Muscles and regions of the neck / by John Simon.

  • Simon, Sir John, 1816-1904.
Date:
1843
    constitutes, in lean subjects, a nianif’est and resisting lamina, yet, in those of an opposite character, it is rendered indistinct by the pre- dominant adipose tissue which occupies its areoliE. Along the side of the neck, from the clavicle to the jaw, these layers are kept asun- der by the p.latysma myoides, which adds, as it were, a third lamina to the subcutaneous ex- pansion ; but both in front and behind, where tlie muscle ceases, they are in close relation, and constitute a single covering to those regions of the neck. Tlie deep layer of this fascia is traversed by the cutaneous nerves and vessels, including the external jugular vein. 2. The cervical fascia is a proper aponeu- rotic investment of this region, and corresponds in its geneml cliaracters to the fibrous sheath- ings of the limbs. Like these, it not only forms a general, compressive, and modelling cincture for the part, but, by various secondary splittings, furnishes dissepiments which isolate the different organs, and allot to each its proper sheath or fascial chamber. It may be briefly, but insufticie'ntly, described as originating from a kind of Uvea alba, or mesial commissure in front, and in its backward course to the spinous processes furnishing a separate investment to every organ which it encounters, and attaching itself, both below and above, to the chief bony eminences which present themselves. (A sec- tion of it, as it thus cellulutes the neck, is re- presented, with Bourgery’s almost invariable accuracy, in a lithograph, (vol. vi. pi, 10,) from which the accompanying woodcut is copied ) It requires, in at least many regions of the neck, a more particular description than this summary contains; and I shall accordingly proceed to consider such portions of it with some detail. The sterno-cleido-viastoideus is enshealhed through its whole extent; the fascia, on reaching its anterior edge, is bi-laminated, encloses the muscle, and becomes again single at its posterior border. When this sheath is laid open by removing its anterior wall, and the muscle carefully everted from its prismatic cell, it will be seen that the posterior lamina is of greater strength than the removed anterior one; and this surface is the one from which the dis- sector may most conveniently trace the further spread of the membrane. He will find that the cervical fascia (of which the portion cover- ing the sterno-cleido-mastoideus is but a se- condary slip) extends itself from behind that muscle in all directions; inwardly to the me- sial line,—outwardly to the trapezius,—up- wardly to the jaw,—downwardly to the cla- vicle. a. Traced inwurdli/, its arrangement difiers in the upper and lower parts of the neck; 1. in that below the os hyoides a su- perficial lamina covers the subhyoid muscles, joins its fellow in the median line, and is fixed below to the interclavicular notch of the ster- num; a second, thin process divides the sterno- thyroid from the sterno-hyoid muscle; a third, stronger one, passing between the sterno-thy- roid and air-tube, covers this latter organ and the thyroid body, is attached below to the inner surface of the manubrium sterni, internally joins the layer from the opposite side, and helps with it to form a raphe, reaching from the os hyoides to the sternal notch. Previously to the divi- sions here mentioned, the fascia encloses the flat tendon and anterior belly of the omo-liyoid muscle; and in a line, which will presently be more particularly indicated, covers the carotid artery, jugular vein, and nervus vagus. .lust external to these parts, along the outer edge of the jugular vein, it detaches a delicate process, which passes behind the vessels, separating them from the sympathetic nerve, and is con- tinued inwardly to join its fellow from the opposite side, as a cellular clothing to the msophagus. 2. Above the os hyoides, the arrangement of the fascia is simpler; covering the mylo-hyoid and submaxillary gland, and inclosing the anterior belly of the digastric, it is fixed to the lower border of the symphysis, and hence to a mesial raphe as far as the os hyoides. It has some deep connexions, to which I shall return directly; and, to the sheath of the great cervical vessels it preserves the same re- lations as below, its deepest process losing itself on the pharynx, b. Traced upwardly, the fascia is seen to split on the inferior edge of the digastric muscle; the superficial lamina is at- tached, behind, to the mastoid process,—in front, joining the part last described, to the lower edge of the jaw,—and, intermediately, ascends upon the parotid gland, which it in- vests ; the deeper layer is fixed to the styloid process of the temporal bone, and gives origin to a remarkable septal slip, (.sometimes called the stylo-rnaxillary ligament,) which, just in front of the posterior belly of the digastric, passes outwardly, is inserted into the deep surface of the superficial lamina and into the angle of the jaw, so serving to separate the space, circum- scribed by the digastric muscle, into two parts, and isolating the parotid gland, which occupies the posterior of these, from the submaxillary, which is situated in the anterior one. Further, this deep layer (joined by a slip from the fascia, which covers the submaxillary gland and is at- tached to the