Anatomy of the Upper Limb Bones

Humerus

• Largest and longest bone of the upper limb.
• Articulates with the glenoid cavity of the scapula via the head of the humerus.
  • Head is a dome-shaped structure.

Key Features of the Humerus

• Anatomical Neck: Narrower region below the head.
• Greater and Lesser Tubercles:
  • Sites for rotator cuff muscle attachment.
  • Between them is the intertubercular sulcus, where the biceps tendon lies.
• Deltoid Tuberosity:
  • Thickened region on the shaft where deltoid muscles attach.
  • Thickened regions often indicate areas of stress and muscle attachment.
• Radial Groove (Posterior View): Pathway for the radial nerve.

Distal End of the Humerus

• Condyles:
  • Trochlea: Articulates with the ulna.
  • Capitulum: Articulates with the radius.
• Fossae:
  • Olecranon Fossa: Accommodates the olecranon when the arm is extended.
  • Coronoid Fossa: Fits the coronoid process when the arm is flexed.
  • Radial Fossa: Helps stabilize the radius during flexion.

Forearm Bones: Radius and Ulna

• Radius: Lateral bone of the forearm.
  • Articulates with the capitulum and radial notch of the ulna.
• Ulna: Medial bone of the forearm.
  • Olecranon: Fits into the olecranon fossa.
  • Trochlear Notch: Interacts with the trochlea of the humerus.

Joints and Membranes

• Proximal Radioulnar Joint:
  • Located at the radial notch of the ulna.
• Distal Radioulnar Joint:
  • Located at the ulnar notch of the radius.
• Interosseous Membrane:
  • Connects radius and ulna, allowing for movement such as pronation where the bones cross.

Thickness Variations

• Ulna: Thicker at the humeral end.
• Radius: Thicker at the wrist end, playing a larger role in wrist articulation.

Other Notable Articulations

• Radial Notch of the Ulna:
  • Site of articulation for the radius.

Conclusion

• The upper limb bones are intricately arranged to allow for a wide range of motions and provide structural support for muscle attachments.
• Upcoming discussions will cover the articulation between the radius, ulna, and the wrist.