Thoracic Limb Anatomy Quiz

Study Notes

The thoracic limb, also known as the pectoral limb or forelimb, is the front limb of a quadruped.
Learning objectives for studying the thoracic limb include identifying the bones (shoulder, brachium, antebrachium, and manus), different parts of the bones, and the actions these bones produce through movement.
Other terms for the thoracic limb include pectoral limb and forelimb.

The clavicle (collarbone) is a vestigial bone not articulated with the skeleton. It's situated near the medial end of the clavicular tendon of the brachiocephalicus muscle. The dog's clavicle usually isn't visible on radiographs.
The scapula is a large, flat bone in the shoulder. It has two surfaces, three borders, and three angles. Note the various fossae (e.g., supraspinous, infraspinous) and the glenoid cavity.
Specific features of the scapula include the spine, acromion, glenoid cavity, cranial and caudal borders, and various processes (e.g., coracoid, supraglenoid, infraglenoid).
The lateral surface of the scapula includes the prominent spine, supraspinous fossa (supraspinatus muscle), and infraspinous fossa (infraspinatus muscle).
The medial or costal surface comprises the subscapular fossa (subscapularis muscle) and serrated face.
Key features of the cranial border are the scapular notch and the rhomboideus muscle. The caudal border and base are also significant for reference.
The supraglenoid tuberosity is a noticeable feature of the scapula, serving as an attachment point for the biceps brachii muscle.
The infraglenoid tubercle is another prominent structure.
The shoulder design in dogs differs from humans since dogs are cursorial animals, lacking the need for lifting, pushing, and pulling with their arms as humans do. It's adapted for speed and agility.

The humerus connects the shoulder and elbow. It's an S-shaped bone with a twist and is the main bone of the brachium.
The humerus has two extremities (proximal and distal) and four surfaces (medial, lateral, cranial, and caudal).
Key features of the humerus include the greater tubercle, lesser tubercle, intertubercular groove, deltoid tuberosity, brachial groove (musculospinal groove), capitulum, trochlea, lateral epicondyle, medial epicondyle, olecranon fossa, and radial fossa.

The radius and ulna cross each other obliquely, making the proximal ulna medial and the distal ulna lateral to the radius.
The radius is shorter than the ulna.
Key features include the cranial and caudal surfaces (convex and concave), the interosseous border, and critical articulations with the humerus (trochlear notch) and carpus (ulnar notch).
The ulna's proximal extremity features the olecranon, which acts as a lever arm for elbow extensor muscles, and the trochlear notch (semilunar notch).

The carpus is the wrist, having a proximal row (radial, ulnar, and accessory) and a distal row of carpal bones. The radial carpal is largest.
Metacarpals are atypical and vestigial, with the first metacarpal usually being present but in a less significant state.
Phalanges, comprising proximal, middle, and distal phalanges, are also present, along with sesamoid bones within the metacarpophalangeal joints.
The ungual crest is a notable feature; it's a thin bone shelf covering the root of the claw.
The ungual process is also critical, as it extends from the distal phalanx into the claw structure.
Detailed diagrams and images are also very important for understanding the precise structures of each bone and their relationships. Note the specific ligaments of the carpus, including the collateral and dorsal elastic ligaments.