Deep fascia in general

Deep fascia in general

Definition:

     a fibrous membrane of variable thickness, devoid of fat,   which invests

• the muscles,
•  the several groups and the individual muscles,
•  the nerves and vessels,
•  various organs and glands
• becomes specialized around the joints to form or strengthen ligaments,

•       and binds all the structures together into a firm compact mass

Modification of deep fascia :

1. Aponeurosis
2. Retinaculum
3. Bursa
4. Capsules of joint
5. Sheath around the neurovascular bundle Ex: carotid sheath
6. Septa – intermuscular septum
7. Ligaments
8. Connective tissue around the muscle fibre(endomysium) , muscle bundle(perimysium ) and muscle (epimysium)

Deep fascia is well define in

1. Limb
2. Neck

SN: very well define deep fascia is iliotibial tract of fascia lata of thigh 

Deep fascia is absent in

1. Most of the face
2. Anterior Abdominal Wall

      to allow extension of abdominal organs.

3. Ischioanal fossa

General features of deep fascia

1. It acts as a base for superficial fascia
2. It is inelastic and tough
3. It is devoid of fat
4. Histologically it is dense irregular connective tissue
5. It contains variable amount of fibroblasts with the ability to contract known as myofibroblasts
6. It is rich in hyaluronic acid
7. It surrounds the muscles, bones, nerves and blood vessels of body
8. It encloses different muscle groups  and also individual muscle
9. It is rich in  Ruffini’s and pacini’s corpuscles which carry proprioception
10. Lacerations of the deep fascia are easily recognized and should be closed

Importance & functions of the deep fascia

1.       It covers the underlying muscles so it  assists them in their action  by the tension and pressure  it exerts on their surfaces.

2.       From its deep surface, septa pass between muscles. These septa may extend to be attached to the bones and form definite intermuscular septa which divide up the interior of the limbs into compartments.

3.       It is thickened in the palm & sole  to form palmer & planter aponeuroses  which provide protective function to deeper structures.

4.       It is thickened around distal joints (e.g. wrist & ankle) to form strong bands (retinacula)                              which hold the underlying tendons in position.

5.       It is thickened opposite the flexor surfaces of the fingers and toes to form tendon sheathes (fibrous flexor sheath)  which hold the tendon and prevent their bending.

Nerve supply of deep fascia Deep fascia

1.       Deep fascia is very sensitive

2.       Its nerve supply and that of subcutaneous periosteum is that of the overlying skin

3.       The nerves to muscles supply the intermuscular septa and deep periosteum

4.       Ruffini, Pacini and rare Golgi Mazzoni corpuscles are also present within  the  deep fascia

Histology of deep fascia

Histologically it is dense irregular connective tissue

Mean thickness of fascia 100-200 µm

It is formed by multiple layers of collagen fibre bundle

Each layer is separated by a thin layer of adipocytes.

Description of single layer :

Each layer is formed by collagen fibres and elastic fibres and ground substance is rich in hyaluronic acid . the size of collagen fibre are variable , wavy coarse and parallel with each other . The alignment of collagen fibre bundle differ from layer to layer . all fascial layers contain a variable amount of fibroblasts with the ability to contract known as myofibroblasts . the star shaped cytoplasm of elongated fibroblast are arranged between collagen fibre bundle. Elastic fibre are arranged between collagen bundles. They are short, branch, not arrange in bundle, less orderly manner to form a irregular mesh.

Numerous vessels and small nerve are present in deep fascia. The arrangement of nerves are more around the vessels.

Interesting facts about deep fascia :

1.       All fascia is connective tissue but not all connective tissue is fascia

2.       Fascia mostly made up by non-living material known as extra cellular matrix . it is like the inner ocean of our bodies.

3.       Deep fascia is made up mostly by collagen fibre, one of the most common protein in body

4.       The density and direction  of collagen fibre of deep fascia is depend on the function of the individual  

Collagen fibres are curve structure why ?

Nature hates straight lines curve structures not only allow for tension to be absorbed but also distributed and transmitted

The arrangement of collagen fibres are multi directional that allow movement in lots of different directions

Interesting point is collagen fibre is also very adaptable and well lay down more fibres in new direction of strain , if the movement and loading is repeated after enough

Continued movement  leads to continued ability to move and stillness leads to stiffness.

The enemy of deep fascia is extended bouts of stillness. Daily regular movement through a wide range without extensive stretching   is likely to maintain the health and flexibility of fascia .

•       An extreme example is that of Amar Bharati a sadhu, who over 40 years ago decided to raise his arm above his head as a tribute to Shiva.

•       Over the years the pain that he first experienced, subsided to numbness.  The collagen fibres surrounding the muscle tissue and the joint will, most probably, have become fibrous and hard.  The effort of holding the arm up will have ceased to be an effort, with the fibres taking over the task of holding the arm in that position.

•       The rest of him keeps doing a good job.  We can see him squatting on the ground demonstrating great flexion ability through his knees, hips and ankles.  It’s a perfect demonstration of how continued movement leads to continued ability to move and how stillness leads to stiffness.