Osteology Session 2 – Sternum, Clavicle, Scapula & Upper-Extremity Bones

Session Overview

  • Session 2 of the pre-course that focuses exclusively on osteology (study of skeletal structure & function)

  • Emphasis is not on microscopic bone composition; rather on:

    • Bony landmarks that serve as muscle / ligament attachment sites

    • Prominences salient during manual palpation in surface-anatomy labs

    • Regions clinically prone to fracture

  • Skeletal elements covered today:

    • Sternum (thorax)

    • Clavicle

    • Scapula

    • Bones of the upper extremity: Humerus, Radius, Ulna, Carpals, Metacarpals, Phalanges

Anatomical Position & Standard Terminology

  • Anatomical position: standing upright, feet flat, arms at sides, palms facing forward

    • All direction/relationship terms default to this posture

  • Core directional terms (simple list before more complex variants):

    • Superior – toward the head (above)

    • Inferior – toward the feet (below)

    • Proximal – nearer to trunk / point of limb attachment

    • Distal – farther from trunk

    • Medial – closer to midline

    • Lateral – farther from midline

  • Cardinal planes of movement (mentioned, detailed in 1st class): sagittal, frontal, transverse

    • Not elaborated in this session, but flagged as essential upcoming content

Synonymous Terminology & Contextual Usage

  • Anatomical vocabulary often has interchangeable pairs ➜ must recognise both

    • Superior / Inferior ↔ Rostral / Caudal ("toward head" / "toward tail")

    • Common in comparative anatomy (e.g.
      rodent research lab)

    • Anterior / Posterior ↔ Ventral / Dorsal

    • “Dorsal fin” mnemonic for dorsal = back

    • Additional positional descriptors that will appear later: Radial, Ulnar, Volar, Plantar, Peripheral, etc.

  • Superficial vs. Deep: relative depth within body; repeated during palpation exercises

Osteology of the Thorax: Sternum

  • Midline bone complex of anterior rib cage ➜ three fused elements:

    1. Manubrium (superior)

    2. Body (middle)

    3. Xiphoid process (inferior)

  • Surface landmarks palpated in lab:

    • Jugular (suprasternal) notch

    • Midline depression at superior manubrium, between medial clavicular heads

    • Sternal angle / Angle of Louis

    • Palpable ridge ~2–3 finger-breadths inferior to jugular notch

    • Junction where manubrium and body fuse; clinically corresponds to 2nd costal cartilage & T4/T5 vertebral level

    • Xiphoid process

    • Tapered inferior tip; orientation may angle inward (less palpable in some individuals)

  • Practical notes:

    • Wide variation in prominence among individuals ➜ anticipate subtle palpation challenges

    • These same steps will be replicated with classmates in first surface-anatomy session

Osteology of the Shoulder Girdle

Clavicle

  • S-shaped ("italic-F") bone acting as strut holding upper limb away from thorax

  • Two ends:

    • Sternal (medial) end – articulates with manubrium

    • Acromial (lateral) end – articulates with scapular acromion

  • Inferior surface landmarks (important for ligament / muscle attachments):

    • Conoid tubercle (anchor for conoid ligament)

    • Trapezoid line (anchor for trapezoid ligament)

  • Clinical relevance:

    • Most frequently fractured long bone; knowledge of curvature & weak points aids diagnosis

Scapula

  • Large, triangular, "wing-shaped" bone positioned posterolaterally on thoracic wall

  • Anterior (costal) surface sits against ribs; Posterior surface faces skin

  • Key anterior landmarks (numbers corresponded to atlas figure):

    • Subscapular fossa, coracoid process, glenoid cavity, etc.

  • Key posterior landmarks:

    • Scapular spine ➜ leads to acromion (lateral expansion) [#2]

    • Supraspinous & infraspinous fossae separated by spine

    • Medial & lateral borders, inferior & superior angles

  • Acromion forms joint with clavicle (acromioclavicular joint)

Osteology of the Arm

Proximal Humerus

  • Proximal head articulates with glenoid cavity of scapula ➜ glenohumeral (shoulder) joint

  • Landmarks:

    • Greater & lesser tubercles – rotator cuff insertions

    • Intertubercular (bicipital) groove – long head biceps tendon path

    • Anatomical vs. surgical necks – surgical neck common fracture site

Distal Humerus

  • Forms elbow with radius & ulna

  • Anterior landmarks:

    • Capitulum (lateral, articulates with radial head)

    • Trochlea (medial, articulates with ulna)

    • Coronoid & radial fossae (receive forearm processes during flexion)

  • Posterior landmark:

    • Olecranon fossa – receives ulna’s olecranon during extension

  • Medial & lateral epicondyles – palpable; common tendinopathy sites (golfer’s & tennis elbow)

Osteology of the Forearm

Ulna

  • Proximal end massive ➜ olecranon, coronoid process, trochlear notch ↔ elbow hinge

  • Distal shaft tapers; head small, capped by ulnar styloid process

Radius

  • Proximal head small & disc-shaped; pivots in radial notch of ulna (pronation/supination)

  • Distal end broad & flat; key wrist articulator

    • Radial styloid process, ulnar notch (receives distal ulna)

  • Relationship: radius & ulna are "mirror imaged" in thickness distribution (proximal vs. distal)

Osteology of the Wrist and Hand

Carpal Bones (8 total in two rows)

  • Proximal row (lateral ➜ medial): Scaphoid, Lunate, Triquetrum, Pisiform

  • Distal row (lateral ➜ medial): Trapezium, Trapezoid, Capitate, Hamate

  • Instructor will provide mnemonic in class (e.g. "Some Lovers Try Positions That They Can’t Handle")

Metacarpals

  • Five long bones, numbered 1−51−5 (thumb → little finger)

  • Serve as palm framework; heads form knuckles

Phalanges

  • Thumb (digit 1) ➜ 2 phalanges (proximal, distal)

  • Digits 2–5 ➜ 3 phalanges each (proximal, middle, distal)

Palpation & Surface-Anatomy Implications

  • Session’s tactile exercise (self-test mimicking lab): locate jugular notch, sternal angle, xiphoid

  • Future labs: partner palpation of scapular spine, acromion, clavicle landmarks, epicondyles, styloid processes

  • Builds 3-D appreciation essential for:

    • Needle placement, surgical approaches, injury assessment

Study Strategies & Resources

  • Free UMN Library digital aids:

    • "AnatomyTV" (Primal Pictures): interactive 3-D bones & soft tissue

    • "Acland’s Video Atlas of Human Anatomy": cadaveric videos including skeletal system

  • Tip: Move bones physically while reciting landmarks; multi-sensory input improves retention

Practical, Ethical & Real-World Connections

  • Fracture identification (clavicle, scaphoid, surgical neck of humerus) depends on landmark knowledge

  • Terminology precision crucial for inter-professional communication (e.g. radiology reports)

  • Understanding variability (e.g. inward-tilted xiphoid) reduces palpation errors & patient discomfort

  • Ethical respect: When palpating peers, obtain consent, maintain professionalism, reiterate purpose (learning anatomy & future patient care)