Clavicle

From Encyclopedia Jr, free information reference for Kids

Right clavicle - from below, and from above.

Left clavicle - from above, and from below.

Collarbone and collar bone redirect here. The eye abnormality is correctly spelled coloboma.

In human anatomy, the clavicle or collar bone is classified as a long bone that makes up part of the shoulder girdle (pectoral girdle). It receives its name from the Latin clavicula ("little key") because the bone rotates along its axis like a key when the shoulder is abducted. (This movement is palpable with the opposite hand).

Clavicles are found in many tetrapods but tend to be rudimentary or absent in those using their forelimbs primarily for support or running and present where the forelimbs are used for grasping or brachiation.

Contents 1 Overview 2 Functions 3 Attachments 4 Development 5 Common clavicle injuries 6 Note about anatomical position 7 Additional images 8 See also 9 External links 10 References 11 Popular References

[edit] Overview

The clavicle is a doubly-curved long bone (the only horizontal long bone in the human body) that connects the arm (upper limb) to the body (trunk), located directly above the first rib. Medially, it articulates with the manubrium of the sternum (breast-bone) at the sternoclavicular joint. At its lateral end it articulates with the acromion of the scapula (shoulder blade) at the acromioclavicular joint. It is shorter, thinner, less curved, and smoother in women than in men. It has a rounded medial end and a flattened lateral end.

[edit] Functions

The clavicle serves several functions:

• It serves as a rigid support from which the scapula and free limb are suspended. This arrangement keeps the upper limb away from the thorax so that the arm has maximum range of movement.
• Covers the cervicoaxillary canal (passageway between the neck and arm), through which several important structures pass.
• Transmits physical impacts from the upper limb to the axial skeleton.

Even though it is classified as a long bone, the clavicle has no medullary (bone marrow) cavity like other long bones. It is made up of spongy (cancellous) bone with a shell of compact bone. The clavicle bone is the only bone that does not have marrow. It is a dermal bone derived from elements originally attached to the skull.

[edit] Attachments

Muscles and ligaments that attach to the clavicle include:

Superior surface:

• Deltoid muscle at the deltoid tubercle, anteriorly on the lateral third.
• Trapezius muscle posteriorly on the lateral third.

Inferior surface:

• Subclavius muscle at the subclavian groove
• Conoid ligament (the medial part of the coracoclavicular ligament) at the conoid tubercle
• Trapezoid ligament (the lateral part of the coracoclavicular ligament) at the trapezoid line

Anterior border:

• Pectoralis major muscle on the medial third (rounded border)
• Deltoid muscle on the lateral third of border in the deltoid tubercle

Posterior border:

• Sternocleidomastoid muscle superiorly, on the medial third (clavicular head of Sternocleidomastoid)
• Sternohyoid inferiorly, on the medial third
• Trapezius on the lateral third

[edit] Development

The clavicle is the first bone to begin the process of hardening (ossification) during development of the embryo, during the 5th and 6th weeks of gestation. However, it is the last of the long bones to finish ossification, at about 21 years of age. It forms by intramembranous ossification.

[edit] Common clavicle injuries

• acromioclavicular dislocation
• sternoclavicular dislocations
• clavicle fractures
• osteolysis
• degeneration of the clavicle

[edit] Note about anatomical position

Note: this article uses some professional terms to explain certain anatomical details. These definitions apply in terms of the body being in anatomical position, i.e., in humans standing with palms of the hands facing forward. These terms are:

• superior - above
• inferior - below
• abduction - the movement of the limb away from the body
• medial - toward the midline
• lateral - away from the midline

Please visit the anatomical position page for more detailed information.

[edit] Additional images

Sternoclavicular articulation. Anterior view.

The left shoulder and acromioclavicular joints, and the proper ligaments of the scapula.

[edit] See also

• Bone terminology
• Terms for anatomical location
• The collarbones are sometimes partly or completely absent in cleidocranial dysostosis
• Wishbone or furcula - the fused clavicles of most birds

[edit] External links

• Illustration
• Fractures

[edit] References

• Chung, Kyung. Board Review Series: Gross Anatomy, 4th edition.
• Moore, Keith L. and Arthur F. Dalley. Clinically Oriented Anatomy, 4th edition.
• Stedman's Medical Dictionary, 27th edition.
• Mosby's Medical, Nursing, and Allied Health Dictionary, 5th ed.

Human Bones

VERTEBRAL COLUMN: vertebrae (cervical - atlas - axis | thoracic | lumbar) | sacrum | coccyx THORAX: sternum | rib cranial bones of SKULL: occipital | parietal | frontal | temporal | sphenoid | ethmoid facial bones of SKULL nasal | maxilla | lacrimal | zygomatic | palatine | inferior nasal conchae | vomer | mandible | hyoid UPPER EXTREMITY: clavicle | scapula | humerus | ulna | radius carpals (scaphoid | lunate bone | triquetral | pisiform | trapezium | trapezoid | capitate | hamate) | metacarpals | phalanges (prox | int | dist) LOWER EXTREMITY: pelvis (ilium, ischium, pubis) | femur | patella | fibula | tibia tarsals (calcaneus | talus | navicular | cuneiform | cuboid ) | metatarsals | phalanges (prox | int | dist) OSSICLES: malleus | incus | stapes

[edit] Popular References

• The Alkaline Trio released a song on their CD "Goddammit!" called "Clavicle", in which they talk about kissing a woman's clavicle.