The external carotid artery gives origin to eight branches, including the two into which it finally divides. For the purposes of description these may be arranged into three sets. 1. Those which are directed forwards, viz., the superior thyroid, the lingual, and the facial. 2. Those which run backwards, — the occipital and posterior auricular; and 3, those which ascend, viz., the ascending pharyngeal branch with the temporal and internal maxillary, — the two terminal branches.
In addition to the principal branches here enumerated, the external carotid wives off several small offsets to the parotid gland.
Peculiarities of the branches
The peculiarities relating to the origin of the branches of this artery will be mentioned under the description of each; but a general view may be here taken of the deviations they present in respect of position and number.
Position of branches
They are not unfrequently crowded together on the parent artery, in some cases, near the commencement, and in others at a higher point of that vessel. Occasionally the branches are found to be distributed at regular distances upon the whole length of the external carotid.
The usual number of branches (eight) has been found to be diminished in two principal ways, — viz., by the removal to another artery of one of the ordinary branches, or by the union into a single trunk of two or three branches which are usually derived* separately from the artery under consideration.
The number of branches derived from the external carotid artery may be augmented by the transfer to this vessel of some branch not ordinarily derived from it, or by the addition to it of some unusual branch. Illustrations of these various peculiarities will be referred to in treating of the individual branches. In this place may be mentioned the not unfrequent presence of a distinct branch for the eterno-mastoid muscle.
Superior thyroid artery
The superior thyroid artery, [a. thyroidea sup.] the first of the anterior set of branches, is given off close to the commencement of the external carotid, immediately below the great cornu of the hyoid bone. From this point the artery curves forwards and downwards, to the upper margin of the thyroid cartilage; it then descends a short distance beneath the omo-hyoid, sterno-hyoid, and sterno-thyroid muscles, furnishing offsets to these muscles, and reaching the anterior surface of the thyroid body, distributes branches to its substance, and communicates freely with the branches of the inferior thyroid artery. The inferior thyroid, it will be afterwards seen in the description of the artery, is distributed to the under surface of the thyroid body.
The superior thyroid artery, taking its rise from the external carotid, while that vessel is placed in the triangular intermuscular space referred to in describing the upper part of the common carotid artery, is covered at first only by the platysma and fascia; but afterwards it is more deeply seated, being beneath the muscles before mentioned.
Besides the branches furnished to the muscles and the thyroid body, as already noticed, together with some to the lowest constrictor of the pharynx, the superior thyroid furnishes the following offsets, which have received distinctive names :
(a) The hyoid, a very small branch, runs transversely inwards just below the os hyoides, and assists in supplying the soft parts connected with that bone. This little artery sometimes forms an arch with its fellow from the opposite side.
(b) A superficial descending branch, which passes downwards a short distance over the sheath of the large cervical vessels, and ramifies in the sterno-mastoid, and the muscles attached to the thyroid cartilage, as well as in the platysma and neighbouring integuments. The position of this branch with respect to the sheath of the carotid artery, is the only circumstance which attaches a degree of interest to it.
(c) The laryngeal branch (superior laryngeal artery) proceeds inwards in company with the superior laryngeal nerve, and pierces the thyro-hyoid membrane. Before entering the larynx this branch is covered by the thyro-hyoid muscle. On reaching the interior of the larynx, it ramifies in the small muscles, the glands, and mucous membrane of that organ.
(d) Crico-thyroid. — A small branch, to be noticed on account of its position rather than its size, crosses over the membrane connecting the thyroid and cricoid cartilages, and communicates with a similar branch from the other side. This little artery may be the source of troublesome hemorrhage in an operation for laryngotomy.
The superior thyroid artery is frequently much larger, or, on the other hand, it may be smaller than usual. In either case the deviation from the accustomed size is accompanied with an opposite alteration in other thyroid arteries ; one change compensating for another. — (See observations on the inferior thyroid artery.)
The superior thyroid is often transferred to the common carotid, and it has been seen, but rarely, conjoined with the lingual branch, or with that and the facial branch of the external carotid.
There are sometimes two superior thyroid arteries. The single vessel has been seen so small that it ended in branches to the stern o-mastoid muscle and the larynx.
Peculiarities of the branches
The hyoid branch is frequently very small or absent.
The laryngeal branch arises not infrequently from the external carotid artery, and likewise, but rarely, from the common carotid.
Examples have occurred of this branch being of very large size. In the case here referred to, the laryngeal artery after passing along the inner side of the thyroid cartilage escaped beneath that cartilage to the thyroid body.
