The External Carotid Artery

Anatomy > Gray's Anatomy of the Human Body > VI. The Arteries > 3a. 2. The External Carotid Artery

Henry Gray (1821–1865). Anatomy of the Human Body. 1918. 3a. 2. The External Carotid Artery (A. Carotis Externa) (Fig. 507).

The external carotid artery begins opposite the upper border of the thyroid cartilage, and, taking a slightly curved course, passes upward and forward, and then inclines backward to the space behind the neck of the mandible, where it divides into the superficial temporal and internal maxillary arteries. It rapidly diminishes in size in its course up the neck, owing to the number and large size of the branches given off from it. In the child, it is somewhat smaller than the internal carotid; but in the adult, the two vessels are of nearly equal size. At its origin, this artery is more superficial, and placed nearer the middle line than the internal carotid, and is contained within the carotid triangle. Relations—The external carotid artery is covered by the skin, superficial fascia, Platysma, deep fascia, and anterior margin of the Sternocleidomastoideus; it is crossed by the hypoglossal nerve, by the lingual, ranine, common facial, and superior thyroid veins; and by the Digastricus and Stylohyoideus; higher up it passes deeply into the substance of the parotid gland, where it lies deep to the facial nerve and the junction of the temporal and internal maxillary veins. Medial to it are the hyoid bone, the wall of the pharynx, the superior laryngeal nerve, and a portion of the parotid gland. Lateral to it, in the lower part of its course, is the internal carotid artery. Posterior to it, near its origin, is the superior laryngeal nerve; and higher up, it is separated from the internal carotid by the Styloglossus and Stylopharyngeus, the glossopharyngeal nerve, the pharyngeal branch of the vagus, and part of the parotid gland. Branches—The branches of the external carotid artery may be divided into four sets. Anterior Posterior Ascending Terminal Superior Thyroid. Occipital. Ascending Superficial Temporal. Lingual. Posterior Auricular. Pharyngeal. Internal Maxillary. External Maxillary. 1. The superior thyroid artery (a. thyreoidea superior) (Fig. 507) arises from the external carotid artery just below the level of the greater cornu of the hyoid bone and ends in the thyroid gland. Relations—From its origin under the anterior border of the Sternocleidomastoideus it runs upward and forward for a short distance in the carotid triangle, where it is covered by the skin, Platysma, and fascia; it then arches downward beneath the Omohyoideus, Sternohyoideus, and Sternothyreoideus. To its medial side are the Constrictor pharyngis inferior and the external branch of the superior laryngeal nerve. Branches—It distributes twigs to the adjacent muscles, and numerous branches to the thyroid gland, anastomosing with its fellow of the opposite side, and with the inferior thyroid arteries. The branches to the gland are generally two in number; one, the larger, supplies principally the anterior surface; on the isthmus of the gland it anastomoses with the corresponding artery of the opposite side: a second branch descends on the posterior surface of the gland and anastomoses with the inferior thyroid artery. Besides the arteries distributed to the muscles and to the thyroid gland, the branches of the superior thyroid are: Hyoid. Superior Laryngeal. Sternocleidomastoid. Cricothyroid. The Hyoid Branch (ramus hyoideus; infrahyoid branch) is small and runs along the lower border of the hyoid bone beneath the Thyreohyoideus and anastomoses with the vessel of the opposite side. The Sternocleidomastoid Branch (ramus sternocleidomastoideus; sternomastoid branch) runs downward and lateralward across the sheath of the common carotid artery, and supplies the Sternocleidomastoideus and neighboring muscles and integument; it frequently arises as a separate branch from the external carotid. The Superior Laryngeal Artery (a. laryngea superior), larger than either of the preceding, accompanies the internal laryngeal branch of the superior laryngeal nerve, beneath the Thyreohyoideus; it pierces the hyothyroid membrane, and supplies the muscles, mucous membrane, and glands of the larynx, anastomosing with the branch from the opposite side. The Cricothyroid Branch (ramus cricothyreoideus) is small and runs transversely across the cricothyroid membrane, communicating with the artery of the opposite side. 2. The lingual artery (a. lingualis) (Fig. 513) arises from the external carotid between the superior thyroid and external maxillary; it first runs obliquely upward and medialward to the greater cornu of the hyoid bone; it then curves