Axis (C2) vs Deltoid
| Property | Axis (C2) | Deltoid |
|---|---|---|
| Latin Name | Axis | Musculus deltoideus |
| Type | Bone | Muscle |
| Body System | Skeletal | Muscular |
| Body Region | Spine | Shoulder |
| Function | The second cervical vertebra that provides a pivot point for rotation of the head. The dens (odontoid process) projects superiorly and acts as the axis around which the atlas rotates. | The primary abductor of the shoulder joint. The anterior fibers flex and medially rotate the arm. The posterior fibers extend and laterally rotate the arm. Gives the shoulder its rounded … |
| Clinical Significance | Odontoid fractures are common cervical spine injuries, especially in elderly patients. Hangman's fracture involves bilateral pars interarticularis fractures of C2. Atlantoaxial instability occurs in rheumatoid arthritis and Down syndrome. | Deltoid paralysis from axillary nerve injury prevents arm abduction. The deltoid is a common site for intramuscular injections. Rotator cuff tears may cause compensatory deltoid overuse. |
| FMA ID | 12520 | 32521 |
Full structure pages
Axis (C2)
Axis
The second cervical vertebra, the axis provides the pivot around which the head rotates. Its defining feature is the dens, or odontoid process, a tooth-like projection that extends superiorly from the body to articulate with …