2 ANATOMY OF THE FASCIA The superficial fascia The deep fascia • anatomy of the hypodermis: trunk • anatomy of the deep fascia: limbs < • anatomy of the hypodermis: limbs • anatomy of the deep fascia: trunk I U L ^ ANATOMY OF THE FASCIA I Superficial fascia Fig. 1.1. Schematic arrangement Adipose Retinaculum Ground of the fasciae in the human body. cell cutis superf. substance The hypodermis lies beneath the t Dermis dermis and it is formed by three Adipose layer layers of connective tissue. These aaaamao layers are often inappropriately Membranous layer called the superficial fascia. The Anatomy Anatomy of the fascia or superficial fascia hypodermis is formed by an adi­ Loose connect, tissue pose layer with the retinaculum Aponeurotic fascia cutis superficial^, a membranous Epimysial fascia layer or true superficial fascia and a Muscular tissue, layer of loose connective tissue with perimysium, endomys. the retinaculum cutis profundus. Beneath the hypodermis are the deep and epimysial fasciae. Fig. 1.2. Microscopic image of th e fasciae of the thigh (25x, Haematoxilin-Eosin stain). The Federative Committee on Anatomical Terminology (FCAT) defines the fascia as either a mem­ brane or another aggregation of connective tissue. In this image, it is evident that the fasciae are more complex than this definition: • superficial fascia (A) • aponeurotic fascia (B) • epimysial fascia (C) • muscular tissue (D). 3 ANATOMY OF THE FASCIA Superficial fascia CHAPTER 1 Fig. 1.3. Superficial fascia, re­ gion of the back, being pulled while attached to a dynanometer. Before breaking, the membranous layer of the superficial fascia in the back exhibits a resistance to stretch of approximately 8 kg in a longitudinal direction and 6 kg in a transversal direction. The abdom­ L ^ inal fascia has a resistance of 2.8 kg in a longitudinal direction and 5.5 kg in a transversal direction; the fascia of the limbs exhibits a resistance ranging from 1.4 kg to 1.7 kg. o CD Fig. 1.4. Nerve within the su­ perficial fascia (immuno-histo- Q </> chemical stain S100, 250x). n Many nerves pass within the su­ Q perficial fascia; in part, these nerves innervate the superficial fascia itself and, in part, they perforate it to reach the skin. The structure and function of the receptors that inner­ vate the skin differ from those that innervate the hypodermis. Fig. 1.5. Superficial fascia of the leg, pulled upwards to highlight the underlying deep fascia. The superficial fascia has the role of: • facilitating mobility of skin with respect to the deeper planes or layers • protecting the superficial ves­ sels (venous and lymphatic) and nerves • separating exteroception, which pertains to the skin, from pro­ prioception, which pertains to the deep fascia. ANATOMY OF THE FASCIA Superficial fascia Fig. 1.6. The adipose layer of the hypodermis, after removal of the skin from the anterior left trunk region. In the abdomen, the superficial fascia known as Scarpa's fascia is found beneath the adipose tissue. Camper has described a second membranous layer of abdominal superficial fascia; this layer actually corresponds to the retinaculum cutis superficialis. In the abdomen, the retinacula of this layer are lying almost parallel to the skin. Fig. 1.7. Superficial fascia over the right latissimus dorsi, pulled upwards by forceps. Anatomy Anatomy of the fascia The superficial fascia in the pos­ terior trunk region is a fibrous, resistant lamina that extends in a homogeneous manner from the neck to the gluteal region. Along the spinous processes, it adheres to the skin; in a transverse direc­ tion, however, it adheres to the underlying muscles to form specific quadrants for each body segment. Fig. 1.8. Superficial fascia on the right side of the neck, with some fibres of the platysma muscle. The superficial fascia in the neck surrounds the platysma muscle and it continues, without inter­ ruption, into the thorax, where it also surrounds and includes the mammary gland. The platysma continues up to the face, inserting onto the mimic muscles that are also comprised within the superfi­ cial fascia. 5 ANATOMY OF THE FASCIA Superficial fascia CHAPTER 1 Fig. 1.9. Mimic muscles in the face, comprised within the su­ perficial fascia. The superficial fascia in the face presents three different conforma­ tions: • it contains some mimic muscles that insert onto the skin • it contains other mimic muscles that insert onto bones • it covers the deep muscles (e.g. masseter) that originate and in­ sert onto bones. o CD Fig. 1.10. Superficial fascia, me­ dial region of left leg, comprising Q to greater saphenous vein. n Along the limbs, the membranous Q layer of the superficial fascia com­ prises the more superficial blood and lymphatic vessels. If the three layers of the hypoder- mis become rigid, then densifica- tion can slow blood return, causing varicose vein formations, as well as the flow of lymph, causing oedema to form. Fig. 1.11. Sole of the foot, with close-packed adipose tissue in a thick web of collagen fibres (reti­ naculum cutis superficialis). The superficial fascia adheres to the deep fascia in the palms of the hand and the soles of the feet. Therefore, the deep layer of loose connective tissue, which normally permits gliding, is absent in these areas. Here, the retinaculum cutis superficialis adheres firmly to the skin guaranteeing that the skin does not slide on the deep fascia. 