<s>[INST] context: Veebral aery [Ret Gray's anatomy 38/e section 10 Cardiovascular system)The coarctation may be:Preductal- where the narrowing is proximal to the ductus aeriosus or ligamentum aeriosum orPostductal- where the narrowing is distal to the ductus aeriosus or ligament= aeriosum.Collateral circulation connects the proximal and the distal aspects of the vessels over time. This collateral circulation will develop mainly from the- subclan,- axillary,- internal thoracic,- superior and inferior epigastric and- intercostal aeries.Following collateral connections may be seen:In the anterior thoracic wall, the internal mammary aeries (arising from subclan aeries) and the epigastric aeries join to form collaterals which supply the abdominal wall and the lower extremities.- Internal mammary aery gives rise to anterior intercostal aeries which forms anastomoses with the posterior intercostals (post intercostals arise from descending aoa).- Superior epigastric aery is terminal branch of internal mammary aery and anastomoses with inferior epigastric aery which arises from external iliac aery.Musculophrenic aery is terminal branch of internal mammary aery and it anastomoses with inferior phrenic and post intercostals.The Para scapular aeries (arising from subclan aery and axillary aeries) connect with the posterior intercostal aeries to form collaterals which supply the distal aoic compament.- The suprascapular aery from the subclan, and the thoraco-acrontial, lateral thoracic and subscapular aeries from the axillary and the first and second posterior intercostal aeries from the costocervical trunk anastomose with other posterior intercostal aeries.One smaller route of collateral formation can be subclan aery- veebral a- spinal aeries- post intercostals and lumbar aery - aoa.We have selected veebral aery as the ans as this appears to be least impoant collateral circulation. It is not mentioned in Gray's anatomy. It's stated as route of collateral formation in the website given in the reference. [/INST] question: In case of coarctation of aoa which of the following is not involved in collateral formation: | options: A: Veebral aery B: Posterior intercostal aery C: Axillary aery D: Subscapular aery | answer: A </s>