downward and forward, forming a loop which is crossed by the hypoglossal nerve, and passing beneath the Digastricus and Stylohyoideus it runs horizontally forward, beneath the Hyoglossus, and finally, ascending almost perpendicularly to the tongue, turns forward on its lower surface as far as the tip, under the name of the profunda linguæ Relations—Its first, or oblique, portion is superficial, and is contained within the carotid triangle; it rests upon the Constrictor pharyngis medius, and is covered by the Platysma and the fascia of the neck. Its second, or curved, portion also lies upon the Constrictor pharyngis medius, being covered at first by the tendon of the Digastricus and by the Stylohyoideus, and afterward by the Hyoglossus. Its third, or horizontal, portion lies between the Hyoglossus and Genioglossus. The fourth, or terminal part, under the name of the profunda linguæ (ranine artery) runs along the under surface of the tongue to its tip; here it is superficial, being covered only by the mucous membrane; above it is the Longitudinalis inferior, and on the medial side the Genioglossus. The hypoglossal nerve crosses the first part of the lingual artery, but is separated from the second part by the Hyoglossus. 13 Branches—The branches of the lingual artery are: 14 Hyoid. Sublingual. Dorsales linguæ. Profunda linguæ. The Hyoid Branch (ramus hyoideus; suprahyoid branch) runs along the upper border of the hyoid bone, supplying the muscles attached to it and anastomosing with its fellow of the opposite side. 15 The Arteriæ Dorsales Linguæ (rami dorsales linguæ) consist usually of two or three small branches which arise beneath the Hyoglossus; they ascend to the back part of the dorsum of the tongue, and supply the mucous membrane in this situation, the glossopalatine arch, the tonsil, soft palate, and epiglottis; anastomosing with the vessels of the opposite side. 16 The Sublingual Artery (a. sublingualis) arises at the anterior margin of the Hyoglossus, and runs forward between the Genioglossus and Mylohyoideus to the sublingual gland. It supplies the gland and gives branches to the Mylohyoideus and neighboring muscles, and to the mucous membrane of the mouth and gums. One branch runs behind the alveolar process of the mandible in the substance of the gum to anastomose with a similar artery from the other side; another pierces the Mylohyoideus and anastomoses with the submental branch of the external maxillary artery. 17 The Arteria Profunda Linguæ (ranine artery; deep lingual artery) is the terminal portion of the lingual artery; it pursues a tortuous course and runs along the under surface of the tongue, below the Longitudinalis inferior, and above the mucous membrane; it lies on the lateral side of the Genioglossus, accompanied by the lingual nerve. At the tip of the tongue, it is said to anastomose with the artery of the opposite side, but this is denied by Hyrtl. In the mouth, these vessels are placed one on either side of the frenulum linguæ. 18 3. The external maxillary artery (a. maxillaris externa; facial artery) (Fig. 508), arises in the carotid triangle a little above the lingual artery and, sheltered by the ramus of the mandible, passes obliquely up beneath the Digastricus and Stylohyoideus, over which it arches to enter a groove on the posterior surface of the submaxillary gland. It then curves upward over the body of the mandible at the antero-inferior angle of the Masseter; passes forward and upward across the cheek to the angle of the mouth, then ascends along the side of the nose, and ends at the medial commissure of the eye, under the name of the angular artery This vessel, both in the neck and on the face, is remarkably tortuous: in the former situation, to accommodate itself to the movements of the pharynx in deglutition; and in the latter, to the movements of the mandible, lips, and cheeks. 19 Relations—In the neck its origin is superficial, being covered by the integument, Platysma, and fascia; it then passes beneath the Digastricus and Stylohyoideus muscles and part of the submaxillary gland, and frequently beneath the hypoglossal nerve. It lies upon the Constrictores pharyngis medius and superior, the latter of which separates it, at the summit of its arch, from the lower and back part of the tonsil. On the face where it passes over the body of the mandible, it is comparatively superficial, lying immediately beneath the Platysma. In its course over the face, it is covered by the integument, the fat of the cheek, and, near the angle of the mouth, by the Platysma, Risorius, and Zygomaticus. It rests on the Buccinator and Caninus, and passes either over or under the infraorbital head of the Quadratus labii superioris. The anterior facial vein lies lateral to the artery, and takes a more direct course across the face, where it is separated from the artery by a considerable interval. In the neck it lies superficial to the artery. The branches of the facial nerve cross the artery from behind forward. 20

