The Appendicular Skeleton
THE SKELETAL SYSTEMThe Appendicular Skeleton
• 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: Turning the hand so that the palm is down Suppine: Turning the hand so that the palm is up
Anatomical position
prone
pronation moves the forearm into the prone position and supination moves it back to the anatomical position
proximal ulna
Proximal and distal joints of the forearm
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)
• 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• Forms part of
hip socket which receives ball-shaped head of femur
ilium
ilium
Hip bones with labels
Pelvis and childbearing• Male/female differences– 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