The laryngeal artery occasionally enters the larynx through a foramen to the thyroid cartilage ; and it has likewise been observed to pass inwards below the cartilage, afterwards distributing branches upwards to the interior of the larynx.
The lingual artery, [a. lingualis] arises from the inner side of the external carotid, between the origin of the superior thyroid and facial arteries. Curving from its origin upwards and inwards, this artery reaches the upper margin of the hyoid bone (its greater cornu), by which it is separated from the superior thyroid artery ; it then passes forwards deeply between the muscles above the hyoid bone, and soon ascends almost perpendicularly to reach the under surface of the tongue, beneath which it makes its final turn forwards to the tip of that organ, assuming the name of ranine artery.
Taking origin in the triangular intermuscular space in which the commencement of the external carotid artery is lodged, the lingual artery is at first comparatively superficial, covered only by the platysma and fascia of the neck ; soon, however, it is crossed by the stylo-hyoid muscle, and then sinks beneath the hyo-glossus muscle, between it and the middle constrictor of the pharynx. It is likewise covered by the anterior belly of the digastric, and by the mylo-hyoid muscle, and rests against the middle constrictor of the pharynx, afterwards against the genio-hyo-glossus.
The hypoglossal nerve courses forwards nearly parallel with the artery, until they both reach the posterior border of the hyo-glossus muscle, where the nerve passes over or on the cutaneous surface of the muscle, and the artery beneath it. At the anterior margin of the hyo-glossus muscle, the nerve is lower than the artery.
The branches of the lingual artery, including the ranine, are as follow : —
The hyoid branch [ram. hyoideus] takes the direction of the hyoid bone, running along its upper border; it supplies the contiguous muscles and skin.
The dorsal artery of the tongue (dorsalis linguae), which is often represented by several smaller branches, arises from the deep portion of the lingual artery, beneath the hyo-glossus muscle. It is named dorsal from its destination, for it ascends to supply the upper part and substance of the tongue, ramifying as far back as the epiglottis.
The sublingual branch, [a. sublingualis] taking origin at the anterior margin of the hyo-glossus. turns slightly outwards beneath the mylo-hyoid muscle, between it and the sublingual gland. It supplies the substance of the gland, and gives branches to the mylo-hyoid and other muscles connected with the maxillary bone. Small branches are also distributed to the mucous membrane of the mouth, and the inside of the gums.
The ranine artery, [a. ranina s. profunda lingua?], from its direction, may be considered the continuation of the lingual artery. It runs forwards beneath the tongue, covered by the mucous membrane, and resting on the genio-hyo-glossus muscle. It is accompanied by the gustatory branch of the fifth nerve. Having reached the tip of the tongue, which it supplies with blood, it anastomoses with the corresponding artery of the other side. The two ranine arteries are placed one on each side of the fraenum of the tongue, covered only by the mucous membrane of the mouth.
The origin of the lingual artery is sometimes by a common trunk with the next branch above it, viz., the facial artery. It is occasionally joined with the superior thyroid.
The hyoid branch is often deficient ; and it appears that there is an inverse condition as to size between this branch and the hyoid branch of the superior thyroid.
The sublingual branch varies in size. It is sometimes derived from the facial artery, and then perforates the mylo-hyoid muscle.
The lingual artery has been seen to give off as unusual branches, the submental and ascending palatine.
The facial artery (art. maxillaris externa, — Anatom. varior. : labialis, — Haller). This artery is named from the distribution of its greater part. Taking origin a little above the lingual artery, it is first directed obliquely forwards and upwards beneath the base of the maxillary bone; and this may be considered the cervical part of the artery. Changing its direction, it passes upwards over the base of the lower maxilla, immediately before the ramus of that bone, at the anterior margin of the masseter muscle which covers the ramus. Commencing here its course upon the face, the facial artery is directed forwards near to the angle of the mouth; and after ascending externally to the nose, terminates near the inner canthus of the eye, where it anastomoses with the ophthalmic artery. In its whole course the artery is tortuous, and this condition is connected in the neck with the changes in size to which the pharynx is liable, and on the face with the mobility of the cheeks and of the lower maxilla.
The cervical part of the facial artery immediately after its origin (which is comparatively superficial, being covered only by the platys- ma and fascia), sinks beneath the digastric and stylo-hyoid muscles, and then beneath the submaxillary gland near its upper part. Emerging from the gland and ascending over the maxilla, it is covered by the platysma, and here the pulsation of the artery is easily felt, and the circulation through it readily controlled by pressure against the bone. In its further progress over the face the facial artery is covered successively (in addition to the integument and a varying quantity of fat) by the platysma and the zygomatic muscles, and it rests against the buccinator, the levator anguli oris, and the levator labii superioris.