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FIG. 508– The arteries of the face and scalp. 98 (Picture From the Classic Gray's Anatomy) ]] Branches'—The branches of the artery may be divided into two sets: those given off in the neck (cervical), and those on the face (facial''). 21 Cervical Branches Facial Branches Ascending Palatine. Inferior Labial. Tonsillar. Superior Labial. Glandular. Lateral Nasal. Submental. Angular. Muscular. Muscular. The Ascending Palatine Artery (a. palatina ascendens) (Fig. 513) arises close to the origin of the external maxillary artery and passes up between the Styloglossus and Stylopharyngeus to the side of the pharynx, along which it is continued between the Constrictor pharyngis superior and the Pterygoideus internus to near the base of the skull. It divides near the Levator veli palatini into two branches: one follows the course of this muscle, and, winding over the upper border of the Constrictor pharyngis superior, supplies the soft palate and the palatine glands, anastomosing with its fellow of the opposite side and with the descending palatine branch of the internal maxillary artery; the other pierces the Constrictor pharyngis superior and supplies the palatine tonsil and auditory tube, anastomosing with the tonsillar and ascending pharyngeal arteries. 22 The Tonsillar Branch (ramus tonsillaris) (Fig. 513) ascends between the Pterygoideus internus and Styloglossus, and then along the side of the pharynx, perforating the Constrictor pharyngis superior, to ramify in the substance of the palatine tonsil and root of the tongue. 23 The Glandular Branches (rami glandulares; submaxillary branches) consist of three or four large vessels, which supply the submaxillary gland, some being prolonged to the neighboring muscles, lymph glands, and integument. 24 The Submental Artery (a. submentalis) the largest of the cervical branches, is given off from the facial artery just as that vessel quits the submaxillary gland: it runs forward upon the Mylohyoideus, just below the body of the mandible, and beneath the Digastricus. It supplies the surrounding muscles, and anastomoses with the sublingual artery and with the mylohyoid branch of the inferior alveolar; at the symphysis menti it turns upward over the border of the mandible and divides into a superficial and a deep branch. The superficial branch passes between the integument and Quadratus labii inferioris, and anastomoses with the inferior labial artery; the deep branch runs between the muscle and the bone, supplies the lip, and anastomoses with the inferior labial and mental arteries. 25

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FIG. 509– The labial coronary arteries, the glands of the lips, and the nerves of the right side seen from the posterior surface after removal of the mucous membrane. (Poirier and Charpy.) (Picture From the Classic Gray's Anatomy) The Inferior Labial Artery (a. labialis inferior; inferior coronary artery) arises near the angle of the mouth; it passes upward and forward beneath the Triangularis and, penetrating the Orbicularis oris, runs in a tortuous course along the edge of the lower lip between this muscle and the mucous membrane. It supplies the labial glands, the mucous membrane, and the muscles of the lower lip; and anastomoses with the artery of the opposite side, and with the mental branch of the inferior alveolar artery. 26 The Superior Labial Artery (a. labialis superior; superior coronary artery) is larger and more tortuous than the inferior. It follows a similar course along the edge of the upper lip, lying between the mucous membrane and the Orbicularis oris, and anastomoses with the artery of the opposite side. It supplies the upper lip, and gives off in its course two or three vessels which ascend to the nose; a septal branch ramifies on the nasal septum as far as the point of the nose, and an alar branch supplies the ala of the nose. 27 The Lateral Nasal branch is derived from the external maxillary as that vessel ascends along the side of the nose. It supplies the ala and dorsum of the nose, anastomosing with its fellow, with the septal and alar branches, with the dorsal nasal branch of the ophthalmic, and with the infraorbital branch of the internal maxillary. 