Regional Anatomy II_Week 2_SU22.pdf

Week 2 Carotid, subclavian, and vertebral arteries Vagus nerve Carotid Artery 3 branches off the aortic arch 1. 2. 3. Brachiocephalic trunk Left common carotid artery Left subclavian artery Carotid Artery ● Two divisions, both contained along with the common carotid artery, within the carotid...

Week 2 Carotid, subclavian, and vertebral arteries Vagus nerve Carotid Artery 3 branches off the aortic arch 1. 2. 3. Brachiocephalic trunk Left common carotid artery Left subclavian artery Carotid Artery ● Two divisions, both contained along with the common carotid artery, within the carotid sheath within the neck ○ ○ ● Internal carotid artery - brain External carotid artery - face and neck The common carotid artery ends when it bifurcates into the internal and external carotid arteries between the hyoid bone and thyroid cartilage (about C3/C4) Carotid Artery Contents of the carotid sheath: ● ● IJV Common carotid artery ○ ○ ● Vagus nerve ○ ● ● Internal carotid artery Parts of the external carotid artery Part of the recurrent laryngeal nerve Deep cervical lymph nodes Ansa cervicalis is embedded in the body of the carotid sheath The upper region of the sheath also contains CN Ⅸ, Ⅺ, Ⅻ External Carotid Artery Branches include: ● ● ● ● ● ● ● ● Superior thyroid artery Lingual artery Ascending pharyngeal artery Facial artery Occipital artery Posterior auricular artery Maxillary artery Superficial temporal artery Subclavian Artery ● ● ● Right subclavian artery is a branch of brachiocephalic trunk and begins posterior to right sternoclavicular joint Left subclavian artery is a branch of aortic arch and begins in superior mediastinum Subclavian artery is divided into 3 parts by scalenus anterior: ○ ○ ○ 1st part - from origin to medial border of scalenus anterior 2nd part - from posterior to scalenus anterior 3rd part - from lateral border of scalenus anterior to lateral border of 1st rib, where it becomes renamed the axillary artery Subclavian Artery ● 1st part: ○ ○ ○ ● 2nd part: ○ ● Vertebral artery Thyrocervical trunk Internal thoracic artery Costocervical trunk (may originate from 1st part) 3rd part gives rise to dorsal scapular artery or may have no branches Subclavian Artery Branches include: ● ● ● ● ● ● ● ● Internal thoracic artery Vertebral artery Thyrocervical trunk Inferior thyroid artery Suprascapular artery Dorsal scapular artery Transverse cervical artery Costocervical trunk Vertebral Artery ● ● Originates from 1st part of subclavian artery Divided into 4 parts ○ ○ ○ ○ 1st (prevertebral) part runs superiorly and posteriorly from subclavian artery to transverse foramen of C6, between longus colli muscle (medial to artery) and scalenus anterior muscle (lateral to artery); inferior cervical sympathetic ganglion (or cervicothoracic/stellate ganglion) lies posterior to 1st part of vertebral artery 2nd (cervical) part ascends through transverse foramina of C6 to C1, anterior to ventral rami of corresponding spinal nerves 3rd (atlantic) part runs medially, posterior to lateral mass of atlas, and enters vertebral canal passing under posterior atlanto-occipital membrane; it lies in a groove on superior surface of posterior arch of atlas and it is a content of suboccipital triangle 4th (intracranial) part pierces dura mater and arachnoid, and ascends into cranial cavity (within subarachnoid space) via foramen magnum; anastomoses with vertebral artery of opposite side to form basilar artery Clinical Considerations ● Subclavian steal syndrome - syndrome of symptoms characterized by subclavian artery stenosis, or relating to arterial insufficiency. Often, the subclavian artery steals retrograde blood from the vertebral artery to supply the arm during exertion. Symptoms may include: ○ ○ ○ ○ ○ ○ ○ ○ ○ Hearing loss Tinnitus Blurred vision Dizziness Vertigo Ataxia Fainting Numbness Pain Clinical Considerations ● ● Commonly diagnosed via Doppler US of the neck arteries; it is difficult to adequately assess the proximal subclavian artery due to general anatomy of the chest wall Severity can vary by grade ○ Grade 1 (pre-subclavian steal syndrome): Reduced antegrade blood flow in the affected artery. ○ Grade 2 (intermittent/partial): Alternating flow of antegrade and retrograde blood flow in the affected artery. Antegrade flow is in the diastolic phase, retrograde flow is in the systolic phase. ○ Grade 3 (permanent/ advanced): Permanent retrograde blood flow in the affected artery. Vagus Nerve ● Latin for “wandering,” it is the primary nerve of the parasympathetic nervous system and contains both motor and sensory fibers. It supplies all organs, with the exception of the adrenal glands. ○ ○ ○ ○ ○ ● Digestion, peristalsis, satiation HR - the right vagus branch innervates the SA node and mediates in the lowering of heart rate Respiratory rate Blood pressure Speech Efferent fibers are responsible for the gag reflex Clinical Considerations ● Vasovagal syncope - a neurologically induced drop in blood pressure and/or a decrease in HR resulting in a momentary loss of consciousness ○ Three types of reflex syncope ■ Vasovagal ■ Situational ■ Carotid