MUSCULI ALAE [MEMBRI THORACICI] - Annotations
(69) M. rhomboideus superficialis; M. rhomboideus profundus. Furbringer (1886;1902) suggested that Mm. rhomboideus superficialis, rhomboideus profundus, and serratus profundus (Annot. 70) are derived from the same muscle primordium; they are innervated by Plexus brachialis accessorius (PNS, Annot. 36 and Fig. ___). These two muscle sheets attach on spinous processes of the last few cervical vertebrae and succeeding thoracic vertebrae, extending in some taxa as far caudally as the cranial margin of the ilium and synsacrum. Both muscles attach on the dorsal (vertebral) margin and medial surface of the scapula, the superficial sheet sometimes extending as far as the adjacent shaft of the clavicle. See Figs. 6.11.
(70) M. serratus superficialis. Synonymy: M. serratus ventralis cranialis et caudalis (Nagamura, Nishida, and Nomura, 1974). Pars cranialis and Pars caudalis are typically present, often nearly continuous at their attachments on the ribs at the level of the uncinate processes, but each part has a separate fleshy insertion on the ventral margin of the scapula, separated by a common aponeurosis It is innervated independently from M. serratus profundus (PNS, Fig. 4). Pars scapulohumeralis is a separate, striated, subcutaneous slip (see Annot. 11; Hikida, 1972; Hikida and Bock, 1974, 1976). See Figs. 6.11.
M. serratus profundus. Usually consists of one to several fasciculi which attach on the caudalmost cervical vertebrae and the cervical ribs, and one or more of the succeeding thoracic ribs, to insert along a continuous line on the medial surface of the scapula. Fedde (1987) indicates that this is an accessory muscle for ventilatory inspiration in contrast to M. serratus superficialis which is an accessory expiratory muscle.
(71) M. scapulohumeralis cranialis. Synonymy: M. dorsalis scapulae (Nagamura, Nishida, and Nomura, 1974); M. proscapulohumeralis (Berger, 1966, 1968). M. scapulohumeralis caudalis. Synonymy: M. teres major et infraspinatus (Fujioka, 1959; Sullivan, 1962); M. dorsalis scapulae (Berger, 1966; Nagamura, Nishida, and Nomura, 1974). M. scapulohumeralis cranialis is not always present in birds, but when present, it is attached on the neck of the scapula (Collum scapulae), immediately behind the glenoid process, and cranial to the attachment of M. scapulohumeralis caudalis (on the lateral or external face of the body of the scapula). M. scapulohumeralis cranialis is usually deep to a retinaculum which attaches M. scapulotriceps ( Annot. 81) to the neck and body of the scapula. It inserts in Fossa pneumotricipitale (Osteo. Annot. l88) near the terminal end of Crus dorsale fossae. M. scapulohumeralis caudalis inserts on the terminal end of Crus ventrale fossae. See Fig. 6.11.
(72) Mm. subcoracoscapulares. A collective name for a muscle set which attaches on the medial face of the proximal end of the scapula, extending to the medial face of the coracoid. In many taxa, four heads are described (Furbringer, 1888,1902). Most recent authors describe two separate muscles, M. subscapularis, typically having two heads, and M. subcoracoideus which may or may not have two heads (Berger, 1966). The muscle complex is innervated by a single motor nerve (N. subcoracoscapularis, PNS, Fig. ___).
(73) M. subscapularis. Typically has two well defined heads, Caput laterale ("Pars externa") and Caput mediale ("Pars interna", Hudson and Lanzillotti, 1964). Substitution of the term "Caput" for "Pars" to identify the two heads is somewhat more appropriate anatomically: two heads of one muscle unite to form a common tendon which inserts on the proximal end of the humerus (Tuberculum ventrale, Osteo. Annot. 187), together with M. subcoracoideus.