28 The Angular Artery (a. angularis) is the terminal part of the external maxillary; it ascends to the medial angle of the orbit, imbedded in the fibers of the angular head of the Quadratus labii superioris, and accompanied by the angular vein. On the cheek it distributes branches which anastomose with the infraorbital; after supplying the lacrimal sac and Orbicularis oculi, it ends by anastomosing with the dorsal nasal branch of the ophthalmic artery. 29 The Muscular Branches in the neck are distributed to the Pterygoideus internus and Stylohyoideus, and on the face to the Masseter and Buccinator. The anastomoses of the external maxillary artery are very numerous, not only with the vessel of the opposite side, but, in the neck with the sublingual branch of the lingual, with the ascending pharyngeal, and by its ascending palatine and tonsillar branches with the palatine branch of the internal maxillary; on the face with the mental branch of the inferior alveolar as it emerges from the mental foramen, with the transverse facial branch of the superficial temporal, with the infraorbital branch of the internal maxillary, and with the dorsal nasal branch of the ophthalmic. 30 Peculiarities—The external maxillary artery not infrequently arises in common with the lingual. It varies in its size and in the extent to which it supplies the face; it occasionally ends as the submental, and not infrequently extends only as high as the angle of the mouth or nose. The deficiency is then compensated for by enlargement of one of the neighboring arteries. 31 4. The occipital artery (a. occipitalis) (Fig. 508) arises from the posterior part of the external carotid, opposite the external maxillary, near the lower margin of the posterior belly of the Digastricus, and ends in the posterior part of the scalp. 32 Course and Relations—At its origin, it is covered by the posterior belly of the Digastricus and the Stylohyoideus, and the hypoglossal nerve winds around it from behind forward; higher up, it crosses the internal carotid artery, the internal jugular vein, and the vagus and accessory nerves. It next ascends to the interval between the transverse process of the atlas and the mastoid process of the temporal bone, and passes horizontally backward, grooving the surface of the latter bone, being covered by the Sternocleidomastoideus, Splenius capitis, Longissimus capitis, and Digastricus, and resting upon the Rectus capitis lateralis, the Obliquus superior, and Semispinalis capitis. It then changes its course and runs vertically upward, pierces the fascia connecting the cranial attachment of the Trapezius with the Sternocleidomastoideus, and ascends in a tortuous course in the superficial fascia of the scalp, where it divides into numerous branches, which reach as high as the vertex of the skull and anastomose with the posterior auricular and superficial temporal arteries. Its terminal portion is accompanied by the greater occipital nerve. 33 Branches—The branches of the occipital artery are: 34 Muscular. Sternocleidomastoid. Auricular.

Meningeal. Descending. The Muscular Branches (rami musculares) supply the Digastricus, Stylohyoideus, Splenius, and Longissimus capitis. 35 The Sternocleidomastoid Artery (a. sternocleidomastoidea; sternomastoid artery) generally arises from the occipital close to its commencement, but sometimes springs directly from the external carotid. It passes downward and backward over the hypoglossal nerve, and enters the substance of the muscle, in company with the accessory nerve. 36 The Auricular Branch (ramus auricularis) supplies the back of the concha and frequently gives off a branch, which enters the skull through the mastoid foramen and supplies the dura mater, the diploë, and the mastoid cells; this latter branch sometimes arises from the occipital artery, and is then known as the mastoid branch 37 The Meningeal Branch (ramus meningeus; dural branch) ascends with the internal jugular vein, and enters the skull through the jugular foramen and condyloid canal, to supply the dura mater in the posterior fossa. 38 The Descending Branch (ramus descendens; arteria princeps cervicis) (Fig. 513), the largest branch of the occipital, descends on the back of the neck, and divides into a superficial and deep portion. The superficial portion runs beneath the Splenius, giving off branches which pierce that muscle to supply the Trapezius and anastomose with the ascending branch of the transverse cervical: the deep portion runs down between the Semispinales capitis and colli, and anastomoses with the vertebral and with the a. profunda cervicalis, a branch of the costocervical trunk. The anastomosis between these vessels assists in establishing the collateral circulation after ligature of the common carotid or subclavian artery. 