MUSCLE TISSUE (Part 4)

tendon, fibrous septa, and internal lateral ligament; (2) inter- nal margin of the coronoid ; MUSCLES AND FASCIA OF UPPER EXTREMITY 153 (3) anterior oblique line of the radius; divided below into four parts, ending in tendons inserted into the second phalanges of the four inner digits. The Deep Muscles. — Flexor profundus digitorum. — Origin, the upper three-fourths of the inner and anterior surface of the ulna, from not quite the ulnar half of the interosseous membrane for the same dis- tance, and from an aponeurosis attached to the pos- terior border of the ulna, common to it, the flexor and extensor carpi ulnaris. Only one tendon (for the index finger) separates above the wrist; in the palm, as the tendons diverge, they give origin to the lumbricales; over the first and second phalanges the tendon is bound down by an osseo-aponeurotic sheath, and oppo- site the first phalanx it passes through an opening in the flexor sublimis tendon, and is finally inserted by an expanded end into the base of the third or last phalanx. The sheaths of the flexor tendons are opposite the first and middle phalanges, and formed of strong transverse bands, ligamenta vaginalia; opposite the joints the bands change into a thin membrane, strength- ened by oblique decussating fibers, so that there are annular or transverse fibers, and crucial or oblique. The sheath has a synovial lining containing small folds, vincula tendinum or ligamenta mucosa, passing between the tendons and bones. Flexor longus pollicis arises from the anterior surface of the radius, below its oblique line to the edge of the pronator quadratus, and from the adjacent part of the interosseous membrane. The tendon passes between the sesamoid bones of the thumb and enters a canal similar to that of the other flexors, to be inserted into the base of the last phalanx of the thumb. Its complete separation from the flexor pro- fundus is characteristic of man. Pronator quadratus, just above the WTist, close to the bones behind the last two muscles, quadrilateral and flat, arises from the pronator ridge and inner part 154 MUSCLE TISSUE of the anterior surface of the ulna for the lower fourth, and from the inferior from the radiocarpal joint; inserted into the anterior surface and anterior margin of the shaft of the radius for a little less than its fourth. The Radial Region. — Three in number, from the lower third of the arm and upper third of the forearm in an almost continuous row. Supinator longiis rises from the upper two-thirds of the external supracondylar ridge of the humerus and external intermuscular septum, limited above by the spiral groove; thin fleshy belly ends at the middle of the forearm in a flat tendon which expands at its insertion into the outer side of the radius at the base of the styloid process. Extensor carpi radialis longior arises from the lower third of the external supracondylar ridge and external intermuscular septum and a few fibers from the com- mon tendon ; inserted into the radial half of the posterior surface of the base of the second metacarpal. Extensor Carpi Radialis Brevior. — Origin, by the common extensor tendon from the outer condyle, septa, external lateral ligament, fascia, and a fibrous arch over the radial nerve and radial recurrent vessels; insertion, into the radial half of the posterior surface of the base of the metacarpal bone of the middle finger. The Posterior Radioulnar Region. — Superficial Layer. — Extensor Communis Digitorum. — Origin, com- mon extensor tendon from the external condyle of the humerus, orbicular ligament, fascia, and septa; there are three fleshy bellies, the innermost divided into two, four passing under the posterior annular ligament; the first and second pass to the index and middle fingers connected by a weak band, always transverse; the first is joined by the extensor indicis tendon at the metacarpophalangeal joint; the third runs to the ring finger and sends a slip to the middle finger tendon; the fourth divides, the outer larger part going to the ring finger, the inner part joining the outer division MUSCLES AND FASCIA OP UPPER EXTREMITY 155 of the extensor minimi digiti tendon; this fourth is the smallest tendon, and receives muscular fibers as far as the wrist. Opposite the metacarpophalangeal joints the tendons are bound down by transverse fibers from the front of the joint, ligamenta dorsalia; inserted into the base of the last phalanx. Extensor minimi digiti arises from the superficial and deep fascia