Anatomy of the Arm

Anatomy of the Arm

• The arm is the region between the shoulder and the elbow and is primarily composed of the humerus.
• The humerus is a long bone, extending from the shoulder joint to the elbow joint. It's the longest bone in the upper arm.
• The humerus articulates with the scapula at the glenoid cavity to form the shoulder joint.
• It articulates with the radius and ulna at the elbow joint.
• Key humerus features include the head, anatomical neck, greater and lesser tubercles, deltoid tuberosity, and medial and lateral epicondyles.
• Arm muscles control flexion, extension, abduction, and adduction at the shoulder and elbow joints.
• Major arm muscles include biceps brachii, triceps brachii, brachioradialis, and coracobrachialis.
• The brachial artery and median nerve carry blood and sensory signals to arm muscles and skin.
• The axillary artery branches from the subclavian artery, supplying blood to the brachial artery.
• The radial and ulnar nerves branch from the brachial plexus, providing sensory function to the forearm and hand.

Anatomy of the Forearm

• The forearm extends between the elbow and the wrist and is composed of two bones: the radius and the ulna.
• The radius is located on the lateral (thumb) side of the forearm.
• The ulna is located on the medial (pinky finger) side of the forearm.
• The radius and ulna are connected by an interosseous membrane, allowing some movement between them.
• Both bones articulate with the humerus at the elbow joint and with carpal bones at the wrist.
• Forearm muscles control wrist and hand movements.
• Forearm muscles are organized into anterior and posterior compartments.
• Anterior compartment muscles cause flexion; posterior compartment muscles cause extension.
• Anterior forearm muscles include flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and flexor digitorum superficialis.
• Posterior forearm muscles include extensor carpi radialis, extensor carpi ulnaris, and extensor digitorum.
• The anterior and posterior compartments are separated by the interosseous membrane.
• The brachial artery branches into the radial and ulnar arteries to supply blood to forearm muscles and structures.
• The median, ulnar, and radial nerves run through the forearm, providing sensory and motor function to the hand.
• These nerves pass through the elbow region and into the forearm and potentially through the elbow region again. This allows them to interact with many forearm and hand muscles.
• Ligaments, tendons, and associated structures of the forearm support movement, stability, and upper extremity function.

Associated Structures

• Forearm tendons attach to various hand and wrist regions.
• The wrist joint is a complex synovial joint formed by the distal ends of the radius and ulna and several carpal bones.
• Carpal bones, combined with the radius and ulna, create the wrist's varying mobility and structure.
• Ligaments stabilize the wrist joint.
• Numerous tendons connect to hand bones, enabling complex hand movements.
• The palm and associated structures support and enable fine finger movements.