(74) M. coracobrachialis cranialis. Synonymy: M. coracobrachialis (Sullivan,1962). The muscle originates on Proc. acrocoracoideus (Osteo. Annot. 171a) of the coracoid and inserts in a distinct fossa on the Planum intertuberculare of the humerus (in some taxa, see Osteo. Annot. 181). \
M. coracobrachialis caudalis. Synonymy: M. flexor coracobrachialis (Simic and Andrejevic,1964). It is attached proximally to the shaft of the coracoid and contributes to formation of Linea intermuscularis ventralis (Osteo. Annot. 174; see Annot. 76). The distal attachment is on Tuberculum ventrale (Osteo. Annot.187) of the humerus, dorsal to the attachments of Mm. subcoracoscapulares (Annot. 72).
(75) M. pectoralis. Simic and Andrejevic (1963, 1964) recognize Pars sternobrachialis and Pars costobrachialis ('thoracobrachialis"), with separate proximal attachments on the sternum and thoracic ribs, respectively, but a common attachment on Crista deltopectoralis (Osteo. Annot. 184). Additional studies of these parts indicate different fiber orientations, and different innervation patterns by two distinct branches from the ventral cord of the brachial plexus (see, e.g., Rosser and George,1986; Dial et al.,1987; Kaplan and Goslow, 1989; Sokoloff et al., 1989).
Aponeurosis (Membrana) intramuscularis is an intramuscular extension of the broad aponeurosis of insertion; muscle fasciculi from Pars costobrachialis attach on it. See Fisher (1946), Kuroda, (1960;1961a, b) and Vanden Berge (1970) for further description. Pars propatagialis, and Partes subcutanea thoracica et abdominalis are fleshy slips which are listed and annotated under Mm. pterylarum (see Annot. 9,12, and Fig. 6.13).
(76) M. supracoracoideus. Synonymy: a "deep head" of M. supracoracoideus is most probably a derivative of M. deltoideus minor (Annot. 80) as originally suggested by Furbringer (M. deltoideus minor, pars ventralis, 1902) and substantiated by Sullivan (1962, "M. coracobrachialis anterior, pars ventralis"). Deep to the attachments of M. pectoralis, attachments of the supracoracoideus to the sternum (Osteo. Annot. 153) and coracoid (Osteo. Annot. 174) result in the formation of discrete linear scars. The tendon lies in a groove (Sulcus supracoracoideus, Osteo. Annot. 172) on the base of the Proc. procoracoideus and enters a bony canal (Canalis triosseus, Osteo. Annot. 177). Insertion is on Tuberculum dorsale of the humerus (Osteo. Annot.182, 183). N. supracoracoideus (PNS Fig. 4) perforates Membrana sternocoracoclavicularis (Arthr. 86, 88) or the body of the coracoid (Osteo. Annot. 172) before entering the deep face of the muscle.
(77) M. latissimus dorsi. Pars cranialis and Pars caudalis, as well as the two parts attaching on feather tracts (Pars interscapularis, Annot. 8; Pars scapulohumeralis, Annot.11), arise by cleavage in a single muscle primordium (Sullivan, 1962). Pars cranialis and Pars caudalis have separate insertions on the humerus. See Fig. 6.11. In penguins, the tendons of both parts pass over a fibrous loop (Retinaculum m. scapulotricipitis, Arthr. Annot. 142) on which is also attached M. scapulotriceps (Fig. 8, Schreiweis, 1982). Considerable variation exists with respect to the presence or absence of one or the other of the skeletal slips to the humerus, as well as in either or both of the slips to the feather tracts, in avian taxa generally (Berger, 1966, 1969).
(78) Complexus m. deltoideus. Buri (1900), in his comprehensive study of the muscles of the shoulder region in birds, together with more recent studies of Brown et al. (1989) on Lig. propatagiale (Arthr. Annot.141), indicate that this muscle complex consists of three principal subdivisions, based on distal attachments: (1) Pars propatagialis which attaches to Lig. propatagiale and Lig. limitans cubiti; (2) Pars major which attaches on Crista deltopectoralis, and (3) Pars minor which attaches on Tuberculum dorsale of the humerus. All three subdivisions attach proximally to bones of the shoulder joint. See Figs. 6.11,12, and 13.
