A. THE VEINS WHICH FORM THE VENA CAVA SUPERIOR.
These are constituted by the veins, 1. Of the head and face ; 2. Of the neck ; 3. Of the upper extremities ; 1. Of the thorax.
I. Veins of the head and face.* —The super ficial veins of the head and face unite to form three principal trunks, which are placed on the anterior, lateral, and posterior aspects of the cranium ; anteriork is seen the Facial vein. —This vein originates in the frontal region from numerous interlacing branches, which usually give rise to one large vein on each side (frontal vein), which is joined by branches from the upper lid (palpe bral) and root of the nose, and by the supra orbital vein; sometimes there is but one frontal vein placed in the mesial line, and dividing into two branches, which descend one on either side of the nose. The frontal vein continues its course in the sulcus along the inner margin of the orbit under the name of angular vein, accompanying the artery of the same name, and receives numerous branches from the orbit, by which a close connexion is maintained between the circulation on the exterior of the cranium and that of the cere brum itself. At the lower margin of the orbit the angular becomes the proper facial vein, which passes downwards and outwards in an almost direct course to the anterior edge of the insertion of the masseter muscle.
The facial vein consequently has a much shorter extent than its corresponding artery, to the outer side of which it is invariably placed ; it passes beneath the zygomatic mus cles, and lies on Steno's duct, just where the latter is about to penetrate between the fibres of the buccinator muscle.
The facial vein receives the folio wing branches. Veins from the aim nasi, the coronary, buccal, infra-orbital, and masseteric veins ; and also several large communicating veins (deep facial or alveolar) from a venous plexus which is lodged in the pterygoid space.
Having passed below the ramus of the jaw, the facial vein enters the digastric space, which it traverses from above downwards and back wards, and lies beneath the platysma myoides and on the submaxillary gland (which con sequently is interposed between the facial vein and artery); this vein next passes across the external carotid artery to terminate in the internal jugular vein, having been previously joined by a large branch of communication from the temporo-maxillary vein. In its
course through the digastric space the facial vein receives (a), the ravine vein, which conies from the inferior surface of the tongue, passes backwards by the side of the frxnum, and accompanies the hypoglossal nerve, between the mylo-hyoid and hyo-glossus muscles; (b), the satellite vein of the gustatory nerve, which is derived from a plexus of superficial veins on the dorsum of the tongue, and com municates freely with the preceding (Cruveil bier); (c), the submental vein, which arises in the sublingual gland ; and (d) several palatine veins which are derived from a venous plexus encircling the tonsil.
In many instances the facial vein unites with the proper lingual veins, and thus forms a common trunk, which throws itself into the internal jugular ; into this common trunk the superior thyroid, pharyngeal, and temporo maxillary veins, will in such a case be fre quently found to open.
On the lateral region of the head are placed the trunks of the temporal and internal max illary veins.
The temporal vein is formed by the union of two branches, which represent the superficial and middle temporal arteries.
The superficial temporal veins form a wide spreading network of vessels on the lateral aspect of the scalp, which communicates with the frontal veins in front, with the occipital behind, and with the temporal veins of the opposite side across the vertex.
The middle temporal veins arise in the sub stance of the temporal muscle, where they are joined, behind the external orbital process, by branches from the orbit : these veins, by their union, form a branch which is placed at first between the temporal muscle and fascia, but subsequently perforates the latter imme diately above the zygoma, and forms with the superficial temporal vein a common trunk, which enters the parotid gland, and unites with the internal maxillary vein.