dhatu oozes out of these pores and reaches all parts of the body through channels of transportation of shukra dhatu (shukravahasrotas). This unctuous part is known as shukra. After puberty, at the time of sexual excitation or urge of ejaculation (vega), the shukra reaches to basti from all over the body and then it is discharged through urethra. This process happens just like ghee is melted by heat.
Upadhatu of Shukra dhatu
Shukra dhatu when subjected to the process of micro-transformation (सूक्ष्मपचनम्), it generates 1 entity which is known as Upadhatus (उपधातु | metabolic by-products which function as body tissues) of Shukra dhatu. As per Acharya Sharangadhara Ojas is the metabolic byproduct (upadhatu) of shukra. However, all acharyas do not agree to this. Some are of the opinion that since Shukra develops as essence of all dhatus there is no metabolic byproduct of it.
Mala of Shukra dhatu
Ayurveda acharyas have opined that Shukra being the purest form of dhatu generated at the end of dhatu nourishment and development pathway, there is no metabolic byproduct or waste formed during its formation. Thus Shukra is devoid of mala.
Qualities of best shukra
The best qualities of Shukra dhatu which is ejaculated out during the process of mating plays the key role in reproduction. Certain qualities of shukra which are helpful in reproduction are known to be best qualities of shukra. The Shukra which is unctuous (snigdha), viscous (ghana), slimy (picchila) in texture, sweet (madhura) in nature (soothing, cool, contains fructose) and looks like white crystal quartz is considered to be a good quality shukra.
Panchabhoutiktwa of Shukra dhatu
Among 5 mahabhutas, Shukra is believed to have dominance of 4 mahabhutas viz Vayu, Agni, Jalam and Prthvi.
Shukra sarata lakshanas
Those who have supreme quality of Shukra dhatu in a body are identified by some characteristic features. These features are called as Shukra-sarata features ( लक्षणानि). These features are manifested on various organs and body parts which reflect beauty and external appearance of a person e.g skin, eyes, teeth. Thus one can identify the quality of Shukra dhatu by assessing presence or absence of following signs in body.
सौम्याः सौम्यप्रेक्षिणः क्षीरपूर्णलोचना इव प्रहर्षबहुलाः स्निग्धवृत्तसारसमसंहतशिखरदशनाः प्रसन्नस्निग्धवर्णस्वरा भ्राजिष्णवो महास्फिचश्च शुक्रसाराः|
ते स्त्रीप्रियोपभोगा बलवन्तः सुखैश्वर्यारोग्यवित्तसम्मानापत्यभाजश्च भवन्ति|| (Char. Samh 8.109) 
Meaning: The persons endowed with the essence of shukra dhatu are gentle (saumya), having charming yet decent appearance (saumyaprekshina), beautiful eyes as if filled with milk (kshirapurnalochana) and immensely exhilarated (praharshabahula). Their teeth are unctuous, rounded, firm, even and compact. They have prominent buttocks (large pelvic girdle). They have pleasant, unctuous complexion and voice. They are brilliant. They are liked by women for enjoyment, are strong and endowed with happiness, leisure, health, wealth, honor, and progeny.
Function of shukra dhatu
Reproduction is the prime function of Shukra dhatu.  In Ayurveda this function is called as Garbhotpadanam (Garbha- Embryo; Utpadanam-generation). Thus, irrespective of the gender, Shukra dhatu present in the body is responsible for the function of reproduction. Apart from that, it also impacts the various psycho-somatic attributes like courage, lust, strength, pleasure, love and affection. It is closely related with human emotions and manas (mind).
Causes of vitiation
Causes of vitiation
The following are the causative factors for the vitiation of channels for transport and transformation of shukra dhatu.[Cha. Sa. Vimana Sthana 5/19]
Consumption of incompatible food, excessive consumption of dry, bitter, astringent, salty, sour, hot food.
Anxiety, distress, distrust, apprehension, rage, exorcism.
Causes related to coitus
Excess intercourse, untimely coitus, coitus other than in vagina, or complete abstinence from it(suppression of discharge of semen), unaware of female desire, untimely ejaculation etc.
Excess exercise, senility, improper usage of surgical instruments, alkali (kshara), heat or cautery (agni), emaciation due to other diseases, repression of natural urges, injury, morbidity causing vitiation of dhatus, doshas individually or collectively reaching reproductive system (retovahasrotas) leads to acute disorders of the shukra (semen). [Cha. Sa. Chikitsa Sthana 30/139]
Importance of Shukra dhatu in preservation of health and wellness
Aphrodisiac therapies (vajikarana) produces lineage of progeny, quick sexual stimulation, enables one to perform sexual act with the women uninterruptedly and promote corpulence and infallible and indestructible semen. [Cha. Sa. Chikitsa Sthana 1/1/9-10] This is one of the most important measures to promote sexual health and prevent diseases.
- Charaka Samhita (Chikitsasthanam Adhyaya 15 Sutram 26)
- Charaka Samhita (Vimanasthanam Adhyaya 5 Sutram 8)
- Sushruta Samhita (Sharirasthanam Adhyaya 9 Sutram 12)
- Charaka Samhita (Chikitsasthanam Adhyaya 15 Sutram 33-35)
- Sharangadhara Samhita (Purvakhanda Adhyaya 5)
- Charaka Samhita (Chikitsasthanam Adhyaya 30 Sutram 40)
- Charaka Samhita (Sharirasthanam Adhyaya 2 Sutram 4)
- Charaka Samhita (Vimanasthanam Adhyaya 8 Sutra 109)
- Available from Charakasamhitaonline.com
- Ashtanga Hrudayam (Sutrasthanam Adhyaya 11 Sutra 4)
- Sushruta Samhita (Sutrasthanam Adhyaya 15 Sutram 5)