The appendicular skeleton consists of the bones of the upper limbs (including the pectoral girdle) and lower limbs (including the pelvic girdle). It enables locomotion and manipulation.
Pectoral Girdle (Shoulder Girdle)
The pectoral girdle connects the upper limbs to the axial skeleton.
| Bone | Count | Key Features |
|---|---|---|
| Clavicle | 2 | S-shaped, sternal end + acromial end, conoid tubercle |
| Scapula | 2 | Triangular, costal surface (subscapular fossa), posterior surface (spine, supraspinous/infraspinous fossa), glenoid cavity, coracoid process, acromion |
Clavicle
- First bone to ossify (intramembranous, fetal week 5)
- Most commonly fractured bone
- Articulations: Sternum (sternoclavicular joint), acromion (acromioclavicular joint)
- Muscles attached: Deltoid, trapezius, pectoralis major, sternocleidomastoid, subclavius
Scapula
Fossae:
| Fossa | Location | Contents/Muscle |
|---|---|---|
| Subscapular | Costal (anterior) | Subscapularis |
| Supraspinous | Posterior (above spine) | Supraspinatus |
| Infraspinous | Posterior (below spine) | Infraspinatus |
Borders: Superior, medial (vertebral), lateral (axillary) Angles: Superior, inferior (at T7 level), lateral (glenoid)
Upper Limb
Arm
Humerus:
| Region | Key Features |
|---|---|
| Proximal | Head, anatomical neck, surgical neck, greater/lesser tubercles, intertubercular sulcus |
| Shaft | Deltoid tuberosity, radial groove (radial nerve) |
| Distal | Capitulum (lateral), trochlea (medial), medial/lateral epicondyles, olecranon fossa (posterior) |
Forearm
| Bone | Key Features | Articulations |
|---|---|---|
| Radius | Head (proximal), radial tuberosity, styloid process (distal) | Humerus (capitulum), ulna, carpals (scaphoid, lunate) |
| Ulna | Olecranon (proximal), coronoid process, trochlear notch, radial notch, styloid process (distal) | Humerus (trochlea), radius |
Interosseous membrane: Connects radius and ulna (force transfer)
Wrist (Carpal Bones)
8 carpal bones in two rows:
| Row | Bones (lateral to medial) |
|---|---|
| Proximal | Scaphoid, lunate, triquetrum, pisiform |
| Distal | Trapezium, trapezoid, capitate, hamate |
Mnemonic (proximal row): Some Lovers Try Positions (Scaphoid, Lunate, Triquetrum, Pisiform) Mnemonic (distal row): That They Can’t Handle (Trapezium, Trapezoid, Capitate, Hamate)
Hand
| Bones | Count per hand | Description |
|---|---|---|
| Metacarpals | 5 | Numbered 1-5 (thumb to little finger) |
| Phalanges | 14 | Thumb: 2 (proximal, distal); Fingers 2-5: 3 each (proximal, middle, distal) |
Pelvic Girdle
The pelvic girdle consists of two hip bones (ossa coxae), the sacrum, and the coccyx.
Hip Bone (Os Coxae)
Each hip bone (innominate bone) is formed from three fused bones:
| Bone | Location | Features |
|---|---|---|
| Ilium | Upper, fan-shaped | Iliac crest, anterior superior/inferior iliac spines, posterior superior/inferior iliac spines, iliac fossa, gluteal lines, auricular surface |
| Ischium | Lower, posterior | Ischial spine, ischial tuberosity, lesser sciatic notch, ischial ramus |
| Pubis | Lower, anterior | Superior/inferior pubic rami, pubic symphysis, pubic crest, obturator foramen |
Acetabulum
- Cup-shaped socket for the femoral head
- Formed by: Ilium (40%), ischium (40%), pubis (20%)
- Acetabular labrum: Fibrocartilage rim
Obturator Foramen
Large opening in the anterior pelvis, closed by the obturator membrane (except obturator canal).
Pelvis
| Feature | Male | Female |
|---|---|---|
| Shape | Heart-shaped (narrow) | Round/oval (wide) |
| Pelvic inlet | Narrow | Wide |
| Pelvic outlet | Narrow | Wide |
| Pubic arch | < 70 degrees | > 80 degrees |
| Iliac wings | Less flared | More flared |
| Obturator foramen | Round | Oval |
| Sacrum | Narrower, longer | Wider, shorter |
Lower Limb
Thigh
Femur:
| Region | Key Features |
|---|---|
| Proximal | Head (fovea capitis), neck, greater/lesser trochanters, intertrochanteric crest/line |
| Shaft | Linea aspera (medial/lateral lips), gluteal tuberosity |
| Distal | Medial/lateral condyles, medial/lateral epicondyles, intercondylar notch, patellar surface |
Patella:
- Largest sesamoid bone
- Embedded in quadriceps tendon
- Triangular with apex (inferior) and base (superior)
- Articular facets for medial/lateral femoral condyles
Leg
| Bone | Key Features | Articulations |
|---|---|---|
| Tibia | Medial (weight-bearing), medial/lateral condyles, tibial tuberosity, anterior crest, medial malleolus | Femur (condyles), talus, fibula |
| Fibula | Lateral (non-weight-bearing), head, lateral malleolus | Tibia, talus (stabilization) |
Interosseous membrane: Connects tibia and fibula
Ankle (Tarsal Bones)
7 tarsal bones:
| Bone | Location | Key Feature |
|---|---|---|
| Talus | Superior | Trochlea (articulates with tibia) |
| Calcaneus | Posterior, inferior | Heel bone, calcaneal tuberosity (Achilles tendon) |
| Navicular | Anterior to talus | Tuberosity |
| Medial cuneiform | Medial (anterior) | Articulates with 1st metatarsal |
| Intermediate cuneiform | Middle | Articulates with 2nd metatarsal |
| Lateral cuneiform | Lateral | Articulates with 3rd metatarsal |
| Cuboid | Lateral (anterior) | Groove for peroneus longus tendon |
Foot
| Bones | Count per foot | Description |
|---|---|---|
| Metatarsals | 5 | Numbered 1-5 (medial to lateral) |
| Phalanges | 14 | Great toe: 2 (proximal, distal); Toes 2-5: 3 each (proximal, middle, distal) |
Arches of the foot:
| Arch | Bones | Function |
|---|---|---|
| Medial longitudinal | Calcaneus, talus, navicular, cuneiforms, metatarsals 1-3 | Shock absorption, weight bearing |
| Lateral longitudinal | Calcaneus, cuboid, metatarsals 4-5 | Stability, propulsion |
| Transverse | Tarsal (cuneiforms, cuboid) and metatarsal bases | Distributes weight, foot flexibility |