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Rakta dhatu is a body component similar to blood tissue. Its important function is to give life or maintain vitality(jivana). Body fluid (rasa dhatu) after acquiring  ‘red’ color is termed as “rakta”(blood). (SAT-B.429)

Rakta dhatu is a body component similar to blood tissue. Its important function is to give life or maintain vitality(jivana). Body fluid (rasa dhatu) after acquiring  ‘red’ color is termed as “rakta”(blood).<ref>Available from http://namstp.ayush.gov.in/#/sat</ref>(SAT-B.429)

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==Etymology and derivation==

==Etymology and derivation==

The word ‘Rakta’ is derived from Sanskrit root “ranj”, meaning–to dye or colour, to affect or move, to excite/glad/charm/delight.  

The word ‘Rakta’ is derived from Sanskrit root “ranj”, meaning–to dye or colour, to affect or move, to excite/glad/charm/delight.<ref>Monier Williams (1899), “रक्त”, in A Sanskrit–English Dictionary, new edition, Oxford: At the Clarendon Press, OCLC 458052227, page 0861.</ref>

==Synonyms ==

==Synonyms ==

Shonita, rudhira, asrik, astra,lohita,kshataja

Shonita, rudhira, asrik, astra,lohita,kshataja

*'''Shonita''': The term is derived from ‘shona’ meaning red color. The term is also applied to denote the female genetic prototype.  

*'''Shonita''': The term is derived from ‘shona’ meaning red color. The term is also applied to denote the female genetic prototype.<ref>Available from https://www.wisdomlib.org/definition/shonita</ref>

*'''Rudhira''': The term is derived from root ‘rudh’ meaning to stop or hold. The blood tissue sustains the life of human beings, hence it is called ‘rudhira’’.  [Su. Sam. Sutra Sthana 14/39]

*'''Rudhira''': The term is derived from root ‘rudh’ meaning to stop or hold. The blood tissue sustains the life of human beings, hence it is called ‘rudhira’’.  [Su. Sam. Sutra Sthana 14/39]

===Location:===

===Location:===

As per contemporary theories, in the early stages of embryogenesis, blood formation (hematopoiesis) occurs in blood islands. These are aggregates of blood cells in the yolk sac.  As development progresses, blood formation occurs in the spleen, liver, and lymph nodes. These are the primary site until the first three months of gestation. In the seventh month of gestation, after the development of bone marrow, it eventually becomes the major site of formation of most of the blood cells for the entire organism. Hematopoietic stem cells (HSCs) in the bone marrow give rise to all of the different mature blood cell types and tissues. In children, hematopoiesis occurs in the marrow of the long bones such as the femur and tibia. In adults, it occurs mainly in the pelvis, cranium, vertebrae, and sternum.  

As per contemporary theories, in the early stages of embryogenesis, blood formation (hematopoiesis) occurs in blood islands. These are aggregates of blood cells in the yolk sac.  As development progresses, blood formation occurs in the spleen, liver, and lymph nodes. These are the primary site until the first three months of gestation. In the seventh month of gestation, after the development of bone marrow, it eventually becomes the major site of formation of most of the blood cells for the entire organism.<ref>Birbrair, Alexander; Frenette, Paul S. (1 March 2016). "Niche heterogeneity in the bone marrow". Annals of the New York Academy of Sciences. 1370 (1): 82–96. Bibcode:2016NYASA1370...82B. doi:10.1111/nyas.13016. ISSN 1749-6632. PMC 4938003. PMID 27015419.</ref> Hematopoietic stem cells (HSCs) in the bone marrow give rise to all of the different mature blood cell types and tissues. In children, hematopoiesis occurs in the marrow of the long bones such as the femur and tibia. In adults, it occurs mainly in the pelvis, cranium, vertebrae, and sternum.<ref>Fernández KS, de Alarcón PA (December 2013). "Development of the hematopoietic system and disorders of hematopoiesis that present during infancy and early childhood". Pediatric Clinics of North America. 60 (6): 1273–89. doi:10.1016/j.pcl.2013.08.002. PMID 24237971</ref>

Sushruta highlighted the presence of adipose tissue ([[meda dhatu]]) in the medulla of bone. The adipose tissue ([[meda dhatu]])  present in long and big bones is known as marrow ([[majja]]). That present inside the small bones is termed as red marrow (saraktameda). [Su. Sa. Sharira Sthana 4/13]

Sushruta highlighted the presence of adipose tissue ([[meda dhatu]]) in the medulla of bone. The adipose tissue ([[meda dhatu]])  present in long and big bones is known as marrow ([[majja]]). That present inside the small bones is termed as red marrow (saraktameda). [Su. Sa. Sharira Sthana 4/13]

This unctuous portion in the bone marrow can be linked to the formation of blood as per current views.

