The human arm, a critical part of our anatomy, is made up of three main bones: the humerus, the ulna, and the radius. These bones work in unison to allow movement at the shoulder, elbow, wrist, and fingers, all of which are integral to our daily activities. For a clearer understanding, here's a detailed diagram of the bones in the arm.

The Bones of the Arm - An Illustrated Diagram

The Humerus

• The humerus, comparable to the femur in the legs, is the longest bone in the arm. It spans from the shoulder to the elbow.
• It consists of three main sections: the upper extremity, the body, and the lower extremity.
• The upper extremity features a hemispherical head, a narrow neck, and two protrusions. It is connected to the scapula (shoulder bone), allowing movement at the shoulder.
• The body of the humerus is cylindrical, resembling a prism at the bottom.
• The lower extremity includes two smooth articular surfaces, the trochlea and capitulum, and two depressions or fossae that form the elbow joint, along with two epicondyles or projections.
• The capitulum and trochlea connect with the radius and ulna, respectively.
• The two depressions of the fossae accommodate projections from the ulna bone.
• The epicondyles, located on either side of the bones, serve as the attachment sites for the muscles of the forearm and fingers.

For more information, check out: The Anatomy & Physiology of the Human Skeletal System

The Radius and Ulna

• The humerus is located in the upper arm, while the radius and ulna are shorter bones that make up the forearm.
• The radius is positioned on the side of the thumb, with the ulna on the opposite side.
• The ulna forms a true hinge joint with the elbow, allowing for extension and flexion movements. It also connects with the bones of the wrist.
• The radius, a bone with a smooth concave surface, is linked to the capitulum or head of the humerus. It connects with the ulna on the side surfaces.
• The radius and ulna bones are parallel to each other. While the ulna is longer, the radius is thicker.

That wraps up our exploration of the bones of the arm. For more fascinating insights, keep visiting: Anatomy & Physiology

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