HUMAN BIOLOGY

the SKeLetaL SyStem 91

Figure 5.4 Animated! The skeletal system is divided into the axial skeleton and the appendicular skeleton. The blue areas are cartilage.

(© Cengage Learning)

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A Skull bones

B Rib cage

C Vertebral column,
or backbone

D Pectoral girdle and

upper limb bones

E Pelvic girdle and

lower limb bones

Axial skeleton Appendicular skeleton

Bones with extensive muscle

attachments, arranged for

great freedom of movement:

Clavicle (collarbone)

Cranial bones
Enclose, protect brain
and sensory organs

Facial bones
Framework for facial area,
support for teeth

These bones and some
vertebrae enclose, protect
heart, lungs; assist breathing:
Sternum (breastbone)
Ribs (twelve pairs)

Vertebrae (twenty-six bones)
Enclose, protect spinal cord;
support skull, upper extremities;
attachment sites for muscles

Intervertebral disks
Fibrous, cartilaginous structures
between vertebrae; absorb
movement-induced stresses;
impart flexibility to backbone

Scapula (shoulder blade)

Humerus (upper arm bone)

Radius (forearm bone)

Metacarpals (palm bones)

Ulna (forearm bone)

Carpals (wrist bones)

Phalanges (thumb, finger bones)

Pelvic girdle (six fused bones)

Supports weight of backbone; helps

protect soft pelvic organs

Femur (thighbone)

Body’s strongest weight-bearing bone;

works with large muscles in locomotion

and in maintaining upright posture

Patella (kneebone)

Protects knee joint; aids leverage

Tibia (lower leg bone)

Major load-bearing role

Fibula (lower leg bone)

Muscle attachment sites;

no load-bearing role

Tarsals (ankle bones)

Metatarsals (sole bones)

Phalanges (toe bones)

ligament

(to knee cap)

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