Definition of Superficial Fascia & Deep Fascia .
[1]. Superficial Fascia .
Superficial fascia is a general coating of the body beneath the skin, made up of loose areolar tissue with varying amounts of fat.
Distribution of Fat in this Fascia .
1. Fat is abundant in the gluteal region (buttocks), lumbar region (flanks),front of the thighs, anterior abdominal wall below the umbilicus, mammary gland , postdeltoid region, and the cervicothoracic region.
2. In females, fat is more abundant and is more evenly distributed than in males.
3. Fat is absent from the eyelids, external ear, penis, and scrotum.
4. The subcutaneous layer of fat is called the panniculus adiposus.
5. In females fat is in the superficial fascia of the lower abdomen, upper thigh, whereas in males it is inside the abdominal cavity. In general, in women fat forms a thicker and more even layer than in men.
6. Fat (adipose tissue) fills the hollow spaces like axilla, orbits and ischiorectal fossa. Fat present around the kidneys in abdomen, supports these organs.
Types of Fats .
1. There are two types of fat, i.e. yellow and brown fat. Most of the body fat is yellow, only in hibernating animals it is brown. The cells of brown fat are smaller with several small droplets and multiple mitochondria.
2. Fat cells are specialized cells, and the size of fat cells increases during accumulation of fat, rather than the number of cells. Any attempt to reduce excessive fat (obesity) must be slow and steady and not drastic, as the latter may cause harm to the body.
Important Features of the Superficial Fascia .
1. Superficial fascia is most distinct in the lower part of the anterior abdominal wall, perineum, and the limbs.
2. It is very thin on the dorsal aspect of the hands and feet, sides of the neck, face, and around the anus.
3. It is very dense in the scalp, palms, and soles.
4. Superficial fascia shows stratification (into two layers) in the lower part of anterior abdominal wall, perineum, and uppermost part of the thighs.
5. It contains:
(a) Subcutaneous muscles in the face, neck and scrotum
(b) Mammary gland
(c) Deeply situated sweat glands
(d) Localized groups of lymph nodes
(e) Cutaneous nerves and vessels. :
Functions of Superficial Fascia .
1. Superficial fascia facilitates movements of the skin.
2. It serves as a soft medium for the passage of the vessels and nerves to the skin.
3. It conserves body heat because fat is a bad conductor of heat.
[2]. Definition of Deep Fascia .
Deep fascia is a fibrous sheet which invests the body beneath the superficial fascia. It is devoid of fat, and is usually inelastic and tough .
Distribution of Deep Fascia .
1. Deep fascia is best defined in the limbs where it forms tough and tight sleeves, and in the neck where it forms a collar.
2. It is ill-defined on the trunk and face.
Important Features of Deep Fascia .
1. Extensions (prolongations) of the deep fascia form:
(a) The intermuscular septa which divide the limb into compartments .
(b) The fibroareolar sheaths for the muscles, vessels and nerves.
2. Thickenings of the deep fascia form:
(a) Retinacula (retention bands) around certain joints like as wrist and ankle.
(b) The palmar and plantar aponeuroses for protection of nerves and blood vessels.
3. Interruptions in the deep fascia on the subcutaneous bones. Deep fascia never crosses a subcutaneous bone. Instead it blends with its periosteum and is bound down to the bone.
Modifications of deep fascia .
1. Forms the intermuscular septa separating functionally different group of muscles into separate compartments .
2. Covers each muscle as epimysium which sends in the septa to enclose each muscle fasciculus known as perimysium. From the perimysium septa pass to enclose each muscle fibre. These fine septa are the endomysium.
Through all these connective tissue septa, e.g. epimysium, perimysium and endomysium, arterioles, capillaries, venules, lymphatics and nerves traverse to reach each muscle fibre .
3. Deep fascia covers each nerve as epineurium, each nerve fascicle as perineurium and individual nerve fibre as endoneurium. These connective tissue coverings support the nerve fibres and carry capillaries and lymphatics .
4. It forms sheaths around large arteries, e.g., carotid sheath, axillary sheath. The deep fascia is dense around the artery and rather loose around the vein to give an allowance for the vein to distend .
5. It modified to form the capsule, synovial membrane and bursae in relation to the joints.
6. It forms tendon sheaths wherever tendons cross over a joint. This mechanism prevents wear and tear of the tendon .
7. In the region of palm and sole it is modified to form aponeuroses, e.g. palmar and plantar aponeuroses which afford protection to the underlying-structures . It also forms septa between various muscles. These septa are specially well developed in the calf muscles of lower limb.
8. 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 .
9 . In the forearm and leg, the deep fascia is modified to form the interosseous membrane, which keeps :-
(a) The two bones at optimum distance.
(b) Increases surface area for attachment of muscles .
(c) Transmits weight from one bone to other.
Functions of Deep Fascia .
1. Deep fascia keeps the underlying structures in position and preserves the characteristic surface contour of the limbs and neck.
2. It provides extra surface for muscular attachments.
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 the tendons.
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