39 The terminal branches of the occipital artery are distributed to the back of the head: they are very tortuous, and lie between the integument and Occipitalis, anastomosing with the artery of the opposite side and with the posterior auricular and temporal arteries, and supplying the Occipitalis, the integument, and pericranium. One of the terminal branches may give off a meningeal twig which passes through the parietal foramen. 40 5. The posterior auricular artery (a. auricularis posterior) (Fig. 508) is small and arises from the external carotid, above the Digastricus and Stylohyoideus, opposite the apex of the styloid process. It ascends, under cover of the parotid gland, on the styloid process of the temporal bone, to the groove between the cartilage of the ear and the mastoid process, immediately above which it divides into its auricular and occipital branches. 41 Branches—Besides several small branches to the Digastricus, Stylohyoideus, and Sternocleidomastoideus, and to the parotid gland, this vessel gives off three branches: 42 Stylomastoid. Auricular. Occipital. The Stylomastoid Artery (a. stylomastoidea) enters the stylomastoid foramen and supplies the tympanic cavity, the tympanic antrum and mastoid cells, and the semicircular canals. In the young subject a branch from this vessel forms, with the anterior tympanic artery from the internal maxillary, a vascular circle, which surrounds the tympanic membrane, and from which delicate vessels ramify on that membrane. It anastomoses with the superficial petrosal branch of the middle meningeal artery by a twig which enters the hiatus canalis facialis. 43 The Auricular Branch (ramus auricularis) ascends behind the ear, beneath the Auricularis posterior, and is distributed to the back of the auricula, upon which it ramifies minutely, some branches curving around the margin of the cartilage, others perforating it, to supply the anterior surface. It anastomoses with the parietal and anterior auricular branches of the superficial temporal. 44 The Occipital Branch (ramus occipitalis) passes backward, over the Sternocleidomastoideus, to the scalp above and behind the ear. It supplies the Occipitalis and the scalp in this situation and anastomoses with the occipital artery. 45 6. The ascending pharyngeal artery (a. pharyngea ascendens) (Fig. 513), the smallest branch of the external carotid, is a long, slender vessel, deeply seated in the neck, beneath the other branches of the external carotid and under the Stylopharyngeus. It arises from the back part of the external carotid, near the commencement of that vessel, and ascends vertically between the internal carotid and the side of the pharynx, to the under surface of the base of the skull, lying on the Longus capitis. 46 Branches—Its branches are: 47 Pharyngeal. Prevertebral. Palatine. Inferior Tympanic. Posterior Meningeal. The Pharyngeal Branches (rami pharyngei) are three or four in number. Two of these descend to supply the Constrictores pharyngis medius and inferior and the Stylopharyngeus, ramifying in their substance and in the mucous membrane lining them. 48 The Palatine Branch varies in size, and may take the place of the ascending palatine branch of the facial artery, when that vessel is small. It passes inward upon the Constrictor pharyngis superior, sends ramifications to the soft palate and tonsil, and supplies a branch to the auditory tube. 49 The Prevertebral Branches are numerous small vessels, which supply the Longi capitis and colli, the sympathetic trunk, the hypoglossal and vagus nerves, and the lymph glands; they anastomose with the ascending cervical artery. 50 The Inferior Tympanic Artery (a. tympanica inferior) is a small branch which passes through a minute foramen in the petrous portion of the temporal bone, in company with the tympanic branch of the glossopharyngeal nerve, to supply the medial wall of the tympanic cavity and anastomose with the other tympanic arteries. 51 The Meningeal Branches are several small vessels, which supply the dura mater. One, the posterior meningeal enters the cranium through the jugular foramen; a second passes through the foramen lacerum; and occasionally a third through the canal for the hypoglossal nerve. 52 7. The superficial temporal artery (a. temporalis superficialis) (Fig. 508), the smaller of the two terminal branches of the external carotid, appears, from its direction, to be the continuation of that vessel. It begins in the substance of the parotid gland, behind the neck of the mandible, and corsses over the posterior root of the zygomatic process of the temporal bone; about 5 cm. above this process it divides into two branches, a frontal and a parietal. 