(79) Complexus m. deltoideus, Pars propatagialis [M. propatagialis]. Synonymy: M. tensor propatagialis, Pars longa, Pars brevis (NAA,1979). This structural subdivision can occur in three forms: (1) a single muscle having s single head of origin, a single belly, and two insertions: Lig. propatagiale and Lig. limitans cubiti, (2) two heads of origin with a single belly, having the same two insertions, and (3) two anatomically separate parts, Caput craniale (formerly M. propatagialis longus) inserting on Lig. propatagiale, and Caput caudale (formerly M. propatagialis brevis), on Lig. limitans cubiti. Associated with one or both parts are fleshy propatagial slips derived from other muscles, including M. cucullaris capitis, M. pectoralis, and M. biceps brachii (Annot. 9). Variations and trends in the morphology and attachments of Caput caudale on M. extensor carpi radialis (Annot. 87) and the dorsal antebrachial fascia at the elbow, have been described in several taxa (Furbringer,1888; Buri,1900; Berger,1966; Hudson et al.,1969; Vanden Berge,1970; Zusi and Bentz,1982). See Fig. 6.13.
(80) Complexus m. deltoideus Pars major [M. deltoideus major]. Caput craniale, attaching on Fibrocartilago humerocapsularis (Arthr. Annot. 100), and Caput caudale, attaching on bones of the shoulder joint, have been described in some taxa, but only a single belly with a suggestion of internal division is present in others (Fig. 6.11; also Berger, 1966, 1969; Raikow, 1977). IRaikow (1985b, Fig. 4) has described and illustrated a third separate head, Caput proximale, in Atrichornis and Menura . There is considerable variation in the number of heads present, relative development of these heads, presence or absence of a "scapular anchor" (retinaculum, Fig. 6.11), and the extent of insertion on Crista deltopectoralis of the humerus (Osteo. Annot. 184). In some taxa, Pars major is much reduced while Pars propatagialis is significantly more developed (Brown,pers. comm.).
Complexus m. deltoideus, Pars minor [M. deltoideus minor]. Synonymy: M. coracobrachialis anterior (Sullivan,1962). Caput ventrale is a separate, ventral, fleshy slip arising from Membrana sternocoracoclavicularis (Arthr. Annot. 86) and inserting more or less in common with Caput dorsale on the proximal end of Crista deltopectoralis, often overlapping the attachment of M. supracoracoideus (Annot. 76) on Tuberculum dorsale of the humerus (Hudson and Lanzillotti, 1964; Berger, 1966; Hudson et al., 1969; Vanden Berge, 1970, and Raikow, 1978). See Fig. 6.11.
(81) M. scapulotriceps. This muscle is attached proximally to the scapula (Osteo. Annot. 169), by a retinaculum superficial to M. scapulohumeralis cranialis (Annot. 71), and to the humerus (Retinaculum m. scapulotricipitis, Arthr. Annot.142; Hudson, Schreiweis, and ChenWang,1972). In penguins, these attachments are united into a single fibrous band (Retinaculum scapulohumerale) which extends from the scapula to the humerus, and over which pass the tendons of M. latissimus dorsi (Annot. 77; Schreiweis,1982). Distally, the muscle has an additional attachment on the humerus (Lig. tricipitale, Arthr. Annot.111). There is a large Os sesamoideum m. scapulotricipitis (Osteo. Annot. 202) present in the tendon of insertion of some taxa (Schreiweis,1982; Zusi and Bentz,1984). The distal attachment is on the dorsal aspect of Proc. cotylaris dorsalis of the ulna (Osteo. Annot. 198). See Fig. 6.11.