6 Deep fascia of ANATOMY OF THE FASCIA the limbs Fig. 1.12. Cross section of the right leg, between the upper third Hypodermis with superficial fascia and the middle third. Aponeurotic The deep fascia or muscular fascia fascia -------------- is found beneath the superficial fascia. Interosseous The deep fascia is divided into: m em brane-------- • aponeurotic fascia, which sur­ rounds the limbs like a stocking Intermuscular and, in part, also the trunk septum ------------ • epimysial fascia, which surrounds Epimysial --------- each single muscle and extends and perimysial into the perimysial and endomy- fascia sial fasciae. (Modified from G Chiarugi & L Bucciante Istituzioni di onatomia delluomo Piccin) Fig. 1.13. Aponeurotic fascia of the limb, onto which a part of the semitendinosus tendon ex­ Anatomy Anatomy of the fascia tends an expansion. In anatomy texts, the muscular fas­ cia is illustrated as if it were a con­ tainer for the various muscles, and no distinction is made between aponeurotic fascia and epimysial fascia. Furthermore, the insertions of muscles onto the overlying apo­ neurotic fascia have never been illustrated in these texts. Fig. 1.14. Antebrachial fascia, which partially extends over the flexor carpi radialis and partially provides origin for this muscle. In anatomical texts, the origins of muscles from the overlying apo­ neurotic fascia have only been de­ scribed but never illustrated. In this photograph, it can be seen how the aponeurotic fascia of the forearm gives origin to many muscle fibres of the flexor carpi radialis. Deep fascia of ANATOMY OF THE FASCIA the limbs CHAPTER 1 Fig. 1.15. Fascia lata, with its multidirectional collagen fibres. The fascia of the limbs is illustrated in anatomical texts without high­ lighting the arrangement of the collagen fibres. The presence of loose connective tissue interposed between the adjacent layers of collagen fibres allows each layer to L ^ move in an independent manner. O CD Fig. 1.16. Fascia lata formed by the tendinous expansions of the Q </> gluteus maximus, gluteus medius n and tensor fascia latae. Q In the 1904 edition of his Anatomy text, Testut describes the tensor fascia lata as a derivation of the tendinous expansions of gluteus maximus, the tensor fascia lat­ ae and the internal and external obliques. The aponeurotic fascia of the upper limb is also formed by tendinous expansions from the pectoralis major and latissimus dorsi. Fig. 1.17. Schematic illustration . Reinforcement formed Gluteus maximus by co||agen fjbres that highlights the arrangement of collagen fibres in the fascia lata. In the fascia lata there are longitu­ dinal collagen fibres (iliotibial tract) that connect the unidirectional mf units together to form mf sequenc­ es; there are also oblique collagen fibres (retinacula, but not those of the dermis) that connect the cen­ Longitudinal collagen vastus lateralis formed tres of fusion together to form mf fibres of the tensor by collagen fibres coming spirals. fascia latae from the gluteus maximus 8 Deep fascia of ANATOMY OF THE FASCIA the limbs Fig. 1.18. Superior and inferior retinacula of the extensors. The retinacula of the ankle are not isolated ligaments or bands. They are comprised within the aponeu­ rotic fascia and are in continuity with the multilayered spiral-form collagen fibres. All of the retinacula around the ankle, wrist, knee, and so forth, give origin to muscular fibres, which, in turn, tension the retinacula. (Modified from G Chiarugi & L Bucciante Istituzioni di anatomia delluomo Piccin) Fig. 1.19. Superior and inferior extensor retinacula of the right ankle (note differences with the above illustration). Anatomy Anatomy of the fascia The three layers of collagen fibres have been highlighted in the reti­ nacula of the ankle and wrist. The cells of these fibres secrete hyal- uronan (Klein DM, 1999). The internal surface of the fasciae has modified fibroblasts that se­ crete hyaluronan (Ellis FD, 1995). Fig. 1.20. Schematic summary of the fasciae in the limbs. /Superf fascia 1 f superficial adipose layer membranous layer The aponeurotic fasciae in the or hypodermis ] [ loose conn, tissue layer limbs form a sleeve or glove that is arranged in parallel to the under­ Arranged in parallel FASCIAE i( lying muscles. The muscles of the OF THE / Superf fascia 11 undulated collagen fibres LIMBS ' or hypodermis]j loose conn.t. layer for gliding limbs connect to the aponeurotic l undulated collagen fibres fasciae either via tendinous expan­ sions or via insertions.