Systematic review of the concept of Yakrutotpatti (embryology of liver)

Abstract

Ayurveda has its own view to understand the development of human body and its various organs. As the quotations are in a concise manner, it is essential to amalgamate the basics stated by various Acharyas with comprehensive explanation of modern science. The liver is a vital organ for metabolism. Acharyas have opined about the genesis of Yakrut (liver) from Rakta Dhatu (blood tissue). Parallel opinion in conventional anatomy states that abundant quantity of blood is responsible for the formation of sinusoids of liver. This huge quantity of blood comes from broken viteline and umbilical veins in the septum transversum. On the other hand, the raw material for the formation of blood cells and liver (septum transversum) is the same, being mesenchymal cells from the mesoderm. The present review was conducted to discover the similarities about the genesis of liver in the opinions of ancient and conventional medical science. This may be useful for utilizing the ancient medical science in a new perspective. Therefore, it is attempted to correlate the genesis of liver in Ayurveda with modern science.

Introduction

According to modern science, the visceral organs can be studied with two perspectives, viz. anatomical observations and physio-pathological derangements. Ayurveda Samhitas concise the study under one heading of “Sharir”. The subject covers the anatomical as well as physiological studies related with the specific organ.[1]

Ayurveda narrates the basic principles including Panchamahabhoota, Tridosha, Saptadhatu, etc., in view of embryology and organogenesis. The various organs generate from different combinations of these Bhavapadarthas. Liver is a vital organ for metabolism. Acharyas have opined about the genesis of Yakrut from Rakta Dhatu (blood tissue). A parallel opinion in conventional anatomy states that an abundant quantity of blood is responsible for the formation of sinusoids of the liver. This huge quantity of blood comes from broken viteline and umbilical veins in the septum transversum. On the other hand, the raw material for the formation of blood cells and liver (septum transversum) is the same, being mesenchymal cells from the mesoderm. Many new diseases like liver cirrhosis, carcinoma liver and hepatitis are introduced by modern science. It is essential to conceptualize the basic genesis of liver in order to form the exact pathogenesis and treatment in Ayurveda. The present research is carried out to understand this concept in the light of contemporary science. This may be helpful while treating the disorders of the liver.

Aim of the Study

This study has been conducted to assess the views of Ayurveda and contemporary science on the basis of genesis of the liver.

Review of the Literature

The liver is a well known organ for Ayurveda. In Vedas, it is named as “Takima” or “Yakna”.[2]

Paryaya (Synonyms)

Synonyms like Kalakhanda,[3] Jyotisthana,[4] Yakrutkhanda,[5] Yakrutpinda,[6] Raktadhara and Raktashaya[7] are found in the ancient literature.

Kalakhand: This word is also used as a synonym of Yakrut in the Sushruta Samhita.

Jyotisthana: Jyoti means Agni. The site of Agni is called the Jyotisthana.

Fetal nutrition usually depends on Ahara Rasa, categorized under maternal factors and Vayu present in Jyotisthana and responsible for cell division. The Ahara Rasa is first received by Jyotisthana, which further nourishes the whole body. Therefore, Jyotisthana means “liver”.

Yakrutkhanda: In Ashtanga Hrudaya, Acharya Vagbhata has used this word with regards to the description of diseases. In modern science, Yakrutkhanda means lobes of liver.

Raktadhara/Raktashaya: Yakrut is a site of Rakta Dhatu. Blood is stored in the liver; therefore, Raktadhara or Raktashaya words have been used in Ayurveda Samhitas.

Varna (Color)

In the classics, various references regarding the color of Yakrut can be seen during the elucidation of signs and symptoms of diseases. The color of Vidradhi is similar to the color of Yakrut,[8] i.e. Krushnalohitam (reddish brown).

Acharya Vagbhata has compared the color of Pittaja Arsha with Shukajihva, i.e. tongue of parrot, Yakrutkhanda and Jalouka.[5] In Sharira Sthana, he has stated the critical condition of the patient in Atisara (diarrhea). - “If the color of stool is like the Yakrutpinda or Mansadhavana, the patient will not survive”.[6]

Svarupa (Appearance)

According to Bruhadarunyaka Upanishad, the appearance of Yakrut and Pleeha are solid structures like mountains.[4]

Sthana (Site)

The site of the liver is below and right to the heart.[9] Acharya Arundatta has given the same statement.[10]

Karya (Physiology of liver)

