Which of the following bones is NOT part of the axial skeleton?

External shoulder rotation is the movement of the humerus bone away from the centerline of the body, rotating the arm so that the palm faces away from the body.
This movement is achieved by the contraction of the external rotator muscles of the shoulder, which include the infraspinatus, teres minor, and posterior fibers of the deltoid muscle.
The joint involved in external shoulder rotation is the glenohumeral joint, also known as the shoulder joint.
The shoulder joint is a ball-and-socket joint formed by the articulation between the head of the humerus bone and the glenoid cavity of the scapula bone.
This joint allows for a range of movements, including:

1. Internal shoulder rotation: This is the opposite movement of external rotation, in which the humerus bone rotates inward toward the centerline of the body, with the palm facing inward.
2. Shoulder flexion: This is the movement of the humerus bone forward and upward, bringing the arm closer to the body's front.
3. Shoulder extension: This is the movement of the humerus bone backward and downward, moving the arm away from the body's front.
4. Shoulder abduction: This is the movement of the humerus bone away from the body's midline, raising the arm out to the side.
5. Shoulder adduction: This is the movement of the humerus bone toward the body's midline, bringing the arm back down to the side of the body.
6. Shoulder horizontal abduction: This is the movement of the humerus bone away from the body's midline at shoulder height.
7. Shoulder horizontal adduction: This is the movement of the humerus bone toward the body's midline at shoulder height.
All of these movements of the glenohumeral joint are important for many daily activities, including reaching, throwing, pushing, pulling, and lifting.

Osteoclasts are the type of cells that increase their activity in response to parathyroid hormone (PTH) and break down bone tissue to release calcium into the blood.

PTH helps maintain the right balance of calcium in the body by stimulating osteoclasts.

Choice A is incorrect because osteoblasts are the type of cells that form new bone tissue by depositing calcium into the bone matrix.

PTH inhibits osteoblasts and reduces bone formation.

Choice B is incorrect because canaliculi are not cells, but small channels within the bone matrix that allow osteocytes to communicate with each other and exchange nutrients and waste.

PTH does not affect canaliculi directly.

Choice D is incorrect because osteocytes are the type of cells that are mature bone cells trapped within the bone matrix.

PTH can stimulate osteocytes to release calcium from the bone, but not as much as osteoclasts.