82) M. humerotriceps. The proximal origin on the humerus may be partially subdivided into "caput mediale," "caput posticum" and "caput breve" by the insertions of other muscles (M. scapulohumeralis cranialis; M. scapulohumeralis caudalis; M. latissimus dorsi) near the Fossa pneumotricipitalis (Osteo. Annot. 188; Buri, 1900), but these are not usually considered important anatomical or functional subdivisions. The terminal distal attachment is on the Olecranon of the ulna (Osteo. Annot. 201).
M. coracotriceps. Synonymy: Caput coracoideum m. anconei (Furbringer,1886); M. anconeus coracoideus (Berger,1966). Rosser and George (1985) have shown that, in Columba, contrary to what has been assumed about a "vestigial" condition of this muscle in birds generally (NAA, 1979; Berger,1966; in ciconiiform birds,Vanden Berge,1970), the histochemical characteristics of the extrafusal fibers and density of muscle spindles suggest that the muscle is entirely tonic in function and serves as an active and extremely sensitive mechanoreceptor, capable of slow and sustained contraction, i.e., a type of "kinesiological monitor" of the state of contraction in M. triceps brachii (Annot. 81, 82), and/or M. expansor secundariorum.
(83) M. biceps brachii. The muscle in birds which corresponds to the biceps brachii in mammals does not have a typical scapular head, but rather heads arising from the coracoid and humerus.The combined aponeurosis forms a broad covering of the Planum intertuberculare (Osteo. Annot. 181) distal to the head of the humerus. Definition of the two proximal attachments is not readily accomplished but in most birds, the attachment to the Crista bicipitalis (Osteo. Annot. 184) of the humerus is the larger and more conspicuous. There is considerable variation among birds in the presence of a single belly and tendon (Baleniceps) or two bellies and two tendons distally (herons, Vanden Berge,1970), and also in the distal attachments on the radius and ulna (Osteo. Annot. 210); in some taxa (Chaetura and other swifts), the muscle is absent (Berger,1966). The propatagial slip is highly variable (Figs. 6.12,13, and Annot. 9).
(84) M. pronator superficialis; M. pronator profundus. Synonymy: "brevis" =superficialis and "longus" =profundus, do not necessarily apply since the so-called "pronator longus" is not always the longer of the two muscles. Both muscles attach on the humerus, M. pronator superficialis on Tuberculum supracondylare ventrale (Osteo. Annot. 196) and M. pronator profundus on Epicondylus ventralis (Osteo. Annot. 178, 194; "Fossa muscularis", Butendieck, 1980: 86, 146, and Fig. 36) in common with the attachment of M. entepicondyo-ulnaris (Annot. 92). See Berger (1966); Raikow (1978), and Bentz (1979) for examples of variation, and Fig. 6.12.
(85) M. flexor carpi ulnaris. The tendon of origin is attached on Proc. flexorius of the humerus (Osteo. Annot. 195), glides through Sulcus tendineus (Osteo. Annot. 203) on the proximal end of the ulna and crosses the "humero-ulnar pulley," Trochlea humeroulnaris, pars tendineae (Bentz and Zusi,1982; Arthr. Annot. 110); it may enclose a sesamoid. The fusiform belly is closely invested by the intermuscular Septum humerocarpale which is derived from the Lig. humerocarpale (Arthr. Annot. 143, 195, and Fig. 5.11). Pars remigialis is represented by a series of fleshy slips obliquely oriented to an insertion on Lig. elasticum interremigiale minor (Arthr. Annot. 197). Both parts attach on Proc. muscularis, Os carpi ulnare (Osteo. Annot. 215). See Figs. 6.12.
The muscle has at least two functional roles: (1) flexion of the wrist over Lig. ulnocarpo-metacarpale ventrale (Arthr. Annot. 120) on Proc. pisiformis (Osteo. Annot. 215a) of the carpometacarpus, and (2) movement and positioning of the flight feathers by way of the attachments of Pars remigialis to the elastic ligament proximally, and indirectly, distally, to the Retinacula ulnocarpo-remigialia and/or Aponeurosis ulnocarporemigialis (Arthr. Annot. 115), both of which attach on Os carpi ulnare. See Buri (1900) and Berger (1966) for examples of variation..