of the forearm, from the orbicular ligament, from the septa between it and common and ulnar exten- sors; its tendon is in a groove between the radius and ulna, and splits into two on the back of the hand, the outer being joined by a slip from the fourth common extensor tendon, and both parts end on the little finger, like the other extensor tendons. Extensor Carpi Ulnaris {Ulnaris Externus). — Origin, common tendon, orbicular ligament, septa, fascia of the forearm, which is connected with the elbow- joint capsule, and anconeus. Insertion, tuberosity of the base of the fifth metacarpal. A bursa is under its tendon of origin in one-fourth of the cases. Anconeus fills the space between the triceps and extensor carpi ulnaris; is flat and triangular, covered by fascia connected with the triceps ; arises by a narrow tendon from a fossa on the inner and posterior part of the external condyle; upper fibers are transverse, the rest pass obliquely down and into the radial aspect of the olecranon and adjacent upper third of the ulna. Deep Layer. — Supinator Brevis. — Origin, external lateral ligament, orbicular ligament, supinator ridge, oblique line of the ulna, and for a short distance on the outer border of the ulna from the fascia covering it, which is connected with the external condyle; it regularly consists of two layers separated by the posterior interosseous nerve; the superficial one rises by aponeurotic fibers, the other by muscular. The fibers pass sling-like around the upper part of the radius to be inserted into a third of its length, limited 156 MUSCLE TISSUE by the anterior and posterior oblique lines to its neck and elbow-joint capsule. Extensor Ossis Metacarpi Pollicis. — Origin, upper part of the outer division of the posterior surface of the ulna below the supinator brevis, from the middle third of the posterior surface of the radius and inter- osseous membrane between. Its tendon passes over those of the radial extensors, and is inserted into the radial side of the base of the metacarpal bone of the thumb, and commonly by a slip into the trapezium, its tendon usually splitting. Extensor longus pollicis arises below the extensor ossis on the middle third of the ulna and from the interosseous membrane for about one inch; its tendon passes over the radial extensors, and is inserted into the posterior aspect of the base of the last phalanx of the thumb. Extensor Indicis Proprius. — Origin, from the ulna below the extensor longus pollicis, and slightly from the interosseous membrane and fascia over the exten- sor carpi ulnaris; unites with the common extensor tendon for the index, and forms the usual insertion. This and the extensor minimi digiti tendon are always on the ulnar side of the respective common extensor tendons. Extensor Brevis Pollicis. — Origin, small part of the interosseous membrane and radius below the middle, next below the extensor ossis; insertion, upper end of the first phalanx of the thumb on its posterior aspect. The Muscles and Fascise of the Hands Fascia of the posterior aspect is a thin layer prolonged from the posterior annular ligament and blending with the extensor expansions over the fingers; deeper than this the interossei are covered by thin aponeuroses. Fascia of the palm consists of a strong central part and two lateral portions which cover the short MUSCLES AND FASCIA OF UPPER EXTREMITY 157 muscles of the thumb and little finger. The central portion is the part commonly called the palmar fascia; it consists of fibers mostly prolonged from the palmaris longus, some from the annular ligament, thus form- ing two superficial layers with vertical fibers, between which is the palmaris brevis muscle; there is a deep layer of transverse fibers. Below, the fascia divides into four processes to join the digital sheaths; offsets are sent back to the deep transverse ligament at the heads of the metacarpals, forming a short canal above each finger for the flexors. Between the processes the transverse layer of fascia covers the lumbrical muscles, digital vessels, and nerves, passing over to the thumb and forefinger. At the clefts of the fingers a transverse band is called the superficial transverse ligament, or Gerdy's fibers. The interossei muscles also have a separate fascia continued below into the deep transverse ligament. The Radial Region. — The following muscles consti- tute the thenar eminence (the fleshy prominence of the palm corresponding to the base of the thumb) and have a great variety of description. Abductor