VAN 121: Veterinary Gross Anatomy-II (2+2)

SHOULDER - LATERAL ASPECT

Dissection

  

The skin flaps made during the dissection of the suprascapular region expose the structures of this region for examination.

Clean the muscles and define the borders.

• Supraspinatus
  • It is a large muscle occupying the supraspinous fossa.
  • Lower down it divides into two parts, which are succeeded by tendon that are inserted to the medial and lateral tuberosities of the humerus.
  • The tendon of origin of biceps passes between the two tendons.

Dissection

• Reflect the lower segments of omotransversarius and brachiocephalicus downward and note the inferior cervial artery terminating in the lower part of supraspinatus.
•  Cut the anterior border of the supraspinatus across about the level of acromion process and follow the suprascapular nerve and artery supplying it.
• Lead the suprascapular nerve under the acromion process into the infraspinatus.
  • Infraspinatus
    • It is a large muscle occupying the infraspinous fossa.
    • In its lower part acromial head of deltoideus covers it.
  • Deltoideus
    • It is a small 'V' shaped muscle lying behind the shoulder covering the infraspinatus and triceps partly.
    • Its anterior acromial head arises from the acromion process of the scapula and the posterior scapular head arises from the posterior border of the scapula.

Dissection

• Cut the tendon of insertion of deltoideus from the deltoid tuberosity and reflect the muscle upwards.
• This operation exposes the teres minor, axillary nerve and the superior branch of the posterior circumflex artery.
• Teres minor
  • It is a small muscle lying behind the shoulder partly under infraspinatus and deltoideus.
  • Carefully clean the muscle and note its artery and nerve entering its posterior border.
• Axillary nerve
  • Now clean the nerve and its branches supplying teres minor, both the heads of deltoideus and a long branch which pass under the acromial head and terminates in the brachiocephalicus at it insertion.
  • The nerve is continued by a long cutaneous branch, which passes backwards under the scapular head, pierces the deep fascia and passes down to supply the skin on the lateral aspect of the arm and the dorsal aspect of the forearm.
• Posterior Circumflex artery
  • The superior branch of this artery supplies the teres minor and deltoid.