Upper Limb Anatomy Quiz

Upper Limb Segments

• Upper limb consists of four major segments: shoulder, arm, forearm, and hand.
• Shoulder is the proximal segment overlapping parts of the trunk, including the pectoral, scapular, and deltoid regions.
• Arm (brachium) connects shoulder and elbow, encompassing anterior and posterior regions with the humerus at the center.
• Forearm (antebrachium) connects elbow and wrist, includes regions overlying radius and ulna.
• Hand (manus) is distal to the forearm and consists of the carpus, metacarpus, and phalanges, serving as a tactile organ.

Pectoral Region Musculature

• Muscles of the pectoral region are categorized as axio-appendicular and scapulohumeral, linking axial and appendicular skeletons.
• Anterior axio-appendicular muscles include pectoralis major, pectoralis minor, subclavius, and serratus anterior.

Pectoralis Major

• Flat, fan-shaped muscle covering the upper half of the thorax.
• Has two proximal attachments: clavicular head (medial half of clavicle) and sternocostal head (anterior surface of sternum and superior six costal cartilages).
• Distally attaches to the lateral lip of the intertubercular groove of the humerus.
• Innervated by lateral and medial pectoral nerves.
• Contraction produces adduction and medial rotation of the arm; clavicular head facilitates flexion, sternocostal head aids in extension.

Clavipectoral Fascia

• Strong fascial sheet located deep to the clavicular head of pectoralis major, filling the space between clavicle and pectoralis minor.
• Structures that pierce it include lateral pectoral nerve, thoraco-acromial artery, cephalic vein, and lymphatics from the breast.

Pectoralis Minor

• Triangular muscle located deep to pectoralis major in the anterior axillary wall.
• Base attaches to the anterior surfaces of the third to fifth ribs at their costal cartilages.
• Apex converges into a tendon that attaches to the coracoid process of the scapula.
• Innervated by the medial pectoral nerve.
• Contracts to pull the coracoid process downward and anteriorly, assisting in scapula stability and elevation of ribs during deep inhalation.

Subclavius

• Small, horizontal muscle positioned inferior to the clavicle and superior to the first rib.
• Proximally attaches to the first rib and its costal cartilage, distally to the inferior surface of the clavicle.
• Innervated by the nerve to subclavius from anterior rami of C5 and C6.
• Stabilizes the shoulder by anchoring and depressing the clavicle, aiding in stabilizing the acromioclavicular joint.

Serratus Anterior

• Forms the medial wall of the axilla, located over the lateral thorax; fibers give it a saw-like appearance.
• Originates from the external surfaces of the lateral parts of the upper eight ribs, inserting along the medial border and inferior angle of the scapula.
• Innervated by the long thoracic nerve from anterior rami of C5, C6, and C7.
• Contraction protracts the scapula, enabling reaching and punching motions; also anchors the scapula and assists in upward rotation during arm abduction above the head.