jaw) prolongs itself around Whar- ton’s duct, between the mylo-hyoid and hyo- glossal muscles, and likewise furnishes origin to the investing cellular tissue of the pharynx. c. Below, the cervical fascia attaches itself around the insertions of the muscles, which it incloses, viz. towards the median line to the notch of the sternum, and—with the sub-hyoid muscles—to the deep surface of the manubrium and to the cartilage of the first rib, and then to the clavicle in its entire length, both around and between the sterno-cleido-mastoid and tr.i- [lezius. in descending to the clavicle, it en- sheathes the posterior belly of the omo-hyoid ; and a firm jirocess of it, folded around this muscle and directed backward to the levator anguli .scapulae, is infixed along the superior costa of that bone, and circumscribes the so- called omo-hyoid space, d. Traced outwardly and backwardli/ the fascia covers in the inter- val between the trapezius and sterno-masioid (posterior triangle) from the clavicle to the oc- ciput, and, on arriving at the anterior edge of the trapezius, splits to enclose it. The further distribution of it, in tl>is direction, is in ac-
    fihews from below the ccrmco-lhomcic aeptum conxtiluting the roof of the thorax, am •*^'*'*^ pasxatje to the t/reat vexseU. It re]>rcxents a tratisiHirse and horizontal section throug second intervertebral disc, and parts at the same level. A, second dorsal vertebra, 15, tranverse division of the maniibriuin sterni. C, first ribs. I), vertebral extremity of second ribs. a, ,1, fascia, extending between the great vessels anti first two ribs. b, b, its insertion at the first ribs. e. c, its inscriinn at the second vcrlcbrie. d, d, lamina between the great vessels, attached centrally to them,— in front to the sternum, where it forms a ciil-de-sac, anti hchinil to the seconil dorsal vertebra. corrlance with the general law of its arratige- ment for the separation of muscles; is tle^li- tute of any particular surgical interest, ami forms no exception to the general ohservations given in a jtreceding article. (See Hack.) A portion (but a very rlistinct portion) of this great aponeurosis is the prr.-verlcbtttl fascia. It extends from the occiput—to which it is c, the aponeurosis, extending within the sternum, y, the trachea. //. the CESophagns. h, the iirtcria innominaia. l, the right vena innoininata. k, the left vena innominata ; tranverse b.an l uni- ting the two sides of the aponeurosis. /. the left carotid artery. m, the left subclavian artery. n, section of the muse. long, colli. fixed in front of the recti capith nntici to the inlet of the chest, where it adheres l^-stde ll c longtis colli, to the neck of the * Inn.ls down the pre-vertelmi lached deeply to the tips of the cesses, and receives by its surface a plal slip horn the cervical fascia just externally to the shcatli of the vessels. An important process is i
    the prolongation which it sends downward on the scaleni; and which partly fixes itself to tlie rib around the attachments of those muscles, partly extends itself, as a strong infundibulum on the brachial plexus and subclavian vessels. I'rom this—their fascial sheath—an horizontal slip detaches itself and passes forward to tlie pos- terior surface of the clavicle, where it fixes itself by two laminje; the upper of these is inserted just above the attachment of the sub- clavius muscle, while the lower is continued into the sheath which that muscle derives from the coraco-costal fascia. I’he horizontal pro- cess separates the cavity of the axilla from the lower triangle of the neck, and the vaginal prolongation, contracting as it descends, be- comes lost in the sheath of the axillary vessels. Finally, as these various layers of fascia at- tach themselves about the inlet of the thorax, (the sub-hyoid part of the cervical aponeurosis in front, and the pre-vertebral behind,) they are connected to one another and to the large vascular and mucous canals, which traverse that passage, by certain horizontal processes of fibrous membrane, which constitute together a kind of diaphragm, or cervico-thoracic septum. Viewed from below this would seem a vaulted membrane, oveiurchiug the tops of the pleu- rae, and giving infundibular passage to the great arterial and venous trunks and to the trachea; viewed from above it would present the various deep implantations of the cervical fascia, and a surface without aperture or breach of continuity, prolonging itself in several di- rections round the canals, which it thus indi- rectly transmits. The obvious use of these ar- rangements is to supply adequate resistance to the atmospheric pressure, which, were it not borne off by the tension of these fasciae, would at each inspiratory effort tend to flatten the trachea, or to rush through the upper strait of the thorax. Allan Burns, who in this country first drew attention to the importance of the cervical fascia, carefully illustrates its func- tions in health, and the inconveniences which accompany its destruction. (Op. cit.) III.