Anterior triangle of the neck - Wikiwand
Lucy Watson flaunts her perky posterior in sizzling throwback as she jokes about preparing for. Posterior triangle neck boundaries in dating danny Pelosi was. as an important landmark in forming boundaries of posterior triangle of neck. of our knowledge has not been found any anatomy literature available till date). The posterior triangle is divided by the inferior belly of the omohyoid muscle into an occipital triangle superior to it and a.
It crosses the transverse process of the atlas, descends deep to the styloid process and the posterior belly of the digastric, and usually pierces the sternomastoid, which it supplies. At the middle of the posterior border of the sternomastoid muscle, the accessory nerve crosses the posterior triangle of the neck obliquely see fig. It passes deep to the anterior border of the trapezius and supplies that muscle. The nerve communicates with cervical nerves The spinal part of the accessory nerve is tested by asking the subject to shrug the shoulders trapezius and then to rotate the head sternomastoid.
It emerges from the brain stem medulla and traverses the hypoglossal canal of the occipital bone. It then descends between the internal carotid artery and the internal jugular vein, deep to the posterior belly of the digastric. The hypoglossal nerve loops anteriorly around the occipital artery and crosses the internal carotid, external carotid, and lingual arteries see figs. It courses lateral to the hyoglossus and passes deep to the digastric and mylohyoid muscles see fig. Most of the branches of the hypoglossal nerve are hypoglossal in origin, whereas others are spinal and are merely travel with the hypoglossal nerve for a short distance.
The meningeal branches, the superior root of the ansa cervicalis, the nerve to the thyrohyoid muscle, and the branch to the geniohyoid muscle consist of cervical fibers.
The branches of the hypoglossal nerve are described in the following paragraphs: Meningeal branches supply the dura of the posterior cranial fossa. The superior root of the ansa cervicalis descends from the hypoglossal nerve to the ansa cervicalis and supplies infrahyoid muscles see fig. The thyrohyoid branch arises in the carotid triangle and supplies the thyrohyoid muscle. The terminal lingual branches supply the extrinsic except the palatoglossus and all intrinsic muscles of the tongue and communicate with the lingual nerve.
The hypoglossal nerve is tested by asking the subject to protrude the tongue genioglossus and intrinsic muscles. A lesion of one hypoglossal nerve would result in deviation of the protruded tongue toward the affected same side. The territory supplied by the subclavian artery extends as far as the forebrain, abdominal wall, and fingers. The left subclavian artery arises directly from the arch of the aorta, whereas the right subclavian is from the brachiocephalic trunk.
The course of each subclavian artery may be considered in three parts: The first part arches superiorly and laterally from posterior to the sternoclavicular joint and is deeply placed under cover of the sternomastoid, sternohyoid, and sternothyroid muscles. The second part of the subclavian artery extends a few centimeters superior to the clavicle.
It lies anterior to the apex of the lung and cupola of the parietal pleura. The third part of the subclavian artery is the most superficial, and its pulsations can be felt on deep pressure.
It lies mainly in the supraclavicular triangle, on the first rib see fig. It can be compressed against the first rib by pressing downward, backward, and medially in the angle between the clavicle and the posterior border of the sternomastoid muscle see fig.
This is also the site of ligation, after which the collateral circulation to the upper limb is generally adequate. The subclavian vein, which is the continuation of the axillary vein, passes anterior to the anterior scalene and unites with the internal jugular vein to form the brachiocephalic vein.
Most of the branches arise from the first part of the subclavian artery. They are described in the following paragraphs: The vertebral artery fig. Arising medial to the anterior scalene, it ascends through the foramina transversaria of the C6 to C1 vertebrae, passes posterior to the lateral mass of the atlas see fig.
It penetrates the posterior atlantooccital membrane and enters the cranial cavity by passing superiorly through the foramen magnum.
The Posterior Triangle of the Neck
At the lower border of the pons, it unites with the vessel of the opposite side to form the basilar artery, which ends by dividing into the two posterior cerebral arteries.
