Anatomy of the Upper Extremities

Introduction

The human upper extremities consist of the shoulders, arms, forearms, wrists, and hands. Understanding the anatomy of these structures is crucial for medical professionals, especially those preparing for the United States Medical Licensing Examination (USMLE). This guide will provide a comprehensive overview of the anatomical features of the upper extremities.

Shoulder

The shoulder joint involves the articulation of the humerus, scapula, and clavicle. Key structures include:

1. Humerus: The upper arm bone that forms the proximal part of the shoulder joint.
2. Scapula: Also known as the shoulder blade, it is a triangular bone that connects the humerus to the clavicle.
3. Clavicle: The collarbone, which connects the scapula to the sternum.

Arm

The arm extends from the shoulder to the elbow and contains the following structures:

1. Biceps brachii: A muscle located in the anterior (front) compartment of the arm, responsible for flexion at the elbow joint.
2. Triceps brachii: A muscle located in the posterior (back) compartment of the arm, responsible for extension at the elbow joint.
3. Brachial artery: The major blood vessel of the arm, supplying oxygenated blood to the upper limb.

Forearm

The forearm extends from the elbow to the wrist and consists of two compartments:

1. Flexor compartment: Contains muscles responsible for flexion of the wrist and fingers, such as the flexor carpi radialis and flexor digitorum superficialis.
2. Extensor compartment: Contains muscles responsible for extension of the wrist and fingers, such as the extensor carpi radialis longus and extensor digitorum.

Wrist

The wrist is a complex joint composed of multiple bones, ligaments, and tendons. Key structures include:

1. Carpal bones: Eight small bones arranged in two rows (proximal and distal) that form the wrist joint, including the scaphoid, lunate, and triquetrum.
2. Flexor retinaculum: A band of connective tissue that forms the roof of the carpal tunnel, protecting the tendons of the wrist and hand.
3. Median nerve: Runs through the carpal tunnel and provides sensory and motor innervation to the hand.

Hand

The hand consists of the palm and fingers, with intricate anatomy crucial for dexterity. Important features include:

1. Metacarpal bones: Five long bones that connect the wrist to the base of the fingers.
2. Phalanges: Finger bones, each finger having three phalanges (proximal, middle, and distal), except for the thumb, which has two.
3. Thenar eminence: The muscular mound at the base of the thumb, crucial for thumb opposition and fine motor skills.

Conclusion

Understanding the anatomy of the upper extremities is essential for medical professionals. This guide has provided a concise overview of the major anatomical structures of the shoulders, arms, forearms, wrists, and hands. Remember to review and practice identifying these structures to excel in USMLE examinations and effectively diagnose and treat upper extremity conditions.