—Regional distribution and sur- gical ANATOMY of the NECK. The posterior parts of the neck having been described in a previous article (see Back), the present will be restricted to an account of its anterior aspect. The cervical vertebrae (by their bodies, inter- vening fibro-cartilaginous discs, and transverse processes), together with the anterior and la- teral vertebral muscles, already described, com- pose the skeleton and supporting fabric of this region; the anterior fibres of the trapezii, as they descend on either side to the inner edge of the acromio-clavicular arch, form its lateral boundaries; the larynx and trachea (covered by their own extrinsic riband-like muscles, and partly covering the pharynx and oesophagus) separate the nearly symmetrical halves of the neck by constituting along its median line a marked columnar relief, in the recesses beside which lie the great cervical vessels; the base of the skull and the oblique line of the jaw are the upper limits of the region; the clavicle (just behind which the great vascular and ner- vous trunks of the upper extremity course) bounds it below; the skin, the plalysma myoides (in its cellular covering), and the cer- vical aponeurosis are stretched across it as ge- neral investments; while the last-named fascia ensheathes the various parts by special pro- cesses from its deeper surface. Thus, in general terms, the structure of the neck may be described; but, for the more pre- cise and particular account, which the impor- tance of its anatomy renders necessary, a division of it into spaces of small extent is convenient. The arrangement, which 1 propose following, differs but little from that usually adopted, and, perhaps, somewhat exceeds it in precision. The upper limits of the neck having been stated as the oblique line of the jaw and the base of the skull (which parts, as we shall pre- sently see, are brought into relation by the attachments of the constrictor pharyngis supe- rior), our highest region has in that direction these parts for its boundary, and extends below as far as the curve of the muscle, from which it is named the digastric space. A small space that can hardly be referreil to the digastric,—from which it is separated by the vaginal process of the temporal bone, and by attachments of fascia,—and which, from the im- portance of its contents, deserves careful consi- deration, is the posterior phari/ageul; it lies closely beneath the base of the skull, (from the vaginal process to the median line) between the pharynx and spine, and includes the carotid, jugular, and condylic canals, and the organs traversing them. If now an oblique line be carried across the neck, from the sterno-clavicular articulation to the tip of the mastoid process, it divides, as a diagonal, the remaining quadrilateral surface of the neck into two triangles; an anterior one having its apex at the sterno-clavicular joint, and its base along the posterior belly of the digastric muscle; a posterior one, having, its base at the inner two-thirds of the cla- vicle,—its apex at the mastoid process,—its posterior side formed by the trapezius,—its an- terior border defined by the imaginary line which demarks it from the anterior triangle. The omo-hyoid muscle, in its reflected course, crosses both these triangles, subdividing them ; and since the angle of its bend falls just on the line of their separation, and since it proceeds from behind the outer third of the clavicle to the body of the hyoid bone, it acts as a second diagonal in the neck, dividing each into an upper and a lower triangular space. Tliese four triangles will be described in detail; and since the sterno-mastoid (which is loo suli- stantial to be treated as a mere boundary-line) enters into all of them, and has to parts of each relations of the exfemest practical importance, some separate, chiefly recapitulatory, consi- deration will be given to its relative anatomy. Finally, to ensure for the oryansof tlie median line the consideration they require (the useful- ness of which mainly depends on their being
    11 Tiewed connectedly), it may be well to lake them in that relation. Thus, (1) « region of the median line, (2) an antero-inferior, (3) an antero-superior, (4) a postero-superior, and (5) a postero-inferior tri- angle, (6) a digastric, and (7) a posterior pha- ryngeal space, are to be severally considered; and a few preliminary remarks may be given to the tegumentary parts, which are more or less common to all. The skin is fine, thin, and extensible, espe- cially below and in front; becoming coarser and more adherent toward the upper part of the posterior triangle; it frequently presents some transverse wrinkling above the hyoid bone, which seems to depend on the platysma myoides; here, too, the follicles are larger and more abundant than in the other parts of the neck, and, in the male subject, the surface is overgrown by the beard. The subcutaneous cellular tissue has already been described; in the upper part of the posterior triangle it be- comes almost inseparably confounded with the cervical aponeurosis ; the platysma myoides lies between its layers and keeps them apart over the greater surface of the neck; the fibres of this muscle are absent in the lower part of the anterior, and upper part of the posterior triangle, and at these spots the two layers of the superficial fascia fall together and are nearly confounded. In the deeper lamina of this texture, subjacent to the platysma in the parts where it lies, run the superficial veins and nerves. external jugular vein commences in the parotid gland, usually by radicles, which correspond to the terminal branches of the ex- ternal carotid artery, temporal, internal maxil- lary, and transverse facial; pierces