Anatomical Position, Attachments, Nerve Supply, and Functions of the Trapezius and Latissimus Dorsi Muscles

Overview

The trapezius and latissimus dorsi muscles are two major muscles of the upper body that play crucial roles in movement and stability.

Anatomical Position

The trapezius is a broad, flat muscle located in the upper back, extending from the base of the skull to the lower thoracic vertebrae.

The latissimus dorsi is a large, flat muscle positioned in the lower back, covering a significant portion of the posterior thorax.

Attachments

• Trapezius: Originates from the occipital bone, ligamentum nuchae, and thoracic spinous processes; inserts onto the clavicle, acromion, and scapular spine.
• Latissimus Dorsi: Arises from the thoracolumbar fascia, iliac crest, lower thoracic, and lumbar spinous processes; inserts onto the humerus.

Nerve Supply and Innervation

Trapezius Muscle

Innervated by the spinal accessory nerve (cranial nerve XI), which provides motor control.

Latissimus Dorsi Muscle

Supplied by the thoracodorsal nerve, originating from the brachial plexus (C6, C7, and C8 nerve roots).

Functions

• Trapezius: Responsible for scapular elevation, retraction, and rotation.
• Latissimus Dorsi: Aids in shoulder extension, adduction, and medial rotation.