The Appendicular Skeleton
THE SKELETAL SYSTEM
The Appendicular Skeleton
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2 pairs of limbs and 2 girdles
Pectoral (shoulder) girdle attaches upper limbs
Pelvic (hip) girdle secures lower limbs
3-Segmented limbs
– Upper = arm
• Humerus
• Radius & Ulna
• Hand
– Lower = leg
• Femur
• Tibia & Fibula
• Foot
Pectoral
Girdle
(Shoulder Girdle)
• Clavicle – anterior: collar bone
• Scapula – posterior: shoulder blade
Scapulae: triangular, paired, but don’t connect
in back (adds thoracic flexibility)
Upper extremity
• Arm or Brachium =
upper arm
– Between shoulder and
elbow (humerus)
• Forearm or
Antebrachium
– Radius & ulna
• Hand includes:
– Wrist (carpus)
– Palm (metacarpus)
– Fingers (phalanges)
Arm
– Humerus is the only
bone
– Head of humerus fits
into scapula
– Distal & medially,
articulates with the ulna
– Distal & laterally
articulates with the
radius
Arm
Right
humerus,
anterior view
Right humerus,
posterior view
Forearm
• 2 bones: articulate with each
other proximally and distally
• Interosseous membrane
between them
• Ulna
– Olecranon process hinges with the
humerus forming elbow
• Radius
– Contributes to wrist joint
– Styloid process anchors a ligament
to wrist (thumb side)
Radius is thinner proximally, like a spool of
thread, and wide distally; ulna is slightly
longer
Right forearm bones,
anterior view
Right forearm bones,
posterior view
In the anatomical position,
the radius is lateral
(thumb side); with
pronation the palm faces
posteriorly and the bones
cross
Left forearm
prone
Anatomical
position
pronation moves the forearm into the
prone position and supination moves it
back to the anatomical position
Prone: Turning the hand so that the
palm is down
Suppine: Turning the hand so that the
palm is up
Proximal and distal joints of the forearm
proximal ulna
Hand
• Proximal is “wrist” – 8 carpal bones
• Palm of hand - 5 metacarpals
• Fingers (or digits) consist of miniature long bones called
phalanges: thumb (“pollex”) has 2; fingers have 3: proximal,
middle, distal
Right hand, 2 views:
Pelvic Girdle
(Hip Girdle)
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Strongly attached to axial skeleton (sacrum)
Deep sockets
More stable than pectoral (shoulder) girdle
Less freedom of movement
Made up of the paired hip bones
– “Bony pelvis” is basin-like structure: hip bones plus
the axial sacrum and coccyx
Hip bone (os coxae): 3 separate bones
in childhood which fuse
• Ilium
• Ischium
• Pubis
Ilium
ilium
• Forms part of
hip socket which
receives ballshaped head of
femur
ilium
Hip bones with labels
Pelvis and childbearing
• Male/female differences
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Large & heavy vs light & delicate
Heart shaped pelvic inlet vs oval
Narrow deep true pelvis vs wide & shallow
Narrow outlet vs wide
Less than 90 degree pubic arch vs more than 90 degree
• Birth canal changes shape as baby descends: head
turns ¼
– Higher: pelvic inlet (brim) - side to side largest
– Lower: pelvic outlet - largest in AP direction
Male vs. Female Pelvis
Lower limb
• Thigh: femur
• Leg (lower
leg)
– Tibia
– Fibula
• Foot
Thigh
• Femur is largest, longest
and strongest bone in the
body
• Head fits in socket of pelvis
• Neck is weakest
Right femur, anterior
view
Right femur,
posterior view
Leg
• Tibia: shin bone
• Fibula
– Interosseous membrane
Right lower leg,
anterior view
Foot
• Tarsus: 7 tarsal bones
– Talus: articulates with tibia
and fibula anteriorly and
calcaneus posteriorly
– Calcaneus: heel bone
– Smaller cuboid, navicular,
and 3 cunieforms (medial,
intermediate and lateral)
• 5 metatarsals
• 14 phalanges
– Great toe is hallux
Right foot, superior (dorsal) view and inferior (plantar) view
Right foot,
lateral and
medial views
Arches