Upadhatu Of Medas: Snayu, Sandhi – Sub Tissues Of Fat

Article by Dr Raghuram Y.S. MD (Ay) and Dr Manasa, B.A.M.S
Medo dhatu is the fat tissue of the body, as per Ayurveda. Snayus (ligaments) and Sandhis (joints) are the upadhatus (sub tissues) of medo dhatu. 

Snayu

Snayus are rope like structures (just like a string of a bow). Their main function is bandhana or binding. They bind together the mamsa (muscles), asthi (bones) and medas (fat).

Developmentally – the essence part or unctuous part of the medas (sneha of medas) undergoes metabolic process (transformation) and forms the Sira’s and Snayus. Some snayus are hairy thin, have network appearance and minute. Thus they cannot be identified with naked eyes.

Types

Snayus are of 4 types –

• Pratanavati Snayus (network shaped) – located in extremities and joints
• Vrutta (round shaped) – also called kandaras
• Pruthula Snayus (flat shaped) – located in the lateral parts of the trunk, chest, back and head regions
• Sushira Snayus (with lumen) – are located at the ends of amashaya (stomach) and pakwashaya (colon) and in the vasti (urinary bladder)

Numbers

Snayus are 900 in number and their distribution is as mentioned below –
Shaka (limbs) – 150 snayus in each limb, i.e. 150×4=600 snayus
Madhya shareera (trunk) – 230 snayus (60 in pelvic region, 80 in theback, 60 in the sides and 30 in the chest)
Jatru urdhwa (above neck) – 70 snayus (36 in neck and 34 in head)

Snayus are generally compared to the ligaments, the structures which bind the bones to the bones. By description, snayus also cover fasciae, tendons and capillaries.

Sandhi

sandhi=saMyogaH
asthi saMyoga sthAnam|(ca.zA.7)

The term Sandhi means samyoga or junction or union or meeting place or association.

In this context sandhi means ‘asthi samyoga sthaana’ or the place where bones meet. Thus sandhi or joint is formed when 2 or more bony ends meet at a place.

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According to other opinions (Sharangadhara Samhita), sandhis are also the meeting place of any two structures in the body. Such sandhis are held together by Kapha.

In general for the purpose of understanding, only asthi-sandhi or bony joints are considered under the term sandhi or sandhis (plural). Other joints like the joints between muscles, blood vessels, ligaments, tendons, etc are usually not considered for counting and description.

Classification

Classification of Sandhis
Depending on the activity, broadly the sandhis are classified as cheshtavanta (movable) and sthira (immobile, fixed or less movable joints) sandhis
Read related: Sandhi Shareera: Study of Bone Joints As Per Ayurveda

Depending on the shape and size, sandhis are classified into 8 types:

• Kora Sandhi (hinge joints) – Example elbow joint, knee joint etc
• Ulukhala or udukhala sandhi (ball and socket joint) – Example hip joint, shoulder joint etc
• Samudga sandhi (box or plate shaped joints) – Example coccygeal joints, iliac joints etc
• Pratara Sandhis (Plain joints) – Example joints of vertebrae
• Tunna Sevani sandhi (sutural joints) – Example skull suture joints, suture joints of pelvic bones etc
• Vayasa Tunda sandhi (crow beak joints) – Example, temporo-mandibular joint
• Mandala Sandhi (cartilaginous joints) Example, cartilaginous joints found in throat, eyes, trachea etc
• Shankavarta Sandhi (Spiral joints) – Example, joints found in the ear

Sandhis are 210 in number, 68 of them are located in the limbs, 59 in trunk and 83 in head and neck.
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