Fourth Lecture of Head and Neck PDF

Fourth lecture of head and neck @barhoom261  Subclavian artery  This artery begins behind the sternoclavicular joint, it arched upward, laterally, and then downward behind the clavicle, it is crossed by scalenus anterior muscle, which divides the artery into three...

Fourth lecture of head and neck @barhoom261  Subclavian artery  This artery begins behind the sternoclavicular joint, it arched upward, laterally, and then downward behind the clavicle, it is crossed by scalenus anterior muscle, which divides the artery into three parts. It ends on the outer border of 1st rib by change its name to axillary artery.  The first part (right side): extends superolaterally from brachiocephalic trunk behind the right sternoclavicular joint, it is related anteriorly to sternocleidomastoid, sternohyoid and sternothyroid, internal jugular vein, vertebral vein, phrenic nerve and vagus nerve (which gives recurrent laryngeal nerve hooking around it) and ansa subclavia (loop from sympathetic trunk). It ends on medial border of scalenus anterior.  The first part (left side): ascends vertical from the arch of aorta, the vagus and phrenic nerve are anterior to it, it lies behind brachiocephalic vein at sternoclavicular joint. The course and relation is the same as the right except that the thoracic duct anterior to it, the left recurrent laryngeal nerve is medial to the artery because it ascends from aortic arch in a groove between trachea and esophagus.  The second part: This is the highest portion of the artery. Anteriorly it is covered by scalenus anterior muscle and phrenic nerve, posteroinferiorly it lies on suprapleural membrane.  The third part: Extends downward and laterally from the lateral border of scalenus anterior muscle to the outer border of 1st rib to becomes axillary artery, it crossed anteriorly by external jugular vein, the subclavian vein lies anterior and inferior to it, posteriorly it lies against inferior trunk of brachial plexus. Branches of subclavian artery 1- From the 1st part: a- vertebral artery. b- thyrocervical trunk. C- internal thoracic artery. 2- From the 2nd part: costocervical trunk. 3- From the 3rd part: sometimes arises the dorsal scapular artery.  Vertebral artery This is the first branch of subclavian artery arises from the superoposterior aspect of the artery. The sympathetic plexus lies medial to the artery and the cervicothoracic ganglia sends branches, which form plexus around the artery; it ascends upward and medially to enters the foramen transversarium of the sixth cervical vertebra. It ascends upward till it reaches the atlas vertebra where it leaves the foramen and grooves the posterior arch of atlas and enters the foramen magnum to supplies the brain. In the neck, it gives spinal branches to the spinal cord and muscular branches to the surrounded muscle.  Thyrocervical trunk  It is a short trunk arises under the medial border of scalenus anterior from the anterior and superior aspect of subclavian artery opposite to internal thoracic artery. This trunk is divided into: 1- Inferior thyroid artery: ascends along the medial border of scalenus anterior, it runs medially in front of the vertebral artery to the lower pole of thyroid gland where it ascends on the posterior surface of the gland, it also supplies parathyroid gland 2- Suprascapular artery: branch of thyrocervical trunk, it passes downward laterally across scalenus anterior muscle to the scapular notch. It supplies supraspinatus and infraspinatus muscles, it anastomose with circumflex scapular and dorsal scapular arteries. 3- Transverse cervical artery: branch of thyrocervical trunk runs laterally across the posterior triangle to the anterior border of trapezius with the accessory nerve. It divided into superficial and deep branch.  Internal thoracic artery Arises from the inferior surface of subclavian artery opposite to thyrocervical trunk, it descends downward medially behind the sternal end of clavicle to the 6th intercostal space where it divides into musculophrenic and superior epigastric artery Costocervical trunk  Arises from the posterior aspect of 2nd part of subclavian artery under scalenus anterior, it arches posteriorly and divided into: 1- Deep cervical artery: passes into the back of neck, it is the main supplies to the muscles of the back of neck. 2- Highest intercostal artery: descend anterior to the neck of 1st rib and gives posterior intercostal artery to the 1st and 2nd intercostal spaces.  Dorsal scapular artery This artery presents in 70% of population, it either arises from the 2nd or 3rd part of subclavian artery, it passes through the brachial plexus descending along the medial border of scapula to rhomboid muscles. It anastomoses with suprascapular and subscapular artery. Subclavian vein It is continuation of axillary vein at outer border of 1st rib, passes in front of scalenus anterior muscle and phrenic nerve. It joins the internal jugular vein to form brachiocephalic vein behind the sternal end of clavicle  External jugular vein Formed behind the angle of mandible by union of posterior division of retromandibular vein and posterior auricular vein descending on sternocleidomastoid muscle towards the middle of clavicle in the posterior triangle, it receives suprascapular, transverse cervical and anterior jugular vein. It ends into the subclavian vein. Ansa cervicalis  Slender nerve presents anterior to carotid sheath, it is formed by two roots.  Inferior root: from the ventral rami of C2 and C3 behind the internal jugular vein. It curves lateral ward usually on the lateral surface of the vein passing downward on the common carotid artery, here it joins the superior root from the hypoglossal nerve (C1) to form a loop called ansa cervicalis at the lower part of the larynx.  This complex consist of nerve fibers from cervical ventral rami some of which form thyrohyoid nerve (C1) while others may supplies the geniohyoid muscle through hypoglossal nerve. The ansa cervicalis supplies the remaining infrahyoid muscles (sternohyoid, sternothyroid and omohyoid). Digastric muscle and Stylohyoid muscle Digastric muscle: Anterior belly arises from the digastric fossa on the inner side of lower border of mandible, the posterior belly arises from mastoid notch. The two bellies descend toward the hyoid bone and unite by intermediate tendon Nerve supply: anterior belly by nerve to mylohyoid whilePosterior belly by facial nerve Stylohyoid muscle: It is medial and parallel to the posterior belly of digastric, it arises from the styloid process passes downward and forward. It divided into two 5 slips pass on either side of intermediate tendon of digastric muscle. It is inserted on hyoid bone. Nerve supply: facial nerve  Omohyoid muscle The inferior belly arises from the upper border of scapula passes upward and medially in the posterior triangle. It ends in intermediate tendon under sternocliedomastoid. The superior belly ascends upward and inserted to hyoid bone (outer border). Nerve supply: ansa cervicalis. Sternohyoid muscle Arises from the posterior aspect of manubrium sterni and sternal end of clavicle, it inserted to the lower border of hyoid bone. Nerve supply: ansa cervicalis. Sternothyroid muscle Presents under sternohyoid muscle arises from posterior surface of manubrium sterni and from the cartilage of 1st rib, it inserted to the oblique line of thyroid cartilage. Nerve supply: ansa cervicalis.  Thyrohyoid muscle Arises from the oblique line of thyroid cartilage to the lower border of greater horn of hyoid bone. Nerve supply: from C1 ventral rami of ansa cervicalis through the hypoglossal nerve.  Clinical notes 1- Vertebral artery injury is due to an intimal tear. The torn, exposed endothelium promotes platelet aggregation and thrombus formation. This thrombus may cause local occlusion of the vessel, but more commonly, the clot will embolize to the cerebral circulation. 2- External jugular vein cannulation indicated in a critically ill patient >12 years of age who requires intravenous access for fluid or medication administration and in whom an extremity vein was not attainable where no obvious peripheral site is noted. 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