This unctuous portion in the bone marrow can be linked to the formation of blood as per current views.

The liver acts as the major blood reservoir.  It stores about 450 milliliters or almost 10 percent of the body's total blood volume. This capacity can increase up to 1 litre in certain cases due to the expanding capacity of the liver. It synthesizes some proteins including coagulation factors I (fibrinogen), II (prothrombin), V, VII, VIII, IX, X, XI, XII, XIII, as well as protein C, protein S and antithrombin. All of these play important roles in blood physiology. Moreover, the liver is a major site of production for thrombopoietin, a glycoprotein hormone that regulates the production of platelets by the bone marrow. The liver plays a major role in glucose, protein, and lipids present in the blood. It also purifies and protects blood from harmful toxins, metabolites, and heavy metals.  

The liver acts as the major blood reservoir.  It stores about 450 milliliters or almost 10 percent of the body's total blood volume. This capacity can increase up to 1 litre in certain cases due to the expanding capacity of the liver. It synthesizes some proteins including coagulation factors I (fibrinogen), II (prothrombin), V, VII, VIII, IX, X, XI, XII, XIII, as well as protein C, protein S and antithrombin. All of these play important roles in blood physiology. Moreover, the liver is a major site of production for thrombopoietin, a glycoprotein hormone that regulates the production of platelets by the bone marrow. The liver plays a major role in glucose, protein, and lipids present in the blood. It also purifies and protects blood from harmful toxins, metabolites, and heavy metals.<ref>Available from https://en.wikipedia.org/wiki/Liver accessed on 15/06/2020</ref>

Thus, bone marrow is the site of formation of blood cells; whereas the liver is the major site in maturation of blood cells and maintaining the physiological status of blood tissue.

Thus, bone marrow is the site of formation of blood cells; whereas the liver is the major site in maturation of blood cells and maintaining the physiological status of blood tissue.

In contemporary physiology, red coloured fraction of blood is considered as rakta dhatu. The colourless fluid (plasma) is considered as rasa dhatu. Thus, rasa and rakta together form “blood”. The red fraction or red blood corpuscles are referred to as rakta dhatu in this article.  

In contemporary physiology, red coloured fraction of blood is considered as rakta dhatu. The colourless fluid (plasma) is considered as rasa dhatu. Thus, rasa and rakta together form “blood”. The red fraction or red blood corpuscles are referred to as rakta dhatu in this article.  

===Composition:===

===Composition:===

Blood is a complex liquid tissue composed of different types of cells. The plasma which represents the matrix of this tissue constitutes over 55% of it. Formed elements that are suspended in the liquid matrix constitute over 45% of blood, these comprise of erythrocytes,leukocytes, and platelets. The characteristic color of blood is due to the erythrocytes present in it. These cells are formed in the red born marrow and they survive for about 80 days in circulation and then disintegrate. Their debris is removed from the blood by liver and spleen. Ranjaka pitta which gives color to rakta may be considered as the ayurvedic analogue of the red cobalt linked enzyme B12 present in the liver.  

Blood is a complex liquid tissue composed of different types of cells. The plasma which represents the matrix of this tissue constitutes over 55% of it. Formed elements that are suspended in the liquid matrix constitute over 45% of blood, these comprise of erythrocytes,leukocytes, and platelets.<ref name=dwaraka>Dwarkanath C. Introduction to Kayachikitsa. Chaukhambha Orientalia. Varanasi; 1996. Third edition.pg.343</ref> The characteristic color of blood is due to the erythrocytes present in it. These cells are formed in the red born marrow and they survive for about 80 days in circulation and then disintegrate. Their debris is removed from the blood by liver and spleen.</ref name=dwaraka> Ranjaka pitta which gives color to rakta may be considered as the ayurvedic analogue of the red cobalt linked enzyme B12 present in the liver.  

===Color: ===

===Color: ===