Muscles of the Back

The back muscles can be categorized into three groups: superficial, intermediate, and deep.

1. Superficial Back Muscles: These muscles are primarily responsible for movements of the shoulder. They include:

   • Trapezius: Elevates, retracts, and rotates the scapula.

   • Latissimus Dorsi: Extends, adducts, and medially rotates the arm.

   • Levator Scapulae: Elevates the scapula.

   • Rhomboid Major and Minor: Retract the scapula and rotate it to depress the glenoid cavity.

2. Intermediate Back Muscles: These muscles are involved in respiratory functions and include:

   • Serratus Posterior Superior: Elevates the ribs.

   • Serratus Posterior Inferior: Depresses the ribs.

3. Deep Back Muscles: Also known as the intrinsic back muscles, they are responsible for movements of the vertebral column and maintaining posture. They include:

   • Erector Spinae: Extends the vertebral column. It is further divided into three muscle groups: iliocostalis, longissimus, and spinalis.

   • Transversospinales: These are smaller muscles including the semispinalis, multifidus, and rotatores, which help in stabilizing and rotating the vertebral column.

Anastomosis Around the Scapula

The anastomosis around the scapula ensures a continuous blood supply to the shoulder region, even if one of the major arteries is blocked. The key arteries involved in this network are:

• Suprascapular Artery: Arises from the thyrocervical trunk and supplies the supraspinatus and infraspinatus muscles.

• Dorsal Scapular Artery: Typically a branch of the subclavian artery, it supplies the levator scapulae, rhomboid major, and rhomboid minor muscles.

• Circumflex Scapular Artery: Branches from the subscapular artery and supplies the teres major, teres minor, and infraspinatus muscles.