The course of the vertebral artery may be considered in four parts: The cervical part ascends posterior to the common carotid artery in the pyramidal space between the longus colli and anterior scalene see Fig.
The vertebral part ofthe artery, accompanied by a venous plexus and sympathetic nerve fibers, gives branches to the spinal cord and vertebrae. The suboccipital and intracranial parts of the vertebral artery have been described already. The internal thoracic artery is described with the thorax.
The thyrocervical trunk divides almost at once into three branches: It is closely related to the middle cervical ganglion and the recurrent laryngeal nerve. It enters the posterior surface of the thyroid gland.
The inferior thyroid artery gives branches to the vertebrae ascending cervical arterylarynx inferior laryngeal arterytrachea, pharynx, esophagus, and thyroid gland. It gives off suprasternal, acromial, and articular branches.
It supplies the trapezius as the superficial cervical artery. The costocervical trunk arches over the cupola of the parietal pleura to reach the neck of the first rib, where it divides into two branches: The dorsal scapular artery generally passes between the trunks of the brachial plexus and accompanies the dorsal scapular nerve to the rhomboid muscles. It may, however, be replaced by a deep branch of the transverse cervical artery.
Abnormal compression of the subclavian or axillary vessels, the brachial plexus, or both produces the signs and symptoms of the "neurovascular compression syndromes" of the upper limb often generically called "thoracic outlet syndromes".
The features of vascular compomise may include pain, paresthesia pricklingnumbness, weakness, discoloration, swelling, ulceration, and gangrene, may be produced also by other causes. The neurovascular bundle to the upper limb is liable to be compressed: Cupola of pleura see fig. It begins at the inlet of the thorax along the sloping internal border ofthe first rib see fig. The cupola and apex of the lung project into the root of the neck up to about 3 cm above the medial third of the clavicle.
The cupola is covered by fascia, the suprapleural membrane attached to the first rib and to C.
The Anterior Triangle of the Neck
The cupola and apex of the lung occupy the pyramidal interval between the scalene muscles and the longus colli and are posterior to the subclavian vessels and anterior scalene.
Sympathetic trunk see figs. The preganglionic fibers leave in the ventral roots and pass through rami communicantes to the thoracic part of the sympathetic trunk. They then ascend to the cervical part of the sympathetic trunk, where they synapse. Postganglionic fibers are distributed to the blood vessels, smooth muscle, and glands of the head and neck. The cervical part of the sympathetic trunk consists of three or four ganglia connected by an intervening cord or cords. Postganglionic fibers leave the trunk by gray rami communicantes and also in branches that go directly to blood vessels or viscera.
Any cause of interruption of sympathetic nerve impulses to the head, including damage to the cervical part of the sympathetic trunk, produces Horner's syndrome: The preganglionic fibers for the eye and orbit are probably from T1 range: C8 to T4and they probably enter the cervicothoracic ganglion.
A local anesthetic injected near the cervicothoracic ganglion will "block" the cervical and upper thoracic ganglia stellate ganglion blockthereby relieving vascular spasm involving the brain or an upper limb.
Cervical ganglia see figs. The superior cervical ganglion lies inferior to the base of the skull and posterior to the internal carotid artery. It distributes postganglionic fibers to cranial nerves IX-XII and cervical nervesthe carotid sinus and body, the pharyngeal plexus and larynx, and the heart. A plexus on the external carotid artery is continued on its branches to the salivary glands.
A large ascending branch from the ganglion, the internal carotid nerve, accompanies the internal carotid artery and forms a plexus that contributes to several cranial nerves, the tympanic and greater petrosal nerves, the ciliary ganglion pupillodilator fibersand the anterior and middle cerebral arteries. The middle cervical ganglion, usually superior to the arch of the inferior thyroid artery, is very variable.