53 Relations—As it crosses the zygomatic process, it is covered by the Auricularis anterior muscle, and by a dense fascia; it is crossed by the temporal and zygomatic branches of the facial nerve and one or two veins, and is accompanied by the auriculotemporal nerve, which lies immediately behind it. 54 Branches—Besides some twigs to the parotid gland, to the temporomandibular joint, and to the Masseter muscle, its branches are: 55 Transverse Facial. Anterior Auricular. Middle Temporal. Frontal. Parietal. The Transverse Facial Artery (a. transversa faciei) is givien off from the superficial temporal before that vessel quits the parotid gland; running forward through the substance of the gland, it passes transversely across the side of the face, between the parotid duct and the lower border of the zygomatic arch, and divides into numerous branches, which supply the parotid gland and duct, the Masseter, and the integument, and anastomose with the external maxillary, masseteric, buccinator, and infraorbital arteries. This vessel rests on the Masseter, and is accompanied by one or two branches of the facial nerve. 56 The Middle Temporal Artery (a. temporalis media) arises immediately above the zygomatic arch, and, perforating the temporal fascia, gives branches to the Temporalis, anastomosing with the deep temporal branches of the internal maxillary. It occasionally gives off a zygomaticoörbital branch which runs along the upper border of the zygomatic arch, between the two layers of the temporal fascia, to the lateral angle of the orbit. This branch, which may arise directly from the superficial temporal artery, supplies the Orbicularis oculi, and anastomoses with the lacrimal and palpebral branches of the ophthalmic artery. 57 The Anterior Auricular Branches (rami auriculares anteriores) are distributed to the anterior portion of the auricula, the lobule, and part of the external meatus, anastomosing with the posterior auricular. 58 The Frontal Branch (ramus frontalis; anterior temporal) runs tortuously upward and forward to the forehead, supplying the muscles, integument, and pericranium in this region, and anastomosing with the supraorbital and frontal arteries. 59 The Parietal Branch (ramus parietalis; posterior temporal) larger than the frontal, curves upward and backward on the side of the head, lying superficial to the temporal fascia, and anastomosing with its fellow of the opposite side, and with the posterior auricular and occipital arteries. 60

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FIG. 510– Plan of branches of internal maxillary artery. (Picture From the Classic Gray's Anatomy) 8. The internal maxillary artery (a. maxillaris interna) (Fig. 510), the larger of the two terminal branches of the external carotid, arises behind the neck of the mandible, and is at first imbedded in the substance of the parotid gland; it passes forward between the ramus of the mandible and the sphenomandibular ligament, and then runs, either superficial or deep to the Pterygoideus externus, to the pterygopalatine fossa. It supplies the deep structures of the face, and may be divided into mandibular, pterygoid and pterygopalatine portions 61 The first or mandibular portion passes horizontally forward, between the ramus of the mandible and the sphenomandibular ligament, where it lies parallel to and a little below the auriculotemporal nerve; it crosses the inferior alveolar nerve, and runs along the lower border of the Pterygoideus externus. 62 The second or pterygoid portion runs obliquely forward and upward under cover of the ramus of the mandible and insertion of the Temporalis, on the superficial (very frequently on the deep) surface of the Pterygoideus externus; it then passes between the two heads of origin of this muscle and enters the fossa. 63 The third or pterygopalatine portion lies in the pterygopalatine fossa in relation with the sphenopalatine ganglion. 64 The branches of this vessel may be divided into three groups (Fig. 511), corresponding with its three divisions. 65 Branches of the First or Mandibular Portions Anterior Tympanic. Middle Meningeal. Deep Auricular. Accessory Meningeal Inferior Alveolar. The Anterior Tympanic Artery (a. tympanica anterior; tympanic artery) passes upward behind the temporomandibular articulation, enters the tympanic cavity through the petrotympanic fissure, and ramifies upon the tympanic membrane, forming a vascular circle around the membrane with the stylomastoid branch of the posterior auricular, and anastomosing with the artery of the pterygoid canal and with the caroticotympanic branch from the internal carotid. 66