Many Acharyas have stated that the main function of Yakrut is to offer red color to Rasa Dhatu, i.e. Ranjana of Rasa Dhatu. However, according to Acharya Vagbhata, this function is carried out by Amashaya,[11] i.e. the stomach. According to Sushruta, the function of Pitta, which has its seats in the liver and spleen, consists of imparting its characteristic pigment (Ragakrut) to the Rasa Dhatu (lymph chyle) and hence it is known as Ranjakagni.[12] Acharya Sharangadhara also has a similar opinion about the formation of blood.[13]

Utpatti

In relation to the development of body parts, Yakrut is developed or generated from Matrujabhava,[14] as stated by Acharya Sushruta and Charaka in Sharira Sthana.[15]

Acharya Sushrut in Sharirsthan states that Yakrut is also engendered from Rakta Dhatu.[16] According to Acharya Arunadatta, the three Bhavapadarthas, i.e. Samana Vayu, Dehoshma, and Rakta Dhatu take part in the formation of Yakrut, Pleeha, and Kloma.[10] While considering these verses, it has been cleared that all the Acharyas were sure about the major role of Rakta Dhatu in the development of Yakrut (liver).

Review of the Modern Literature

Development of liver and the bile duct

The liver begins as a hollow endodermal bud from the foregut during the 3^rd week of the gestation. The bud separates into two parts, viz. hepatic and biliary. The hepatic part contains bipotential progenitor cells that differentiate into hepatocytes or ductal cells that form the early primitive bile duct. This collection of rapidly growing cells penetrates in the adjacent mesodermal tissue (septum transversum), and it is met with an ingrowing capillary plexus from the vetelline and umbilical veins, which ultimately form sinusoids. The biliary part of the endodermal bud will form the gall bladder and extra hepatic bile duct. Due to the connection between these growing masses of cells and foregut, bile comes into gastro-intestinal tract and it begins to flow at about the 12^th week of intrauterine life. Hemopoietic cells, Kupffer's cells and connective tissue cells are derived from the mesoderm of septum transeversum.

The fetal liver has major hemopoitic function up to the first and second trimesters. This subsides during the last 2 months of intrauterine life so that only few hemopoietic cells remain at birth.[17] The similarities and opinions about hepatogenesis are depicted in Table 1.

Table 1.

Similarities and opinions about hepatogenesis

Discussion

According to Ayurveda Samhitas, the liver develops from Rakta Dhatu. The correlation of this in modern science is:

The development of liver is from the hepatic bud and septum transeversum that is the unsplit part of the mesoderm.

On the first hand, the mesoderm produces septum transversum and the liver develops from the same. On the other hand, the mesoderm also produces mesenchymal cells, which in turn produce myoblast, chondroblast, lymphoblast, hemocytoblast,[18] etc. The blood cells develop from hemocytoblast and lymphoblast. Last but not the least, it is seen that the raw material for liver and blood is the same, i.e. mesoderm.

Secondarily, septum transversum is the first site of maternal blood. The umbilical and vitelline veins open at the septum transversum; due to this, the septum transversum is rich in blood supply.[19] Hepatic bud grows in the septum transversum and, due to it, the umbilical and vitelline veins are broken up forming the liver sinusoids.[20] It indicates that blood plays an important role in the development of liver. Hence, in this manner, the references in Ayurveda can be correlated with modern science regarding the development of Yakrut.

According to Ayurveda, the Rasa Dhatu, which comes to Yakrut and Pleeha, get colored by Ranjakagni. But, this is too difficult to correlate with modern science. In the term of modern science, it can be matched with hematopoiesis. Hematopoiesis is carried out by Yakrut only in intrauterine life. However, after birth, this is carried out by red bone marrow. In some pathological conditions, the liver may help in forming blood cells with red bone marrow. Actually, the function of Yakrut is metabolism of fats, proteins, etc., or storage of certain vitamins, nutrients or glycogen and not coloring the chyle. On the whole, the term of Ranjakagni related to the liver is too difficult to match with any of the components present in the liver.

The above discussion shows that embryological origin of liver is blood tissue as per Ayurveda as well as modern science. Hence, in case of any liver disorder, the baseline treatment for blood disorders may be adopted. However, the study opens a new window on the applicability of this concept in management of hepatic disorders. The efficacy of drugs acting on Raktavahasrotasa, like Sariva, Manjishtha, Triphala, etc., needs to be evaluated in the perspective of hepatic disorders.

Conclusion

Except the method of presentation, no differentiation is being identified in the development of liver in both Ayurvedic as well as modern perspectives. In view of the above facts, it is clear that Ayurvedic classics have a fabulous scientific approach in understanding the fundamentals in general and Rachana Sharira in particular.