The vertebral ganglion generally lies anterior to the vertebral artery and inferior to the arch of the inferior thyroid artery. Cords connect this ganglion with those above and below, and another cord, the ansa subclavia, loops around and forms a plexus on the first part of the subclavian artery. The cervicothoracic stellate ganglion comprises two variably fused components: It lies posterior to the vertebral artery and anterior to the C7 transverse process and the neck of the first rib. Preganglionic rami come from the T1 nerve, and postganglionic gray rami go to cervical nerves and the T1 nerve.
These fibers enter the brachial plexus and are distributed to the upper limb. Other branches of the ganglion go to the heart and to the subclavian and vertebral arteries. The vertebral plexus is ultimately distributed along the basilar artery. The plexuses on the posterior cerebral arteries may be derived from the vertebral or internal carotid plexuses. Internal jugular vein fig. It commences in the jugular foramen as the continuation of the sigmoid sinus.
At the base of the skull, the internal carotid artery in the carotid canal lies anterior to the internal jugular vein in the jugular foramenand the two vessels are there separated by cranial nerves IX-XII see fig.
The internal jugular vein descends in the carotid sheath and is hidden by the sternomastoid muscle. The internal and common carotid arteries accompany the vein medially, and the vagus lies posterior to and between the vein and the arteries.
The deep cervical lymph nodes lie along the course of the internal jugular vein. The vein passes deep to the interval between the two heads of the sternomastoid muscle see fig. Dilatations are found at its beginning and near its end superior and inferior bulbs. The tributaries, which are variable, include the inferior petrosal sinus and the pharyngeal, lingual, and superior and middle thyroid veins.
The right lymphatic duct or on the left the thoracic duct opens usually into the internal jugular vein at or near its junction with the subclavian vein.
CHAPTER THE NECK
Thoracic duct The thoracic duct receives the lymph from most of the body, including the left side of the head and neck. It receives the left jugular trunk and ends variably anterior to the first part of the left subclavian artery in or near the angle between the left internal jugular and subclavian veins.
The right lymphatic duct receives the lymph from the right side of the head and neck, right upper limb, and right side of the thorax. This duct, which is seldom present as a single structure fig. Lymphatic drainage of head and neck All the lymphatic vessels from the head and neck drain into the deep cervical nodes, either 1 directly from the tissues or 2 indirectly after traversing a more superficial group of nodes.
Several of these groups of lymph nodes form a "pericervical collar" at the junction of the head and neck fig. The superficial tissues drain into these groups and also into the superficial cervical nodes.
The superficial cervical nodes are in 1 the posterior triangle along the external jugular vein and 2 the anterior triangle along the anterior jugular vein. The deep cervical nodes include several groups, the most important of which forms a chain along the internal jugular vein, mostly under cover of the sternomastoid muscle.
The jugulodigastric node lies on the internal jugular vein immediately inferior to the posterior belly of the digastric. It receives important afferents from the posterior tongue and from the tonsils. The jugulo-omohyoid node lies on the vein immediately superior to the middle tendon of the omohyoid. It receives afferents from the tongue.
One group of deep nodes is found in the posterior triangle and is related to the accessory nerve. Other groups are prelaryngeal, pretracheal, paratracheal, and retropharyngeal. These take part in the drainage of deeper structures e. The efferent vessels from the deep cervical nodes form the jugular trunk, which usually joins the thoracic duct on the left and enters the internal jugular-subclavian junction on the right.
Cervical plexus The ventral rami of cervical nerves unite to form the cervical plexus, whereas those of cervical nerves and the first thoracic nerve form the brachial plexus. The cervical plexus is an irregular series of loops from which the branches arise. Cutaneous areas and muscles are thereby supplied by more than one spinal nerve table The cutaneous branches all emerge near the middle of the posterior border of the sternomastoid muscle see fig.
The cervical plexus lies anterior to the levator scapulae and middle scalene, under cover of the internal jugular vein and the sternomastoid. The ventral rami receive postganglionic rami communicantes from the cervical sympathetic ganglia. The ansa cervicalis is a loop on or in the carotid sheath. It is formed by fibers of cervical nerves see figs.
