Deep fascia in general

Deep fascia in general

Deep fascia

Definition: Deep fascia is a fascia, a layer of dense irregular connective tissue that wraps the neck, the limbs and body wall like a bandage or stocking 

It covers muscles, nerves, bone and blood vessel.

Important features of deep fascia:

·         It is devoid of fat

·         It is inelastic and tough

·         It has nerve supply and very sensitive structure.

·         It is a golden rule that when fascia approaches bone it becomes attached to it , blending with the covering periosteum

<script data-ad-client="ca-pub-3738618711723990" async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>

Distribution of deep fascia

Very well developed: 

1.       iliotibial tract of fascia lata

2.       palmar and planter aponeurosis

3.       flexor and extensor retinaculum

Well developed:

• In the limbs,  it forms tough &  tight sleeves
•  In the neck, it forms a collar.

So thin usually considered as absent:

·         Over the rectus sheath of abdomen

·         Over the trunk  except thoracolumbar fascia at the back of thorax & abdomen

Absent

·         Face except  parotid fascia

·         Ischioanal fascia

Why thickness of deep fascia is different in different parts of body?

Why deep fascia is very well developed is particular location of body: 

1.      iliotibial tract of fascia lata : abduct and stabilized and steady the hip and knee joints during walking and running by putting tension on iliotibial tract

1.      palmar and planter aponeurosis : Deep fascia of particular location is not only thick and also send fibrous strands to skin, so hand and feet is fixed and not wobbly  e.g. palmar and plantar aponeuroses which afford protection to the underlying-structures and help to firm grip.

2.      flexor and extensor retinaculum : prevents spring out of tendon during their movement

Why deep fascia is Well developed in particular location of body :  

In the limbs, 

• it forms tough &  tight sleeves : the tight stocking around muscles not only contours the extremity but also plays an important role in the return of blood to the heart against the gravity 

In the neck,

•  investing layer of deep fascia  forms a collar.
• Prevertebral fascia forms vertebral compartment and help for positioning head
• Pretracheal fascia forms visceral compartment (it surrounds trachea, larynx , esophagus ,the glands of neck : thyroid , parathyroid , thymus )
• Carotid sheath forms vascular compartment
• The primary functions of deep fascia of neck is prevent spread of infection from one compartment to another compartment

Why deep fascia is so thin usually considered as absent in some location of body :

·         Over the rectus sheath of abdomen: deep fascia is thin where considerable expansion is needed

·         Abdomen enlarges in obesity ,  pregnancy , ascitis .

·         Over the trunk  except thoracolumbar fascia at the back of thorax & abdomen

Why deep fascia is absent in some location of the body

·         Face except  parotid fascia : facial muscles are inserted into skin of the face so deep fascia is absent in face

·         Ischioanal fascia : only the lateral wall of the ischioanal fossa is lined by fascia of obturator internus

Modification of deep fascia:

2.      Each muscle is covered by deep fascia known as epimysium which sends in the septa to enclose each muscle fasciculus known as perimysium. From the perimysium septa pass to enclose each Muscle fiber. These fine septa are the endomysium. This connective tissue layer support the muscle and convey nerve , blood vessels and lymphatics.

3.      Deep fascia covers each nerve as epineurium, each nerve fascicle as perineurium and individual nerve fibered as endoneurium. These connective tissue coverings support the nerve fibers and carry capillaries and lymphatics.

4.      From deep fascia , the intermuscular septa is arises which  separating functionally different group of muscles into separate compartments.

5.      It also forms septa between various muscles. These septa are specially well developed in the calf muscles of lower limb. The contraction of calf muscles in the tight sleeve of deep fascia helps in pushing the venous blood and lymph towards the ‘heart. Thus the deep fascia helps in venous and lymphatic return from the lower limb.

6.      The deep fascia is dense around the artery and rather loose around the vein to give an allowance for the vein to distend.
deep fascia forms sheaths around large arteries, e.g. carotid sheath, axillary sheath

7.      Deep fascia is modified to form the capsule, synovial membrane and bursae in relation to the joints.

8.      Deep fascis forms tendon sheaths wherever tendons cross over a joint. This mechanism prevents wear and tear of the tendon.

9.       In the region of palm and sole it is modified  to form aponeuroses. in the forearm and leg, the deep fascia is modified to form the interosseous membrane, which keeps:

• The two bones at optimum distance.
• Increases surface area for attachment of muscles.
• Transmits weight from one bone to other

Functions of Deep Fascia:

1. Deep fascia keeps the underlying structures in position an preserves the characteristic surface contour of the limbs and neck.
2. It provides extra surface for muscular attachment
3. It helps in venous and lymphatic return.
4. It assists muscles in their action by the degree of tension and pressure it exerts upon their surfaces.
5. The retinacula act as pulleys and serve to prevent the loss of power. In such situations the friction is minimized by the synovial sheaths of tendons.

Clinical importance of deep fascia:

It is used as material for surgical repair. Example: fascia lata of thigh use to repair a hernial defect or defect in the dura mater