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Explain the upper arm bones

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humerus anatomy

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humerus anatomy upper arm bone proximal shaft distal ends

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labeled diagram of humerus bone upper arm anatomy proximal shaft distal landmarks

The upper arm has one bone: the humerus. It is a long bone running from the shoulder to the elbow. The radius and ulna are the two bones of the forearm, not the upper arm.

Main parts of the humerus

  1. Upper (proximal) end: shoulder
    • Head: rounded upper part that fits into the glenoid cavity of the scapula, forming the shoulder joint.
    • Greater tubercle and lesser tubercle: bony projections where important shoulder muscles attach.
    • Surgical neck: narrow area just below the head, a common fracture site.
  2. Shaft: middle portion
    • Long central part of the bone.
    • The deltoid tuberosity on its outer side is where the deltoid muscle attaches.
    • A groove on the back, the radial groove, carries the radial nerve and profunda brachii artery.
  3. Lower (distal) end: elbow
    • Capitulum: articulates with the head of the radius.
    • Trochlea: articulates with the ulna.
    • Medial and lateral epicondyles: projections above the elbow that provide attachment for forearm muscles.
    • The ulnar nerve passes behind the medial epicondyle, the “funny bone” area.
The humerus therefore helps form both the shoulder joint and the elbow joint, and provides attachment points for many arm and forearm muscles. A useful overview of these landmarks is available from TeachMeAnatomy’s humerus guide.
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