It is a membranous lamina consisting of fibro-areolar tissue, the meshes of which are filled with fatty or adipose tissue. Therefore, it is also known as Panniculus adiposus.
A) DEEP FASCIA
It is a dense elastic membrane forming coverings for the muscles and in some cases affording for them blind surfaces for attachments. It is devoid of fat cells, and is usually tough and inelastic.
CHARACTERISTICS:
1.It is ill-defined in the trunk and practically absent on the face to allow facial expression.
2.It is well developed in the limbs where it forms tight collar.
3.In the limbs it sends extensions which forms :-
- Intermuscular septa (or intermuscular aponeuroses). Fibrous sheath of vessels and nerves.
- Its thickenings in limbs are responsible for formation of retinacula (S-retinaculum).
- It is interrupted on the subcutaneous bones, e.g., clavicle and tibia. Here it blends with the periosteum.
FUNCTIONS:
It forms a strong investment which serves following purposes:
i)It binds down the muscles collectively.
ii)It may give separate sheath to each muscle.
iii)It provides fibrous sheaths to neurovascular bundles, e.g., axillary sheath, carotid sheath, femoral sheath, etc.
It increases the range of mobility by providing attachments to muscles, e.g., Iliotibial tract provides attachments to Gluteus maximus and tensor fascia latae and thereby increase their range of mobility up to tibia bone.
It forms intermuscular septa which are the prolongations of deep fascia investing the limb-muscles, which separate the various muscle-groups. These septa are attached to the periosteum.
It forms retinacula which are odd localized thickenings of deep fascia consisting of transversely running collagen fibres. These retinacula (bands) serve the following purposes.
i) They form retaining bands near the wrist and ankle joint to hold down the tendons.
ii) They form osseofibrous canals by being attached to adjacent bony prominences. These canals are meant for passage of tendons.
iii)They act as pulleys for tendons of muscles, when they are contracting. In this way they minimize the loss of power. The tendons are provided with synovial sheaths in the regions of retinacula in order to minimize friction.
Retinacular thickenings of deep fascia are also seen in :-
i)The Palm of the hand. (It forms palmar aponeurosis). The sole of foot. (It forms plantar aponeurosis).
ii) The Flexor Surface of digits.
These thickening have to serve following purposes :-
a)Restraining effect
b)Protective effect (In hand & sole).
It improves the efficiency of the venous return in lower limbs, due to the pumping effect of the muscles invested by it.It helps in lymph flow.
NERVE SUPPLY:
Deep fascia is very sensitive. Its nerve supply and that of subcutaneous periosteum, where no deep fascia exist, is that of underlying skin. The nerve no muscles do not supply the investing layer of deep fascia, but only the fibrous tissue of deep intermuscular spaces.
SYNOVIAL BURSAE
These are sac like structures lined by synovial membrane and contain synovial fluid. They develop at those places where friction is liable to occur during sliding of tendons.
Most of the bursae develop during foetal life.
Sites:
They are seen at two sites:
1. The point where a tendon twists around a bone, e.g., patellar tendon slides over the keen joint.
2. Subcutaneous bony point which is subjected to pressure e.g., Tibial tuberosity during prayer.
Types:
1.Advantitious bursae:
They are not present at birth and develop in response to unusual pressure or muscular activity.
i.At the elbow due to writing
ii. At the buttocks in hand-weavers.
Subtendinous synovial bursae:
These are those bursae which intervene between :-
i.Tendon and bone: e.g., Bursae between the tendon of popliteus and lateral condyle of the femur.
Tendon and ligament:
a) Bursa between the fibular collateral ligament and tendon of biceps femoris.
b)Bursa between the tendons of sartorius, gracilis and semitendinosy and tibial collateral ligament.
c)Tendon and tendons: e.g., bursa between tendons of semimembranosus and semitendinosus.
Submuscular synovial bursa:
These are those bursae which are present between tendons and muscles, e.g., Bursa between the tendon of biceps brachii and deltoid muscle (sub-acromial bursa).
Sub-fascial synovial bursa:
These are those bursae which lie beneath the fascial or aponeurotic sheets, e.g., Bursa over the upper surface of acromion.
Subcutaneous synovial bursae:
These are those bursae which are present between a bony prominence and subcutaneous tissue or skin, e.g.
- Sub-cutaneous pre-aptellar bursa
- Sub-cutaneous infra-patellar bursa
TENDON-SYNOVIAL SHEATHS
These are defined as the coverings of tendons at certain sites and consist of two concentric layers of synovial membrane with their smooth- surfaces facing one another and separated by an interval containing synovial fluid.
Sites:
They are present at following sites :-
i)The point where a tendon passes under a ligamentous band, e.g., tendon of long head of the biceps passing under intertubercular ligament.
ii)The site where tendon passes through osseo-fibrous canal, e.g., flexor tendons of palm.
Construction and structure:
iii)The synovial sheath is composed of two layers which are continuous with each other at their extremities :-
1.The inner or visceral layer: It is loosely attached to the tendon.
2.Outer or Parietal layer: It intervenes between the visceral layer and surrounding structures and lies in the osseofibrous canal or tunnel.
3.The visceral and parietal layers are connected by a long reflection of synovial membrance called mesotendon or mesentery of tendon.
The blood vessels and nerves are carried along with mesotendon to the visceral layer.
In the digital synovial tendon sheaths the mesotendons are modified into cord like structures called VINCULA TENDINUM.
Where there is no synovial sheath, the tendons are invested by fibroareolar tissue.
RAPHES
It is a linear fibrous band formed by interdigitation of the short tendinous ends of fibres of flat muscle sheets. It can elongate passively by separation of its attached ends.
Example:
- Pterygomandibular raphe : It is formed by inter-digitation of buccinator and superior constrictor muscles. The length of this raphe varies with the position of the mandible.Mylohyoid raphe : It is formed by interdigitation of two my- lohyoid muscles.
- Pharyngeal raphe : It belongs to pharyngeal constrictors.
- Anococcygeal raphe : It is the raphe of levator-ani.
- Linea alba: It is formed by interdigitation of anterior abdo- minal muscles.
LIGAMENTS
There are fibrous bands of connective tissue which connect the adjacent bones of a joint. They are practically inelastic and unstretchable and help in stability of joints.
CLASSIFICATION:
1.According to composition, i.e. main C.T. fibre content :
2.White fibrous tissue ligaments (collagenous tissue):
3.Most of the ligaments of the body are composed of white fibrous tissue. They show following properties :
i)In-elastic
ii)Unstretchable
They are usually not subjected to prolonged strain except the sacro- iliac ligaments and inter vertebral discs, which are never free from strain of the whole of the body except in recumbancy (bending).
- Ligamentun Flava (Elastic tissue):
- They show following properties :-
i) Yellow in colour
ii) Elastic
iii)Stretchable
Examples:
i)Ligamentum flava between the laminae of vertebrae. Capsular ligaments of joints of auditory ossicles. According to relation with the articular capsule of the joint :
ii) Extracapsular: They lie out side the joint capsule, e.g., Iliofermoral ligament of the hip joint.
FUNCTIONS:
1.Intra capsular ligaments: They lie within the joint capsule, e.g., cruciate ligaments of the knee joint.
2.They play a role in stability of the joint.
Due to their rich nerve supply they play an important role in reflex activity which further improves the stabilizing ability.