pollicis. Adductor pollici^ obHquus. Flexor brevis pollicis. Adductor trans versus Opponens pollicis. pollicis. The Ulnar Region. — ^The following muscles constitute the hypothenar eminence. (The fleshy prominence of the palm corresponding to the fleshy part over the metacarpal bone of the little finger.) Abductor minimi digiti. Opponens minimi digiti. Flexor brevis minimi digiti. Palmaris brevis. The Middle Palmar Region. — The dorsal interossei are four in number, one for each space, not rising above the level of the bones, and numbered from without inward. Each rises from the two bones 158 MUSCLE TISSUE between which it is placed, most extensively from that supporting the finger upon which it acts. The tendon is inserted partly into the base of the first phalanx and partly into the extensor tendon. The palmar interossei are three in number, are adduc- tors, and each rises' from the lateral surface of the meta- carpal of the finger on which it acts. They terminate like the posterior tendons. The first belongs to the ulnar side of the index, the second and third to the radial sides of the ring and little fingers. The lumbricales are four small muscles, not always well-defined. They arise from the tendons of the flexor profundus digitorum. Actions of Muscles of the Forearm and Hand. — Pronation by the pronator teres and quadratus and flexor carpi radialis slightly; pronator teres flexes the forearm; can only pronate when the radius is intact. Supination by the supinator brevis, biceps, and supinator longus; the latter is a flexor of the elbow and brings the forearm into midsupination. Radial extensors of the wrist flex the elbow; others from the external condyle extend. Flexion #/ the tvrist by the flexor carpi ulnaris and radialis, by the flexors of the fingers and palmaris longus. Extension of the wrist by the extensor carpi ulnaris, the two radial extensors, and extensors of the fingers. Abduction of the wrist by the radial flexor and radial extensors and extensors of the thumb. Adduction of the wrist by the flexor and extensor carpi ulnares. The flexor carpi radialis and extensor carpi ulnaris act on the radiocarpal joint; the flexor carpi ulnaris and radial extensors on the midcarpal joint. The extensors of the wrist are moderators of the long flexors of the fingers; the flexors of the wrist are moderators of the extensors of the fingers. MUSCLES AND FASCIJE OF LOWER EXTREMITY 159 The posterior interossei abduct the fingers from the middle one; the palmar adduct; the interossei and lumbricales flex the first phalanx and extend the last two. Flexion in the fingers. Extension in the fingers. First phalanx, by the interossei By the extensor communis, and lumbricales. Second phalanx, by the flexor By the interossei and lumbri- sublimis. cales. Third phalanx, by the flexor By the interossei and lumbri- profundus. cales. When we flex the fingers they tend to approach, due to the lateral ligaments and obliquity of the tendons. The palmaris longus makes tense the palmar fascia, feebly flexes the forearm and wrist; all the muscles from the condyle feebly flex the forearm. Palmaris brevis wrinkles the skin over the hypothe- nar eminence and protects the ulnar vessels and nerve from pressure when a foreign body is grasped. Extension in the thumb is in the plane of abduction of the fingers, and its abduction is a movement forward. The action of its muscles and those of the little finger are indicated by their names; the flexors of the first phalanx in either case also extend the last, as the inter- ossei would. The ulnar extensor and flexor of the carpus are moderators of the thumb extensors. There are three flexors of the wrist (including the palmaris longus) and three extensors, three flexors of the fingers and three extensors, three flexors of the thumb and three extensors. THE MUSCLES AND FASCIiE OF THE LOWER EXTREMITY Fasciae of the Thigh The superficial fascia is continuous with that of other parts of the body. 160 MUSCLE TISSUE The deep fascia or fascia lata is a strong membrane forming a continuous sheath around the limb. It descends on the gluteus medius as far as the upper border of the gluteus maximus, which muscle it encases, and over the great trochanter a great part of the muscle is inserted between its layers. From the forepart of the iliac crest to the outer tuberosity of the tibia is the iliotibial band, w^hich receives the insertions of the tensor vaginae femoris and gluteus maximus muscles. The fascia lata has various deep processes; one