The facial vein is separated by a considerable interval from the artery on the face. It takes nearly a straight course upwards instead of inclining forward near the angle of the mouth, and it is not tortuous like the artery.
Branches of the portio dura nerve cross the vessel, and the infra-orbital nerve is beneath it, separated by the fibres of the elevator of the upper lip.
Branches of the Facial artery
The branches of the facial artery are numerous, and may conveniently be divided into two sets, — the first consisting of those given off before the vessel turns over the lower maxillary bone (cervical branches), usually three or four in number; the second, which varies from five to six, being those distri- buted to the face.
The following branches are derived from the facial artery below the maxillary bone :
The inferior or ascending palatine (palatina adscendens, — Haller), ascends be- tween the stylo-glossus and the stylo-pharyngeus muscles, and reaches the pharynx close by the border of the internal pterygoid muscle. After having given small branches to the tonsil, the styloid muscles, and the Eustachian tube, it divides, near the levator palati muscle, into two branches, one of which follows the course of the circumflexus palati muscle, and is distributed to the soft palate and its glands, whilst the other penetrates to the tonsil, and ramifies upon it with the branch to be next described. — The place of this artery upon the palate is often taken by the ascending pharyngeal. For the distribution of the vessels in that case, see the ascending pharyngeal artery.
The tonsillar branch [a. tonsillaris] ascends along the side of the pharynx, and penetrates the superior constrictor of the pharynx to terminate in small vessels upon the tonsil and the side of the tongue near its root.
The glandular branches are a numerous series which enter the substance of the submaxillary gland, whilst the artery is in contact with it; some of them are pro- longed upon the side of the tongue.
The submental (submentalis arteria, — Haller), the largest branch arising from the facial in the neck, leaves that artery near the point at which it turns upwards to the face, and runs forwards below the base of the maxillary bone upon the mylo-hyoid muscle and beneath the digastric. Giving branches in its course to the submaxillary gland and to the muscles attached to the jaw, it reaches the symphysis of the chin and divides into two branches ; one of which, running more superficially than the other, passes between the depressor muscle of the lower lip and the skin, supplying both, whilst the other enters between that muscle and the bone, and ramifies in the substance of the lip, communicating with the inferior labial artery, which is to be next described.
Of the second series of branches, — those derived from the facial artery upon the side of the face, — some which are directed outwards to the muscles, as the masseter and buccinator, require only to be indicated. Those which are described with some detail have the opposite course inwards, and they are as follows : —
The inferior labial branch [a. mentalis] , arises immediately after the facial artery has turned over the maxilla, and running forwards beneath the depressor anguli oris, distributes branches to the skin, and the muscles of the lower lip, anasto- mosing with the inferior coronary and submental branches, and with the inferior dental branch derived from the internal maxillary.
The coronary artery of the lower lip (coronaria labri inferioris, — Haller), arises near the angle of the mouth, as often in conjunction with the superior coronary as from the facial separately, and after penetrating the muscular fibres surrounding the orifice of the mouth, takes a transverse and tortuous course between those fibres and the mucous membrane of the lip, and inosculates with the corresponding artery of the opposite side. Small branches from this artery ascend to supply the orbicular and depressor muscles, the glands, and other structures of the lower lip, whilst others descend towards the chin, and communicate there with branches from other sources.
The coronary artery of the upper lip,* (coronaria labri superioris, — Haller,) i, is larger and more tortuous than the preceding branch, with which it often arises. Like the artery of the lower lip, it runs across between the muscles and mucous membrane of the upper lip, and inosculates with the corresponding artery of the opposite side. In addition to supplying the whole thickness of the upper lip, this artery gives two or three small branches to the nose. One of these, named the artery of the septum, runs along the septum of the nares, on which it ramifies as far as the point of the nose; another reaches the ala of the nose.
The lateral nasal artery turns inwards to the side of the nose beneath the common elevator of the nose and lip, and sends branches to the ala and the dorsum of the nose. This artery anastomoses with the nasal branch of the ophthalmic, with the artery of the septum narium, and with the infra-orbital artery.
Angular artery [a. angularis]. — Under this name is recognised the end of the facial artery, which inosculates at the inner side of the orbit with the ophthalmic artery. It is accompanied by a considerable vein (the angular vein).
It may here be remarked, that a communication between the superficial and deep branches of the external carotid is established by the anastomoses of the facial artery with ihe infra-orbital, inferior dental, and nasal branches of the internal maxillary, and between the external and the internal carotids by the anastomoses of the facial with the ophthalmic arteries.
Peculiarities of the facial artery and its branches.