It has a superior root, which descends from the hypoglossal nerve but consists of spinal fibersand an inferior root, which connects the ansa with cervcial nerves 2 and 3. The ansa and its superior root supply the infrahyoid muscles but the thyrohyoid receives its cervical fibers directly from the hypoglossal nerve. The phrenic nerve arises chiefly from C4 and supplies the diaphragm and the serosa of the thorax and abdomen.
It often has a root from C3 and usually an accessory root from C5 see fig. The phrenic nerve, formed at the lateral border of the anterior scalene, descends on the anterior surface of that muscle see fig.
It lies deep to the prevertebral fascia, is crossed by the transverse cervical and suprascapular arteries fig. It passes between the subclavian artery and vein see fig. Damage to the phrenic nerve collapses a lung by paralyzing and thereby elevating the hemidiaphragm. The subclavian artery passes posterior to the anterior scalene, whereas the phrenic nerve lies on the muscle. The anterior scalene arises from the anterior tubercles; the middle and posterior scalene the latter often absent or blended with the middle arise from the posterior tubercles of the cervical transverse processes.
The ventral rami of the cervical nerves emerge between the anterior and posterior tubercles; hence the brachial plexus emerges between the anterior scalene and the middle scalene. The scalenes may act as muscles of inspiration even during quiet breathing; they become active during strong expiratory effects, and they may be important in coughing and straining.
A pyramidal interval occurs between the scalemes laterally and the longus colli medially, and into this the pleura and apex of the lung project upward fig. The fascia of the neck comprises three layers: The investing layer is attached to the major bony prominences: The layer surrounds the trapezius, roofs the posterior triangle, surrounds the sternomastoid, and roofs the anterior triangle.
It forms the sheaths of the parotid and submandibular glands. At the manubrium, it bounds the suprasternal space, which encloses the sternal heads of the sternomastoid and the jugular venous arch. The visceral pretracheal layer, limited to the anterior neck, is more extensive than its name suggests. It lies inferior to the hyoid bone and is attached to the oblique lines of the thyroid cartilage and to the cricoid cartilage.
It surrounds the thyroid gland, forming its sheath, and it invests the infrahyoid muscles and the air and food passages.
Infections from the head and neck can spread anterior to the trachea or posterior to the esophagus and reach the superior mediastinum in the thorax. The prevertebral layer is attached to the base of the skull and to the transverse processes of the cervical vertebrae.
It covers the pre vertebral muscles, scalenes, phrenic nerve, and deep muscles of the back, and therefore the floor of the posterior triangle.
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Anterior to the subclavian artery, it is prolonged laterally as the axillary sheath, which also invests the brachial plexus. The carotid sheath, which is fused with all three layers of the cervical fascia, is a condensation around the common and internal carotid arteries, internal jugular vein, and vagus nerve. Prevertebral muscles see table The longus capitis, which covers the superior part of the longus colli, extends from the inferior cervical vertebrae to the occipital bone.
The longus colli see fig. The recti capitis anterior and lateralis connect the atlas to the occipital bone. The longus colli is active during talking, coughing, and swallowing. The pre vertebral muscles and sternomastoid muscles act with, and as antagonists to, the upper deep muscles of the back.
Questions Why is the sternomastoid known officially as the sternocleidomastoid muscle? Actually, the muscle is therefore sternomastoid and cleido-occipital and there are deeper cleidomastoid fibers. The muscle is the anatomical and clinical key to the neck, dividing it into anterior and posterior triangles.
The development of the sternomastoid muscle and trapezius is complicated J. The triangle contains the external carotid artery and its three anterior branches facial, lingual, and superior thyroidthe hypoglossal nerve, and the greater horn of the hyoid see figs.
More deeply placed are the superior laryngeal nerve and C. Case Report During routine dissection of a South Indian female cadaver of about 40 years of age in our medical college, we found a rare combination of variation of external jugular vein on both side of neck and trapezius muscle on the right side. Externally the neck region was intact and normal without any visible abnormalities, mass or surgical scars.