is internal to the tensor vaginae femoris on the surface of the vastus externus. There are external and internal intermuscular septa inserted into the linea aspera. The Gluteal Region (Buttocks) Gluteus Maximus. — A quadrilateral, very coarse muscle. Origin, posterior fourth of the external lip of the iliac crest and rough surface between it and the posterior gluteal line, the last two pieces of the sacrum and first three of the coccyx, great sacrosciatic liga- ment, and aponeurosis of the erector spinae. The upper half and superficial fibers of the lower half are inserted into the fascia lata and continued into the iliotibial band; the deeper portion of the low^er half into the gluteal ridge on the upper third of the shaft of the femur. Gluteus Medius. — Origin, ilium between the crest, the posterior and middle curved lines, and from the fascia covering it; to insert on the outer surface of the great trochanter; a small bursa between the bone and tendon. Gluteus minimus is covered by the preceding, and arises from the whole surface on the ilium between the middle and inferior curved lines, fibers converge into an aponeurotic tendon on the outside of the muscle, MUSCLES AND FASCIA OF LOWER EXTREMITY IGl inserted into an impression on the front of the great trochanter. Actions of the glutei on the lower limb: Flexion. Extension. Glut, med., anterior fibers. Glut, maximus. Glut, min., anterior fibers. Glut, med., posterior fibers. Glut, min., posterior fibers. Adduction. Abduction. Glut, med., anterior fibers (in Glut., max., slight. sitting posture. fstrong, whole Glut, min., anterior fibers (in Glut. med. I muscle, espe- sitting posture). Glut. min. jcially mid- ( portion. Rotate in. Rotate out. Glut, med., anterior fibers. Glut. max. Glut, min., anterior fibers. Glut, med., posterior fibers. Glut, min., posterior fibers. The gluteus maximus extends the trunk on the thigh as in ascending stairs; in walking it is not used, as the erect position is maintained by ligaments; steadies and supports the knee by the iliotibial band. The iliopsoas flexes the thigh and rotates out; flexes the body on the thigh; the psoas bends the lumbar spine forward and laterally. Psoas parvus makes tense the iliac fascia. The Thigh Muscles These are arranged in three sets — anterior, poste- rior, and internal, with superficial and deep layers, the former passing over two joints, the latter over one. The Anterior Femoral Region. — Tensor vaginoe femoris (tensor fasciae) lies in a groove between the gluteus medius, rectus, and sartorius. Origin, anterior part of the external lip of the iliac crest, notch between the two spines; insertion, between the two layers of the fascia lata three or four inches below the great trochanter, and from the insertion fibers are prolonged into the iliotibial band. 162 MUSCLE TISSUE Sartorius (Tailor Muscle). — Origin, anterior superior spine of the ilium and small part of the notch imme- diately below; insertion, inner surface of the tibia near the tubercle, sending an expansion from the upper border to the capsule, one from the lower border to the fascia of the leg, and one to the tibia behind the tendons of the gracilis and semitendinosus. Quadriceps Femoris. — Largest muscle of the body, four parts closely united, (a) Rectus femoris, in a straight line from the pelvis to the patella. Origin, by two heads, anterior one from the anterior inferior spine, and posterior from the impression just above the acetabulum; they join at an angle of 60 degrees close below the acetabulum; the tendon is anterior above, then in centre of the muscle. The lower tendon becomes free three inches above the patella; is attached to the upper margin of that bone, and helps form the common tendons. (b) The vastus externus is the outer part of the quad- riceps. Origin, narrow and aponeurotic from the upper half of the anterior intertrochanteric line, outer part of the root of the great trochanter, outer side of the gluteal ridge, upper half of the outer lip of the linea aspera, from external intermuscular septum, and a strong aponeurosis extending over the upper two- thirds of the muscle. Aponeurosis of insertion occupies the deep surface of the muscle, joins the common tendon, and sends expansion to the lateral patellar ligaments and rectus tendon. (c) The vastus internus arises from a superficial aponeurosis and deeper fibers from the spiral line, inner lip of the linea aspera, and from tendons of the adductor longus and magnus; they end in a deep aponeurosis which