The facial artery not unfrequently arises by a common trunk with the lingual. Occasionally it arises above its usual position, and then descends beneath the angle of the jaw to assume its ordinary course.
This artery varies much in size, and in the extent to which it is distributed. It has been observed, very rarely, however, to end as the submental, not reaching the side of the face ; in some cases it supplies the face only as high as the lower lip. The deficiency of the facial artery is most frequently compensated for by an enlargement of the nasal branches of the ophthalmic at the inner side of the orbit; occasionally by branches from the transverse facial or internal maxillary.
The ascending palatine artery is in some instances transferred to the external carotid. This branch varies in size and the extent to which it reaches. Not unfrequently it is expended without furnishing any branch to the soft palate. When it is thus reduced in size, the pharyngeal artery takes its place on the soft palate. — (See the observations on the pharyngeal artery.)
The tonsillar branch is not unfrequently altogether wanting.
The submental branch has been observed to take its rise from the lingual artery. On the other hand, the facial artery, instead of the lingual, has been found to furnish the branch which supplies the sublingual gland.
The occipital artery, [a. occipitalis,] has a long and winding course, running at first deeply upwards before the upper cervical vertebrae, then horizontally along the outer part of the base
* The name coronary artery of the upper and lower lips respectively (coronaria labri superioris v. inferioris), is stated by Haller to have been taken by him from Winslow. But this anatomist after describing the course of the arteries, concludes by mentioning that they anastomose one with the other, " and thereby form a kind of arteria coronaria labiorurn." So that the designation originally, and not inaptly, applied to the circle formed by the union of the labial arteries of opposite sides around the mouth, has come to be used for each vessel singly of the skull, and finally turning upwards on the occiput, to ramify- beneath the integument. Arising from the posterior aspect of the external carotid, usually opposite the facial artery, this vessel in its upward course sinks beneath the posterior belly of the digastric muscle and the parotid gland, and reaches the interval between the transverse process of the atlas and the mastoid process of the temporal bone. From that point it turns horizontally backwards along the skull, beneath the mastoid process of the temporal bone and the sterno-mastoid, splenius, digastric and trachelo-mastoid muscles. In this part of its course the vessel rests against the upper end of the complexus, by which and by the fibres of the superior oblique and larger rectus muscles, it is separated from the occipital bone. Lastly, changing its direction a second time, and piercing the cranial attachment of the trapezius, it ascends beneath the integument on the back of the head, accompanied by the great occipital nerve, and divides into numerous branches. Whilst in the neck, the occipital artery crosses over the internal carotid artery, the vagus and spinal accessory nerves, and the internal jugular vein ; and the hypoglossal nerve turns from behind over it at its origin.
The following branches are given from the occipital artery :
Small muscular offsets to the digastric and stylo-hyoid muscles, and one of larger size to the sterno-mastoid. This last is so regular a branch that it is known as the sterno-mastoid branch. Afterwards —
An auricular branch to the back part of the concha of the ear, and two or three other muscular branches to the splenius and trachelo-mastoid.
Cervical branch. — (Ramus princeps cervicalis, — Haller.) — To the back part of the neck the occipital artery furnishes a branch thus designated. Descending a short way, this vessel divides into a superficial and a deep branch. The former ramifies beneath the splenius, sending offsets through that muscle to the tra- pezius ; while the deep branch passes beneath the complexus and anastomoses with the vertebral and the deep cervical branch of the superior intercostal. The muscles in the immediate neighbourhood are furnished with small arteries from the cervical branch of the occipital. — The size of this branch varies very much.
The meningeal branch runs up with the internal jugular vein, enters the skull through the foramen lacerum posterius, and ramifies in the dura mater of the posterior fossa of the base of the skull. A branch from the pharyngeal artery may be found to enter the skull through the same foramen.
The superficial or cranial branches of the occipital artery pursue a tortuous course between the integument and occipito-frontalis muscle ; and in proceeding upwards on the skull they separate into diverging branches, which communicate with the branches of the opposite artery, as well as with those of the posterior auricular artery, and of the temporal artery at the vertex and side of the skull. Branches are distributed to the fleshy fibres of the occipital muscle, to the epi- cranial aponeurosis, and to the pericranium, others to the skin, and one (a mastoid branch) enters the skull through the mastoid foramen, and ramifies in the dura mater.
The origin of the occipital, though usually opposite the facial, is sometimes placed higher or lower than that point. This artery is occasionally derived from the internal carotid, and from the ascending cervical branch of the inferior thyroid — an offset of the subclavian artery.
