Overview
This lecture introduces the appendicular skeleton, focusing on the upper extremity bones and their key features, connections, and anatomical landmarks.
Introduction to the Appendicular Skeleton
- The appendicular skeleton consists of the upper and lower extremities.
- The upper extremity connects to the axial skeleton only at the sternoclavicular joint.
The Clavicle
- The clavicle is the most commonly broken bone in the upper limb.
- The sternal end (blunt side) attaches to the sternum; the other end attaches to the scapula (shoulder).
- The clavicle acts as a strut or roof above the first rib and humerus.
- The upper side is smooth, while the underside is roughened for muscle attachment.
- The shape (convex then concave) helps determine left from right clavicle.
Locating Ribs Using Landmarks
- The first rib is difficult to palpate because it's under the clavicle; the second rib can be found using the sternal angle.
The Scapula
- The scapula does not articulate directly with the ribs or axial skeleton.
- Sixteen muscles attach to the scapula, contributing to its stability.
- Key landmarks: acromion process, spine, coracoid process (not to be confused with coronoid process), glenoid cavity (glenoid fossa), supraspinous and infraspinous fossae, medial and lateral borders.
- Levator scapulae muscle inserts at a specific location on the scapula.
The Humerus
- The humerus is the bone of the brachium (upper arm).
- Anterior landmarks: head (points medially), greater and lesser tubercles, intertubercular groove (houses biceps tendon).
- Posterior landmark: radial groove for the radial nerve and artery.
- Deltoid tuberosity is the insertion point for the deltoid muscle.
- Distal landmarks: medial and lateral epicondyles, capitulum, and trochlea.
- The medial epicondyle has a groove for the ulnar nerve, known as the “funny bone.”
Key Terms & Definitions
- Sternoclavicular joint — the only bony connection between the upper limb and axial skeleton.
- Clavicle — collarbone; connects sternum and scapula.
- Scapula — shoulder blade; provides attachment for many muscles.
- Acromion process — extension of the scapular spine that forms the shoulder tip.
- Coracoid process — hook-like projection on the scapula, not to be confused with coronoid process.
- Glenoid cavity/fossa — scapular depression for the head of the humerus.
- Tubercle — small rounded projections on bones (greater, lesser on the humerus).
- Epicondyle — bony projections on the distal humerus for muscle attachment.
- Deltoid tuberosity — lateral humerus ridge for deltoid muscle insertion.
- Ulnar nerve — nerve running behind medial epicondyle (“funny bone”).
Action Items / Next Steps
- Review bone landmarks and their functions for the clavicle, scapula, and humerus.
- Practice palpating these features on yourself if possible.
- Prepare for learning the ulna and radius in the following lecture.