In a Subclan aery block at the outer border of 1st rib, all of the following aeries help in maintaining the circulation to upper limb exceptaEUR'

Superior thoracic [Ref: BDC 4/e, Vol. 1, p 56, 82; Snell's Clinical Anatomy 6/e, p A rich anastomoses exists around the scapula between branches of subclan aery (first pa) & the axillary aery (third pa).This anastomoses provides a collateral circulation through which blood can flow to the limb when the distal pa of subclan aery or the proximal pa of axillary aery is blocked.Anastomosis around the scapula: Formed by branches of?Subclan aery - first pa- Suprascapular aery- Deep branch of transverse cervical aeryAxillary aery - third pa- Subscapular aery & its circumflex scapular branchThere are other smaller anastomoses over the acromion process, which also helps to maintain. flow to arm. (BDC Vol 1, 4/e, p 82)Anastomoses over the acromion process: Formed by -a)Acromial br. of thoraco-acromial aeryb)Acromial br. of suprascapular aeryc)Acromial br. of posterior circumflex humeral aeryThe subscapular aery also forms anastomoses with intercostal aeries.Review of branches of subclan & axillary aery : Subclan Aery (3 pas) The right subclan aery arises from the brachiocephalic trunk, the left from the aoic arch. The scalenus anterior muscle divides it into 3 pas.Ist pa- from origin to the medial border of the scalenus anterior muscle.IInd pa- lies behind the scalenus anterior muscle.IIh-d pa- from the lateral margin of scalenus anterior to the outer border of the first rib, where the aery becomes the axillary aery.Axillary aery is crossed by pectoralis minor muscle which divides it into three pas.