the fascia near the angle of the jaw, and directs itself al- most vertically toward the middle of the cla- vicle, in the deep layer of superficial fascia; just at the edge of the clavicular insertion of the stemo-mastoid muscle it bends inward, pierces the aponeurosis, and discharges itself into the subclavian vein. It thus very ob- liquely crosses the sterno-cleido-mastoideus from its anterior to its posterior edge, sepa- rated from that muscle by its fascial sheath; the auricular nerve runs upward parallel to its posterior border; the platysma covers it in its whole course with fibres which cross its direction ; its place of discharge into the subclavian vein is usually just opposite the scalenus anticus, covered by fascia and by the sterno-mastoid muscle. It receives superficial occipital, superior and posterior scapular veins ; branches from the posterior triangle of the neck, and from the trapezius; it has uncertain and irregular communication with the anterior jugular vein, and receives a certain, though not regular, branch from the internal jugular; this IS usually given to it at the lower part of the parotid, or on its emergence from that gland, and occasionally seems to constitute its com- mencement. Obvious surgical inferences from the anatomy of this vein are : the relief that its communication with the internal jugular en- ables it to give, when opened in cases of cere- bral congestion; the eligibility of its line of passage over the tliick belly of the sterno- mastoid for tliat mode of venesection; the ne- cessity for dividing some fibres of the platysma transversely to their length (by an incision nearly in the direction of the sterno-mastoid) in order to obtain a clear opening and free jet of blood ; the need for care in this operation, but still more in proportion as the vein is wounded lower in the neck, to hinder the possibility of air being inspired through its cavity. T\\a anterior jugular vein is an irregular sub- cutaneous supplement to the external: it com- mences in the submental region, near the hyoid bone; descends vertically beside the median line, receiving branches from the larynx, and sometimes from the thyroid body; on arriving at the sternum, or near that bone, it bends horizontally outward, piercing the fascia, and runs behind the origin of the sterno-mastoid, to throw itself into the subclavian vein, somewhat within the termination of the external jugular. It generally has free communications with its fellow and with the internal and external ju- gular. Its size is in inverse proportion to that of the external; and, in absence of this, it is generally a very considerable branch; it is sometimes single and mesial; but more usually two exist, which are commonly of unequal calibre. The superficial nerves are of two classes, being partly derived from the cervical plexus, partly from the portio dura. The cervical plexus sends its superficial branchings in three directions : the mastoid and auricular pass upward ; the anterior cervical runs forward ; the supra-clavicular and super- acromial, as their names denote, descend more or less obliquely. The mastoid, originating from the second cervical nerve, winds upwardly across the sple- nitis, and almost parallel with the posterior edge of the sterno-mistoid, which it crosses in its ascent. It pierces the fascia soon after its origin, and becomes subcutaneous. Its distri- bution is entirely to the skin of the mastoid and occipital regions. The auricular, rising from the second and third cervical nerves by a trunk, common to it with the anterior cervical, di- rectly pierces the fascia, loops round the pos- terior edge of the sterno-mastoid, and ascends across its surface (the fascial sheath intervening) toward the angle of the jaw; where, after sup- plying twigs to the integuments over the pa- rotid gland, it divides into terminal branches, which are distributed to the external and in- ternal surfaces of the auricle and to the adjoin- ing integument, in a manner which need not be particularised in the present article. In crossing the sterno-mastoid it is parallel to the external jugular vein, and behind it. The anterior cervical rises in common with the last, and pierces the fascia in its company; liends at right angles across the sterno-mastoid muscle, and is itself crossed by the external jugular vein. On arriving at the edge of the muscle, it di- vides into many twigs, which, traversing the platysma at several spots, distribute themselves to the skin of the anterior triangle of the neck, and to tliat of the adjacent part of the digastric