(86) M. flexor digitorum superficialis. Synonymy: M. flexor digitorum sublimis. M. flexor digitorum profundus. Both muscles develop from a common muscle primordium from which is also derived M. flexor carpi ulnaris (Annot. 85; Sullivan,1962; Shellswell and Wolpert,1977). The superficial flexor is separated from the other two muscles by Septum humerocarpale (Arthr. Annot. 195). See Fig. 6.12. M. flexor digitorum superficialis demonstrates considerable variation in birds generally. At its origin, it is typically associated with Lig. humerocarpale (Arthr. Annot. 143) and may show a reciprocal variation in development relative to that of the ligament (see review in Berger, 1966). The tendons of M. flexor digitorum superficialis and M. flexor digitorum profundus pass under the Retinaculum flexorium (see Fig. 6.12, and Arthr. Annot. 114) in a common sheath on the ventral aspect of Os carpi ulnare. The tendon of the deep flexor passes over Proc. pisiformis (Osteo. Annot. 215a), which functions like a pulley, and the tendon terminates on Phalanx distalis digiti majoris. The superficial tendon terminates on Phalanx proximalis. A vinculum between the tendons is described in melanerpine woodpeckers and sapsuckers (Goodge, 1972).
(87) M. extensor carpi radialis. Synonymy: M. extensor metacarpi radialis. Substitution of the name "extensor carpi" for both the radial and ulnar extensor muscles is more appropriate since these muscles are functionally "extensors of the wrist (carpus)". According to Berger (1966) there is typically a dorsal and a ventral head of origin, in some taxa from different areas of the humerus (see Zusi and Bentz, 1982), receiving one or more attachments from Lig. limitans cubiti (see M. deltoideus, Pars propatagialis, Annot. 79; Arthr. Annot.141). One or two tendons insert on Proc. extensorius of Os metacarpale alulare. See Fig. 6.11.
(88) M. extensor carpi ulnaris. Synonymy: M. extensor metacarpi ulnaris (NAA,1979); M. flexor metacarpi ulnaris (Stegmann,1978), but see Annot. 87 and Berger (1966). There are two proximal attachments of this muscle: (1) on the distal end of the humerus (Epicondylus dorsalis, Osteo. Annot. 178, 194), and (2) on the proximal end of the ulna ("ulnar anchor," Retinaculum m. extensoris carpi ulnaris, Arthr. Annot. 144). In hummingbirds, swifts, and suboscines, Bentz and Zusi (1982) describe a second retinaculum - like structure, containing a large sesamoid, and continuous with Trochlea humeroulnaris (Arthr. Annot. 110).
The distal tendon of extensor carpi ulnaris, with that of M. extensor digitorum communis, lies in a fibro-osseous canal (Incisura tendinosa, Osteo. Annot. 209) on the distal end of Ulna. Where the tendons cross the dorsum of the wrist they pass under a retinaculum (Lig. m. extensoris carpi ulnaris, Arthr. Annot. 144; Lig. digitometacarpale, Stegmann, 1978; Lig. ossis metacarpi et primae phalangis digiti secundi, Stettenheim, 1959) which functionally redirects the force of the tendons toward their respective attachments: M. extensor carpalis ulnaris on Proc. intermetacarpalis (Osteo. Annot. 221), and M. extensor digitorum communis on the cranial aspect of Phalanx proximalis digiti majoris. The tendon of the common digital extensor also lies in a bony sulcus on the dorso-distal aspect of the major metacarpal. See Fig. 6.11.
(89) M. ulnometacarpalis dorsalis has a proximal attachment on the ulna (Lig. m. ulnometacarpalis dorsalis, Arthr.Annot. 145) and overlies Incisura tendinosa (Osteo. Annot. 209) and its extensor tendons (Mm. extensor carpi ulnaris and extensor digitorum communis, Annot. 88). The insertion on Os metacarpale minor is sometimes divided by proximal fibers of M. flexor digiti minoris (Annot. 99). See Fig. 6.11.
