Surface Features or Markings of Bones

Overview of Bone Surface Features

• Every bone presents unique external (surface) and internal (cancellous/medullary) architecture.

• Surface morphology reflects functional relationships with soft tissues and neighboring bones.

  • Elevations/Projections → sites of tendon, ligament, and muscular attachment OR articular contact with another bone.

  • Depressions/Perforations → pathways/entrances for vessels and nerves; articulation sockets; sinus cavities.

• Reading these landmarks allows clinicians and anatomists to reconstruct the course of arteries, veins, nerves, and muscle groups without direct visualization.

Functional Groups of Landmarks

Elevations / Projections (Attachment or Articulation)

• Crest – prominent ridge/border (e.g., iliac crest of os coxae).

• Line – less-prominent ridge, often a subtle raised line.

• Spine – relatively sharp, pointed projection (e.g., vertebral spinous process).

• Epicondyle – projection sitting superior to a condyle; increases surface for ligament/tendon attachment (e.g., medial/lateral epicondyles of femur).

• Condyle – rounded articular process usually covered with cartilage (e.g., femoral condyles).

• Head – large rounded proximal end of a bone forming a joint (e.g., humeral head).

• Facet – small, flat, smooth articular surface (e.g., costal facets on thoracic vertebrae).

• Process – general term for any projection or prominence (e.g., mastoid process).

• RamUS – arm-like bar/branch or bridge of bone (e.g., mandibular ramus)

• Trochanter – very large, blunt process unique to femur; primary muscle leverage site.

• Tuberosity – (remember big city)large, rounded, roughened prominence (e.g., ischial tuberosity).

• Tubercle – small, rounded prominence (e.g., greater/lesser tubercles of humerus; rib tubercle).

Depressions / Openings (Passage or Cavity)

• Alveolus – socket; classic example = tooth socket in maxilla/mandible.

• Fossa – broad, shallow depression (e.g., glenoid fossa of scapula).

• Groove (Sulcus) – narrow furrow tracking a nerve or vessel (e.g., intertubercular sulcus of humerus).

• Sulcus – synonymous with groove; relatively narrow channel.

• Foramen – hole/perforation for vessels or nerves (e.g., jugular foramen).

• Fissure – slit-like opening between bones (e.g., superior orbital fissure).

• Meatus – canal-like passage; external opening called an “external meatus” (e.g., external auditory meatus).

• Sinus – air-filled cavity within bone (e.g., maxillary sinus)

  • NOTE: “Sinus” in neuroanatomy can also reference venous channels (e.g., \text{superior\ sagittal\ sinus}).

Mnemonic & Study Tips

• Group terms by function (attachment vs. passage) to aid recall.

• Add bone name to term during lab practicals (e.g., “Greater tubercle – humerus”).

• Palpate exemplary landmarks on your own skeleton model to correlate 3-D form with definitions.