The occipital artery sometimes passes over the trachelo-mastoid muscle, instead of beneath it. The chief portion of the vessel was found, but in a single instance however, to pass over the sterno-mastoid muscle, only a small artery being placed in the usual position. The artery has, in a few instances, been seen to turn backwards below the transverse process of the atlas.
The posterior auricular and the pharyngeal arteries sometimes take origin from the occipital.
Posterior auricular artery.
The posterior auricular artery [a. auricularis post.], a small vessel, arises from the carotid, a little higher up than the latter. It ascends, under cover of the parotid gland, and resting upon the styloid process of the temporal bone, to reach the angle formed by the cartilage of the ear with the mastoid process at the side of the head. The portio dura of the seventh nerve crosses over this little artery, and the spinal, accessory turns behind it. Somewhat above the mastoid portion of the temporal bone it divides into two sets of branches, of which one set inclines forwards to anastomose with the posterior divisions of the temporal artery, and the other backwards towards the occiput, on which they communicate with the occipital artery. The following are the branches given from the posterior auricular artery :
Several small branches to the parotid gland and the digastric muscle.
The stylo-mastoid branch enters the foramen of that name in the temporal bone, and, on reaching the tympanum, divides into delicate vessels, which pass, some to the mastoid cells, others to the labyrinth. One branch will constantly be found, in young subjects, to form, with the tympanic branch of the internal maxillary artery, which enters the fissure of Glaser. a vascular circle around the auditory meatus, from which delicate offsets ramify upon the membrana tympani. This small tympanic branch sometimes arises from the occipital artery.
As it passes the back of the ear, the auricular artery gives one or two proper auricular branches, which supply the posterior surface of the concha, and turn over the margin, or perforate the substance of the auricle to gain its anterior surface.
The posterior auricular artery is frequently very small, and has been seen to end in the stylo-mastoid branch. It is often a branch of the occipital.
Associated by its position with the posterior branches of the external carotid, viz., the occipital and posterior auricular, a small vessel named from its destination sterno-mastoid, is not unfrequently met with.
The temporal artery, [a. temporalis] is one of the two branches into which the external carotid artery divides a little below the condyle of the lower jaw. It continues upwards in the direction of the parent vessel, whilst the other branch (the internal maxillary) sinks under the lower maxillary bone. The temporal artery is at first embedded in the substance of the parotid gland, where it lies in the interval between the meatus of the ear and the condyle of the lower jaw. Pursuing its course upwards, this vessel soon reaches the cutaneous surface of the zygoma (at its root), on which it may be readily compressed. Continuing to ascend it lies close beneath the skin, supported by the temporal muscle and its fascia; and, about two inches above the zygoma, divides into two branches, which again subdivide and ramify beneath the integument on the side and upper part of the head.
The temporal artery gives off the following branches:
Several small offsets to the parotid gland, some articular branches to the articulation of the lower jaw, and one or two branches to the masseter muscle.
The transverse artery of the face, (transversalis faciei) arises whilst the temporal artery is deeply seated in the parotid gland, through the substance of which it runs forwards, so as to get between the parotid duct and the zygoma, resting on the masseter muscle, and accompanied by one or two transverse branches of the facial nerve. It gives small vessels to the parotid gland, the masseter muscle, and the neighboring integument, and divides into three or four branches, which are distributed to the side of the face, anastomosing with the infra-orbital and facial arteries.
The middle temporal branch [a. temporalis media] arises close above the zygoma, and immediately perforating the temporal fascia, sends branches to the temporal muscle, which often communicate with the deep temporal branches of the internal maxillary artery. An offset from this artery is sometimes found to run on to the outer angle of the orbit, where, after giving branches to the orbicularis palpebrarum, it anastomoses with the lachrymal branch of the ophthalmic artery.
The anterior auricular branches, [a. auriculares ant.] two or more in number (superior and inferior), arise above the branch last described. They are distributed to the fore part of the pinna and the lobe of the ear, and a part of the external meatus, anastomosing with the ramifications of the posterior auricular artery.
One of the two terminal branches of the temporal artery, the anterior temporal, inclines forwards as it ascends over the temporal fascia, and ramifies extensively over the forehead, supplying the orbicular and occipito-frontal muscles, the pericranium, and the skin, and communicating with the supra-orbital and frontal branches of the ophthalmic artery. On the upper part of the cranium the branches of this artery are directed from before backwards. — When it is desired to take blood from the temporal artery, the anterior temporal branch is selected for the operation.
The posterior temporal, which is larger than the anterior, passes back on the side of the head, above the ear, and over the temporal fascia; its branches ramify freely in the coverings of the cranium, both upwards to the vertex, where they communicate with those of' the corresponding vessel on the opposite side, and backwards to join with those of the occipital and posterior auricular arteries.