The tendon of M. ulnometacarpalis ventralis is passes over a sulcus between Tuberculum carpale and Condylus ventralis on the distal ulna (Osteo. Annot. 206, 207; Butendieck, 1980, Fig. 40) and ventrad over Os carpi radiale ( "Sulcus tendineus", Butendieck, 1980, Fig. 42), deep to the tendons of M. extensor carpi radialis (Annot. 87), proximal to its insertion on the dorsal face of the base of Proc. extensorius, Os metacarpale alulare. See Fig. 6.12.
(90) M. extensor longus alulae. Synonymy: M. extensor pollicis longus; M. extensor longus digiti II. An ulnar and a radial head of origin have been described (Rosser, 1980).
M. extensor longus digiti majoris. Synonymy: M. extensor indicis longus; M. extensor longus digiti III. Pars distalis is topographically located in the manus proper and, when present, it unites with the tendon of Pars proximalis. This distal head has been designated M. flexor metacarpi brevis (Fisher and Goodman, 1955; Berger, 1966) but, according to Sullivan (1962), Pars distalis ("M. extensor medius brevis") is derived from M. extensor longus digiti majoris ("M. extensor medius longus") in which case it would represent "M. extensor brevis digiti majoris". The tendon terminates on the distal phalanx of the major digit while the corresponding tendon branch of M. extensor digitorum communis attaches on the proximal phalanx.
(91) M. ectepicondylo-ulnaris. Synonymy: M. anconeus (Berger,1966, and many others). The muscle has its origin on the Epicondylus dorsalis ("ectepicondyle", Osteo. Annot.194) of the humerus; its origin is more or less opposite that of M. entepicondylo-ulnaris (Annot. 92). Although "M. anconeus" has been widely used for this muscle, having a topographical resemblance to the anconeus muscle in mammals, the name "anconeus" also has been used for M. triceps brachii. See Fig. 6.11.
(92) M. entepicondylo-ulnaris. Synonymy: M. anconeus medialis (Fujioka,1959); to many avian anatomists, the "gallinaceous" muscle. It has been described only in the kiwi (Apteryx), in Tinamiformes (Hudson et al.,1972), in Galliformes (Hudson and Lanzillotti,1964), and in some Anatidae (Sy,1936; Zusi and Bentz,1978). Beddard (1884) described an "anconeus internus" in Scopus which suggests M. entepicondylo-ulnaris, but this has never been substantiated. The origin of this muscle is on Epicondylus ventralis of the humerus, in common with the attachment of M. pronator profundus (Annot. 84); see also Butendieck (1980, Fig. 36, "Fossa muscularis"). It inserts on the proximal caudoventral face of the ulna.
(93) M. interosseous dorsalis; M. interosseous ventralis. Synonymy: ventralis is also known as "palmaris" or "volaris." The two muscles largely fill the intermetacarpal space; however, M. interosseous ventralis is sometimes unipennate (Vanden Berge, 1970) and the ventral part of the space may be somewhat more exposed.
(94) M. extensor brevis alulae. Synonymy: M. extensor pollicis brevis; M. extensor brevis digiti II.
M. levator alulae. A small muscle on the dorsum of the alula in the Galapagos Cormorant, Compsohelios [Nannopterum] harrisi, recently described and illustrated by Livezey (pers. com.).
(95) M. abductor alulae. Synonymy: M. abductor pollicis; M. abductor digiti II.
(96) M. flexor alulae. Synonymy: M. flexor pollicis; M. flexor digiti II.
(97) M. adductor alulae. Synonymy: M. adductor pollicis; M. adductor digiti II.
(98) M. abductor digiti majoris. Synonymy: M. abductor indicis; M. abductor digiti III.
(99) M. flexor digiti minoris. Synonymy: M. flexor digiti III or IV.