Anatomical Description of the Upper Back and Shoulder Blades

Anatomical Description of the Upper Back and Shoulder Blades

The upper back, also known as the thoracic spine, and the shoulder blades (scapulae) form a complex network of bones, muscles, ligaments, and joints that provide structure, protect vital organs, and allow for a wide range of motion.

The structure of the upper back and shoulder blades allows for a wide range of movements, including lifting, pulling, and pushing. However, this area can be prone to injury and conditions such as thoracic spine pain, scapular pain, and shoulder impingement.

Bones: The thoracic spine consists of 12 vertebrae, labeled T1 to T12, which are unique in that they each have a pair of ribs attached, forming the rib cage that protects vital organs such as the heart and lungs. The scapula, or shoulder blade, is a flat, triangular bone located on the upper back that connects the humerus (upper arm bone) with the clavicle (collar bone) to form the shoulder joint.

Muscles:

Several key muscles and muscle groups play a role in upper back structure and movement:

  1. Trapezius: This large, kite-shaped muscle group spans the back of the neck, shoulders, and upper spine, facilitating movement of the neck and shoulders.
  2. Rhomboids: These muscles connect the scapula (shoulder blade) with the spine and aid in retracting the scapula.
  3. Latissimus dorsi: This large muscle spans the mid and lower back and aids in arm movement.
  4. Erector spinae: This muscle group runs vertically on each side of the vertebral column and is responsible for extending and rotating the spine.

Ligaments & Tendons: Ligaments are tough bands of tissue that connect bones to each other, providing stability to the joints. Tendons connect muscles to bones, allowing for movement. In the shoulder, the joint capsule is a group of ligaments that surround the shoulder joint, and the rotator cuff tendons are particularly important for shoulder movement and stability. Key ligaments in the upper back include:

  1. Anterior longitudinal ligament: Runs down the anterior portion of the vertebrae, preventing hyperextension.
  2. Posterior longitudinal ligament: Runs within the vertebral canal along the posterior aspect of the vertebrae, limiting flexion.
  3. Ligamentum flavum: Connects the laminae (part of the vertebrae), assisting in maintaining posture and bending and twisting.
  4. Supraspinous and interspinous ligaments: These ligaments connect adjacent spinous processes, limiting flexion and rotation.

Nerves: The brachial plexus is a network of nerves that originates from the neck and provides sensation and motor control to the shoulder, arm, and hand. The thoracic spine is also the location of the thoracic part of the spinal cord, which sends and receives signals to and from the lower parts of the body.

Blood Supply: The subclavian and axillary arteries, among others, supply blood to the shoulder and upper back region.

Fascial Compartments: The upper back does not traditionally contain distinct fascial compartments, but it is covered by a dense and tough layer of connective tissue known as the thoracolumbar fascia.

Joint Anatomy: The main joints in this region include the thoracic facet joints, which connect the thoracic vertebrae to each other, and the glenohumeral joint, which is the ball-and-socket joint where the humerus fits into the scapula. There’s also the acromioclavicular joint where the clavicle meets the scapula, and the sternoclavicular joint where the clavicle meets the sternum (breastbone).

The upper back contains:

  1. Vertebral bodies: Separated by intervertebral discs that act as shock absorbers.
  2. Facet joints: Synovial joints that help to stabilize the spine and limit its range of motion.
  3. Costovertebral and costotransverse joints: Joints where the ribs articulate with the vertebrae.

Bursa Sacs: While the upper back does not contain bursae, the nearby shoulder region has several bursae, including the subacromial bursa, which can impact upper back function.

Kinesiology: The movements of the upper back primarily involve the shoulders and neck and include:

  1. Flexion and extension: Bending forward and backward, primarily controlled by the erector spinae and the abdominal muscles.
  2. Lateral flexion: Bending to the side, involving the quadratus lumborum and erector spinae.

Rotation: Turning to the side, which is more restricted in the thoracic spine due to the attachment of the rib cage.