The temporal artery is frequently tortuous, especially in aged persons. Occasionally a large unusual branch runs forward above the zygoma to the upper part of the orbit. The temporal artery may join with the ophthalmic, and furnish large frontal arteries. — The transverse artery of the face varies in size ; occasionally it is much larger than usual, and takes the place of a defective facial artery. In some instances the transverse artery is transferred to the external carotid.
The internal maxillary artery, [a. maxillaris interna] the deep terminal branch of the external carotid a, and which in size, though not in direction, is the continuation of that vessel, pursues a winding course under cover of the ramus of the lower maxilla. From its place of origin, where it is concealed by the parotid gland, the artery curves forward and assumes for a short space a horizontal course, sinking immediately under the maxilla, between that bone and the internal lateral ligament of the temporo-maxillary joint; and here it lies below the narrow end of the external pterygoid muscle, and crosses over the inferior dental nerve. Speedily changing its course, the internal maxillary artery passes obliquely forward and upward over the outer surface of the same muscle (not unfrequently beneath it), and under cover of the ramus of the lower maxilla, and of the lower end of the temporal muscle. Approaching the superior maxillary bone, and op- posite the interval between the two heads of the external pterygoid muscle, the artery bends inwards to the spheno-maxillary fossa, where it furnishes the terminal branches.
For sake of greater facility in arranging the numerous branches furnished by this artery, it will be considered as divisible into three parts, each giving origin to a group of branches. The first division is that short part connected with the ramus of the lower maxilla, and placed between that bone and the internal lateral ligament of the temporo-maxillary articulation; the second is defined by the connexion of the vessel with the muscles ; while the third division includes that portion which is again in close connexion with bone, viz., with the superior maxilla and the fossa which it contributes to form. — It is to be understood that this, like most other methods of merely artificial arrangement, is not free from objection.
a. The branches given from the first part of the internal maxillary artery, — that between the lower maxilla and the lateral ligament of the joint, — are the tympanic, the middle and small meningeal, and the inferior dental, each of which, it may be observed, passes into an osseous foramen or canal.
The tympanic branch [a. tympanica] passes deeply behind the articulation of the lower jaw, and enters the fissure of Glaser, supplying the laxator tympani muscle, and the tympanic cavity, where it ramifies upon the membrana tympani. It anastomoses in the tympanum with the stylo-mastoid and vidian arteries. This little artery varies in its place of origin, in different cases.
The middle meningeal or great meningeal artery, [a. meningea media, s. magna, s. spinosa] is by far the largest of the branches which supply the dura mater. It arises from the internal maxillary artery between the lateral ligament and the lower jaw, and passes directly upwards under cover of the external pterygoid muscle to the spinous foramen of the sphenoid bone. Through that foramen it reaches the interior of the skull, where it ramifies between the dura mater and the internal surface of the cranial bones, its numerous ramifications spreading over the sides and top of the cranium, along the deep arborescent grooves formed on the inner surface of the bones. In its course within the cranium the middle meningeal artery ascends upon the middle fossa of the skull to the anterior inferior angle of the parietal bone, where it becomes lodged in a deep groove — some- times in a distinct canal in that bone. From this point it divides into numerous branches, which spread out, some upwards over the parietal bone as high as the vertex, and others backwards even to the occipital bone.
Immediately after it has entered the cavity of the cranium, the middle meningeal artery gives minute branches to the ganglion of the fifth nerve, and to the dura mater near the sella turcica. One small branch (petrosal branch : artery of the facial nerve, — Cruveilhier) runs backwards and outwards over the petrous portion of the temporal bone, enters the hiatus Fallopii, and passes along the aqueduct, sending offsets which anastomose with the stylo-mastoid artery. As it ascends through the middle fossa of the skull, the middle meningeal artery sends branches which extend forwards to the orbit, and are found to inosculate with the lachrymal, or some other branch of the ophthalmic artery. — The branches of this artery supply the bones as well as the dura mater, to which. membrane they adhere closely when the skull is detached from it.
The middle meningeal artery is accompanied by two veins.
The small meningeal artery, c, [a. meningea parva,] sometimes arises from the preceding branch. It enters the skull through the foramen ovale, to supply the dura mater in the middle fossa.
The inferior maxillary, or dental artery, d d, [a. dentalis s. alveolaris inferior] descends to enter the dental canal, accompanied by the inferior dental nerve, and then runs along the canal together with the nerve as far forwards as the mental foramen, through which it escapes on the face. As it enters the foramen in the lower maxilla this artery gives off the mylo-hyoid branch, which with a nerve runs in a groove below the dental foramen, and ramifies on the under surface of the mylo-hyoid muscle.