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FIG. 511– Plan of branches of internal maxillary artery. (Picture From the Classic Gray's Anatomy) The Deep Auricular Artery (a. auricularis profunda) often arises in common with the preceding. It ascends in the substance of the parotid gland, behind the temporomandibular articulation, pierces the cartilaginous or bony wall of the external acoustic meatus, and supplies its cuticular lining and the outer surface of the tympanic membrane. It gives a branch to the temporomandibular joint. 67 The Middle Meningeal Artery (a. meningea media; medidural artery) is the largest of the arteries which supply the dura mater. It ascends between the sphenomandibular ligament and the Pterygoideus externus, and between the two roots of the auriculotemporal nerve to the foramen spinosum of the sphenoid bone, through which it enters the cranium; it then runs forward in a groove on the great wing of the sphenoid bone, and divides into two branches, anterior and posterior. The anterior branch the larger, crosses the great wing of the sphenoid, reaches the groove, or canal, in the sphenoidal angle of the parietal bone, and then divides into branches which spread out between the dura mater and internal surface of the cranium, some passing upward as far as the vertex, and others backward to the occipital region. The posterior branch curves backward on the squama of the temporal bone, and, reaching the parietal some distance in front of its mastoid angle, divides into branches which supply the posterior part of the dura mater and cranium. The branches of the middle meningeal artery are distributed partly to the dura mater, but chiefly to the bones; they anastomose with the arteries of the opposite side, and with the anterior and posterior meningeal. 68 The middle meningeal on entering the cranium gives off the following branches: (1) Numerous small vessels supply the semilunar ganglion and the dura mater in this situation. (2) A superficial petrosal branch enters the hiatus of the facial canal, supplies the facial nerve, and anastomoses with the stylomastoid branch of the posterior auricular artery. (3) A superior tympanic artery runs in the canal for the Tensor tympani, and supplies this muscle and the lining membrane of the canal. (4) Orbital branches pass through the superior orbital fissure or through separate canals in the great wing of the sphenoid, to anastomose with the lacrimal or other branches of the ophthalmic artery. (5) Temporal branches pass through foramina in the great wing of the sphenoid, and anastomose in the temporal fossa with the deep temporal arteries. 69 The Accessory Meningeal Branch (ramus meningeus accessorius; small meningeal or parvidural branch) is sometimes derived from the preceding. It enters the skull through the foramen ovale, and supplies the semilunar ganglion and dura mater. 70 The Inferior Alveolar Artery (a. alveolaris inferior; inferior dental artery) descends with the inferior alveolar nerve to the mandibular foramen on the medial surface of the ramus of the mandible. It runs along the mandibular canal in the substance of the bone, accompanied by the nerve, and opposite the first premolar tooth divides into two branches, incisor and mental. The incisor branch is continued forward beneath the incisor teeth as far as the middle line, where it anastomoses with the artery of the opposite side; the mental branch escapes with the nerve at the mental foramen, supplies the chin, and anastomoses with the submental and inferior labial arteries. Near its origin the inferior alveolar artery gives off a lingual branch which descends with the lingual nerve and supplies the mucous membrane of the mouth. As the inferior alveolar artery enters the foramen, it gives off a mylohyoid branch which runs in the mylohyoid groove, and ramifies on the under surface of the Mylohyoideus. The inferior alveolar artery and its incisor branch during their course through the substance of the bone give off a few twigs which are lost in the cancellous tissue, and a series of branches which correspond in number to the roots of the teeth: these enter the minute apertures at the extremities of the roots, and supply the pulp of the teeth. 71 Branches of the Second or Pterygoid Portion— 72 Deep Temporal. Masseteric. Pterygoid. Buccinator. The Deep Temporal Branches two in number, anterior and posterior ascend between the Temporalis and the pericranium; they supply the muscle, and anastomose with the middle temporal artery; the anterior communicates with the lacrimal artery by means of small branches which perforate the zygomatic bone and great wing of the sphenoid. 73 The Pterygoid Branches (rami pterygoidei), irregular in their number and origin, supply the Pterygoidei. 