The right external jugular vein was formed as usual by joining of posterior division of retromandibular vein with posterior auricular vein at the level of angle of mandible and then it bifurcated opposite to the sternocleidomastoid muscle, descended for 6 cm and reunited again well below the sternocleidomastoid muscle in the posterior triangle of neck.
No structure was passing between the bifurcated veins. The vein then pierced the deep cervical fascia above the clavicle, passed between the tendon of cleido-occipitalis cervicalis muscle, trapezius and the clavicle, and then drained into the right suprascapular vein at right angle Figures 1, 2. Suprascapular vein was large and drained into subclavian vein. The left external jugular vein was normal except that it was draining into internal jugular vein Figure 3. Dissection of right posterior triangle of neck showing the external jugular vein passing through triangle formed by clavicle, cleido-occipitalis cervicalis muscle and trapezius muscle.
Dissection showing right external jugular vein draining into suprascapular vein. Dissection of left posterior triangle showing left external jugular vein draining into internal jugular vein. This tendon inserted on posterior surface of clavicle at junction between medial one third and lateral two third. The muscle fibers of the variant muscle originated from the medial part of the superior nuchal line. This aberrant muscle resembled to the cleido-occipitalis cervicalis portion of trapezius.
It measured about 8 cm in length and was supplied by branch of spinal accessory nerve Figure 1. The external jugular vein passed through the triangle formed by the cleido-occipitalis cervicalis, trapezius and clavicle. As the vein passes between the tendon of cleido-occipitalis cervicalis and clavicle, it may get compressed during certain actions of the trapezius muscle as in rotation and elevation of scapula.
Discussion Variation of external jugular vein has been reported frequently. Duplication of external jugular vein is rare and has been reported earlier by Comert and Comert [ 3 ].
Till now there has been no report of external jugular vein ending into suprascapular vein at right angle. External jugular vein is developed from the postero-superior part of the venous ring of jugulocephalic vein cephalic vein which is present around the developing clavicle when the embryo is about 22 mm long [ 4 ].
Most of embryonic veins arise as capillary plexus which anastomose with each other and latter fuse and enlarge, giving rise to fewer and larger veins. Thus new vein appear with subsequent atrophy and replaced by other veins [ 5 ], during which one of the venous channel persists even when the other evolves and thus the external jugular vein may have remained doubled in a small segment.
Lesser's Triangle It is a triangle contained within the submandibular triangle. Its boundaries are the hypoglossal nerve, and the anterior and posterior belly of the digastric muscle [Figure 2]. This triangle was named after a German surgeon named Ladislaus Leon Lesser, who lived from to Anterior belly of digastric and intermediate tendon of digastric forms the inferior boundary, superior border by hypoglossal nerve and posterior border is formed by posterior margin of mylohyoid muscle at the intermediate tendon of digastric muscle.
Floor of this is formed by hyoglossus and mylohyoid muscles. Schematic drawing of Lesser's, Beclard's and Pirogoff's Triangle adopted from Tubbs et al Pirogoff's Triangle It was named after Russian surgeon and scientist Nikolai I Pirogoff —who performed the first description of this anatomic area of the neck. Following are the boundaries of this triangle: Superior boundary is formed by hypoglossal nerve, inferior boundary is formed by intermediate tendon of digastric muscle and posterior border is formed by posterior border of mylohyoid muscle [Figure 2].
It is also considered that this triangle is posterior continuation of Lesser's triangle. Greater cornu of hyoid bone forms the inferior boundary, posterior belly of digastric muscle forms superior boundary, and posterior border of hyoglossus muscle forms posterior boundary and its base [Figure 2].
It is also known as posterior triangle of lingual artery and contents of this triangle are lingual artery and hypoglossal nerve. Sometimes, arcus raninus, i. This triangle also helps in ligating external carotid artery.