In its course through the bone the inferior dental artery lies beneath the roots of the teeth, and gives off at intervals small offsets, which ascend to enter the minute apertures in the extremities of the fangs, and supply the pulp of each tooth. From the mental foramen a branch is continued forwards beneath the incisor teeth, supplying them with minute vessels, and inosculating at the sym- physis of the chin with a corresponding artery from the opposite side. The terminal or mental branches of the inferior dental artery anastomose on the face with the inferior coronary and submental arteries, and assist in supplying the soft parts covering the front of the lower jaw.
b. The second group of branches (those given from the internal maxillary artery whilst in connexion with the muscles) are, the deep temporal, the pterygoid, the masseteric, and the buccal, — that is to say, the branches which supply the muscles.
The deep temporal branches, [a. temporalis profunda ant. et. post.] two in number (anterior and posterior), ascend between the temporal muscle and the pericranium, along which they ramify, supplying that muscle, and anastomosing with the branches of the other temporal arteries, and also through small foramina in the malar bone, with minute branches of the lachrymal artery.
The pterygoid branches [a. pterygoideae] include several small, short offsets, irregular in their number and place of origin, which are distributed to the pterygoid muscles.
The masseteric [a. masseterica] is a small but regular branch which passes from within outwards, above the sigmoid notch of the lower maxillary bone, and is distributed to the inner or deeper surface of the masseter muscle. This branch is often joined at its origin with the posterior temporal branch. It anastomoses with the masseteric branches derived from other arteries.
The buccal branch [a. buccalis] runs obliquely forwards upon the buccinator muscle with the buccal nerve ; it is distributed to that and other muscles of the cheek, and anastomoses with the branches of the facial artery.
c. The branches given from the last part of the internal maxillary artery — while it is in connexion with the superior maxillary bone, and in the spheno-maxillary fossa, — are the following, viz., the alveolar, and the infra-orbital, directed forwards; the descending palatine, turning downwards; the vidian and pterygopalatine which run backwards; and the nasal or spheno-palatine, proceeding inwards. These branches, like the first series, enter bony foramina or canals.
The alveolar or superior maxillary branch, g, arises near the tuberosity of the maxillary bone, usually in common with the infra-orbital branch, and runs tortuously forwards upon its outer surface, giving several branches (one being larger than the remainder, the superior dental — dentalis maxilla? superioris, — Halier) which enter the foramina in the bone and reach the alveolar cavities, where they pass into the fangs, and supply the pulps of the upper molar and bicuspid teeth; other branches supply the gums; and some small ones pierce the bone, and ramify in the lining membrane of the antrum of Highmore.
The infra-orbital artery, h h, [a. infra-orbitalis] arising generally by a common trunk with the preceding branch, runs horizontally forwards from the artery just as it is about to enter the spheno-maxillary fossa, and though much smaller, is continuous in direction with the parent vessel. It passes into the infra-orbital canal, and after having traversed the canal accompanied with the superior maxillary nerve, emerges upon the face at the infra-orbital foramen, under cover of the levator labii superioris.
Whilst in the canal, the infra-orbital artery gives off small vessels, which pass upwards into the orbit, and enter the inferior rectus and the inferior oblique muscle of the eye, and the lachrymal gland. Other small branches proceed downwards to supply the front teeth. On the face it gives branches upwards to the lachrymal sac and inner angle of the orbit, anastomosing with the nasal branches of the ophthalmic and facial arteries, and it sends other branches down- wards beneath the levator labii superioris, which join with the ramifications of the transverse facial and buccal branches.
The descending palatine (palatina superior, — Haller), is one of the three branches which are given off deeply within the spheno-maxillary fossa. It descends perpendicularly through the posterior palatine canal, with the palatine nerve, and thus reaches the back part of the roof of the mouth, where it runs along the hard palate to the inner side of the alveolar border, supplying the gums, and the mucous membrane, and other parts of the palate. In front it ends in a small vessel which ascends through the anterior palatine foramen, and anastomoses with the artery of the septum (nasal) derived from the spheno-palatine branch.
While descending in the proper osseous canal, or before entering it, the palatine artery gives small branches which pass away through small diverging canals in the bone, to end in the soft palate, upon which they communicate with the ascending palatine artery.
Vidian [a. vidiana]. — Near the origin of the descending palatine artery, or from a common trunk with it, a small branch, having a reflex course, passes directly backwards to enter the vidian canal with the vidian nerve. Hence it is termed the vidian or pterygoid branch. It is distributed to the Eustachian tube and top of the pharynx, and sends a small vessel into the tympanum.
