Surgical Anatomy Part 5

The external jugular vein, H, Plate 4, as it descends the neck from the angle of the jaw obliquely backwards over the sterno-mastoid muscle, may be easily compressed and opened in any part of its course. This vein courses downwards upon the neck in relation to that branch of the superficial cervical plexus, named auricularis magnus nerve, Q, Plate 4, G, Plate 3. The nerve is generally situated behind the vein, to which it lies sometimes in close proximity, and is liable, therefore, to be accidentally injured in the performance of phlebotomy upon the external jugular vein. The coats of the external jugular vein, E, Plate 3, are said to hold connexion with some of the fibres of the platysma-myoides muscle, A A, Plate 3, and that therefore, if the vessel be divided transversely, the two orifices will remain patent for a time.

The position of the carotid artery protects the vessel, in some degree, against the suicidal act, as generally attempted. The depth of the incision necessary to reach the main blood-vessels from the fore part of the neck is so considerable that the wound seldom effects more than the opening of some part of the larynx. The ossified condition of the thyroid and cricoid parts of the laryngeal apparatus affords a protection to the vessels. The more oblique the incision happens to be, the greater probability is there that the wound is comparatively superficial, owing to the circ.u.mstance of the instrument having encountered one or more parts of the hyo-laryngeal range; but woeful chance sometimes directs the weapon horizontally through that membranous interval between the thyroid and hyoid pieces, in which case, as also in that where the laryngeal pieces persist permanently cartilaginous, the resistance to the cutting instrument is much less.

The anatomical position of the parotid, H, Plate 3, and submaxillary glands, W, Plate 4, is so important, that their extirpation, while in a state of disease, will almost unavoidably concern other princ.i.p.al structures. Whether the diseased parotid gland itself or a lymphatic body lying in connexion with it, be the subject of operation, it seldom happens that the temporo-maxillary branch of the external carotid, F, escapes the knife. But an accident, much more liable to occur, and one which produces a great inconvenience afterwards to the subject, is that of dividing the portio-dura nerve, S, Plate 4, at its exit from the stylo-mastoid foramen, the consequence being that almost all the muscles of facial expression become paralyzed. The ma.s.seter, L, Plate 3, pterygoid, buccinator, 15, Plate 4, and the facial fibres of the platysma muscles, A O, Plate 3, still, however, preserve their power, as these structures are innervated from a different source. The orbicularis oculi muscle, which is princ.i.p.ally supplied by the portio-dura nerve, is paralyzed, though it still retains a partial power of contraction, owing to the anatomical fact that some terminal twigs of the third or motor pair of nerves of the orbit branch into this muscle.

The facial artery, V, and the facial vein, U, Plate 4, are in close connexion with the submaxillary gland. Oftentimes they traverse the substance of it. The lingual nerve and artery lie in some part of their course immediately beneath the gland. The former two are generally divided when the gland is excised; the latter two are liable to be wounded in the same operation.

DESCRIPTION OF PLATES 3 & 4.

PLATE 3.

A A A. Subcutaneous platysma myoides muscle, lying on the face, neck, and upper part of chest, and covering the structures contained in the two surgical triangles of the neck.

B. Lip of the thyroid cartilage.

C. Clavicular attachment of the trapezius muscle.

D. Some lymphatic bodies of the post triangle.

E. External jugular vein.

F. Occipital artery, close to which are seen some branches of the occipitalis minor nerve of the cervical plexus.

G. Auricularis magnus nerve of the superficial cervical plexus.

H. Parotid gland.

I. Temporal artery, with its accompanying vein.

K. Zygoma.

L. Ma.s.seter muscle, crossed by the parotid duct, and some fibres of platysma.

M. Facial vein.

N. Buccinator muscle.

O. Facial artery seen through fibres of platysma.

P. Mastoid half of sterno-mastoid muscle.

Q. Locality beneath which the commencements of the subclavian and carotid arteries lie.

R. Locality of the subclavian artery in the third part of its course.

S. Locality of the common carotid artery at its division into internal and external carotids.

[Ill.u.s.tration: Right side of the head, showing blood vessels, muscles and other internal organs. ]

Plate 3

PLATE 4.

A. Subclavian artery pa.s.sing beneath the clavicle, where it is crossed by some blood-vessels and nerves.

B. Sternal attachment of the sterno-mastoid muscle, marking the situation of the root of common carotid.

C. Common carotid at its point of division, uncovered by sterno-mastoid.

D. External carotid artery branching into lingual, facial, temporal, and occipital arteries.

E. Internal carotid artery.

F. Temporo-maxillary branch of external carotid artery.

G. Temporal artery and temporal vein, with some ascending temporal branches of portio-dura nerve.

H. External jugular vein descending from the angle of the jaw, where it is formed by the union of temporal and maxillary veins.

I. Brachial plexus of nerves in connexion with A, the subclavian artery.

K. Posterior half of the omo-hyoid muscle.

L. Transversalis colli artery.

M. Posterior scapular artery.

N. Scalenus anticus muscle.

O. Lymphatic bodies of the posterior triangle of neck.

P. Superficial descending branches of the cervical plexus of nerves.

Q. Auricularis magnus nerve ascending to join the portio-dura.

R. Occipital artery, accompanied by its nerve, and also by some branches of the occipitalis minor nerve, a branch of cervical plexus.

S. Portio-dura, or motor division of seventh pair of cerebral nerves.

T. Parotid duct.

U. Facial vein.

V. Facial artery.