Veterinary Gross Anatomy-II

AXILLA

Dissection

• Cut the deep pectoral close to its origin from the sternum and reflect it gently towards the limb, which can be moderately abducted to open up the axilla, which is an artificial space unlike in man.
• The contents of the axilla are numerous, which must be cleaned by a careful dissection and removal of loose tissue enveloping them.
• At this stage, note the perforating inter costal nerves and arteries.
• Brachial vein: This large vein reaches the anterior border of the first rib, enters the thoracic inlet and joins the jugular confluence.
• Brachial artery: It emerges from the thoracic inlet by winding round the anterior border of the first rib, below the insertion of scalenus ventralis, crosses the axilla obliquely backwards and it continued down the arm. Its branches in the axilla are
  • The external thoracic artery
  • The suprascapular artery
  • The subscapular artery. At this stage, course of the first branch only can be noted.
• External thoracic artery: It arises from the posterior border of the brachial artery a little behind the first rib, passes backwards detaching a branch to the superficial pectorals and ramifies on the deep face of the deep pectoral.
• Pectoral nerves: These are three or four nerves. Two of them arise from the anterior part of the brachial plexus, one supplying the superficial pectoral and the other supplying the outer face of the deep pectoral. The other two arise from the posterior part of the plexus and pass with the external thoracic nerve on the deep face of the deep pectoral and terminate in it.