The ptery go-palatine (pharyngeus supremus. — Haller), [a. pterygo-palatina, s. palatina sup.] a very small branch, often arises with the spheno-palatine. It passes backwards through the pterygo-palatine canal to reach the top of the pharynx, to which and to the Eustachian tube and sphenoidal cells, it is distributed.
The nasal or spheno-palatine artery [a. spheno-palatina s.nasalis post.] enters the foramen of that name, by which it reaches the cavity of the nose at the back part of the superior meatus. There, lying between the mucous membrane and the periosteum, it divides into two or three branches ; of these some ramify extensively over the spongy bones, and others supply the posterior ethmoidal cells as well as the antrum. One long branch (the artery of the septum) runs forwards along the septum nasi, between the mucous membrane and the periosteum, to the fore part of the nasal fossa, where it ends in a small vessel which enters the upper end of the anterior palatine canal, and joins an ascending branch from the descending palatine artery.
Peculiarities -The internal maxillary artery is very constant in its place of origin. It has, however, been seen to arise from the facial.
But this artery often deviates from the course described as the more usual one — passing under cover of the external pterygoid muscle (between the two pterygoids), and crossing the third division of the fifth nerve. In this case the artery comes forward in the interval between the two heads of the muscle to its accus- tomed position near the superior maxillary bone. It has likewise been observed to escape from under cover of the external pterygoid by piercing the middle of that muscle. When the artery is placed beneath the muscle, it has been found lodged in a notch in the posterior margin of the external pterygoid plate, and bound down by fibrous structure. In the process of bone referred to, instead of a depression there is occasionally a foramen, which probably lodges the artery.
The branches of the internal maxillary artery present few peculiarities worthy of note.
The middle meningeal artery occasionally furnishes the lachrymal artery (usually an offset of the ophthalmic), — a peculiarity which may be looked on as resulting from the enlargement of an ordinary anastomosing branch.
In a case in which the internal carotid was wanting, two tortuous branches from the internal maxillary entered the foramen rotundum and foramen ovale, to supply its place.
The pharyngeal artery, [a. pharyngeus adscendens] is a long slender vessel, (the smallest branch of the external carotid which has received a distinctive designation,) ascends deeply in the neck, and lies concealed from view until some of the branches of the external carotid artery and the stylo-pharyngeus muscle are drawn aside. It arises most commonly from half an inch to an inch above the origin of the external carotid, and in its straight course upwards rests on the rectus capitis anticus, close to the surface of the pharynx, between it and the internal carotid artery, and is thus directed up towards the base of the skull. Its branches, which are necessarily very small, may, from a consideration of their destination, be divided into three sets, viz., those to the pharynx: a set directed outwards : and meningeal branches.
The pharyngeal branches, for the most part, pass inwards to the pharynx. One or two small and variable branches ramify in the middle and inferior constrictors. Higher up than these is a larger and more regular branch, which runs upon the upper constrictor, and sends small ramifications to the Eustachian tube, the soft palate, and the tonsil.
This last-named, or palatine branch, is sometimes of considerable size, and supplies the soft palate, taking the place of the inferior palatine branch of the facial artery, which, in such cases, is small. The arrangement of this artery of the palate is as follows. After passing above the superior constrictor it divides into two branches, of which one arches across the upper part of the soft palate, running beneath the mucous membrane on its fore part ; whilst the other and larger branch is disposed in a similar manner near the free margin of the same part, both vessels anastomosing with those of the opposite side. Other small branches likewise ramify beneath the mucous membrane behind the soft palate.
The external branches of the pharyngeal artery consist of very small and irregular vessels, which are distributed to the following parts, viz. — the rectus anticus muscle, the first cervical ganglion of the sympathetic nerve, some of the cerebral nerves as they issue from the skull, and the lymphatic glands of the neck. Some of them anastomose with the ascending cervical branch of the subclavian artery.
The meningeal branches, the terminal branches of the ascending pharyngeal artery, are those which pass through the foramina at the base of the skull : one or two of them accompany the internal jugular vein through the foramen lacerum posterius ; whilst another, which passes through the foramen lacerum medium basis cranii, enters the cranial cavity, and is distributed to the dura mater.
The place of origin of the pharyngeal from the external carotid artery varies considerably. It is not infrequently distant from the commencement of the external carotid less than half an inch, or more than one inch (the limits within which it has been stated to take its origin in most cases) and it is occasionally found to spring from the bifurcation of the common carotid. More- over, examples from time to time present themselves of this artery being given from an unusual source — as from the occipital or the internal carotid artery.
Two pharyngeal arteries have been observed in a few instances.