    space. This nerve, wliere crossed by the external jugular vein, gives one or two inimite twigs, which follow Its direction toward the angle of the jaw. The supra-cluvicvlar and super-acroniiaL are the two superlicial branches in which tlie plexus terminates: as they descend, they di- vide into a lash of twigs, which diverge in the posterior triangle of the neck, and at various heights pierce its fascia, become subjacent to the platysma, and contribute to supply it. Their ultimate branching takes a very wide range : the inner filaments obliquely cross the clavicular origin of the sterno-mastoid ; the outer, the anterior fibres of the trapezius; the middle ones, the clavicle itself; and are dis- tributed, in their respective regions, to the in- teguments of the scapula, shoulder, chest, and sternum. The branch from thepoi'tio dura, which enters the neck, is the lower division of its cervico- facial part. From near the angle of the jaw, where it traverses the fascia, it passes toward the hyoid bone, and supplies the platysma from its deeper side. Some of these twigs, approaching the cutaneous surface of the muscle in the anterior triangle of the neck, communicate with filaments of the anterior cer- vical nerve. 1. Mesial region of the neck.—This presents diflerent relations, as considered above or below the level of the os hyoides. Above the os hyoides, and extending from the body of that bone to the symphysis of the lower jaw, is the narrow space which separates the anterior bellies of the digastric muscles. It is an elongated triangle, broadest below—where the tendons of the digastrics are kept apart by the body of the hyoid bone—having its apex above, where these, having expanded into the fleshy anterior bellies, are infixed side by side at the median line of the jaw. The platysmata in their cellular sheath cover this space, and sometimes decussate across it with each other. The cervical aponeurosis likewise extends over it, adhering to its bony limits, and strength- ened by the tendinous slip, which is derived from the digastric. Deeper than the digastrics are seen the fibres of the mylo-hyoid muscles, meeting in the median raphe, which runs along the space. The natural direction of this raphe is almost antero-posterior, and that of the fibres which meet in it almost horizontally transverse: but when (as in any operation on this part of the neck) the head is thrown back and the chin elevated, the raphe presents a considerable downward slope, and the fibres of the mylo- hyoid have a corresponding obliquity. The same observation applies to the deeper fibres which course from the tubercles within the sym- physis to the body of the hyoid bone—those, namely, of the genio-hyoid and genio-hyo-glos- sal muscles. This little region can hardly be said to have any special surgical relations; it contains neither vessels nor nerves of size ;its injuries only assume importance when they extend beyond it into the adjoining digastric space; its diseases derive no peculiarities from their situation, and for the most part belong to the integuments, which are vascular, highly lolliculated, and in the male densely bearded : sycosis often extends to them, and they are a frequent seat of sebaceous tumours. Below the os hyoides, the anatomy, which involves the surgical relations of the larynx and trachea, becomes of extreme importance. Be- tween the two layers of the fascia superlicialis the platysma no longer intervenes; they ac- cordingly lie together and are blended. The vaginal processes of cervical fascia, which have isolated the sub-hyoid muscles, become united into a strong and single raphe along the middle line, from above to within a short distance of the sternal notch; but here the layers remain distinct, a superficial one fixing itself to the notch and to the interclavicular ligament, while the deeper one descends with the muscles into the mediastinum. The interval contains loose cellular tissue, and sometimes (as Burns no- ticed) an absorbent gland. Accordingly, in the very median line, an operator may expose the larynx, trachea, or thyroid body without divi- ding or displacing any portion of muscle ; but a lateral deviation from this imaginary line would imply an exposure of the sub-hyoid muscles on one side or on the other. Indeed, the muscles so nearly approach to the line in question, and constitute in their laminar ar- rangement so useful a guide to the subjacent parts, that the bare possibility of avoiding them is wisely neglected, and the surgeon learns from them his nearness to the organs which they cover. In tracing, from the hyoid bone downward, the irregular profile of tlie air-tube, the finger may distinguish through the integument the following changes of outline. 1. A horizontal semicircular notch, limited below by the pro- minent angle of the thyroid cartilage, and cor- responding, in the interval of the muscles, to the thyro-hyoid membrane; the lateral parts of this give passage, as we shall presently see, to the laryngeal artery and nerve, but its mesial part, with which alone we are now occupied, has only a small twig from the thyroid artery ramifying over it: the membrane is thick, and composed of strong vertical fibres in the median line; it becomes weaker and of laxer tissue in proceeding backward. Its deep aspect contri- butes to the skeleton of the pharynx, and cor- responds to the epiglottis, from the attached portion of which it is separated only by cel- lular tissue and the epiglottidean gland ; while, above, the mucous membrane, in being folded fonvard to the epiglottis, intervenes between it and the membrane. This notch is frequently invaded by the knife of the suicide; and there is perhaps no part of the neck on which a gash may be inflicted with less serious injury : the large vessels are far removed, and the larynx lies below the blade, which may, if near to the hyoid bone, enter the pharynx above the epi- glottidean fold of mucous membrane, leaving the ejiiglcttis unhurt, or, if more nearly ap- proached to the thyroid border of the space, may partly or entirely sever that cartilage from its inferior attachments. No special surgical operation belongs to the space; if indeed we