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How do you tell a right humerus from a left humerus?

Last updated date: 15th Jul 2024
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Hint: The humerus is a long bone that runs from the shoulder to the elbow in the arm. It is made up of three sections that connect the scapula to the two lower arm bones, the radius, and the ulna. A rounded head, a narrow neck, and two short processes comprise the humeral upper extremity (tubercles, sometimes called tuberosities).

Complete answer:
In humans, the articular surface of the humerus head is hemispherical; two rounded projections below and to one side receive muscles that rotate the arm from the scapula. The shaft has a triangular cross-section that is roughened where the muscles attach. The humerus's lower end has two smooth articular surfaces (capitulum and trochlea), as well as two depressions (fossae) that are part of the elbow joint, and two projections (epicondyles).

The capitulum articulates with the radius laterally, while the trochlea, a spool-shaped surface, articulates with the ulna. The olecranon fossa, behind and above the trochlea, and the coronoid fossa, in front and above, receive ulnar projections as the elbow is alternately straightened and flexed. The epicondyles, one on each side of the bone, serve as points of attachment for muscles concerned with movements of the forearm and fingers.

The humerus is the long bone that runs from the shoulder to the elbow in the arm. It is a left humerus if the capitulum is on the left side of the bone. It is a right humerus if the capitulum is on the right side.

Note: Primitive amphibian fossils had little, if any, shaft connecting the upper and lower extremities, resulting in very short limbs. The humerus, on the other hand, has a shape similar to that of humans in most living tetrapods. The lower extremity of many reptiles and some primitive mammals has a large foramen, or opening, through which nerves and blood vessels can pass.