Bones of the Upper Body Form the
Thorax and Arms 130
Articulations Form Where Bones Join
• The thoracic bones consist of the sternum and 12 pairs of
ribs, as shown. The thoracic cage protects the heart and
lungs and provides attachment points for muscles.
• An articulation (joint) is where two bones, cartilage and
bone, or teeth and bone make contact. The structure of a
joint determines its strength and flexibility.
• Figure 5.11a
Structurally, joints are classified as fibrous, cartilaginous,
and synovial. Functionally, they can be immovable (syn-
arthroses), partially movable (amphiarthroses), or freely
Fibrous joints have no cavity and the bones are held togeth-
er by irregular connective tissue. The types of fibrous joints
depend on the thickness of the connective tissue: sutures
(immovable), syndesmoses (slightly movable), or interosse-
ous membranes (slightly movable).
Cartilaginous joints have no cavity, and the bones are held
together by cartilage. As shown, they include immovable
synchondroses with hyaline cartilage and slightly movable
symphyses with fibrocartilage.
• The shoulder consists of the clavicle and scapula, which form
the pectoral girdle and attach the upper limb to the trunk.
• The 30 bones of the upper limb consist of the humerus,
ulna, radius, carpals (8), metacarpals (5), and phalanges (14).
Bones of the Lower Body
Form the Pelvic Girdle
and Legs 132
• The pelvis consists of coxal (hip)
bones attached to the sacrum and to
each other. Each coxal bone is com-
posed of a fused ilium, ischium, and
• As shown, the 30 bones of the lower
limb include the femur, tibia, fibula,
tarsals (8), metatarsals (5), and phalan-
• The medial and longitudinal arches of
the foot distribute weight and provide
support and leverage.
The lower body • Figure 5.12a
Joints • Figure 5.13
(epiphyseal growth plates
connected by cartilage)
• Synovial joints contain a fluid-filled cavity and are freely
movable. Their structures are complex, with several parts,
including articular cartilage, articular capsule, synovial
fluid, accessory discs, and ligaments.
• Six types of synovial joints allow various types of move-