1) The anterior and posterior circumflex humeral arteries originate from the third part of the axillary artery and pass around the surgical neck of the humerus. 2) They anastomose with each other around the surgical neck, forming a connection between the axillary artery and branches of nearby arteries. 3) This anastomosis acts as collateral circulation in cases where the axillary artery is obstructed, allowing blood to still reach the arm.