74 The Masseteric Artery (a. masseterica) is small and passes lateralward through the mandibular notch to the deep surface of the Masseter. It supplies the muscle, and anastomoses with the masseteric branches of the external maxillary and with the transverse facial artery. 75 The Buccinator Artery (a. buccinatoria; buccal artery) is small and runs obliquely forward, between the Pterygoideus internus and the insertion of the Temporalis, to the outer surface of the Buccinator, to which it is distributed, anastomosing with branches of the external maxillary and with the infraorbital. 76 Branches of the Third or Pterygopalatine Portion— 77 Posterior Superior Alveolar. Artery of the Pterygoid Canal. Infraorbital. Pharyngeal. Descending Palatine. Sphenopalatine. The Posterior Superior Alveolar Artery (a. alveolaris superior posterior; alveolar or posterior dental artery) is given off from the internal maxillary, frequently in conjunction with the infraorbital just as the trunk of the vessel is passing into the pterygopalatine fossa. Descending upon the tuberosity of the maxilla, it divides into numerous branches, some of which enter the alveolar canals, to supply the molar and premolar teeth and the lining of the maxillary sinus, while others are continued forward on the alveolar process to supply the gums. 78 The Infraorbital Artery (a. infraorbitalis) appears, from its direction, to be the continuation of the trunk of the internal maxillary, but often arises in conjunction with the posterior superior alveolar. It runs along the infraorbital groove and canal with the infraorbital nerve, and emerges on the face through the infraorbital foramen, beneath the infraorbital head of the Quadratus labii superioris. While in the canal, it gives off ('a') orbital branches which assist in supplying the Rectus inferior and Obliquus inferior and the lacrimal sac, and ('b') anterior superior alveolar branches which descend through the anterior alveolar canals to supply the upper incisor and canine teeth and the mucous membrane of the maxillary sinus. On the face, some branches pass upward to the medial angle of the orbit and the lacrimal sac, anastomosing with the angular branch of the external maxillary artery; others run toward the nose, anastomosing with the dorsal nasal branch of the ophthalmic; and others descend between the Quadratus labii superioris and the Caninus, and anastomose with the external maxillary, transverse facial, and buccinator arteries. The four remaining branches arise from that portion of the internal maxillary which is contained in the pterygopalatine fossa. 79 The Descending Palatine Artery (a. palatina descendens) descends through the pterygopalatine canal with the anterior palatine branch of the sphenopalatine ganglion, and, emerging from the greater palatine foramen, runs forward in a groove on the medial side of the alveolar border of the hard palate to the incisive canal; the terminal branch of the artery passes upward through this canal to anastomose with the sphenopalatine artery. Branches are distributed to the gums, the palatine glands, and the mucous membrane of the roof of the mouth; while in the pterygopalatine canal it gives off twigs which descend in the lesser palatine canals to supply the soft palate and palatine tonsil, anastomosing with the ascending palatine artery. 80 The Artery of the Pterygoid Canal (a. canalis pterygoidei; Vidian artery) passes backward along the pterygoid canal with the corresponding nerve. It is distributed to the upper part of the pharynx and to the auditory tube, sending into the tympanic cavity a small branch which anastomoses with the other tympanic arteries. 81 The Pharyngeal Branch is very small; it runs backward through the pharyngeal canal with the pharyngeal nerve, and is distributed to the upper part of the pharynx and to the auditory tube. 82 The Sphenopalatine Artery (a. sphenopalatina; nasopalatine artery) passes through the sphenopalatine foramen into the cavity of the nose, at the back part of the superior meatus. Here it gives off its posterior lateral nasal branches which spread forward over the conchæ and meatuses, anastomose with the ethmoidal arteries and the nasal branches of the descending palatine, and assist in supplying the frontal, maxillary, ethmoidal, and sphenoidal sinuses. Crossing the under surface of the sphenoid the sphenopalatine artery ends on the nasal septum as the posterior septal branches these anastomose with the ethmoidal arteries and the septal branch of the superior labial; one branch descends in a groove on the vomer to the incisive canal and anastomoses with the descending palatine artery. 83 Note 98 The muscular tissue of the lips must be supposed to have been cut away, in order to show the course of the labial arteries.

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